{-
(c) The University of Glasgow 2006
(c) The AQUA Project, Glasgow University, 1996-1998

-}

{-# LANGUAGE CPP, TupleSections, ScopedTypeVariables, MultiWayIf #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE LambdaCase #-}

{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

-- | Typecheck type and class declarations
module GHC.Tc.TyCl (
        tcTyAndClassDecls,

        -- Functions used by GHC.Tc.TyCl.Instance to check
        -- data/type family instance declarations
        kcConDecls, tcConDecls, DataDeclInfo(..),
        dataDeclChecks, checkValidTyCon,
        tcFamTyPats, tcTyFamInstEqn,
        tcAddTyFamInstCtxt, tcMkDataFamInstCtxt, tcAddDataFamInstCtxt,
        unravelFamInstPats, addConsistencyConstraints,
        wrongKindOfFamily
    ) where

#include "HsVersions.h"

import GHC.Prelude

import GHC.Driver.Env
import GHC.Driver.Session

import GHC.Hs

import GHC.Tc.TyCl.Build
import GHC.Tc.Solver( pushLevelAndSolveEqualities, pushLevelAndSolveEqualitiesX
                    , reportUnsolvedEqualities )
import GHC.Tc.Utils.Monad
import GHC.Tc.Utils.Env
import GHC.Tc.Utils.Unify( unifyType, emitResidualTvConstraint )
import GHC.Tc.Types.Constraint( emptyWC )
import GHC.Tc.Validity
import GHC.Tc.Utils.Zonk
import GHC.Tc.TyCl.Utils
import GHC.Tc.TyCl.Class
import {-# SOURCE #-} GHC.Tc.TyCl.Instance( tcInstDecls1 )
import GHC.Tc.Deriv (DerivInfo(..))
import GHC.Tc.Gen.HsType
import GHC.Tc.Instance.Class( AssocInstInfo(..) )
import GHC.Tc.Utils.TcMType
import GHC.Tc.Utils.TcType
import GHC.Tc.Instance.Family
import GHC.Tc.Types.Origin

import GHC.Builtin.Types (oneDataConTy,  unitTy, makeRecoveryTyCon )

import GHC.Rename.Env( lookupConstructorFields )

import GHC.Core.Multiplicity
import GHC.Core.FamInstEnv
import GHC.Core.Coercion
import GHC.Core.Type
import GHC.Core.TyCo.Rep   -- for checkValidRoles
import GHC.Core.TyCo.Ppr( pprTyVars )
import GHC.Core.Class
import GHC.Core.Coercion.Axiom
import GHC.Core.TyCon
import GHC.Core.DataCon
import GHC.Core.Unify

import GHC.Types.Id
import GHC.Types.Var
import GHC.Types.Var.Env
import GHC.Types.Var.Set
import GHC.Types.Name
import GHC.Types.Name.Set
import GHC.Types.Name.Env
import GHC.Types.SrcLoc
import GHC.Types.SourceFile
import GHC.Types.Unique
import GHC.Types.Basic
import qualified GHC.LanguageExtensions as LangExt

import GHC.Data.FastString
import GHC.Data.Maybe
import GHC.Data.List.SetOps

import GHC.Unit

import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Utils.Misc

import Control.Monad
import Data.Function ( on )
import Data.Functor.Identity
import Data.List (nubBy, partition)
import Data.List.NonEmpty ( NonEmpty(..) )
import qualified Data.Set as Set
import Data.Tuple( swap )

{-
************************************************************************
*                                                                      *
\subsection{Type checking for type and class declarations}
*                                                                      *
************************************************************************

Note [Grouping of type and class declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tcTyAndClassDecls is called on a list of `TyClGroup`s. Each group is a strongly
connected component of mutually dependent types and classes. We kind check and
type check each group separately to enhance kind polymorphism. Take the
following example:

  type Id a = a
  data X = X (Id Int)

If we were to kind check the two declarations together, we would give Id the
kind * -> *, since we apply it to an Int in the definition of X. But we can do
better than that, since Id really is kind polymorphic, and should get kind
forall (k::*). k -> k. Since it does not depend on anything else, it can be
kind-checked by itself, hence getting the most general kind. We then kind check
X, which works fine because we then know the polymorphic kind of Id, and simply
instantiate k to *.

Note [Check role annotations in a second pass]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Role inference potentially depends on the types of all of the datacons declared
in a mutually recursive group. The validity of a role annotation, in turn,
depends on the result of role inference. Because the types of datacons might
be ill-formed (see #7175 and Note [rejigConRes]) we must check
*all* the tycons in a group for validity before checking *any* of the roles.
Thus, we take two passes over the resulting tycons, first checking for general
validity and then checking for valid role annotations.
-}

tcTyAndClassDecls :: [TyClGroup GhcRn]      -- Mutually-recursive groups in
                                            -- dependency order
                  -> TcM ( TcGblEnv         -- Input env extended by types and
                                            -- classes
                                            -- and their implicit Ids,DataCons
                         , [InstInfo GhcRn] -- Source-code instance decls info
                         , [DerivInfo]      -- Deriving info
                         )
-- Fails if there are any errors
tcTyAndClassDecls :: [TyClGroup GhcRn] -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcTyAndClassDecls [TyClGroup GhcRn]
tyclds_s
  -- The code recovers internally, but if anything gave rise to
  -- an error we'd better stop now, to avoid a cascade
  -- Type check each group in dependency order folding the global env
  = forall r. TcM r -> TcM r
checkNoErrs forall a b. (a -> b) -> a -> b
$ [InstInfo GhcRn]
-> [DerivInfo]
-> [TyClGroup GhcRn]
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
fold_env [] [] [TyClGroup GhcRn]
tyclds_s
  where
    fold_env :: [InstInfo GhcRn]
             -> [DerivInfo]
             -> [TyClGroup GhcRn]
             -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
    fold_env :: [InstInfo GhcRn]
-> [DerivInfo]
-> [TyClGroup GhcRn]
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
fold_env [InstInfo GhcRn]
inst_info [DerivInfo]
deriv_info []
      = do { TcGblEnv
gbl_env <- forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv
           ; forall (m :: * -> *) a. Monad m => a -> m a
return (TcGblEnv
gbl_env, [InstInfo GhcRn]
inst_info, [DerivInfo]
deriv_info) }
    fold_env [InstInfo GhcRn]
inst_info [DerivInfo]
deriv_info (TyClGroup GhcRn
tyclds:[TyClGroup GhcRn]
tyclds_s)
      = do { (TcGblEnv
tcg_env, [InstInfo GhcRn]
inst_info', [DerivInfo]
deriv_info') <- TyClGroup GhcRn -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcTyClGroup TyClGroup GhcRn
tyclds
           ; forall gbl lcl a. gbl -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setGblEnv TcGblEnv
tcg_env forall a b. (a -> b) -> a -> b
$
               -- remaining groups are typechecked in the extended global env.
             [InstInfo GhcRn]
-> [DerivInfo]
-> [TyClGroup GhcRn]
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
fold_env ([InstInfo GhcRn]
inst_info' forall a. [a] -> [a] -> [a]
++ [InstInfo GhcRn]
inst_info)
                      ([DerivInfo]
deriv_info' forall a. [a] -> [a] -> [a]
++ [DerivInfo]
deriv_info)
                      [TyClGroup GhcRn]
tyclds_s }

tcTyClGroup :: TyClGroup GhcRn
            -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-- Typecheck one strongly-connected component of type, class, and instance decls
-- See Note [TyClGroups and dependency analysis] in GHC.Hs.Decls
tcTyClGroup :: TyClGroup GhcRn -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcTyClGroup (TyClGroup { group_tyclds :: forall pass. TyClGroup pass -> [LTyClDecl pass]
group_tyclds = [LTyClDecl GhcRn]
tyclds
                       , group_roles :: forall pass. TyClGroup pass -> [LRoleAnnotDecl pass]
group_roles  = [LRoleAnnotDecl GhcRn]
roles
                       , group_kisigs :: forall pass. TyClGroup pass -> [LStandaloneKindSig pass]
group_kisigs = [LStandaloneKindSig GhcRn]
kisigs
                       , group_instds :: forall pass. TyClGroup pass -> [LInstDecl pass]
group_instds = [LInstDecl GhcRn]
instds })
  = do { let role_annots :: RoleAnnotEnv
role_annots = [LRoleAnnotDecl GhcRn] -> RoleAnnotEnv
mkRoleAnnotEnv [LRoleAnnotDecl GhcRn]
roles

           -- Step 1: Typecheck the standalone kind signatures and type/class declarations
       ; String -> SDoc -> TcRn ()
traceTc String
"---- tcTyClGroup ---- {" SDoc
empty
       ; String -> SDoc -> TcRn ()
traceTc String
"Decls for" (forall a. Outputable a => a -> SDoc
ppr (forall a b. (a -> b) -> [a] -> [b]
map (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [LTyClDecl GhcRn]
tyclds))
       ; ([TyCon]
tyclss, [DerivInfo]
data_deriv_info, NameSet
kindless) <-
           forall r. TcTypeEnv -> TcM r -> TcM r
tcExtendKindEnv ([LTyClDecl GhcRn] -> TcTypeEnv
mkPromotionErrorEnv [LTyClDecl GhcRn]
tyclds) forall a b. (a -> b) -> a -> b
$ -- See Note [Type environment evolution]
           do { NameEnv Type
kisig_env <- forall a. [(Name, a)] -> NameEnv a
mkNameEnv forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
traverse LStandaloneKindSig GhcRn -> TcM (Name, Type)
tcStandaloneKindSig [LStandaloneKindSig GhcRn]
kisigs
              ; [LTyClDecl GhcRn]
-> NameEnv Type
-> RoleAnnotEnv
-> TcM ([TyCon], [DerivInfo], NameSet)
tcTyClDecls [LTyClDecl GhcRn]
tyclds NameEnv Type
kisig_env RoleAnnotEnv
role_annots }

           -- Step 1.5: Make sure we don't have any type synonym cycles
       ; String -> SDoc -> TcRn ()
traceTc String
"Starting synonym cycle check" (forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)
       ; HomeUnit
home_unit <- HscEnv -> HomeUnit
hsc_home_unit forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall gbl lcl. TcRnIf gbl lcl HscEnv
getTopEnv
       ; Unit -> [TyCon] -> [LTyClDecl GhcRn] -> TcRn ()
checkSynCycles (HomeUnit -> Unit
homeUnitAsUnit HomeUnit
home_unit) [TyCon]
tyclss [LTyClDecl GhcRn]
tyclds
       ; String -> SDoc -> TcRn ()
traceTc String
"Done synonym cycle check" (forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)

           -- Step 2: Perform the validity check on those types/classes
           -- We can do this now because we are done with the recursive knot
           -- Do it before Step 3 (adding implicit things) because the latter
           -- expects well-formed TyCons
       ; String -> SDoc -> TcRn ()
traceTc String
"Starting validity check" (forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)
       ; [TyCon]
tyclss <- forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM TyCon -> TcM [TyCon]
checkValidTyCl [TyCon]
tyclss
       ; String -> SDoc -> TcRn ()
traceTc String
"Done validity check" (forall a. Outputable a => a -> SDoc
ppr [TyCon]
tyclss)
       ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (forall r. TcRn r -> TcRn r -> TcRn r
recoverM (forall (m :: * -> *) a. Monad m => a -> m a
return ()) forall b c a. (b -> c) -> (a -> b) -> a -> c
. RoleAnnotEnv -> TyCon -> TcRn ()
checkValidRoleAnnots RoleAnnotEnv
role_annots) [TyCon]
tyclss
           -- See Note [Check role annotations in a second pass]

       ; String -> SDoc -> TcRn ()
traceTc String
"---- end tcTyClGroup ---- }" SDoc
empty

           -- Step 3: Add the implicit things;
           -- we want them in the environment because
           -- they may be mentioned in interface files
       ; TcGblEnv
gbl_env <- [TyCon] -> TcM TcGblEnv
addTyConsToGblEnv [TyCon]
tyclss

           -- Step 4: check instance declarations
       ; (TcGblEnv
gbl_env', [InstInfo GhcRn]
inst_info, [DerivInfo]
datafam_deriv_info) <-
         forall gbl lcl a. gbl -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setGblEnv TcGblEnv
gbl_env forall a b. (a -> b) -> a -> b
$
         [LInstDecl GhcRn] -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcInstDecls1 [LInstDecl GhcRn]
instds

       ; let deriv_info :: [DerivInfo]
deriv_info = [DerivInfo]
datafam_deriv_info forall a. [a] -> [a] -> [a]
++ [DerivInfo]
data_deriv_info
       ; let gbl_env'' :: TcGblEnv
gbl_env'' = TcGblEnv
gbl_env'
                { tcg_ksigs :: NameSet
tcg_ksigs = TcGblEnv -> NameSet
tcg_ksigs TcGblEnv
gbl_env' NameSet -> NameSet -> NameSet
`unionNameSet` NameSet
kindless }
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (TcGblEnv
gbl_env'', [InstInfo GhcRn]
inst_info, [DerivInfo]
deriv_info) }

-- Gives the kind for every TyCon that has a standalone kind signature
type KindSigEnv = NameEnv Kind

tcTyClDecls
  :: [LTyClDecl GhcRn]
  -> KindSigEnv
  -> RoleAnnotEnv
  -> TcM ([TyCon], [DerivInfo], NameSet)
tcTyClDecls :: [LTyClDecl GhcRn]
-> NameEnv Type
-> RoleAnnotEnv
-> TcM ([TyCon], [DerivInfo], NameSet)
tcTyClDecls [LTyClDecl GhcRn]
tyclds NameEnv Type
kisig_env RoleAnnotEnv
role_annots
  = do {    -- Step 1: kind-check this group and returns the final
            -- (possibly-polymorphic) kind of each TyCon and Class
            -- See Note [Kind checking for type and class decls]
         ([TyCon]
tc_tycons, NameSet
kindless) <- NameEnv Type -> [LTyClDecl GhcRn] -> TcM ([TyCon], NameSet)
kcTyClGroup NameEnv Type
kisig_env [LTyClDecl GhcRn]
tyclds
       ; String -> SDoc -> TcRn ()
traceTc String
"tcTyAndCl generalized kinds" ([SDoc] -> SDoc
vcat (forall a b. (a -> b) -> [a] -> [b]
map TyCon -> SDoc
ppr_tc_tycon [TyCon]
tc_tycons))

            -- Step 2: type-check all groups together, returning
            -- the final TyCons and Classes
            --
            -- NB: We have to be careful here to NOT eagerly unfold
            -- type synonyms, as we have not tested for type synonym
            -- loops yet and could fall into a black hole.
       ; forall a env. (a -> IOEnv env a) -> IOEnv env a
fixM forall a b. (a -> b) -> a -> b
$ \ ~([TyCon]
rec_tyclss, [DerivInfo]
_, NameSet
_) -> do
           { TcGblEnv
tcg_env <- forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv
                 -- Forced so we don't retain a reference to the TcGblEnv
           ; let !src :: HscSource
src  = TcGblEnv -> HscSource
tcg_src TcGblEnv
tcg_env
                 roles :: Name -> [Role]
roles = HscSource -> RoleAnnotEnv -> [TyCon] -> Name -> [Role]
inferRoles HscSource
src RoleAnnotEnv
role_annots [TyCon]
rec_tyclss

                 -- Populate environment with knot-tied ATyCon for TyCons
                 -- NB: if the decls mention any ill-staged data cons
                 -- (see Note [Recursion and promoting data constructors])
                 -- we will have failed already in kcTyClGroup, so no worries here
           ; ([TyCon]
tycons, [[DerivInfo]]
data_deriv_infos) <-
             forall r. [(Name, TyThing)] -> TcM r -> TcM r
tcExtendRecEnv ([TyCon] -> [TyCon] -> [(Name, TyThing)]
zipRecTyClss [TyCon]
tc_tycons [TyCon]
rec_tyclss) forall a b. (a -> b) -> a -> b
$

                 -- Also extend the local type envt with bindings giving
                 -- a TcTyCon for each knot-tied TyCon or Class
                 -- See Note [Type checking recursive type and class declarations]
                 -- and Note [Type environment evolution]
             forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
tc_tycons forall a b. (a -> b) -> a -> b
$

                 -- Kind and type check declarations for this group
               forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM ((Name -> [Role]) -> LTyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl Name -> [Role]
roles) [LTyClDecl GhcRn]
tyclds
           ; forall (m :: * -> *) a. Monad m => a -> m a
return ([TyCon]
tycons, forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[DerivInfo]]
data_deriv_infos, NameSet
kindless)
           } }
  where
    ppr_tc_tycon :: TyCon -> SDoc
ppr_tc_tycon TyCon
tc = SDoc -> SDoc
parens ([SDoc] -> SDoc
sep [ forall a. Outputable a => a -> SDoc
ppr (TyCon -> Name
tyConName TyCon
tc) SDoc -> SDoc -> SDoc
<> SDoc
comma
                                  , forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyConBinder]
tyConBinders TyCon
tc) SDoc -> SDoc -> SDoc
<> SDoc
comma
                                  , forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConResKind TyCon
tc)
                                  , forall a. Outputable a => a -> SDoc
ppr (TyCon -> Bool
isTcTyCon TyCon
tc) ])

zipRecTyClss :: [TcTyCon]
             -> [TyCon]           -- Knot-tied
             -> [(Name,TyThing)]
-- Build a name-TyThing mapping for the TyCons bound by decls
-- being careful not to look at the knot-tied [TyThing]
-- The TyThings in the result list must have a visible ATyCon,
-- because typechecking types (in, say, tcTyClDecl) looks at
-- this outer constructor
zipRecTyClss :: [TyCon] -> [TyCon] -> [(Name, TyThing)]
zipRecTyClss [TyCon]
tc_tycons [TyCon]
rec_tycons
  = [ (Name
name, TyCon -> TyThing
ATyCon (Name -> TyCon
get Name
name)) | TyCon
tc_tycon <- [TyCon]
tc_tycons, let name :: Name
name = forall a. NamedThing a => a -> Name
getName TyCon
tc_tycon ]
  where
    rec_tc_env :: NameEnv TyCon
    rec_tc_env :: NameEnv TyCon
rec_tc_env = forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr TyCon -> NameEnv TyCon -> NameEnv TyCon
add_tc forall a. NameEnv a
emptyNameEnv [TyCon]
rec_tycons

    add_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
    add_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
add_tc TyCon
tc NameEnv TyCon
env = forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr TyCon -> NameEnv TyCon -> NameEnv TyCon
add_one_tc NameEnv TyCon
env (TyCon
tc forall a. a -> [a] -> [a]
: TyCon -> [TyCon]
tyConATs TyCon
tc)

    add_one_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
    add_one_tc :: TyCon -> NameEnv TyCon -> NameEnv TyCon
add_one_tc TyCon
tc NameEnv TyCon
env = forall a. NameEnv a -> Name -> a -> NameEnv a
extendNameEnv NameEnv TyCon
env (TyCon -> Name
tyConName TyCon
tc) TyCon
tc

    get :: Name -> TyCon
get Name
name = case forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv TyCon
rec_tc_env Name
name of
                 Just TyCon
tc -> TyCon
tc
                 Maybe TyCon
other   -> forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"zipRecTyClss" (forall a. Outputable a => a -> SDoc
ppr Name
name SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Maybe TyCon
other)

{-
************************************************************************
*                                                                      *
                Kind checking
*                                                                      *
************************************************************************

Note [Kind checking for type and class decls]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Kind checking is done thus:

   1. Make up a kind variable for each parameter of the declarations,
      and extend the kind environment (which is in the TcLclEnv)

   2. Kind check the declarations

We need to kind check all types in the mutually recursive group
before we know the kind of the type variables.  For example:

  class C a where
     op :: D b => a -> b -> b

  class D c where
     bop :: (Monad c) => ...

Here, the kind of the locally-polymorphic type variable "b"
depends on *all the uses of class D*.  For example, the use of
Monad c in bop's type signature means that D must have kind Type->Type.

Note: we don't treat type synonyms specially (we used to, in the past);
in particular, even if we have a type synonym cycle, we still kind check
it normally, and test for cycles later (checkSynCycles).  The reason
we can get away with this is because we have more systematic TYPE r
inference, which means that we can do unification between kinds that
aren't lifted (this historically was not true.)

The downside of not directly reading off the kinds of the RHS of
type synonyms in topological order is that we don't transparently
support making synonyms of types with higher-rank kinds.  But
you can always specify a CUSK directly to make this work out.
See tc269 for an example.

Note [CUSKs and PolyKinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

    data T (a :: *) = MkT (S a)   -- Has CUSK
    data S a = MkS (T Int) (S a)  -- No CUSK

Via inferInitialKinds we get
  T :: * -> *
  S :: kappa -> *

Then we call kcTyClDecl on each decl in the group, to constrain the
kind unification variables.  BUT we /skip/ the RHS of any decl with
a CUSK.  Here we skip the RHS of T, so we eventually get
  S :: forall k. k -> *

This gets us more polymorphism than we would otherwise get, similar
(but implemented strangely differently from) the treatment of type
signatures in value declarations.

However, we only want to do so when we have PolyKinds.
When we have NoPolyKinds, we don't skip those decls, because we have defaulting
(#16609). Skipping won't bring us more polymorphism when we have defaulting.
Consider

  data T1 a = MkT1 T2        -- No CUSK
  data T2 = MkT2 (T1 Maybe)  -- Has CUSK

If we skip the rhs of T2 during kind-checking, the kind of a remains unsolved.
With PolyKinds, we do generalization to get T1 :: forall a. a -> *. And the
program type-checks.
But with NoPolyKinds, we do defaulting to get T1 :: * -> *. Defaulting happens
in quantifyTyVars, which is called from generaliseTcTyCon. Then type-checking
(T1 Maybe) will throw a type error.

Summary: with PolyKinds, we must skip; with NoPolyKinds, we must /not/ skip.

Open type families
~~~~~~~~~~~~~~~~~~
This treatment of type synonyms only applies to Haskell 98-style synonyms.
General type functions can be recursive, and hence, appear in `alg_decls'.

The kind of an open type family is solely determinded by its kind signature;
hence, only kind signatures participate in the construction of the initial
kind environment (as constructed by `inferInitialKind'). In fact, we ignore
instances of families altogether in the following. However, we need to include
the kinds of *associated* families into the construction of the initial kind
environment. (This is handled by `allDecls').

See also Note [Kind checking recursive type and class declarations]

Note [How TcTyCons work]
~~~~~~~~~~~~~~~~~~~~~~~~
TcTyCons are used for two distinct purposes

1.  When recovering from a type error in a type declaration,
    we want to put the erroneous TyCon in the environment in a
    way that won't lead to more errors.  We use a TcTyCon for this;
    see makeRecoveryTyCon.

2.  When checking a type/class declaration (in module GHC.Tc.TyCl), we come
    upon knowledge of the eventual tycon in bits and pieces.

      S1) First, we use inferInitialKinds to look over the user-provided
          kind signature of a tycon (including, for example, the number
          of parameters written to the tycon) to get an initial shape of
          the tycon's kind.  We record that shape in a TcTyCon.

          For CUSK tycons, the TcTyCon has the final, generalised kind.
          For non-CUSK tycons, the TcTyCon has as its tyConBinders only
          the explicit arguments given -- no kind variables, etc.

      S2) Then, using these initial kinds, we kind-check the body of the
          tycon (class methods, data constructors, etc.), filling in the
          metavariables in the tycon's initial kind.

      S3) We then generalize to get the (non-CUSK) tycon's final, fixed
          kind. Finally, once this has happened for all tycons in a
          mutually recursive group, we can desugar the lot.

    For convenience, we store partially-known tycons in TcTyCons, which
    might store meta-variables. These TcTyCons are stored in the local
    environment in GHC.Tc.TyCl, until the real full TyCons can be created
    during desugaring. A desugared program should never have a TcTyCon.

3.  In a TcTyCon, everything is zonked after the kind-checking pass (S2).

4.  tyConScopedTyVars.  A challenging piece in all of this is that we
    end up taking three separate passes over every declaration:
      - one in inferInitialKind (this pass look only at the head, not the body)
      - one in kcTyClDecls (to kind-check the body)
      - a final one in tcTyClDecls (to desugar)

    In the latter two passes, we need to connect the user-written type
    variables in an LHsQTyVars with the variables in the tycon's
    inferred kind. Because the tycon might not have a CUSK, this
    matching up is, in general, quite hard to do.  (Look through the
    git history between Dec 2015 and Apr 2016 for
    GHC.Tc.Gen.HsType.splitTelescopeTvs!)

    Instead of trying, we just store the list of type variables to
    bring into scope, in the tyConScopedTyVars field of the TcTyCon.
    These tyvars are brought into scope in GHC.Tc.Gen.HsType.bindTyClTyVars.

    In a TcTyCon, why is tyConScopedTyVars :: [(Name,TcTyVar)] rather
    than just [TcTyVar]?  Consider these mutually-recursive decls
       data T (a :: k1) b = MkT (S a b)
       data S (c :: k2) d = MkS (T c d)
    We start with k1 bound to kappa1, and k2 to kappa2; so initially
    in the (Name,TcTyVar) pairs the Name is that of the TcTyVar. But
    then kappa1 and kappa2 get unified; so after the zonking in
    'generalise' in 'kcTyClGroup' the Name and TcTyVar may differ.

See also Note [Type checking recursive type and class declarations].

Note [Swizzling the tyvars before generaliseTcTyCon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This Note only applies when /inferring/ the kind of a TyCon.
If there is a separate kind signature, or a CUSK, we take an entirely
different code path.

For inference, consider
   class C (f :: k) x where
      type T f
      op :: D f => blah
   class D (g :: j) y where
      op :: C g => y -> blah

Here C and D are considered mutually recursive.  Neither has a CUSK.
Just before generalisation we have the (un-quantified) kinds
   C :: k1 -> k2 -> Constraint
   T :: k1 -> Type
   D :: k1 -> Type -> Constraint
Notice that f's kind and g's kind have been unified to 'k1'. We say
that k1 is the "representative" of k in C's decl, and of j in D's decl.

Now when quantifying, we'd like to end up with
   C :: forall {k2}. forall k. k -> k2 -> Constraint
   T :: forall k. k -> Type
   D :: forall j. j -> Type -> Constraint

That is, we want to swizzle the representative to have the Name given
by the user. Partly this is to improve error messages and the output of
:info in GHCi.  But it is /also/ important because the code for a
default method may mention the class variable(s), but at that point
(tcClassDecl2), we only have the final class tyvars available.
(Alternatively, we could record the scoped type variables in the
TyCon, but it's a nuisance to do so.)

Notes:

* On the input to generaliseTyClDecl, the mapping between the
  user-specified Name and the representative TyVar is recorded in the
  tyConScopedTyVars of the TcTyCon.  NB: you first need to zonk to see
  this representative TyVar.

* The swizzling is actually performed by swizzleTcTyConBndrs

* We must do the swizzling across the whole class decl. Consider
     class C f where
       type S (f :: k)
       type T f
  Here f's kind k is a parameter of C, and its identity is shared
  with S and T.  So if we swizzle the representative k at all, we
  must do so consistently for the entire declaration.

  Hence the call to check_duplicate_tc_binders is in generaliseTyClDecl,
  rather than in generaliseTcTyCon.

There are errors to catch here.  Suppose we had
   class E (f :: j) (g :: k) where
     op :: SameKind f g -> blah

Then, just before generalisation we will have the (unquantified)
   E :: k1 -> k1 -> Constraint

That's bad!  Two distinctly-named tyvars (j and k) have ended up with
the same representative k1.  So when swizzling, we check (in
check_duplicate_tc_binders) that two distinct source names map
to the same representative.

Here's an interesting case:
    class C1 f where
      type S (f :: k1)
      type T (f :: k2)
Here k1 and k2 are different Names, but they end up mapped to the
same representative TyVar.  To make the swizzling consistent (remember
we must have a single k across C1, S and T) we reject the program.

Another interesting case
    class C2 f where
      type S (f :: k) (p::Type)
      type T (f :: k) (p::Type->Type)

Here the two k's (and the two p's) get distinct Uniques, because they
are seen by the renamer as locally bound in S and T resp.  But again
the two (distinct) k's end up bound to the same representative TyVar.
You might argue that this should be accepted, but it's definitely
rejected (via an entirely different code path) if you add a kind sig:
    type C2' :: j -> Constraint
    class C2' f where
      type S (f :: k) (p::Type)
We get
    • Expected kind ‘j’, but ‘f’ has kind ‘k’
    • In the associated type family declaration for ‘S’

So we reject C2 too, even without the kind signature.  We have
to do a bit of work to get a good error message, since both k's
look the same to the user.

Another case
    class C3 (f :: k1) where
      type S (f :: k2)

This will be rejected too.


Note [Type environment evolution]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As we typecheck a group of declarations the type environment evolves.
Consider for example:
  data B (a :: Type) = MkB (Proxy 'MkB)

We do the following steps:

  1. Start of tcTyClDecls: use mkPromotionErrorEnv to initialise the
     type env with promotion errors
            B   :-> TyConPE
            MkB :-> DataConPE

  2. kcTyCLGroup
      - Do inferInitialKinds, which will signal a promotion
        error if B is used in any of the kinds needed to initialise
        B's kind (e.g. (a :: Type)) here

      - Extend the type env with these initial kinds (monomorphic for
        decls that lack a CUSK)
            B :-> TcTyCon <initial kind>
        (thereby overriding the B :-> TyConPE binding)
        and do kcLTyClDecl on each decl to get equality constraints on
        all those initial kinds

      - Generalise the initial kind, making a poly-kinded TcTyCon

  3. Back in tcTyDecls, extend the envt with bindings of the poly-kinded
     TcTyCons, again overriding the promotion-error bindings.

     But note that the data constructor promotion errors are still in place
     so that (in our example) a use of MkB will still be signalled as
     an error.

  4. Typecheck the decls.

  5. In tcTyClGroup, extend the envt with bindings for TyCon and DataCons


Note [Missed opportunity to retain higher-rank kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In 'kcTyClGroup', there is a missed opportunity to make kind
inference work in a few more cases.  The idea is analogous
to Note [Single function non-recursive binding special-case]:

     * If we have an SCC with a single decl, which is non-recursive,
       instead of creating a unification variable representing the
       kind of the decl and unifying it with the rhs, we can just
       read the type directly of the rhs.

     * Furthermore, we can update our SCC analysis to ignore
       dependencies on declarations which have CUSKs: we don't
       have to kind-check these all at once, since we can use
       the CUSK to initialize the kind environment.

Unfortunately this requires reworking a bit of the code in
'kcLTyClDecl' so I've decided to punt unless someone shouts about it.

Note [Don't process associated types in getInitialKind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Previously, we processed associated types in the thing_inside in getInitialKind,
but this was wrong -- we want to do ATs sepearately.
The consequence for not doing it this way is #15142:

  class ListTuple (tuple :: Type) (as :: [(k, Type)]) where
    type ListToTuple as :: Type

We assign k a kind kappa[1]. When checking the tuple (k, Type), we try to unify
kappa ~ Type, but this gets deferred because we bumped the TcLevel as we bring
`tuple` into scope. Thus, when we check ListToTuple, kappa[1] still hasn't
unified with Type. And then, when we generalize the kind of ListToTuple (which
indeed has a CUSK, according to the rules), we skolemize the free metavariable
kappa. Note that we wouldn't skolemize kappa when generalizing the kind of ListTuple,
because the solveEqualities in kcInferDeclHeader is at TcLevel 1 and so kappa[1]
will unify with Type.

Bottom line: as associated types should have no effect on a CUSK enclosing class,
we move processing them to a separate action, run after the outer kind has
been generalized.

-}

kcTyClGroup :: KindSigEnv -> [LTyClDecl GhcRn] -> TcM ([TcTyCon], NameSet)

-- Kind check this group, kind generalize, and return the resulting local env
-- This binds the TyCons and Classes of the group, but not the DataCons
-- See Note [Kind checking for type and class decls]
-- and Note [Inferring kinds for type declarations]
--
-- The NameSet returned contains kindless tycon names, without CUSK or SAKS.
kcTyClGroup :: NameEnv Type -> [LTyClDecl GhcRn] -> TcM ([TyCon], NameSet)
kcTyClGroup NameEnv Type
kisig_env [LTyClDecl GhcRn]
decls
  = do  { Module
mod <- forall (m :: * -> *). HasModule m => m Module
getModule
        ; String -> SDoc -> TcRn ()
traceTc String
"---- kcTyClGroup ---- {"
                  (String -> SDoc
text String
"module" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Module
mod SDoc -> SDoc -> SDoc
$$ [SDoc] -> SDoc
vcat (forall a b. (a -> b) -> [a] -> [b]
map forall a. Outputable a => a -> SDoc
ppr [LTyClDecl GhcRn]
decls))

          -- Kind checking;
          --    1. Bind kind variables for decls
          --    2. Kind-check decls
          --    3. Generalise the inferred kinds
          -- See Note [Kind checking for type and class decls]

        ; Bool
cusks_enabled <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.CUSKs forall (f :: * -> *). Applicative f => f Bool -> f Bool -> f Bool
<&&> forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.PolyKinds
                    -- See Note [CUSKs and PolyKinds]
        ; let ([GenLocated SrcSpanAnnA (TyClDecl GhcRn)]
kindless_decls, [(GenLocated SrcSpanAnnA (TyClDecl GhcRn), SAKS_or_CUSK)]
kinded_decls) = forall a b c. (a -> Either b c) -> [a] -> ([b], [c])
partitionWith GenLocated SrcSpanAnnA (TyClDecl GhcRn)
-> Either
     (GenLocated SrcSpanAnnA (TyClDecl GhcRn))
     (GenLocated SrcSpanAnnA (TyClDecl GhcRn), SAKS_or_CUSK)
get_kind [LTyClDecl GhcRn]
decls
              kindless_names :: NameSet
kindless_names = [Name] -> NameSet
mkNameSet forall a b. (a -> b) -> a -> b
$ forall a b. (a -> b) -> [a] -> [b]
map forall {p :: Pass} {l}.
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
GenLocated l (TyClDecl (GhcPass p)) -> IdGhcP p
get_name [GenLocated SrcSpanAnnA (TyClDecl GhcRn)]
kindless_decls

              get_name :: GenLocated l (TyClDecl (GhcPass p)) -> IdP (GhcPass p)
get_name GenLocated l (TyClDecl (GhcPass p))
d = forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName (forall l e. GenLocated l e -> e
unLoc GenLocated l (TyClDecl (GhcPass p))
d)

              get_kind :: GenLocated SrcSpanAnnA (TyClDecl GhcRn)
-> Either
     (GenLocated SrcSpanAnnA (TyClDecl GhcRn))
     (GenLocated SrcSpanAnnA (TyClDecl GhcRn), SAKS_or_CUSK)
get_kind GenLocated SrcSpanAnnA (TyClDecl GhcRn)
d
                | Just Type
ki <- forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv Type
kisig_env (forall {p :: Pass} {l}.
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
GenLocated l (TyClDecl (GhcPass p)) -> IdGhcP p
get_name GenLocated SrcSpanAnnA (TyClDecl GhcRn)
d)
                = forall a b. b -> Either a b
Right (GenLocated SrcSpanAnnA (TyClDecl GhcRn)
d, Type -> SAKS_or_CUSK
SAKS Type
ki)

                | Bool
cusks_enabled Bool -> Bool -> Bool
&& TyClDecl GhcRn -> Bool
hsDeclHasCusk (forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpanAnnA (TyClDecl GhcRn)
d)
                = forall a b. b -> Either a b
Right (GenLocated SrcSpanAnnA (TyClDecl GhcRn)
d, SAKS_or_CUSK
CUSK)

                | Bool
otherwise = forall a b. a -> Either a b
Left GenLocated SrcSpanAnnA (TyClDecl GhcRn)
d

        ; [TyCon]
checked_tcs <- forall r. TcM r -> TcM r
checkNoErrs forall a b. (a -> b) -> a -> b
$
                         [(LTyClDecl GhcRn, SAKS_or_CUSK)] -> TcM [TyCon]
checkInitialKinds [(GenLocated SrcSpanAnnA (TyClDecl GhcRn), SAKS_or_CUSK)]
kinded_decls
                         -- checkNoErrs because we are about to extend
                         -- the envt with these tycons, and we get
                         -- knock-on errors if we have tycons with
                         -- malformed kinds

        ; [TyCon]
inferred_tcs
            <- forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
checked_tcs  forall a b. (a -> b) -> a -> b
$
               forall a. SkolemInfo -> [TyVar] -> TcM a -> TcM a
pushLevelAndSolveEqualities SkolemInfo
UnkSkol [] forall a b. (a -> b) -> a -> b
$
                     -- We are going to kind-generalise, so unification
                     -- variables in here must be one level in
               do {  -- Step 1: Bind kind variables for all decls
                    [TyCon]
mono_tcs <- [LTyClDecl GhcRn] -> TcM [TyCon]
inferInitialKinds [GenLocated SrcSpanAnnA (TyClDecl GhcRn)]
kindless_decls

                  ; String -> SDoc -> TcRn ()
traceTc String
"kcTyClGroup: initial kinds" forall a b. (a -> b) -> a -> b
$
                    [TyCon] -> SDoc
ppr_tc_kinds [TyCon]
mono_tcs

                    -- Step 2: Set extended envt, kind-check the decls
                    -- NB: the environment extension overrides the tycon
                    --     promotion-errors bindings
                    --     See Note [Type environment evolution]
                  ; forall r. TcM r -> TcM r
checkNoErrs forall a b. (a -> b) -> a -> b
$
                    forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
mono_tcs forall a b. (a -> b) -> a -> b
$
                    forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ LTyClDecl GhcRn -> TcRn ()
kcLTyClDecl [GenLocated SrcSpanAnnA (TyClDecl GhcRn)]
kindless_decls

                  ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon]
mono_tcs }

        -- Step 3: generalisation
        -- Finally, go through each tycon and give it its final kind,
        -- with all the required, specified, and inferred variables
        -- in order.
        ; let inferred_tc_env :: NameEnv TyCon
inferred_tc_env = forall a. [(Name, a)] -> NameEnv a
mkNameEnv forall a b. (a -> b) -> a -> b
$
                                forall a b. (a -> b) -> [a] -> [b]
map (\TyCon
tc -> (TyCon -> Name
tyConName TyCon
tc, TyCon
tc)) [TyCon]
inferred_tcs
        ; [TyCon]
generalized_tcs <- forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM (NameEnv TyCon -> LTyClDecl GhcRn -> TcM [TyCon]
generaliseTyClDecl NameEnv TyCon
inferred_tc_env)
                                        [GenLocated SrcSpanAnnA (TyClDecl GhcRn)]
kindless_decls

        ; let poly_tcs :: [TyCon]
poly_tcs = [TyCon]
checked_tcs forall a. [a] -> [a] -> [a]
++ [TyCon]
generalized_tcs
        ; String -> SDoc -> TcRn ()
traceTc String
"---- kcTyClGroup end ---- }" ([TyCon] -> SDoc
ppr_tc_kinds [TyCon]
poly_tcs)
        ; forall (m :: * -> *) a. Monad m => a -> m a
return ([TyCon]
poly_tcs, NameSet
kindless_names) }
  where
    ppr_tc_kinds :: [TyCon] -> SDoc
ppr_tc_kinds [TyCon]
tcs = [SDoc] -> SDoc
vcat (forall a b. (a -> b) -> [a] -> [b]
map TyCon -> SDoc
pp_tc [TyCon]
tcs)
    pp_tc :: TyCon -> SDoc
pp_tc TyCon
tc = forall a. Outputable a => a -> SDoc
ppr (TyCon -> Name
tyConName TyCon
tc) SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConKind TyCon
tc)

type ScopedPairs = [(Name, TcTyVar)]
  -- The ScopedPairs for a TcTyCon are precisely
  --    specified-tvs ++ required-tvs
  -- You can distinguish them because there are tyConArity required-tvs

generaliseTyClDecl :: NameEnv TcTyCon -> LTyClDecl GhcRn -> TcM [TcTyCon]
-- See Note [Swizzling the tyvars before generaliseTcTyCon]
generaliseTyClDecl :: NameEnv TyCon -> LTyClDecl GhcRn -> TcM [TyCon]
generaliseTyClDecl NameEnv TyCon
inferred_tc_env (L SrcSpanAnnA
_ TyClDecl GhcRn
decl)
  = do { let names_in_this_decl :: [Name]
             names_in_this_decl :: [Name]
names_in_this_decl = TyClDecl GhcRn -> [Name]
tycld_names TyClDecl GhcRn
decl

       -- Extract the specified/required binders and skolemise them
       ; [(TyCon, [(Name, TyVar)])]
tc_with_tvs  <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> TcM (TyCon, [(Name, TyVar)])
skolemise_tc_tycon [Name]
names_in_this_decl

       -- Zonk, to manifest the side-effects of skolemisation to the swizzler
       -- NB: it's important to skolemise them all before this step. E.g.
       --         class C f where { type T (f :: k) }
       --     We only skolemise k when looking at T's binders,
       --     but k appears in f's kind in C's binders.
       ; [(TyCon, [(Name, TyVar)], Type)]
tc_infos <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TyCon, [(Name, TyVar)]) -> TcM (TyCon, [(Name, TyVar)], Type)
zonk_tc_tycon [(TyCon, [(Name, TyVar)])]
tc_with_tvs

       -- Swizzle
       ; [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos <- forall a. TyClDecl GhcRn -> TcM a -> TcM a
tcAddDeclCtxt TyClDecl GhcRn
decl ([(TyCon, [(Name, TyVar)], Type)]
-> TcM [(TyCon, [(Name, TyVar)], Type)]
swizzleTcTyConBndrs [(TyCon, [(Name, TyVar)], Type)]
tc_infos)

       -- And finally generalise
       ; forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndReportM (TyCon, [(Name, TyVar)], Type) -> TcM TyCon
generaliseTcTyCon [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos }
  where
    tycld_names :: TyClDecl GhcRn -> [Name]
    tycld_names :: TyClDecl GhcRn -> [Name]
tycld_names TyClDecl GhcRn
decl = forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl forall a. a -> [a] -> [a]
: TyClDecl GhcRn -> [Name]
at_names TyClDecl GhcRn
decl

    at_names :: TyClDecl GhcRn -> [Name]
    at_names :: TyClDecl GhcRn -> [Name]
at_names (ClassDecl { tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats }) = forall a b. (a -> b) -> [a] -> [b]
map (forall (p :: Pass). FamilyDecl (GhcPass p) -> IdP (GhcPass p)
familyDeclName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [LFamilyDecl GhcRn]
ats
    at_names TyClDecl GhcRn
_ = []  -- Only class decls have associated types

    skolemise_tc_tycon :: Name -> TcM (TcTyCon, ScopedPairs)
    -- Zonk and skolemise the Specified and Required binders
    skolemise_tc_tycon :: Name -> TcM (TyCon, [(Name, TyVar)])
skolemise_tc_tycon Name
tc_name
      = do { let tc :: TyCon
tc = forall a. NameEnv a -> Name -> a
lookupNameEnv_NF NameEnv TyCon
inferred_tc_env Name
tc_name
                      -- This lookup should not fail
           ; [(Name, TyVar)]
scoped_prs <- forall (m :: * -> *) b c a.
Monad m =>
(b -> m c) -> [(a, b)] -> m [(a, c)]
mapSndM TyVar -> TcM TyVar
zonkAndSkolemise (TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
tc)
           ; forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, [(Name, TyVar)]
scoped_prs) }

    zonk_tc_tycon :: (TcTyCon, ScopedPairs) -> TcM (TcTyCon, ScopedPairs, TcKind)
    zonk_tc_tycon :: (TyCon, [(Name, TyVar)]) -> TcM (TyCon, [(Name, TyVar)], Type)
zonk_tc_tycon (TyCon
tc, [(Name, TyVar)]
scoped_prs)
      = do { [(Name, TyVar)]
scoped_prs <- forall (m :: * -> *) b c a.
Monad m =>
(b -> m c) -> [(a, b)] -> m [(a, c)]
mapSndM HasDebugCallStack => TyVar -> TcM TyVar
zonkTcTyVarToTyVar [(Name, TyVar)]
scoped_prs
                           -- We really have to do this again, even though
                           -- we have just done zonkAndSkolemise
           ; Type
res_kind   <- Type -> TcM Type
zonkTcType (TyCon -> Type
tyConResKind TyCon
tc)
           ; forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, [(Name, TyVar)]
scoped_prs, Type
res_kind) }

swizzleTcTyConBndrs :: [(TcTyCon, ScopedPairs, TcKind)]
                -> TcM [(TcTyCon, ScopedPairs, TcKind)]
swizzleTcTyConBndrs :: [(TyCon, [(Name, TyVar)], Type)]
-> TcM [(TyCon, [(Name, TyVar)], Type)]
swizzleTcTyConBndrs [(TyCon, [(Name, TyVar)], Type)]
tc_infos
  | forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all (Name, TyVar) -> Bool
no_swizzle [(Name, TyVar)]
swizzle_prs
    -- This fast path happens almost all the time
    -- See Note [Cloning for type variable binders] in GHC.Tc.Gen.HsType
    -- "Almost all the time" means not the case of mutual recursion with
    -- polymorphic kinds.
  = do { String -> SDoc -> TcRn ()
traceTc String
"Skipping swizzleTcTyConBndrs for" (forall a. Outputable a => a -> SDoc
ppr (forall a b. (a -> b) -> [a] -> [b]
map forall a b c. (a, b, c) -> a
fstOf3 [(TyCon, [(Name, TyVar)], Type)]
tc_infos))
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [(TyCon, [(Name, TyVar)], Type)]
tc_infos }

  | Bool
otherwise
  = do { TcRn ()
check_duplicate_tc_binders

       ; String -> SDoc -> TcRn ()
traceTc String
"swizzleTcTyConBndrs" forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"before" SDoc -> SDoc -> SDoc
<+> forall {a} {a} {c}. Outputable a => [(a, [(a, TyVar)], c)] -> SDoc
ppr_infos [(TyCon, [(Name, TyVar)], Type)]
tc_infos
              , String -> SDoc
text String
"swizzle_prs" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [(Name, TyVar)]
swizzle_prs
              , String -> SDoc
text String
"after" SDoc -> SDoc -> SDoc
<+> forall {a} {a} {c}. Outputable a => [(a, [(a, TyVar)], c)] -> SDoc
ppr_infos [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos ]

       ; forall (m :: * -> *) a. Monad m => a -> m a
return [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos }

  where
    swizzled_infos :: [(TyCon, [(Name, TyVar)], Type)]
swizzled_infos =  [ (TyCon
tc, forall b c a. (b -> c) -> [(a, b)] -> [(a, c)]
mapSnd TyVar -> TyVar
swizzle_var [(Name, TyVar)]
scoped_prs, Type -> Type
swizzle_ty Type
kind)
                      | (TyCon
tc, [(Name, TyVar)]
scoped_prs, Type
kind) <- [(TyCon, [(Name, TyVar)], Type)]
tc_infos ]

    swizzle_prs :: [(Name,TyVar)]
    -- Pairs the user-specified Name with its representative TyVar
    -- See Note [Swizzling the tyvars before generaliseTcTyCon]
    swizzle_prs :: [(Name, TyVar)]
swizzle_prs = [ (Name, TyVar)
pr | (TyCon
_, [(Name, TyVar)]
prs, Type
_) <- [(TyCon, [(Name, TyVar)], Type)]
tc_infos, (Name, TyVar)
pr <- [(Name, TyVar)]
prs ]

    no_swizzle :: (Name,TyVar) -> Bool
    no_swizzle :: (Name, TyVar) -> Bool
no_swizzle (Name
nm, TyVar
tv) = Name
nm forall a. Eq a => a -> a -> Bool
== TyVar -> Name
tyVarName TyVar
tv

    ppr_infos :: [(a, [(a, TyVar)], c)] -> SDoc
ppr_infos [(a, [(a, TyVar)], c)]
infos = [SDoc] -> SDoc
vcat [ forall a. Outputable a => a -> SDoc
ppr a
tc SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars (forall a b. (a -> b) -> [a] -> [b]
map forall a b. (a, b) -> b
snd [(a, TyVar)]
prs)
                           | (a
tc, [(a, TyVar)]
prs, c
_) <- [(a, [(a, TyVar)], c)]
infos ]

    -- Check for duplicates
    -- E.g. data SameKind (a::k) (b::k)
    --      data T (a::k1) (b::k2) = MkT (SameKind a b)
    -- Here k1 and k2 start as TyVarTvs, and get unified with each other
    -- If this happens, things get very confused later, so fail fast
    check_duplicate_tc_binders :: TcM ()
    check_duplicate_tc_binders :: TcRn ()
check_duplicate_tc_binders = forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (forall (t :: * -> *) a. Foldable t => t a -> Bool
null [(Name, Name)]
err_prs) forall a b. (a -> b) -> a -> b
$
                                 do { forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (Name, Name) -> TcRn ()
report_dup [(Name, Name)]
err_prs; forall env a. IOEnv env a
failM }

    -------------- Error reporting ------------
    err_prs :: [(Name,Name)]
    err_prs :: [(Name, Name)]
err_prs = [ (Name
n1,Name
n2)
              | (Name, TyVar)
pr :| [(Name, TyVar)]
prs <- forall a. (a -> a -> Bool) -> [a] -> [NonEmpty a]
findDupsEq (forall a. Eq a => a -> a -> Bool
(==) forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
`on` forall a b. (a, b) -> b
snd) [(Name, TyVar)]
swizzle_prs
              , (Name
n1,TyVar
_):(Name
n2,TyVar
_):[(Name, TyVar)]
_ <- [forall a. (a -> a -> Bool) -> [a] -> [a]
nubBy (forall a. Eq a => a -> a -> Bool
(==) forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
`on` forall a b. (a, b) -> a
fst) ((Name, TyVar)
prforall a. a -> [a] -> [a]
:[(Name, TyVar)]
prs)] ]
              -- This nubBy avoids bogus error reports when we have
              --    [("f", f), ..., ("f",f)....] in swizzle_prs
              -- which happens with  class C f where { type T f }

    report_dup :: (Name,Name) -> TcM ()
    report_dup :: (Name, Name) -> TcRn ()
report_dup (Name
n1,Name
n2)
      = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (forall a. NamedThing a => a -> SrcSpan
getSrcSpan Name
n2) forall a b. (a -> b) -> a -> b
$ SDoc -> TcRn ()
addErrTc forall a b. (a -> b) -> a -> b
$
        SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Different names for the same type variable:") Arity
2 SDoc
info
      where
        info :: SDoc
info | Name -> OccName
nameOccName Name
n1 forall a. Eq a => a -> a -> Bool
/= Name -> OccName
nameOccName Name
n2
             = SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
n1) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"and" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
n2)
             | Bool
otherwise -- Same OccNames! See C2 in
                         -- Note [Swizzling the tyvars before generaliseTcTyCon]
             = [SDoc] -> SDoc
vcat [ SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
n1) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"bound at" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (forall a. NamedThing a => a -> SrcLoc
getSrcLoc Name
n1)
                    , SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
n2) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"bound at" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (forall a. NamedThing a => a -> SrcLoc
getSrcLoc Name
n2) ]

    -------------- The swizzler ------------
    -- This does a deep traverse, simply doing a
    -- Name-to-Name change, governed by swizzle_env
    -- The 'swap' is what gets from the representative TyVar
    -- back to the original user-specified Name
    swizzle_env :: VarEnv Name
swizzle_env = forall a. [(TyVar, a)] -> VarEnv a
mkVarEnv (forall a b. (a -> b) -> [a] -> [b]
map forall a b. (a, b) -> (b, a)
swap [(Name, TyVar)]
swizzle_prs)

    swizzleMapper :: TyCoMapper () Identity
    swizzleMapper :: TyCoMapper () Identity
swizzleMapper = TyCoMapper { tcm_tyvar :: () -> TyVar -> Identity Type
tcm_tyvar = forall {m :: * -> *} {p}. Monad m => p -> TyVar -> m Type
swizzle_tv
                               , tcm_covar :: () -> TyVar -> Identity Coercion
tcm_covar = forall {m :: * -> *} {p}. Monad m => p -> TyVar -> m Coercion
swizzle_cv
                               , tcm_hole :: () -> CoercionHole -> Identity Coercion
tcm_hole  = forall {a} {p} {a}. Outputable a => p -> a -> a
swizzle_hole
                               , tcm_tycobinder :: () -> TyVar -> ArgFlag -> Identity ((), TyVar)
tcm_tycobinder = forall {m :: * -> *} {p} {p}.
Monad m =>
p -> TyVar -> p -> m ((), TyVar)
swizzle_bndr
                               , tcm_tycon :: TyCon -> Identity TyCon
tcm_tycon      = forall {a} {a}. Outputable a => a -> a
swizzle_tycon }
    swizzle_hole :: p -> a -> a
swizzle_hole  p
_ a
hole = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"swizzle_hole" (forall a. Outputable a => a -> SDoc
ppr a
hole)
       -- These types are pre-zonked
    swizzle_tycon :: a -> a
swizzle_tycon a
tc = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"swizzle_tc" (forall a. Outputable a => a -> SDoc
ppr a
tc)
       -- TcTyCons can't appear in kinds (yet)
    swizzle_tv :: p -> TyVar -> m Type
swizzle_tv p
_ TyVar
tv = forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar -> Type
mkTyVarTy (TyVar -> TyVar
swizzle_var TyVar
tv))
    swizzle_cv :: p -> TyVar -> m Coercion
swizzle_cv p
_ TyVar
cv = forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar -> Coercion
mkCoVarCo (TyVar -> TyVar
swizzle_var TyVar
cv))

    swizzle_bndr :: p -> TyVar -> p -> m ((), TyVar)
swizzle_bndr p
_ TyVar
tcv p
_
      = forall (m :: * -> *) a. Monad m => a -> m a
return ((), TyVar -> TyVar
swizzle_var TyVar
tcv)

    swizzle_var :: Var -> Var
    swizzle_var :: TyVar -> TyVar
swizzle_var TyVar
v
      | Just Name
nm <- forall a. VarEnv a -> TyVar -> Maybe a
lookupVarEnv VarEnv Name
swizzle_env TyVar
v
      = (Type -> Type) -> TyVar -> TyVar
updateVarType Type -> Type
swizzle_ty (TyVar
v TyVar -> Name -> TyVar
`setVarName` Name
nm)
      | Bool
otherwise
      = (Type -> Type) -> TyVar -> TyVar
updateVarType Type -> Type
swizzle_ty TyVar
v

    (Type -> Identity Type
map_type, [Type] -> Identity [Type]
_, Coercion -> Identity Coercion
_, [Coercion] -> Identity [Coercion]
_) = forall (m :: * -> *).
Monad m =>
TyCoMapper () m
-> (Type -> m Type, [Type] -> m [Type], Coercion -> m Coercion,
    [Coercion] -> m [Coercion])
mapTyCo TyCoMapper () Identity
swizzleMapper
    swizzle_ty :: Type -> Type
swizzle_ty Type
ty = forall a. Identity a -> a
runIdentity (Type -> Identity Type
map_type Type
ty)


generaliseTcTyCon :: (TcTyCon, ScopedPairs, TcKind) -> TcM TcTyCon
generaliseTcTyCon :: (TyCon, [(Name, TyVar)], Type) -> TcM TyCon
generaliseTcTyCon (TyCon
tc, [(Name, TyVar)]
scoped_prs, Type
tc_res_kind)
  -- See Note [Required, Specified, and Inferred for types]
  = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (forall a. NamedThing a => a -> SrcSpan
getSrcSpan TyCon
tc) forall a b. (a -> b) -> a -> b
$
    forall a. TyCon -> TcM a -> TcM a
addTyConCtxt TyCon
tc forall a b. (a -> b) -> a -> b
$
    do { -- Step 1: Separate Specified from Required variables
         -- NB: spec_req_tvs = spec_tvs ++ req_tvs
         --     And req_tvs is 1-1 with tyConTyVars
         --     See Note [Scoped tyvars in a TcTyCon] in GHC.Core.TyCon
       ; let spec_req_tvs :: [TyVar]
spec_req_tvs        = forall a b. (a -> b) -> [a] -> [b]
map forall a b. (a, b) -> b
snd [(Name, TyVar)]
scoped_prs
             n_spec :: Arity
n_spec              = forall (t :: * -> *) a. Foldable t => t a -> Arity
length [TyVar]
spec_req_tvs forall a. Num a => a -> a -> a
- TyCon -> Arity
tyConArity TyCon
tc
             ([TyVar]
spec_tvs, [TyVar]
req_tvs) = forall a. Arity -> [a] -> ([a], [a])
splitAt Arity
n_spec [TyVar]
spec_req_tvs
             sorted_spec_tvs :: [TyVar]
sorted_spec_tvs     = [TyVar] -> [TyVar]
scopedSort [TyVar]
spec_tvs
                 -- NB: We can't do the sort until we've zonked
                 --     Maintain the L-R order of scoped_tvs

       -- Step 2a: find all the Inferred variables we want to quantify over
       ; CandidatesQTvs
dvs1 <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfKinds forall a b. (a -> b) -> a -> b
$
                 (Type
tc_res_kind forall a. a -> [a] -> [a]
: forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Type
tyVarKind [TyVar]
spec_req_tvs)
       ; let dvs2 :: CandidatesQTvs
dvs2 = CandidatesQTvs
dvs1 CandidatesQTvs -> [TyVar] -> CandidatesQTvs
`delCandidates` [TyVar]
spec_req_tvs

       -- Step 2b: quantify, mainly meaning skolemise the free variables
       -- Returned 'inferred' are scope-sorted and skolemised
       ; [TyVar]
inferred <- CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
dvs2

       ; String -> SDoc -> TcRn ()
traceTc String
"generaliseTcTyCon: pre zonk"
           ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"tycon =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr TyCon
tc
                 , String -> SDoc
text String
"spec_req_tvs =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
spec_req_tvs
                 , String -> SDoc
text String
"tc_res_kind =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Type
tc_res_kind
                 , String -> SDoc
text String
"dvs1 =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr CandidatesQTvs
dvs1
                 , String -> SDoc
text String
"inferred =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
inferred ])

       -- Step 3: Final zonk (following kind generalisation)
       -- See Note [Swizzling the tyvars before generaliseTcTyCon]
       ; ZonkEnv
ze <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; (ZonkEnv
ze, [TyVar]
inferred)        <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX      ZonkEnv
ze [TyVar]
inferred
       ; (ZonkEnv
ze, [TyVar]
sorted_spec_tvs) <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX      ZonkEnv
ze [TyVar]
sorted_spec_tvs
       ; (ZonkEnv
ze, [TyVar]
req_tvs)         <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX      ZonkEnv
ze [TyVar]
req_tvs
       ; Type
tc_res_kind           <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
tc_res_kind

       ; String -> SDoc -> TcRn ()
traceTc String
"generaliseTcTyCon: post zonk" forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"tycon =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr TyCon
tc
              , String -> SDoc
text String
"inferred =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
inferred
              , String -> SDoc
text String
"spec_req_tvs =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
spec_req_tvs
              , String -> SDoc
text String
"sorted_spec_tvs =" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
sorted_spec_tvs
              , String -> SDoc
text String
"req_tvs =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [TyVar]
req_tvs
              , String -> SDoc
text String
"zonk-env =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr ZonkEnv
ze ]

       -- Step 4: Make the TyConBinders.
       ; let dep_fv_set :: VarSet
dep_fv_set     = CandidatesQTvs -> VarSet
candidateKindVars CandidatesQTvs
dvs1
             inferred_tcbs :: [TyConBinder]
inferred_tcbs  = ArgFlag -> [TyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Inferred [TyVar]
inferred
             specified_tcbs :: [TyConBinder]
specified_tcbs = ArgFlag -> [TyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Specified [TyVar]
sorted_spec_tvs
             required_tcbs :: [TyConBinder]
required_tcbs  = forall a b. (a -> b) -> [a] -> [b]
map (VarSet -> TyVar -> TyConBinder
mkRequiredTyConBinder VarSet
dep_fv_set) [TyVar]
req_tvs

       -- Step 5: Assemble the final list.
             final_tcbs :: [TyConBinder]
final_tcbs = forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [ [TyConBinder]
inferred_tcbs
                                 , [TyConBinder]
specified_tcbs
                                 , [TyConBinder]
required_tcbs ]

       -- Step 6: Make the result TcTyCon
             tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon (TyCon -> Name
tyConName TyCon
tc) [TyConBinder]
final_tcbs Type
tc_res_kind
                            ([TyVar] -> [(Name, TyVar)]
mkTyVarNamePairs ([TyVar]
sorted_spec_tvs forall a. [a] -> [a] -> [a]
++ [TyVar]
req_tvs))
                            Bool
True {- it's generalised now -}
                            (TyCon -> TyConFlavour
tyConFlavour TyCon
tc)

       ; String -> SDoc -> TcRn ()
traceTc String
"generaliseTcTyCon done" forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"tycon =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr TyCon
tc
              , String -> SDoc
text String
"tc_res_kind =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Type
tc_res_kind
              , String -> SDoc
text String
"dep_fv_set =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr VarSet
dep_fv_set
              , String -> SDoc
text String
"inferred_tcbs =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
inferred_tcbs
              , String -> SDoc
text String
"specified_tcbs =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
specified_tcbs
              , String -> SDoc
text String
"required_tcbs =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
required_tcbs
              , String -> SDoc
text String
"final_tcbs =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
final_tcbs ]

       -- Step 7: Check for validity.
       -- We do this here because we're about to put the tycon into the
       -- the environment, and we don't want anything malformed there
       ; TyCon -> TcRn ()
checkTyConTelescope TyCon
tycon

       ; forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }

{- Note [Required, Specified, and Inferred for types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Each forall'd type variable in a type or kind is one of

  * Required: an argument must be provided at every call site

  * Specified: the argument can be inferred at call sites, but
    may be instantiated with visible type/kind application

  * Inferred: the argument must be inferred at call sites; it
    is unavailable for use with visible type/kind application.

Why have Inferred at all? Because we just can't make user-facing
promises about the ordering of some variables. These might swizzle
around even between minor released. By forbidding visible type
application, we ensure users aren't caught unawares.

Go read Note [VarBndrs, TyCoVarBinders, TyConBinders, and visibility] in GHC.Core.TyCo.Rep.

The question for this Note is this:
   given a TyClDecl, how are its quantified type variables classified?
Much of the debate is memorialized in #15743.

Here is our design choice. When inferring the ordering of variables
for a TyCl declaration (that is, for those variables that the user
has not specified the order with an explicit `forall`), we use the
following order:

 1. Inferred variables
 2. Specified variables; in the left-to-right order in which
    the user wrote them, modified by scopedSort (see below)
    to put them in depdendency order.
 3. Required variables before a top-level ::
 4. All variables after a top-level ::

If this ordering does not make a valid telescope, we reject the definition.

Example:
  data SameKind :: k -> k -> *
  data Bad a (c :: Proxy b) (d :: Proxy a) (x :: SameKind b d)

For Bad:
  - a, c, d, x are Required; they are explicitly listed by the user
    as the positional arguments of Bad
  - b is Specified; it appears explicitly in a kind signature
  - k, the kind of a, is Inferred; it is not mentioned explicitly at all

Putting variables in the order Inferred, Specified, Required
gives us this telescope:
  Inferred:  k
  Specified: b : Proxy a
  Required : (a : k) (c : Proxy b) (d : Proxy a) (x : SameKind b d)

But this order is ill-scoped, because b's kind mentions a, which occurs
after b in the telescope. So we reject Bad.

Associated types
~~~~~~~~~~~~~~~~
For associated types everything above is determined by the
associated-type declaration alone, ignoring the class header.
Here is an example (#15592)
  class C (a :: k) b where
    type F (x :: b a)

In the kind of C, 'k' is Specified.  But what about F?
In the kind of F,

 * Should k be Inferred or Specified?  It's Specified for C,
   but not mentioned in F's declaration.

 * In which order should the Specified variables a and b occur?
   It's clearly 'a' then 'b' in C's declaration, but the L-R ordering
   in F's declaration is 'b' then 'a'.

In both cases we make the choice by looking at F's declaration alone,
so it gets the kind
   F :: forall {k}. forall b a. b a -> Type

How it works
~~~~~~~~~~~~
These design choices are implemented by two completely different code
paths for

  * Declarations with a standalone kind signature or a complete user-specified
    kind signature (CUSK). Handled by the kcCheckDeclHeader.

  * Declarations without a kind signature (standalone or CUSK) are handled by
    kcInferDeclHeader; see Note [Inferring kinds for type declarations].

Note that neither code path worries about point (4) above, as this
is nicely handled by not mangling the res_kind. (Mangling res_kinds is done
*after* all this stuff, in tcDataDefn's call to etaExpandAlgTyCon.)

We can tell Inferred apart from Specified by looking at the scoped
tyvars; Specified are always included there.

Design alternatives
~~~~~~~~~~~~~~~~~~~
* For associated types we considered putting the class variables
  before the local variables, in a nod to the treatment for class
  methods. But it got too compilicated; see #15592, comment:21ff.

* We rigidly require the ordering above, even though we could be much more
  permissive. Relevant musings are at
  https://gitlab.haskell.org/ghc/ghc/issues/15743#note_161623
  The bottom line conclusion is that, if the user wants a different ordering,
  then can specify it themselves, and it is better to be predictable and dumb
  than clever and capricious.

  I (Richard) conjecture we could be fully permissive, allowing all classes
  of variables to intermix. We would have to augment ScopedSort to refuse to
  reorder Required variables (or check that it wouldn't have). But this would
  allow more programs. See #15743 for examples. Interestingly, Idris seems
  to allow this intermixing. The intermixing would be fully specified, in that
  we can be sure that inference wouldn't change between versions. However,
  would users be able to predict it? That I cannot answer.

Test cases (and tickets) relevant to these design decisions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  T15591*
  T15592*
  T15743*

Note [Inferring kinds for type declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This note deals with /inference/ for type declarations
that do not have a CUSK.  Consider
  data T (a :: k1) k2 (x :: k2) = MkT (S a k2 x)
  data S (b :: k3) k4 (y :: k4) = MkS (T b k4 y)

We do kind inference as follows:

* Step 1: inferInitialKinds, and in particular kcInferDeclHeader.
  Make a unification variable for each of the Required and Specified
  type variables in the header.

  Record the connection between the Names the user wrote and the
  fresh unification variables in the tcTyConScopedTyVars field
  of the TcTyCon we are making
      [ (a,  aa)
      , (k1, kk1)
      , (k2, kk2)
      , (x,  xx) ]
  (I'm using the convention that double letter like 'aa' or 'kk'
  mean a unification variable.)

  These unification variables
    - Are TyVarTvs: that is, unification variables that can
      unify only with other type variables.
      See Note [TyVarTv] in GHC.Tc.Utils.TcMType

    - Have complete fresh Names; see GHC.Tc.Utils.TcMType
      Note [Unification variables need fresh Names]

  Assign initial monomorphic kinds to S, T
          T :: kk1 -> * -> kk2 -> *
          S :: kk3 -> * -> kk4 -> *

* Step 2: kcTyClDecl. Extend the environment with a TcTyCon for S and
  T, with these monomorphic kinds.  Now kind-check the declarations,
  and solve the resulting equalities.  The goal here is to discover
  constraints on all these unification variables.

  Here we find that kk1 := kk3, and kk2 := kk4.

  This is why we can't use skolems for kk1 etc; they have to
  unify with each other.

* Step 3: generaliseTcTyCon. Generalise each TyCon in turn.
  We find the free variables of the kind, skolemise them,
  sort them out into Inferred/Required/Specified (see the above
  Note [Required, Specified, and Inferred for types]),
  and perform some validity checks.

  This makes the utterly-final TyConBinders for the TyCon.

  All this is very similar at the level of terms: see GHC.Tc.Gen.Bind
  Note [Quantified variables in partial type signatures]

  But there are some tricky corners: Note [Tricky scoping in generaliseTcTyCon]

* Step 4.  Extend the type environment with a TcTyCon for S and T, now
  with their utterly-final polymorphic kinds (needed for recursive
  occurrences of S, T).  Now typecheck the declarations, and build the
  final AlgTyCon for S and T resp.

The first three steps are in kcTyClGroup; the fourth is in
tcTyClDecls.

There are some wrinkles

* Do not default TyVarTvs.  We always want to kind-generalise over
  TyVarTvs, and /not/ default them to Type. By definition a TyVarTv is
  not allowed to unify with a type; it must stand for a type
  variable. Hence the check in GHC.Tc.Solver.defaultTyVarTcS, and
  GHC.Tc.Utils.TcMType.defaultTyVar.  Here's another example (#14555):
     data Exp :: [TYPE rep] -> TYPE rep -> Type where
        Lam :: Exp (a:xs) b -> Exp xs (a -> b)
  We want to kind-generalise over the 'rep' variable.
  #14563 is another example.

* Duplicate type variables. Consider #11203
    data SameKind :: k -> k -> *
    data Q (a :: k1) (b :: k2) c = MkQ (SameKind a b)
  Here we will unify k1 with k2, but this time doing so is an error,
  because k1 and k2 are bound in the same declaration.

  We spot this during validity checking (findDupTyVarTvs),
  in generaliseTcTyCon.

* Required arguments.  Even the Required arguments should be made
  into TyVarTvs, not skolems.  Consider
    data T k (a :: k)
  Here, k is a Required, dependent variable. For uniformity, it is helpful
  to have k be a TyVarTv, in parallel with other dependent variables.

* Duplicate skolemisation is expected.  When generalising in Step 3,
  we may find that one of the variables we want to quantify has
  already been skolemised.  For example, suppose we have already
  generalise S. When we come to T we'll find that kk1 (now the same as
  kk3) has already been skolemised.

  That's fine -- but it means that
    a) when collecting quantification candidates, in
       candidateQTyVarsOfKind, we must collect skolems
    b) quantifyTyVars should be a no-op on such a skolem

Note [Tricky scoping in generaliseTcTyCon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider #16342
  class C (a::ka) x where
    cop :: D a x => x -> Proxy a -> Proxy a
    cop _ x = x :: Proxy (a::ka)

  class D (b::kb) y where
    dop :: C b y => y -> Proxy b -> Proxy b
    dop _ x = x :: Proxy (b::kb)

C and D are mutually recursive, by the time we get to
generaliseTcTyCon we'll have unified kka := kkb.

But when typechecking the default declarations for 'cop' and 'dop' in
tcDlassDecl2 we need {a, ka} and {b, kb} respectively to be in scope.
But at that point all we have is the utterly-final Class itself.

Conclusion: the classTyVars of a class must have the same Name as
that originally assigned by the user.  In our example, C must have
classTyVars {a, ka, x} while D has classTyVars {a, kb, y}.  Despite
the fact that kka and kkb got unified!

We achieve this sleight of hand in generaliseTcTyCon, using
the specialised function zonkRecTyVarBndrs.  We make the call
   zonkRecTyVarBndrs [ka,a,x] [kkb,aa,xxx]
where the [ka,a,x] are the Names originally assigned by the user, and
[kkb,aa,xx] are the corresponding (post-zonking, skolemised) TcTyVars.
zonkRecTyVarBndrs builds a recursive ZonkEnv that binds
   kkb :-> (ka :: <zonked kind of kkb>)
   aa  :-> (a  :: <konked kind of aa>)
   etc
That is, it maps each skolemised TcTyVars to the utterly-final
TyVar to put in the class, with its correct user-specified name.
When generalising D we'll do the same thing, but the ZonkEnv will map
   kkb :-> (kb :: <zonked kind of kkb>)
   bb  :-> (b  :: <konked kind of bb>)
   etc
Note that 'kkb' again appears in the domain of the mapping, but this
time mapped to 'kb'.  That's how C and D end up with differently-named
final TyVars despite the fact that we unified kka:=kkb

zonkRecTyVarBndrs we need to do knot-tying because of the need to
apply this same substitution to the kind of each.

Note [Inferring visible dependent quantification]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

  data T k :: k -> Type where
    MkT1 :: T Type Int
    MkT2 :: T (Type -> Type) Maybe

This looks like it should work. However, it is polymorphically recursive,
as the uses of T in the constructor types specialize the k in the kind
of T. This trips up our dear users (#17131, #17541), and so we add
a "landmark" context (which cannot be suppressed) whenever we
spot inferred visible dependent quantification (VDQ).

It's hard to know when we've actually been tripped up by polymorphic recursion
specifically, so we just include a note to users whenever we infer VDQ. The
testsuite did not show up a single spurious inclusion of this message.

The context is added in addVDQNote, which looks for a visible TyConBinder
that also appears in the TyCon's kind. (I first looked at the kind for
a visible, dependent quantifier, but Note [No polymorphic recursion] in
GHC.Tc.Gen.HsType defeats that approach.) addVDQNote is used in kcTyClDecl,
which is used only when inferring the kind of a tycon (never with a CUSK or
SAK).

Once upon a time, I (Richard E) thought that the tycon-kind could
not be a forall-type. But this is wrong: data T :: forall k. k -> Type
(with -XNoCUSKs) could end up here. And this is all OK.


-}

--------------
tcExtendKindEnvWithTyCons :: [TcTyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons :: forall a. [TyCon] -> TcM a -> TcM a
tcExtendKindEnvWithTyCons [TyCon]
tcs
  = forall r. [(Name, TcTyThing)] -> TcM r -> TcM r
tcExtendKindEnvList [ (TyCon -> Name
tyConName TyCon
tc, TyCon -> TcTyThing
ATcTyCon TyCon
tc) | TyCon
tc <- [TyCon]
tcs ]

--------------
mkPromotionErrorEnv :: [LTyClDecl GhcRn] -> TcTypeEnv
-- Maps each tycon/datacon to a suitable promotion error
--    tc :-> APromotionErr TyConPE
--    dc :-> APromotionErr RecDataConPE
--    See Note [Recursion and promoting data constructors]

mkPromotionErrorEnv :: [LTyClDecl GhcRn] -> TcTypeEnv
mkPromotionErrorEnv [LTyClDecl GhcRn]
decls
  = forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (forall a. NameEnv a -> NameEnv a -> NameEnv a
plusNameEnv forall b c a. (b -> c) -> (a -> b) -> a -> c
. TyClDecl GhcRn -> TcTypeEnv
mk_prom_err_env forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc)
          forall a. NameEnv a
emptyNameEnv [LTyClDecl GhcRn]
decls

mk_prom_err_env :: TyClDecl GhcRn -> TcTypeEnv
mk_prom_err_env :: TyClDecl GhcRn -> TcTypeEnv
mk_prom_err_env (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
nm, tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats })
  = forall a. Name -> a -> NameEnv a
unitNameEnv Name
nm (PromotionErr -> TcTyThing
APromotionErr PromotionErr
ClassPE)
    forall a. NameEnv a -> NameEnv a -> NameEnv a
`plusNameEnv`
    forall a. [(Name, a)] -> NameEnv a
mkNameEnv [ (forall (p :: Pass). FamilyDecl (GhcPass p) -> IdP (GhcPass p)
familyDeclName FamilyDecl GhcRn
at, PromotionErr -> TcTyThing
APromotionErr PromotionErr
TyConPE)
              | L SrcSpanAnnA
_ FamilyDecl GhcRn
at <- [LFamilyDecl GhcRn]
ats ]

mk_prom_err_env (DataDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
name
                          , tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn { dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons = [LConDecl GhcRn]
cons } })
  = forall a. Name -> a -> NameEnv a
unitNameEnv Name
name (PromotionErr -> TcTyThing
APromotionErr PromotionErr
TyConPE)
    forall a. NameEnv a -> NameEnv a -> NameEnv a
`plusNameEnv`
    forall a. [(Name, a)] -> NameEnv a
mkNameEnv [ (Name
con, PromotionErr -> TcTyThing
APromotionErr PromotionErr
RecDataConPE)
              | L SrcSpanAnnA
_ ConDecl GhcRn
con' <- [LConDecl GhcRn]
cons
              , L SrcSpanAnnN
_ Name
con  <- ConDecl GhcRn -> [GenLocated SrcSpanAnnN Name]
getConNames ConDecl GhcRn
con' ]

mk_prom_err_env TyClDecl GhcRn
decl
  = forall a. Name -> a -> NameEnv a
unitNameEnv (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl) (PromotionErr -> TcTyThing
APromotionErr PromotionErr
TyConPE)
    -- Works for family declarations too

--------------
inferInitialKinds :: [LTyClDecl GhcRn] -> TcM [TcTyCon]
-- Returns a TcTyCon for each TyCon bound by the decls,
-- each with its initial kind

inferInitialKinds :: [LTyClDecl GhcRn] -> TcM [TyCon]
inferInitialKinds [LTyClDecl GhcRn]
decls
  = do { String -> SDoc -> TcRn ()
traceTc String
"inferInitialKinds {" forall a b. (a -> b) -> a -> b
$ forall a. Outputable a => a -> SDoc
ppr (forall a b. (a -> b) -> [a] -> [b]
map (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [LTyClDecl GhcRn]
decls)
       ; [TyCon]
tcs <- forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM forall {ann}.
GenLocated (SrcSpanAnn' ann) (TyClDecl GhcRn) -> TcM [TyCon]
infer_initial_kind [LTyClDecl GhcRn]
decls
       ; String -> SDoc -> TcRn ()
traceTc String
"inferInitialKinds done }" SDoc
empty
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon]
tcs }
  where
    infer_initial_kind :: GenLocated (SrcSpanAnn' ann) (TyClDecl GhcRn) -> TcM [TyCon]
infer_initial_kind = forall a b ann.
(a -> TcM b) -> GenLocated (SrcSpanAnn' ann) a -> TcM b
addLocMA (InitialKindStrategy -> TyClDecl GhcRn -> TcM [TyCon]
getInitialKind InitialKindStrategy
InitialKindInfer)

-- Check type/class declarations against their standalone kind signatures or
-- CUSKs, producing a generalized TcTyCon for each.
checkInitialKinds :: [(LTyClDecl GhcRn, SAKS_or_CUSK)] -> TcM [TcTyCon]
checkInitialKinds :: [(LTyClDecl GhcRn, SAKS_or_CUSK)] -> TcM [TyCon]
checkInitialKinds [(LTyClDecl GhcRn, SAKS_or_CUSK)]
decls
  = do { String -> SDoc -> TcRn ()
traceTc String
"checkInitialKinds {" forall a b. (a -> b) -> a -> b
$ forall a. Outputable a => a -> SDoc
ppr (forall a c b. (a -> c) -> [(a, b)] -> [(c, b)]
mapFst (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [(LTyClDecl GhcRn, SAKS_or_CUSK)]
decls)
       ; [TyCon]
tcs <- forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM forall {ann}.
(GenLocated (SrcSpanAnn' ann) (TyClDecl GhcRn), SAKS_or_CUSK)
-> TcM [TyCon]
check_initial_kind [(LTyClDecl GhcRn, SAKS_or_CUSK)]
decls
       ; String -> SDoc -> TcRn ()
traceTc String
"checkInitialKinds done }" SDoc
empty
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon]
tcs }
  where
    check_initial_kind :: (GenLocated (SrcSpanAnn' ann) (TyClDecl GhcRn), SAKS_or_CUSK)
-> TcM [TyCon]
check_initial_kind (GenLocated (SrcSpanAnn' ann) (TyClDecl GhcRn)
ldecl, SAKS_or_CUSK
msig) =
      forall a b ann.
(a -> TcM b) -> GenLocated (SrcSpanAnn' ann) a -> TcM b
addLocMA (InitialKindStrategy -> TyClDecl GhcRn -> TcM [TyCon]
getInitialKind (SAKS_or_CUSK -> InitialKindStrategy
InitialKindCheck SAKS_or_CUSK
msig)) GenLocated (SrcSpanAnn' ann) (TyClDecl GhcRn)
ldecl

-- | Get the initial kind of a TyClDecl, either generalized or non-generalized,
-- depending on the 'InitialKindStrategy'.
getInitialKind :: InitialKindStrategy -> TyClDecl GhcRn -> TcM [TcTyCon]

-- Allocate a fresh kind variable for each TyCon and Class
-- For each tycon, return a TcTyCon with kind k
-- where k is the kind of tc, derived from the LHS
--         of the definition (and probably including
--         kind unification variables)
--      Example: data T a b = ...
--      return (T, kv1 -> kv2 -> kv3)
--
-- This pass deals with (ie incorporates into the kind it produces)
--   * The kind signatures on type-variable binders
--   * The result kinds signature on a TyClDecl
--
-- No family instances are passed to checkInitialKinds/inferInitialKinds
getInitialKind :: InitialKindStrategy -> TyClDecl GhcRn -> TcM [TyCon]
getInitialKind InitialKindStrategy
strategy
    (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
name
               , tcdTyVars :: forall pass. TyClDecl pass -> LHsQTyVars pass
tcdTyVars = LHsQTyVars GhcRn
ktvs
               , tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats })
  = do { TyCon
cls <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader InitialKindStrategy
strategy Name
name TyConFlavour
ClassFlavour LHsQTyVars GhcRn
ktvs forall a b. (a -> b) -> a -> b
$
                forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
constraintKind)
       ; let parent_tv_prs :: [(Name, TyVar)]
parent_tv_prs = TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
cls
            -- See Note [Don't process associated types in getInitialKind]
       ; [TyCon]
inner_tcs <-
           forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
parent_tv_prs forall a b. (a -> b) -> a -> b
$
           forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (forall a b ann.
(a -> TcM b) -> GenLocated (SrcSpanAnn' ann) a -> TcM b
addLocMA (TyCon -> FamilyDecl GhcRn -> TcM TyCon
getAssocFamInitialKind TyCon
cls)) [LFamilyDecl GhcRn]
ats
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
cls forall a. a -> [a] -> [a]
: [TyCon]
inner_tcs) }
  where
    getAssocFamInitialKind :: TyCon -> FamilyDecl GhcRn -> TcM TyCon
getAssocFamInitialKind TyCon
cls =
      case InitialKindStrategy
strategy of
        InitialKindStrategy
InitialKindInfer -> Maybe TyCon -> FamilyDecl GhcRn -> TcM TyCon
get_fam_decl_initial_kind (forall a. a -> Maybe a
Just TyCon
cls)
        InitialKindCheck SAKS_or_CUSK
_ -> TyCon -> FamilyDecl GhcRn -> TcM TyCon
check_initial_kind_assoc_fam TyCon
cls

getInitialKind InitialKindStrategy
strategy
    (DataDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
name
              , tcdTyVars :: forall pass. TyClDecl pass -> LHsQTyVars pass
tcdTyVars = LHsQTyVars GhcRn
ktvs
              , tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn { dd_kindSig :: forall pass. HsDataDefn pass -> Maybe (LHsKind pass)
dd_kindSig = Maybe (LHsKind GhcRn)
m_sig
                                         , dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND = NewOrData
new_or_data } })
  = do  { let flav :: TyConFlavour
flav = NewOrData -> TyConFlavour
newOrDataToFlavour NewOrData
new_or_data
              ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
DataKindCtxt Name
name
        ; TyCon
tc <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader InitialKindStrategy
strategy Name
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs forall a b. (a -> b) -> a -> b
$
                case Maybe (LHsKind GhcRn)
m_sig of
                  Just LHsKind GhcRn
ksig -> Type -> ContextKind
TheKind forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsKind GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsKind GhcRn
ksig
                  Maybe (LHsKind GhcRn)
Nothing   -> forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ InitialKindStrategy -> NewOrData -> ContextKind
dataDeclDefaultResultKind InitialKindStrategy
strategy NewOrData
new_or_data
        ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

getInitialKind InitialKindStrategy
InitialKindInfer (FamDecl { tcdFam :: forall pass. TyClDecl pass -> FamilyDecl pass
tcdFam = FamilyDecl GhcRn
decl })
  = do { TyCon
tc <- Maybe TyCon -> FamilyDecl GhcRn -> TcM TyCon
get_fam_decl_initial_kind forall a. Maybe a
Nothing FamilyDecl GhcRn
decl
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

getInitialKind (InitialKindCheck SAKS_or_CUSK
msig) (FamDecl { tcdFam :: forall pass. TyClDecl pass -> FamilyDecl pass
tcdFam =
  FamilyDecl { fdLName :: forall pass. FamilyDecl pass -> LIdP pass
fdLName     = forall l e. GenLocated l e -> e
unLoc -> Name
name
             , fdTyVars :: forall pass. FamilyDecl pass -> LHsQTyVars pass
fdTyVars    = LHsQTyVars GhcRn
ktvs
             , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = forall l e. GenLocated l e -> e
unLoc -> FamilyResultSig GhcRn
resultSig
             , fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo      = FamilyInfo GhcRn
info } } )
  = do { let flav :: TyConFlavour
flav = forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav forall a. Maybe a
Nothing FamilyInfo GhcRn
info
             ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TyFamResKindCtxt Name
name
       ; TyCon
tc <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader (SAKS_or_CUSK -> InitialKindStrategy
InitialKindCheck SAKS_or_CUSK
msig) Name
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs forall a b. (a -> b) -> a -> b
$
               case forall (p :: Pass).
FamilyResultSig (GhcPass p) -> Maybe (LHsKind (GhcPass p))
famResultKindSignature FamilyResultSig GhcRn
resultSig of
                 Just LHsKind GhcRn
ksig -> Type -> ContextKind
TheKind forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsKind GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsKind GhcRn
ksig
                 Maybe (LHsKind GhcRn)
Nothing ->
                   case SAKS_or_CUSK
msig of
                     SAKS_or_CUSK
CUSK -> forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
liftedTypeKind)
                     SAKS Type
_ -> forall (m :: * -> *) a. Monad m => a -> m a
return ContextKind
AnyKind
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

getInitialKind InitialKindStrategy
strategy
    (SynDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
name
             , tcdTyVars :: forall pass. TyClDecl pass -> LHsQTyVars pass
tcdTyVars = LHsQTyVars GhcRn
ktvs
             , tcdRhs :: forall pass. TyClDecl pass -> LHsType pass
tcdRhs = LHsKind GhcRn
rhs })
  = do { let ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TySynKindCtxt Name
name
       ; TyCon
tc <- InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader InitialKindStrategy
strategy Name
name TyConFlavour
TypeSynonymFlavour LHsQTyVars GhcRn
ktvs forall a b. (a -> b) -> a -> b
$
               case forall (p :: Pass).
LHsType (GhcPass p) -> Maybe (LHsType (GhcPass p))
hsTyKindSig LHsKind GhcRn
rhs of
                 Just LHsKind GhcRn
rhs_sig -> Type -> ContextKind
TheKind forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsKind GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsKind GhcRn
rhs_sig
                 Maybe (LHsKind GhcRn)
Nothing -> forall (m :: * -> *) a. Monad m => a -> m a
return ContextKind
AnyKind
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }

get_fam_decl_initial_kind
  :: Maybe TcTyCon -- ^ Just cls <=> this is an associated family of class cls
  -> FamilyDecl GhcRn
  -> TcM TcTyCon
get_fam_decl_initial_kind :: Maybe TyCon -> FamilyDecl GhcRn -> TcM TyCon
get_fam_decl_initial_kind Maybe TyCon
mb_parent_tycon
    FamilyDecl { fdLName :: forall pass. FamilyDecl pass -> LIdP pass
fdLName     = L SrcSpanAnnN
_ Name
name
               , fdTyVars :: forall pass. FamilyDecl pass -> LHsQTyVars pass
fdTyVars    = LHsQTyVars GhcRn
ktvs
               , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = L SrcSpan
_ FamilyResultSig GhcRn
resultSig
               , fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo      = FamilyInfo GhcRn
info }
  = InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader InitialKindStrategy
InitialKindInfer Name
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs forall a b. (a -> b) -> a -> b
$
    case FamilyResultSig GhcRn
resultSig of
      KindSig XCKindSig GhcRn
_ LHsKind GhcRn
ki                            -> Type -> ContextKind
TheKind forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsKind GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsKind GhcRn
ki
      TyVarSig XTyVarSig GhcRn
_ (L SrcSpanAnnA
_ (KindedTyVar XKindedTyVar GhcRn
_ ()
_ LIdP GhcRn
_ LHsKind GhcRn
ki)) -> Type -> ContextKind
TheKind forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsKind GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsKind GhcRn
ki
      FamilyResultSig GhcRn
_ -- open type families have * return kind by default
        | TyConFlavour -> Bool
tcFlavourIsOpen TyConFlavour
flav              -> forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
liftedTypeKind)
               -- closed type families have their return kind inferred
               -- by default
        | Bool
otherwise                         -> forall (m :: * -> *) a. Monad m => a -> m a
return ContextKind
AnyKind
  where
    flav :: TyConFlavour
flav = forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav Maybe TyCon
mb_parent_tycon FamilyInfo GhcRn
info
    ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TyFamResKindCtxt Name
name

-- See Note [Standalone kind signatures for associated types]
check_initial_kind_assoc_fam
  :: TcTyCon -- parent class
  -> FamilyDecl GhcRn
  -> TcM TcTyCon
check_initial_kind_assoc_fam :: TyCon -> FamilyDecl GhcRn -> TcM TyCon
check_initial_kind_assoc_fam TyCon
cls
  FamilyDecl
    { fdLName :: forall pass. FamilyDecl pass -> LIdP pass
fdLName     = forall l e. GenLocated l e -> e
unLoc -> Name
name
    , fdTyVars :: forall pass. FamilyDecl pass -> LHsQTyVars pass
fdTyVars    = LHsQTyVars GhcRn
ktvs
    , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = forall l e. GenLocated l e -> e
unLoc -> FamilyResultSig GhcRn
resultSig
    , fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo      = FamilyInfo GhcRn
info }
  = InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader (SAKS_or_CUSK -> InitialKindStrategy
InitialKindCheck SAKS_or_CUSK
CUSK) Name
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs forall a b. (a -> b) -> a -> b
$
    case forall (p :: Pass).
FamilyResultSig (GhcPass p) -> Maybe (LHsKind (GhcPass p))
famResultKindSignature FamilyResultSig GhcRn
resultSig of
      Just LHsKind GhcRn
ksig -> Type -> ContextKind
TheKind forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UserTypeCtxt -> LHsKind GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsKind GhcRn
ksig
      Maybe (LHsKind GhcRn)
Nothing -> forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> ContextKind
TheKind Type
liftedTypeKind)
  where
    ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
TyFamResKindCtxt Name
name
    flav :: TyConFlavour
flav = forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav (forall a. a -> Maybe a
Just TyCon
cls) FamilyInfo GhcRn
info

{- Note [Standalone kind signatures for associated types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If associated types had standalone kind signatures, would they wear them

---------------------------+------------------------------
  like this? (OUT)         |   or like this? (IN)
---------------------------+------------------------------
  type T :: Type -> Type   |   class C a where
  class C a where          |     type T :: Type -> Type
    type T a               |     type T a

The (IN) variant is syntactically ambiguous:

  class C a where
    type T :: a   -- standalone kind signature?
    type T :: a   -- declaration header?

The (OUT) variant does not suffer from this issue, but it might not be the
direction in which we want to take Haskell: we seek to unify type families and
functions, and, by extension, associated types with class methods. And yet we
give class methods their signatures inside the class, not outside. Neither do
we have the counterpart of InstanceSigs for StandaloneKindSignatures.

For now, we dodge the question by using CUSKs for associated types instead of
standalone kind signatures. This is a simple addition to the rule we used to
have before standalone kind signatures:

  old rule:  associated type has a CUSK iff its parent class has a CUSK
  new rule:  associated type has a CUSK iff its parent class has a CUSK or a standalone kind signature

-}

-- See Note [Data declaration default result kind]
dataDeclDefaultResultKind :: InitialKindStrategy ->  NewOrData -> ContextKind
dataDeclDefaultResultKind :: InitialKindStrategy -> NewOrData -> ContextKind
dataDeclDefaultResultKind InitialKindStrategy
strategy NewOrData
new_or_data
  | NewOrData
NewType <- NewOrData
new_or_data
  = ContextKind
OpenKind -- See Note [Implementation of UnliftedNewtypes], point <Error Messages>.
  | NewOrData
DataType <- NewOrData
new_or_data
  , InitialKindCheck (SAKS Type
_) <- InitialKindStrategy
strategy
  = ContextKind
OpenKind -- See Note [Implementation of UnliftedDatatypes]
  | Bool
otherwise
  = Type -> ContextKind
TheKind Type
liftedTypeKind

{- Note [Data declaration default result kind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When the user has not written an inline result kind annotation on a data
declaration, we assume it to be 'Type'. That is, the following declarations
D1 and D2 are considered equivalent:

  data D1         where ...
  data D2 :: Type where ...

The consequence of this assumption is that we reject D3 even though we
accept D4:

  data D3 where
    MkD3 :: ... -> D3 param

  data D4 :: Type -> Type where
    MkD4 :: ... -> D4 param

However, there are two twists:

  * For unlifted newtypes, we must relax the assumed result kind to (TYPE r):

      newtype D5 where
        MkD5 :: Int# -> D5

    See Note [Implementation of UnliftedNewtypes], STEP 1 and it's sub-note
    <Error Messages>.

  * For unlifted datatypes, we must relax the assumed result kind to
    (TYPE (BoxedRep l)) in the presence of a SAKS:

      type D6 :: Type -> TYPE (BoxedRep Unlifted)
      data D6 a = MkD6 a

    Otherwise, it would be impossible to declare unlifted data types in H98
    syntax (which doesn't allow specification of a result kind).

-}

---------------------------------
getFamFlav
  :: Maybe TcTyCon    -- ^ Just cls <=> this is an associated family of class cls
  -> FamilyInfo pass
  -> TyConFlavour
getFamFlav :: forall pass. Maybe TyCon -> FamilyInfo pass -> TyConFlavour
getFamFlav Maybe TyCon
mb_parent_tycon FamilyInfo pass
info =
  case FamilyInfo pass
info of
    FamilyInfo pass
DataFamily         -> Maybe TyCon -> TyConFlavour
DataFamilyFlavour Maybe TyCon
mb_parent_tycon
    FamilyInfo pass
OpenTypeFamily     -> Maybe TyCon -> TyConFlavour
OpenTypeFamilyFlavour Maybe TyCon
mb_parent_tycon
    ClosedTypeFamily Maybe [LTyFamInstEqn pass]
_ -> ASSERT( isNothing mb_parent_tycon ) -- See Note [Closed type family mb_parent_tycon]
                          TyConFlavour
ClosedTypeFamilyFlavour

{- Note [Closed type family mb_parent_tycon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There's no way to write a closed type family inside a class declaration:

  class C a where
    type family F a where  -- error: parse error on input ‘where’

In fact, it is not clear what the meaning of such a declaration would be.
Therefore, 'mb_parent_tycon' of any closed type family has to be Nothing.
-}

------------------------------------------------------------------------
kcLTyClDecl :: LTyClDecl GhcRn -> TcM ()
  -- See Note [Kind checking for type and class decls]
  -- Called only for declarations without a signature (no CUSKs or SAKs here)
kcLTyClDecl :: LTyClDecl GhcRn -> TcRn ()
kcLTyClDecl (L SrcSpanAnnA
loc TyClDecl GhcRn
decl)
  = forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc forall a b. (a -> b) -> a -> b
$
    do { TyCon
tycon <- HasDebugCallStack => Name -> TcM TyCon
tcLookupTcTyCon IdP GhcRn
tc_name
       ; String -> SDoc -> TcRn ()
traceTc String
"kcTyClDecl {" (forall a. Outputable a => a -> SDoc
ppr IdP GhcRn
tc_name)
       ; forall a. TyCon -> TcM a -> TcM a
addVDQNote TyCon
tycon forall a b. (a -> b) -> a -> b
$   -- See Note [Inferring visible dependent quantification]
         forall a. SDoc -> TcM a -> TcM a
addErrCtxt (TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl) forall a b. (a -> b) -> a -> b
$
         TyClDecl GhcRn -> TyCon -> TcRn ()
kcTyClDecl TyClDecl GhcRn
decl TyCon
tycon
       ; String -> SDoc -> TcRn ()
traceTc String
"kcTyClDecl done }" (forall a. Outputable a => a -> SDoc
ppr IdP GhcRn
tc_name) }
  where
    tc_name :: IdP GhcRn
tc_name = forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl

kcTyClDecl :: TyClDecl GhcRn -> TcTyCon -> TcM ()
-- This function is used solely for its side effect on kind variables
-- NB kind signatures on the type variables and
--    result kind signature have already been dealt with
--    by inferInitialKind, so we can ignore them here.

kcTyClDecl :: TyClDecl GhcRn -> TyCon -> TcRn ()
kcTyClDecl (DataDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName    = (L SrcSpanAnnN
_ Name
name), tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn GhcRn
defn }) TyCon
tycon
  | HsDataDefn { dd_ctxt :: forall pass. HsDataDefn pass -> Maybe (LHsContext pass)
dd_ctxt = Maybe (LHsContext GhcRn)
ctxt, dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons = [LConDecl GhcRn]
cons, dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND = NewOrData
new_or_data } <- HsDataDefn GhcRn
defn
  = forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
_ Type
_ ->
       -- NB: binding these tyvars isn't necessary for GADTs, but it does no
       -- harm.  For GADTs, each data con brings its own tyvars into scope,
       -- and the ones from this bindTyClTyVars are either not mentioned or
       -- (conceivably) shadowed.
    do { String -> SDoc -> TcRn ()
traceTc String
"kcTyClDecl" (forall a. Outputable a => a -> SDoc
ppr TyCon
tycon SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyVar]
tyConTyVars TyCon
tycon) SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConResKind TyCon
tycon))
       ; [Type]
_ <- Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
ctxt
       ; NewOrData -> Type -> [LConDecl GhcRn] -> TcRn ()
kcConDecls NewOrData
new_or_data (TyCon -> Type
tyConResKind TyCon
tycon) [LConDecl GhcRn]
cons
       }

kcTyClDecl (SynDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
name, tcdRhs :: forall pass. TyClDecl pass -> LHsType pass
tcdRhs = LHsKind GhcRn
rhs }) TyCon
_tycon
  = forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
_ Type
res_kind ->
    forall a. TcM a -> TcRn ()
discardResult forall a b. (a -> b) -> a -> b
$ LHsKind GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsKind GhcRn
rhs (Type -> ContextKind
TheKind Type
res_kind)
        -- NB: check against the result kind that we allocated
        -- in inferInitialKinds.

kcTyClDecl (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
name
                      , tcdCtxt :: forall pass. TyClDecl pass -> Maybe (LHsContext pass)
tcdCtxt = Maybe (LHsContext GhcRn)
ctxt, tcdSigs :: forall pass. TyClDecl pass -> [LSig pass]
tcdSigs = [LSig GhcRn]
sigs }) TyCon
_tycon
  = forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
_ Type
_ ->
    do  { [Type]
_ <- Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
ctxt
        ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (forall a. (a -> TcRn ()) -> LocatedA a -> TcRn ()
wrapLocMA_ Sig GhcRn -> TcRn ()
kc_sig) [LSig GhcRn]
sigs }
  where
    kc_sig :: Sig GhcRn -> TcRn ()
kc_sig (ClassOpSig XClassOpSig GhcRn
_ Bool
_ [LIdP GhcRn]
nms LHsSigType GhcRn
op_ty) = [GenLocated SrcSpanAnnN Name] -> LHsSigType GhcRn -> TcRn ()
kcClassSigType [LIdP GhcRn]
nms LHsSigType GhcRn
op_ty
    kc_sig Sig GhcRn
_                          = forall (m :: * -> *) a. Monad m => a -> m a
return ()

kcTyClDecl (FamDecl XFamDecl GhcRn
_ (FamilyDecl { fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo   = FamilyInfo GhcRn
fd_info })) TyCon
fam_tc
-- closed type families look at their equations, but other families don't
-- do anything here
  = case FamilyInfo GhcRn
fd_info of
      ClosedTypeFamily (Just [LTyFamInstEqn GhcRn]
eqns) -> forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (TyCon -> LTyFamInstEqn GhcRn -> TcRn ()
kcTyFamInstEqn TyCon
fam_tc) [LTyFamInstEqn GhcRn]
eqns
      FamilyInfo GhcRn
_ -> forall (m :: * -> *) a. Monad m => a -> m a
return ()

-------------------

-- Kind-check the types of the arguments to a data constructor.
-- This includes doing kind unification if the type is a newtype.
-- See Note [Implementation of UnliftedNewtypes] for why we need
-- the first two arguments.
kcConArgTys :: NewOrData -> Kind -> [HsScaled GhcRn (LHsType GhcRn)] -> TcM ()
kcConArgTys :: NewOrData -> Type -> [HsScaled GhcRn (LHsKind GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind [HsScaled GhcRn (LHsKind GhcRn)]
arg_tys = do
  { let exp_kind :: ContextKind
exp_kind = NewOrData -> Type -> ContextKind
getArgExpKind NewOrData
new_or_data Type
res_kind
  ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
t a -> (a -> m b) -> m ()
forM_ [HsScaled GhcRn (LHsKind GhcRn)]
arg_tys (\(HsScaled HsArrow GhcRn
mult GenLocated SrcSpanAnnA (HsType GhcRn)
ty) -> do Type
_ <- LHsKind GhcRn -> ContextKind -> TcM Type
tcCheckLHsType (forall (p :: Pass). LHsType (GhcPass p) -> LHsType (GhcPass p)
getBangType GenLocated SrcSpanAnnA (HsType GhcRn)
ty) ContextKind
exp_kind
                                             HsArrow GhcRn -> TcM Type
tcMult HsArrow GhcRn
mult)
    -- See Note [Implementation of UnliftedNewtypes], STEP 2
  }

-- Kind-check the types of arguments to a Haskell98 data constructor.
kcConH98Args :: NewOrData -> Kind -> HsConDeclH98Details GhcRn -> TcM ()
kcConH98Args :: NewOrData -> Type -> HsConDeclH98Details GhcRn -> TcRn ()
kcConH98Args NewOrData
new_or_data Type
res_kind HsConDeclH98Details GhcRn
con_args = case HsConDeclH98Details GhcRn
con_args of
  PrefixCon [Void]
_ [HsScaled GhcRn (LHsKind GhcRn)]
tys   -> NewOrData -> Type -> [HsScaled GhcRn (LHsKind GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind [HsScaled GhcRn (LHsKind GhcRn)]
tys
  InfixCon HsScaled GhcRn (LHsKind GhcRn)
ty1 HsScaled GhcRn (LHsKind GhcRn)
ty2  -> NewOrData -> Type -> [HsScaled GhcRn (LHsKind GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind [HsScaled GhcRn (LHsKind GhcRn)
ty1, HsScaled GhcRn (LHsKind GhcRn)
ty2]
  RecCon (L SrcSpanAnnL
_ [GenLocated SrcSpanAnnA (ConDeclField GhcRn)]
flds) -> NewOrData -> Type -> [HsScaled GhcRn (LHsKind GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind forall a b. (a -> b) -> a -> b
$
                       forall a b. (a -> b) -> [a] -> [b]
map (forall a pass. a -> HsScaled pass a
hsLinear forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall pass. ConDeclField pass -> LBangType pass
cd_fld_type forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [GenLocated SrcSpanAnnA (ConDeclField GhcRn)]
flds

-- Kind-check the types of arguments to a GADT data constructor.
kcConGADTArgs :: NewOrData -> Kind -> HsConDeclGADTDetails GhcRn -> TcM ()
kcConGADTArgs :: NewOrData -> Type -> HsConDeclGADTDetails GhcRn -> TcRn ()
kcConGADTArgs NewOrData
new_or_data Type
res_kind HsConDeclGADTDetails GhcRn
con_args = case HsConDeclGADTDetails GhcRn
con_args of
  PrefixConGADT [HsScaled GhcRn (LHsKind GhcRn)]
tys     -> NewOrData -> Type -> [HsScaled GhcRn (LHsKind GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind [HsScaled GhcRn (LHsKind GhcRn)]
tys
  RecConGADT (L SrcSpanAnnL
_ [GenLocated SrcSpanAnnA (ConDeclField GhcRn)]
flds) -> NewOrData -> Type -> [HsScaled GhcRn (LHsKind GhcRn)] -> TcRn ()
kcConArgTys NewOrData
new_or_data Type
res_kind forall a b. (a -> b) -> a -> b
$
                           forall a b. (a -> b) -> [a] -> [b]
map (forall a pass. a -> HsScaled pass a
hsLinear forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall pass. ConDeclField pass -> LBangType pass
cd_fld_type forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [GenLocated SrcSpanAnnA (ConDeclField GhcRn)]
flds

kcConDecls :: NewOrData
           -> Kind             -- The result kind signature
                               --   Used only in H98 case
           -> [LConDecl GhcRn] -- The data constructors
           -> TcM ()
-- See Note [kcConDecls: kind-checking data type decls]
kcConDecls :: NewOrData -> Type -> [LConDecl GhcRn] -> TcRn ()
kcConDecls NewOrData
new_or_data Type
tc_res_kind [LConDecl GhcRn]
cons
  = forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (forall a. (a -> TcRn ()) -> LocatedA a -> TcRn ()
wrapLocMA_ (NewOrData -> Type -> ConDecl GhcRn -> TcRn ()
kcConDecl NewOrData
new_or_data Type
tc_res_kind)) [LConDecl GhcRn]
cons

-- Kind check a data constructor. In additional to the data constructor,
-- we also need to know about whether or not its corresponding type was
-- declared with data or newtype, and we need to know the result kind of
-- this type. See Note [Implementation of UnliftedNewtypes] for why
-- we need the first two arguments.
kcConDecl :: NewOrData
          -> Kind  -- Result kind of the type constructor
                   -- Usually Type but can be TYPE UnliftedRep
                   -- or even TYPE r, in the case of unlifted newtype
                   -- Used only in H98 case
          -> ConDecl GhcRn
          -> TcM ()
kcConDecl :: NewOrData -> Type -> ConDecl GhcRn -> TcRn ()
kcConDecl NewOrData
new_or_data Type
tc_res_kind (ConDeclH98
  { con_name :: forall pass. ConDecl pass -> LIdP pass
con_name = LIdP GhcRn
name, con_ex_tvs :: forall pass. ConDecl pass -> [LHsTyVarBndr Specificity pass]
con_ex_tvs = [LHsTyVarBndr Specificity GhcRn]
ex_tvs
  , con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (LHsContext GhcRn)
ex_ctxt, con_args :: forall pass. ConDecl pass -> HsConDeclH98Details pass
con_args = HsConDeclH98Details GhcRn
args })
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([GenLocated SrcSpanAnnN Name] -> SDoc
dataConCtxt [LIdP GhcRn
name]) forall a b. (a -> b) -> a -> b
$
    forall a. TcM a -> TcRn ()
discardResult                   forall a b. (a -> b) -> a -> b
$
    forall flag a.
OutputableBndrFlag flag 'Renamed =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
bindExplicitTKBndrs_Tv [LHsTyVarBndr Specificity GhcRn]
ex_tvs forall a b. (a -> b) -> a -> b
$
    do { [Type]
_ <- Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
ex_ctxt
       ; NewOrData -> Type -> HsConDeclH98Details GhcRn -> TcRn ()
kcConH98Args NewOrData
new_or_data Type
tc_res_kind HsConDeclH98Details GhcRn
args
         -- We don't need to check the telescope here,
         -- because that's done in tcConDecl
       }

kcConDecl NewOrData
new_or_data
          Type
_tc_res_kind   -- Not used in GADT case (and doesn't make sense)
          (ConDeclGADT
    { con_names :: forall pass. ConDecl pass -> [LIdP pass]
con_names = [LIdP GhcRn]
names, con_bndrs :: forall pass. ConDecl pass -> XRec pass (HsOuterSigTyVarBndrs pass)
con_bndrs = L SrcSpanAnnA
_ HsOuterSigTyVarBndrs GhcRn
outer_bndrs, con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (LHsContext GhcRn)
cxt
    , con_g_args :: forall pass. ConDecl pass -> HsConDeclGADTDetails pass
con_g_args = HsConDeclGADTDetails GhcRn
args, con_res_ty :: forall pass. ConDecl pass -> LHsType pass
con_res_ty = LHsKind GhcRn
res_ty })
  = -- See Note [kcConDecls: kind-checking data type decls]
    forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([GenLocated SrcSpanAnnN Name] -> SDoc
dataConCtxt [LIdP GhcRn]
names) forall a b. (a -> b) -> a -> b
$
    forall a. TcM a -> TcRn ()
discardResult                      forall a b. (a -> b) -> a -> b
$
    forall a.
HsOuterSigTyVarBndrs GhcRn
-> TcM a -> TcM (HsOuterSigTyVarBndrs GhcTc, a)
bindOuterSigTKBndrs_Tv HsOuterSigTyVarBndrs GhcRn
outer_bndrs forall a b. (a -> b) -> a -> b
$
        -- Why "_Tv"?  See Note [Using TyVarTvs for kind-checking GADTs]
    do { [Type]
_ <- Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
cxt
       ; String -> SDoc -> TcRn ()
traceTc String
"kcConDecl:GADT {" (forall a. Outputable a => a -> SDoc
ppr [LIdP GhcRn]
names SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr LHsKind GhcRn
res_ty)
       ; Type
con_res_kind <- TcM Type
newOpenTypeKind
       ; Type
_ <- LHsKind GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsKind GhcRn
res_ty (Type -> ContextKind
TheKind Type
con_res_kind)
       ; NewOrData -> Type -> HsConDeclGADTDetails GhcRn -> TcRn ()
kcConGADTArgs NewOrData
new_or_data Type
con_res_kind HsConDeclGADTDetails GhcRn
args
       ; String -> SDoc -> TcRn ()
traceTc String
"kcConDecl:GADT }" (forall a. Outputable a => a -> SDoc
ppr [LIdP GhcRn]
names SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr Type
con_res_kind)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return () }

{- Note [kcConDecls: kind-checking data type decls]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kcConDecls is used when we are inferring the kind of the type
constructor in a data type declaration.  E.g.
    data T f a = MkT (f a)
we want to infer the kind of 'f' and 'a'. The basic plan is described
in Note [Inferring kinds for type declarations]; here we are doing Step 2.

In the GADT case we may have this:
   data T f a where
      MkT :: forall g b. g b -> T g b

Notice that the variables f,a, and g,b are quite distinct.
Nevertheless, the type signature for MkT must still influence the kind
T which is (remember Step 1) something like
  T :: kappa1 -> kappa2 -> Type
Otherwise we'd infer the bogus kind
  T :: forall k1 k2. k1 -> k2 -> Type.

The type signature for MkT influences the kind of T simply by
kind-checking the result type (T g b), which will force 'f' and 'g' to
have the same kinds. This is the call to
    tcCheckLHsType res_ty (TheKind con_res_kind)
Because this is the result type of an arrow, we know the kind must be
of form (TYPE rr), and we get better error messages if we enforce that
here (e.g. test gadt10).

For unlifted newtypes only, we must ensure that the argument kind
and result kind are the same:
* In the H98 case, we need the result kind of the TyCon, to unify with
  the argument kind.

* In GADT syntax, this unification happens via the result kind passed
  to kcConGADTArgs. The tycon's result kind is not used at all in the
  GADT case.

Note [Using TyVarTvs for kind-checking GADTs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

  data Proxy a where
    MkProxy1 :: forall k (b :: k). Proxy b
    MkProxy2 :: forall j (c :: j). Proxy c

It seems reasonable that this should be accepted. But something very strange
is going on here: when we're kind-checking this declaration, we need to unify
the kind of `a` with k and j -- even though k and j's scopes are local to the type of
MkProxy{1,2}.

In effect, we are simply gathering constraints on the shape of Proxy's
kind, with no skolemisation or implication constraints involved at all.

The best approach we've come up with is to use TyVarTvs during the
kind-checking pass, rather than ordinary skolems. This is why we use
the "_Tv" variant, bindOuterSigTKBndrs_Tv.

Our only goal is to gather constraints on the kind of the type constructor;
we do not certify that the data declaration is well-kinded. For example:

  data SameKind :: k -> k -> Type
  data Bad a where
    MkBad :: forall k1 k2 (a :: k1) (b :: k2). Bad (SameKind a b)

which would be accepted by kcConDecl because k1 and k2 are
TyVarTvs. It is correctly rejected in the second pass, tcConDecl.
(Test case: polykinds/TyVarTvKinds3)

One drawback of this approach is sometimes it will accept a definition that
a (hypothetical) declarative specification would likely reject. As a general
rule, we don't want to allow polymorphic recursion without a CUSK. Indeed,
the whole point of CUSKs is to allow polymorphic recursion. Yet, the TyVarTvs
approach allows a limited form of polymorphic recursion *without* a CUSK.

To wit:
  data T a = forall k (b :: k). MkT (T b) Int
  (test case: dependent/should_compile/T14066a)

Note that this is polymorphically recursive, with the recursive occurrence
of T used at a kind other than a's kind. The approach outlined here accepts
this definition, because this kind is still a kind variable (and so the
TyVarTvs unify). Stepping back, I (Richard) have a hard time envisioning a
way to describe exactly what declarations will be accepted and which will
be rejected (without a CUSK). However, the accepted definitions are indeed
well-kinded and any rejected definitions would be accepted with a CUSK,
and so this wrinkle need not cause anyone to lose sleep.

Note [Recursion and promoting data constructors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We don't want to allow promotion in a strongly connected component
when kind checking.

Consider:
  data T f = K (f (K Any))

When kind checking the `data T' declaration the local env contains the
mappings:
  T -> ATcTyCon <some initial kind>
  K -> APromotionErr

APromotionErr is only used for DataCons, and only used during type checking
in tcTyClGroup.


************************************************************************
*                                                                      *
\subsection{Type checking}
*                                                                      *
************************************************************************

Note [Type checking recursive type and class declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At this point we have completed *kind-checking* of a mutually
recursive group of type/class decls (done in kcTyClGroup). However,
we discarded the kind-checked types (eg RHSs of data type decls);
note that kcTyClDecl returns ().  There are two reasons:

  * It's convenient, because we don't have to rebuild a
    kinded HsDecl (a fairly elaborate type)

  * It's necessary, because after kind-generalisation, the
    TyCons/Classes may now be kind-polymorphic, and hence need
    to be given kind arguments.

Example:
       data T f a = MkT (f a) (T f a)
During kind-checking, we give T the kind T :: k1 -> k2 -> *
and figure out constraints on k1, k2 etc. Then we generalise
to get   T :: forall k. (k->*) -> k -> *
So now the (T f a) in the RHS must be elaborated to (T k f a).

However, during tcTyClDecl of T (above) we will be in a recursive
"knot". So we aren't allowed to look at the TyCon T itself; we are only
allowed to put it (lazily) in the returned structures.  But when
kind-checking the RHS of T's decl, we *do* need to know T's kind (so
that we can correctly elaboarate (T k f a).  How can we get T's kind
without looking at T?  Delicate answer: during tcTyClDecl, we extend

  *Global* env with T -> ATyCon (the (not yet built) final TyCon for T)
  *Local*  env with T -> ATcTyCon (TcTyCon with the polymorphic kind of T)

Then:

  * During GHC.Tc.Gen.HsType.tcTyVar we look in the *local* env, to get the
    fully-known, not knot-tied TcTyCon for T.

  * Then, in GHC.Tc.Utils.Zonk.zonkTcTypeToType (and zonkTcTyCon in particular)
    we look in the *global* env to get the TyCon.

This fancy footwork (with two bindings for T) is only necessary for the
TyCons or Classes of this recursive group.  Earlier, finished groups,
live in the global env only.

See also Note [Kind checking recursive type and class declarations]

Note [Kind checking recursive type and class declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Before we can type-check the decls, we must kind check them. This
is done by establishing an "initial kind", which is a rather uninformed
guess at a tycon's kind (by counting arguments, mainly) and then
using this initial kind for recursive occurrences.

The initial kind is stored in exactly the same way during
kind-checking as it is during type-checking (Note [Type checking
recursive type and class declarations]): in the *local* environment,
with ATcTyCon. But we still must store *something* in the *global*
environment. Even though we discard the result of kind-checking, we
sometimes need to produce error messages. These error messages will
want to refer to the tycons being checked, except that they don't
exist yet, and it would be Terribly Annoying to get the error messages
to refer back to HsSyn. So we create a TcTyCon and put it in the
global env. This tycon can print out its name and knows its kind, but
any other action taken on it will panic. Note that TcTyCons are *not*
knot-tied, unlike the rather valid but knot-tied ones that occur
during type-checking.

Note [Declarations for wired-in things]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For wired-in things we simply ignore the declaration
and take the wired-in information.  That avoids complications.
e.g. the need to make the data constructor worker name for
     a constraint tuple match the wired-in one

Note [Datatype return kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are several poorly lit corners around datatype/newtype return kinds.
This Note explains these.  We cover data/newtype families and instances
in Note [Data family/instance return kinds].

data    T a :: <kind> where ...   -- See Point DT4
newtype T a :: <kind> where ...   -- See Point DT5

DT1 Where this applies: Only GADT syntax for data/newtype/instance declarations
    can have declared return kinds. This Note does not apply to Haskell98
    syntax.

DT2 Where these kinds come from: The return kind is part of the TyCon kind, gotten either
     by checkInitialKind (standalone kind signature / CUSK) or
     inferInitialKind. It is extracted by bindTyClTyVars in tcTyClDecl1. It is
     then passed to tcDataDefn.

DT3 Eta-expansion: Any forall-bound variables and function arguments in a result kind
    become parameters to the type. That is, when we say

     data T a :: Type -> Type where ...

    we really mean for T to have two parameters. The second parameter
    is produced by processing the return kind in etaExpandAlgTyCon,
    called in tcDataDefn.

    See also Note [TyConBinders for the result kind signatures of a data type]
    in GHC.Tc.Gen.HsType.

DT4 Datatype return kind restriction: A data type return kind must end
    in a type that, after type-synonym expansion, yields `TYPE LiftedRep`. By
    "end in", we mean we strip any foralls and function arguments off before
    checking.

    Examples:
      data T1 :: Type                          -- good
      data T2 :: Bool -> Type                  -- good
      data T3 :: Bool -> forall k. Type        -- strange, but still accepted
      data T4 :: forall k. k -> Type           -- good
      data T5 :: Bool                          -- bad
      data T6 :: Type -> Bool                  -- bad

    Exactly the same applies to data instance (but not data family)
    declarations.  Examples
      data instance D1 :: Type                 -- good
      data instance D2 :: Bool -> Type         -- good

    We can "look through" type synonyms
      type Star = Type
      data T7 :: Bool -> Star                  -- good (synonym expansion ok)
      type Arrow = (->)
      data T8 :: Arrow Bool Type               -- good (ditto)

    But we specifically do *not* do type family reduction here.
      type family ARROW where
        ARROW = (->)
      data T9 :: ARROW Bool Type               -- bad

      type family F a where
        F Int  = Bool
        F Bool = Type
      data T10 :: Bool -> F Bool               -- bad

    The /principle/ here is that in the TyCon for a data type or data instance,
    we must be able to lay out all the type-variable binders, one by one, until
    we reach (TYPE xx).  There is no place for a cast here.  We could add one,
    but let's not!

    This check is done in checkDataKindSig. For data declarations, this
    call is in tcDataDefn; for data instances, this call is in tcDataFamInstDecl.

DT5 Newtype return kind restriction.
    If -XUnliftedNewtypes is not on, then newtypes are treated just
    like datatypes --- see (4) above.

    If -XUnliftedNewtypes is on, then a newtype return kind must end in
    TYPE xyz, for some xyz (after type synonym expansion). The "xyz"
    may include type families, but the TYPE part must be visible
    /without/ expanding type families (only synonyms).

    This kind is unified with the kind of the representation type (the
    type of the one argument to the one constructor). See also steps
    (2) and (3) of Note [Implementation of UnliftedNewtypes].

    The checks are done in the same places as for datatypes.
    Examples (assume -XUnliftedNewtypes):

      newtype N1 :: Type                       -- good
      newtype N2 :: Bool -> Type               -- good
      newtype N3 :: forall r. Bool -> TYPE r   -- good

      type family F (t :: Type) :: RuntimeRep
      newtype N4 :: forall t -> TYPE (F t)     -- good

      type family STAR where
        STAR = Type
      newtype N5 :: Bool -> STAR               -- bad

Note [Data family/instance return kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Within this note, understand "instance" to mean data or newtype
instance, and understand "family" to mean data family. No type
families or classes here. Some examples:

data family T a :: <kind>          -- See Point DF56

data    instance T [a] :: <kind> where ...   -- See Point DF2
newtype instance T [a] :: <kind> where ...   -- See Point DF2

Here is the Plan for Data Families:

DF0 Where these kinds come from:

    Families: The return kind is either written in a standalone signature
     or extracted from a family declaration in getInitialKind.
     If a family declaration is missing a result kind, it is assumed to be
     Type. This assumption is in getInitialKind for CUSKs or
     get_fam_decl_initial_kind for non-signature & non-CUSK cases.

   Instances: The data family already has a known kind. The return kind
     of an instance is then calculated by applying the data family tycon
     to the patterns provided, as computed by the typeKind lhs_ty in the
     end of tcDataFamInstHeader. In the case of an instance written in GADT
     syntax, there are potentially *two* return kinds: the one computed from
     applying the data family tycon to the patterns, and the one given by
     the user. This second kind is checked by the tc_kind_sig function within
     tcDataFamInstHeader. See also DF3, below.

DF1 In a data/newtype instance, we treat the kind of the /data family/,
    once instantiated, as the "master kind" for the representation
    TyCon.  For example:
        data family T1 :: Type -> Type -> Type
        data instance T1 Int :: F Bool -> Type where ...
    The "master kind" for the representation TyCon R:T1Int comes
    from T1, not from the signature on the data instance.  It is as
    if we declared
        data R:T1Int :: Type -> Type where ...
     See Note [Liberalising data family return kinds] for an alternative
     plan.  But this current plan is simple, and ensures that all instances
     are simple instantiations of the master, without strange casts.

     An example with non-trivial instantiation:
        data family T2 :: forall k. Type -> k
        data instance T2 :: Type -> Type -> Type where ...
     Here 'k' gets instantiated with (Type -> Type), driven by
     the signature on the 'data instance'. (See also DT3 of
     Note [Datatype return kinds] about eta-expansion, which applies here,
     too; see tcDataFamInstDecl's call of etaExpandAlgTyCon.)

     A newtype example:

       data Color = Red | Blue
       type family Interpret (x :: Color) :: RuntimeRep where
         Interpret 'Red = 'IntRep
         Interpret 'Blue = 'WordRep
       data family Foo (x :: Color) :: TYPE (Interpret x)
       newtype instance Foo 'Red :: TYPE IntRep where
         FooRedC :: Int# -> Foo 'Red

    Here we get that Foo 'Red :: TYPE (Interpret Red), and our
    representation newtype looks like
         newtype R:FooRed :: TYPE (Interpret Red) where
            FooRedC :: Int# -> R:FooRed
    Remember: the master kind comes from the /family/ tycon.

DF2 /After/ this instantiation, the return kind of the master kind
    must obey the usual rules for data/newtype return kinds (DT4, DT5)
    of Note [Datatype return kinds].  Examples:
        data family T3 k :: k
        data instance T3 Type where ...          -- OK
        data instance T3 (Type->Type) where ...  -- OK
        data instance T3 (F Int) where ...       -- Not OK

DF3 Any kind signatures on the data/newtype instance are checked for
    equality with the master kind (and hence may guide instantiation)
    but are otherwise ignored. So in the T1 example above, we check
    that (F Int ~ Type) by unification; but otherwise ignore the
    user-supplied signature from the /family/ not the /instance/.

    We must be sure to instantiate any trailing invisible binders
    before doing this unification.  See the call to tcInstInvisibleBinders
    in tcDataFamInstHeader. For example:
       data family D :: forall k. k
       data instance D :: Type               -- forall k. k   <:  Type
       data instance D :: Type -> Type       -- forall k. k   <:  Type -> Type
         -- NB: these do not overlap
    we must instantiate D before unifying with the signature in the
    data instance declaration

DF4 We also (redundantly) check that any user-specified return kind
    signature in the data instance also obeys DT4/DT5.  For example we
    reject
        data family T1 :: Type -> Type -> Type
        data instance T1 Int :: Type -> F Int
    even if (F Int ~ Type).  We could omit this check, because we
    use the master kind; but it seems more uniform to check it, again
    with checkDataKindSig.

DF5 Data /family/ return kind restrictions. Consider
       data family D8 a :: F a
    where F is a type family.  No data/newtype instance can instantiate
    this so that it obeys the rules of DT4 or DT5.  So GHC proactively
    rejects the data /family/ declaration if it can never satisfy (DT4)/(DT5).
    Remember that a data family supports both data and newtype instances.

    More precisely, the return kind of a data family must be either
        * TYPE xyz (for some type xyz) or
        * a kind variable
    Only in these cases can a data/newtype instance possibly satisfy (DT4)/(DT5).
    This is checked by the call to checkDataKindSig in tcFamDecl1.  Examples:

      data family D1 :: Type              -- good
      data family D2 :: Bool -> Type      -- good
      data family D3 k :: k               -- good
      data family D4 :: forall k -> k     -- good
      data family D5 :: forall k. k -> k  -- good
      data family D6 :: forall r. TYPE r  -- good
      data family D7 :: Bool -> STAR      -- bad (see STAR from point 5)

DF6 Two return kinds for instances: If an instance has two return kinds,
    one from the family declaration and one from the instance declaration
    (see point DF3 above), they are unified. More accurately, we make sure
    that the kind of the applied data family is a subkind of the user-written
    kind. GHC.Tc.Gen.HsType.checkExpectedKind normally does this check for types, but
    that's overkill for our needs here. Instead, we just instantiate any
    invisible binders in the (instantiated) kind of the data family
    (called lhs_kind in tcDataFamInstHeader) with tcInstInvisibleTyBinders
    and then unify the resulting kind with the kind written by the user.
    This unification naturally produces a coercion, which we can drop, as
    the kind annotation on the instance is redundant (except perhaps for
    effects of unification).

    This all is Wrinkle (3) in Note [Implementation of UnliftedNewtypes].

Note [Liberalising data family return kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Could we allow this?
   type family F a where { F Int = Type }
   data family T a :: F a
   data instance T Int where
      MkT :: T Int

In the 'data instance', T Int :: F Int, and F Int = Type, so all seems
well.  But there are lots of complications:

* The representation constructor R:TInt presumably has kind Type.
  So the axiom connecting the two would have to look like
       axTInt :: T Int ~ R:TInt |> sym axFInt
  and that doesn't match expectation in DataFamInstTyCon
  in AlgTyConFlav

* The wrapper can't have type
     $WMkT :: Int -> T Int
  because T Int has the wrong kind.  It would have to be
     $WMkT :: Int -> (T Int) |> axFInt

* The code for $WMkT would also be more complicated, needing
  two coherence coercions. Try it!

* Code for pattern matching would be complicated in an
  exactly dual way.

So yes, we could allow this, but we currently do not. That's
why we have DF2 in Note [Data family/instance return kinds].

Note [Implementation of UnliftedNewtypes]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Expected behavior of UnliftedNewtypes:

* Proposal: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0013-unlifted-newtypes.rst
* Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/98

What follows is a high-level overview of the implementation of the
proposal.

STEP 1: Getting the initial kind, as done by inferInitialKind. We have
two sub-cases:

* With a SAK/CUSK: no change in kind-checking; the tycon is given the kind
  the user writes, whatever it may be.

* Without a SAK/CUSK: If there is no kind signature, the tycon is given
  a kind `TYPE r`, for a fresh unification variable `r`. We do this even
  when -XUnliftedNewtypes is not on; see <Error Messages>, below.

STEP 2: Kind-checking, as done by kcTyClDecl. This step is skipped for CUSKs.
The key function here is kcConDecl, which looks at an individual constructor
declaration. When we are processing a newtype (but whether or not -XUnliftedNewtypes
is enabled; see <Error Messages>, below), we generate a correct ContextKind
for the checking argument types: see getArgExpKind.

Examples of newtypes affected by STEP 2, assuming -XUnliftedNewtypes is
enabled (we use r0 to denote a unification variable):

newtype Foo rep = MkFoo (forall (a :: TYPE rep). a)
+ kcConDecl unifies (TYPE r0) with (TYPE rep), where (TYPE r0)
  is the kind that inferInitialKind invented for (Foo rep).

data Color = Red | Blue
type family Interpret (x :: Color) :: RuntimeRep where
  Interpret 'Red = 'IntRep
  Interpret 'Blue = 'WordRep
data family Foo (x :: Color) :: TYPE (Interpret x)
newtype instance Foo 'Red = FooRedC Int#
+ kcConDecl unifies TYPE (Interpret 'Red) with TYPE 'IntRep

Note that, in the GADT case, we might have a kind signature with arrows
(newtype XYZ a b :: Type -> Type where ...). We want only the final
component of the kind for checking in kcConDecl, so we call etaExpandAlgTyCon
in kcTyClDecl.

STEP 3: Type-checking (desugaring), as done by tcTyClDecl. The key function
here is tcConDecl. Once again, we must use getArgExpKind to ensure that the
representation type's kind matches that of the newtype, for two reasons:

  A. It is possible that a GADT has a CUSK. (Note that this is *not*
     possible for H98 types.) Recall that CUSK types don't go through
     kcTyClDecl, so we might not have done this kind check.
  B. We need to produce the coercion to put on the argument type
     if the kinds are different (for both H98 and GADT).

Example of (B):

type family F a where
  F Int = LiftedRep

newtype N :: TYPE (F Int) where
  MkN :: Int -> N

We really need to have the argument to MkN be (Int |> TYPE (sym axF)), where
axF :: F Int ~ LiftedRep. That way, the argument kind is the same as the
newtype kind, which is the principal correctness condition for newtypes.

Wrinkle: Consider (#17021, typecheck/should_fail/T17021)

    type family Id (x :: a) :: a where
      Id x = x

    newtype T :: TYPE (Id LiftedRep) where
      MkT :: Int -> T

  In the type of MkT, we must end with (Int |> TYPE (sym axId)) -> T,
  never Int -> (T |> TYPE axId); otherwise, the result type of the
  constructor wouldn't match the datatype. However, type-checking the
  HsType T might reasonably result in (T |> hole). We thus must ensure
  that this cast is dropped, forcing the type-checker to add one to
  the Int instead.

  Why is it always safe to drop the cast? This result type is type-checked by
  tcHsOpenType, so its kind definitely looks like TYPE r, for some r. It is
  important that even after dropping the cast, the type's kind has the form
  TYPE r. This is guaranteed by restrictions on the kinds of datatypes.
  For example, a declaration like `newtype T :: Id Type` is rejected: a
  newtype's final kind always has the form TYPE r, just as we want.

Note that this is possible in the H98 case only for a data family, because
the H98 syntax doesn't permit a kind signature on the newtype itself.

There are also some changes for dealing with families:

1. In tcFamDecl1, we suppress a tcIsLiftedTypeKind check if
   UnliftedNewtypes is on. This allows us to write things like:
     data family Foo :: TYPE 'IntRep

2. In a newtype instance (with -XUnliftedNewtypes), if the user does
   not write a kind signature, we want to allow the possibility that
   the kind is not Type, so we use newOpenTypeKind instead of liftedTypeKind.
   This is done in tcDataFamInstHeader in GHC.Tc.TyCl.Instance. Example:

       data family Bar (a :: RuntimeRep) :: TYPE a
       newtype instance Bar 'IntRep = BarIntC Int#
       newtype instance Bar 'WordRep :: TYPE 'WordRep where
         BarWordC :: Word# -> Bar 'WordRep

   The data instance corresponding to IntRep does not specify a kind signature,
   so tc_kind_sig just returns `TYPE r0` (where `r0` is a fresh metavariable).
   The data instance corresponding to WordRep does have a kind signature, so
   we use that kind signature.

3. A data family and its newtype instance may be declared with slightly
   different kinds. See point DF6 in Note [Data family/instance return kinds]

There's also a change in the renamer:

* In GHC.RenameSource.rnTyClDecl, enabling UnliftedNewtypes changes what is means
  for a newtype to have a CUSK. This is necessary since UnliftedNewtypes
  means that, for newtypes without kind signatures, we must use the field
  inside the data constructor to determine the result kind.
  See Note [Unlifted Newtypes and CUSKs] for more detail.

For completeness, it was also necessary to make coerce work on
unlifted types, resolving #13595.

<Error Messages>: It's tempting to think that the expected kind for a newtype
constructor argument when -XUnliftedNewtypes is *not* enabled should just be Type.
But this leads to difficulty in suggesting to enable UnliftedNewtypes. Here is
an example:

  newtype A = MkA Int#

If we expect the argument to MkA to have kind Type, then we get a kind-mismatch
error. The problem is that there is no way to connect this mismatch error to
-XUnliftedNewtypes, and suggest enabling the extension. So, instead, we allow
the A to type-check, but then find the problem when doing validity checking (and
where we get make a suitable error message). One potential worry is

  {-# LANGUAGE PolyKinds #-}
  newtype B a = MkB a

This turns out OK, because unconstrained RuntimeReps default to LiftedRep, just
as we would like. Another potential problem comes in a case like

  -- no UnliftedNewtypes

  data family D :: k
  newtype instance D = MkD Any

Here, we want inference to tell us that k should be instantiated to Type in
the instance. With the approach described here (checking for Type only in
the validity checker), that will not happen. But I cannot think of a non-contrived
example that will notice this lack of inference, so it seems better to improve
error messages than be able to infer this instantiation.

Note [Implementation of UnliftedDatatypes]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Expected behavior of UnliftedDatatypes:

* Proposal: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0265-unlifted-datatypes.rst
* Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/265

The implementation heavily leans on Note [Implementation of UnliftedNewtypes].

In the frontend, the following tweaks have been made in the typechecker:

* STEP 1: In the inferInitialKinds phase, newExpectedKind gives data type
  constructors a result kind of `TYPE r` with a fresh unification variable
  `r :: RuntimeRep` when there is a SAKS. (Same as for UnliftedNewtypes.)
  Not needed with a CUSK, because it can't specify result kinds.
  If there's a GADTSyntax result kind signature, we keep on using that kind.

  Similarly, for data instances without a kind signature, we use
  `TYPE r` as the result kind, to support the following code:

    data family F a :: UnliftedType
    data instance F Int = TInt

  The ommission of a kind signature for `F` should not mean a result kind
  of `Type` (and thus a kind error) here.

* STEP 2: No change to kcTyClDecl.

* STEP 3: In GHC.Tc.Gen.HsType.checkDataKindSig, we make sure that the result
  kind of the data declaration is actually `Type` or `TYPE (BoxedRep l)`,
  for some `l`. If UnliftedDatatypes is not activated, we emit an error with a
  suggestion in the latter case.

  Why not start out with `TYPE (BoxedRep l)` in the first place? Because then
  we get worse kind error messages in e.g. saks_fail010:

     -     Couldn't match expected kind: TYPE ('GHC.Types.BoxedRep t0)
     -                  with actual kind: * -> *
     +     Expected a type, but found something with kind ‘* -> *’
           In the data type declaration for ‘T’

  It seems `TYPE r` already has appropriate pretty-printing support.

The changes to Core, STG and Cmm are of rather cosmetic nature.
The IRs are already well-equipped to handle unlifted types, and unlifted
datatypes are just a new sub-class thereof.
-}

tcTyClDecl :: RolesInfo -> LTyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl :: (Name -> [Role]) -> LTyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl Name -> [Role]
roles_info (L SrcSpanAnnA
loc TyClDecl GhcRn
decl)
  | Just TyThing
thing <- Name -> Maybe TyThing
wiredInNameTyThing_maybe (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl)
  = case TyThing
thing of -- See Note [Declarations for wired-in things]
      ATyCon TyCon
tc -> forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, TyCon -> TyClDecl GhcRn -> [DerivInfo]
wiredInDerivInfo TyCon
tc TyClDecl GhcRn
decl)
      TyThing
_ -> forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcTyClDecl" (forall a. Outputable a => a -> SDoc
ppr TyThing
thing)

  | Bool
otherwise
  = forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc forall a b. (a -> b) -> a -> b
$ forall a. TyClDecl GhcRn -> TcM a -> TcM a
tcAddDeclCtxt TyClDecl GhcRn
decl forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"---- tcTyClDecl ---- {" (forall a. Outputable a => a -> SDoc
ppr TyClDecl GhcRn
decl)
       ; (TyCon
tc, [DerivInfo]
deriv_infos) <- Maybe Class
-> (Name -> [Role]) -> TyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl1 forall a. Maybe a
Nothing Name -> [Role]
roles_info TyClDecl GhcRn
decl
       ; String -> SDoc -> TcRn ()
traceTc String
"---- tcTyClDecl end ---- }" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tc, [DerivInfo]
deriv_infos) }

noDerivInfos :: a -> (a, [DerivInfo])
noDerivInfos :: forall a. a -> (a, [DerivInfo])
noDerivInfos a
a = (a
a, [])

wiredInDerivInfo :: TyCon -> TyClDecl GhcRn -> [DerivInfo]
wiredInDerivInfo :: TyCon -> TyClDecl GhcRn -> [DerivInfo]
wiredInDerivInfo TyCon
tycon TyClDecl GhcRn
decl
  | DataDecl { tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn GhcRn
dataDefn } <- TyClDecl GhcRn
decl
  , HsDataDefn { dd_derivs :: forall pass. HsDataDefn pass -> HsDeriving pass
dd_derivs = HsDeriving GhcRn
derivs } <- HsDataDefn GhcRn
dataDefn
  = [ DerivInfo { di_rep_tc :: TyCon
di_rep_tc = TyCon
tycon
                , di_scoped_tvs :: [(Name, TyVar)]
di_scoped_tvs =
                    if TyCon -> Bool
isFunTyCon TyCon
tycon Bool -> Bool -> Bool
|| TyCon -> Bool
isPrimTyCon TyCon
tycon
                       then []  -- no tyConTyVars
                       else [TyVar] -> [(Name, TyVar)]
mkTyVarNamePairs (TyCon -> [TyVar]
tyConTyVars TyCon
tycon)
                , di_clauses :: HsDeriving GhcRn
di_clauses = HsDeriving GhcRn
derivs
                , di_ctxt :: SDoc
di_ctxt = TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl } ]
wiredInDerivInfo TyCon
_ TyClDecl GhcRn
_ = []

  -- "type family" declarations
tcTyClDecl1 :: Maybe Class -> RolesInfo -> TyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl1 :: Maybe Class
-> (Name -> [Role]) -> TyClDecl GhcRn -> TcM (TyCon, [DerivInfo])
tcTyClDecl1 Maybe Class
parent Name -> [Role]
_roles_info (FamDecl { tcdFam :: forall pass. TyClDecl pass -> FamilyDecl pass
tcdFam = FamilyDecl GhcRn
fd })
  = forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap forall a. a -> (a, [DerivInfo])
noDerivInfos forall a b. (a -> b) -> a -> b
$
    Maybe Class -> FamilyDecl GhcRn -> TcM TyCon
tcFamDecl1 Maybe Class
parent FamilyDecl GhcRn
fd

  -- "type" synonym declaration
tcTyClDecl1 Maybe Class
_parent Name -> [Role]
roles_info
            (SynDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
tc_name
                     , tcdRhs :: forall pass. TyClDecl pass -> LHsType pass
tcdRhs   = LHsKind GhcRn
rhs })
  = ASSERT( isNothing _parent )
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap forall a. a -> (a, [DerivInfo])
noDerivInfos forall a b. (a -> b) -> a -> b
$
    (Name -> [Role]) -> Name -> LHsKind GhcRn -> TcM TyCon
tcTySynRhs Name -> [Role]
roles_info Name
tc_name LHsKind GhcRn
rhs

  -- "data/newtype" declaration
tcTyClDecl1 Maybe Class
_parent Name -> [Role]
roles_info
            decl :: TyClDecl GhcRn
decl@(DataDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
tc_name
                           , tcdDataDefn :: forall pass. TyClDecl pass -> HsDataDefn pass
tcdDataDefn = HsDataDefn GhcRn
defn })
  = ASSERT( isNothing _parent )
    SDoc
-> (Name -> [Role])
-> Name
-> HsDataDefn GhcRn
-> TcM (TyCon, [DerivInfo])
tcDataDefn (TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl) Name -> [Role]
roles_info Name
tc_name HsDataDefn GhcRn
defn

tcTyClDecl1 Maybe Class
_parent Name -> [Role]
roles_info
            (ClassDecl { tcdLName :: forall pass. TyClDecl pass -> LIdP pass
tcdLName = L SrcSpanAnnN
_ Name
class_name
                       , tcdCtxt :: forall pass. TyClDecl pass -> Maybe (LHsContext pass)
tcdCtxt = Maybe (LHsContext GhcRn)
hs_ctxt
                       , tcdMeths :: forall pass. TyClDecl pass -> LHsBinds pass
tcdMeths = LHsBinds GhcRn
meths
                       , tcdFDs :: forall pass. TyClDecl pass -> [LHsFunDep pass]
tcdFDs = [LHsFunDep GhcRn]
fundeps
                       , tcdSigs :: forall pass. TyClDecl pass -> [LSig pass]
tcdSigs = [LSig GhcRn]
sigs
                       , tcdATs :: forall pass. TyClDecl pass -> [LFamilyDecl pass]
tcdATs = [LFamilyDecl GhcRn]
ats
                       , tcdATDefs :: forall pass. TyClDecl pass -> [LTyFamDefltDecl pass]
tcdATDefs = [LTyFamDefltDecl GhcRn]
at_defs })
  = ASSERT( isNothing _parent )
    do { Class
clas <- (Name -> [Role])
-> Name
-> Maybe (LHsContext GhcRn)
-> LHsBinds GhcRn
-> [LHsFunDep GhcRn]
-> [LSig GhcRn]
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM Class
tcClassDecl1 Name -> [Role]
roles_info Name
class_name Maybe (LHsContext GhcRn)
hs_ctxt
                              LHsBinds GhcRn
meths [LHsFunDep GhcRn]
fundeps [LSig GhcRn]
sigs [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall a. a -> (a, [DerivInfo])
noDerivInfos (Class -> TyCon
classTyCon Class
clas)) }


{- *********************************************************************
*                                                                      *
          Class declarations
*                                                                      *
********************************************************************* -}

tcClassDecl1 :: RolesInfo -> Name -> Maybe (LHsContext GhcRn)
             -> LHsBinds GhcRn -> [LHsFunDep GhcRn] -> [LSig GhcRn]
             -> [LFamilyDecl GhcRn] -> [LTyFamDefltDecl GhcRn]
             -> TcM Class
tcClassDecl1 :: (Name -> [Role])
-> Name
-> Maybe (LHsContext GhcRn)
-> LHsBinds GhcRn
-> [LHsFunDep GhcRn]
-> [LSig GhcRn]
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM Class
tcClassDecl1 Name -> [Role]
roles_info Name
class_name Maybe (LHsContext GhcRn)
hs_ctxt LHsBinds GhcRn
meths [LHsFunDep GhcRn]
fundeps [LSig GhcRn]
sigs [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
  = forall a env. (a -> IOEnv env a) -> IOEnv env a
fixM forall a b. (a -> b) -> a -> b
$ \ Class
clas ->
    -- We need the knot because 'clas' is passed into tcClassATs
    forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
class_name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind ->
    do { Type -> TcRn ()
checkClassKindSig Type
res_kind
       ; String -> SDoc -> TcRn ()
traceTc String
"tcClassDecl 1" (forall a. Outputable a => a -> SDoc
ppr Name
class_name SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
binders)
       ; let tycon_name :: Name
tycon_name = Name
class_name        -- We use the same name
             roles :: [Role]
roles = Name -> [Role]
roles_info Name
tycon_name  -- for TyCon and Class

       ; ([Type]
ctxt, [([TyVar], [TyVar])]
fds, [TcMethInfo]
sig_stuff, [ClassATItem]
at_stuff)
            <- forall a. SkolemInfo -> [TyVar] -> TcM a -> TcM a
pushLevelAndSolveEqualities SkolemInfo
skol_info (forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
binders) forall a b. (a -> b) -> a -> b
$
               -- The (binderVars binders) is needed bring into scope the
               -- skolems bound by the class decl header (#17841)
               do { [Type]
ctxt <- Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
hs_ctxt
                  ; [([TyVar], [TyVar])]
fds  <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (forall a b ann.
(a -> TcM b) -> GenLocated (SrcSpanAnn' ann) a -> TcM b
addLocMA FunDep GhcRn -> TcM ([TyVar], [TyVar])
tc_fundep) [LHsFunDep GhcRn]
fundeps
                  ; [TcMethInfo]
sig_stuff <- Name -> [LSig GhcRn] -> LHsBinds GhcRn -> TcM [TcMethInfo]
tcClassSigs Name
class_name [LSig GhcRn]
sigs LHsBinds GhcRn
meths
                  ; [ClassATItem]
at_stuff  <- Name
-> Class
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM [ClassATItem]
tcClassATs Name
class_name Class
clas [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
                  ; forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
ctxt, [([TyVar], [TyVar])]
fds, [TcMethInfo]
sig_stuff, [ClassATItem]
at_stuff) }

       -- See Note [Error on unconstrained meta-variables] in GHC.Tc.Utils.TcMType
       -- Example: (typecheck/should_fail/T17562)
       --   type C :: Type -> Type -> Constraint
       --   class (forall a. a b ~ a c) => C b c
       -- The kind of `a` is unconstrained.
       ; CandidatesQTvs
dvs <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfTypes [Type]
ctxt
       ; let mk_doc :: TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc TidyEnv
tidy_env = do { (TidyEnv
tidy_env2, [Type]
ctxt) <- TidyEnv -> [Type] -> TcM (TidyEnv, [Type])
zonkTidyTcTypes TidyEnv
tidy_env [Type]
ctxt
                                  ; forall (m :: * -> *) a. Monad m => a -> m a
return ( TidyEnv
tidy_env2
                                           , [SDoc] -> SDoc
sep [ String -> SDoc
text String
"the class context:"
                                                 , [Type] -> SDoc
pprTheta [Type]
ctxt ] ) }
       ; CandidatesQTvs
-> (TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc))
-> TcRn ()
doNotQuantifyTyVars CandidatesQTvs
dvs TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc

       -- The pushLevelAndSolveEqualities will report errors for any
       -- unsolved equalities, so these zonks should not encounter
       -- any unfilled coercion variables unless there is such an error
       -- The zonk also squeeze out the TcTyCons, and converts
       -- Skolems to tyvars.
       ; ZonkEnv
ze        <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; [Type]
ctxt      <- ZonkEnv -> [Type] -> TcM [Type]
zonkTcTypesToTypesX ZonkEnv
ze [Type]
ctxt
       ; [TcMethInfo]
sig_stuff <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (ZonkEnv -> TcMethInfo -> TcM TcMethInfo
zonkTcMethInfoToMethInfoX ZonkEnv
ze) [TcMethInfo]
sig_stuff
         -- ToDo: do we need to zonk at_stuff?

       -- TODO: Allow us to distinguish between abstract class,
       -- and concrete class with no methods (maybe by
       -- specifying a trailing where or not

       ; ClassMinimalDef
mindef <- Name -> [LSig GhcRn] -> [TcMethInfo] -> TcM ClassMinimalDef
tcClassMinimalDef Name
class_name [LSig GhcRn]
sigs [TcMethInfo]
sig_stuff
       ; Bool
is_boot <- IOEnv (Env TcGblEnv TcLclEnv) Bool
tcIsHsBootOrSig
       ; let body :: Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
body | Bool
is_boot, forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Type]
ctxt, forall (t :: * -> *) a. Foldable t => t a -> Bool
null [ClassATItem]
at_stuff, forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TcMethInfo]
sig_stuff
                  = forall a. Maybe a
Nothing
                  | Bool
otherwise
                  = forall a. a -> Maybe a
Just ([Type]
ctxt, [ClassATItem]
at_stuff, [TcMethInfo]
sig_stuff, ClassMinimalDef
mindef)

       ; Class
clas <- forall m n.
Name
-> [TyConBinder]
-> [Role]
-> [([TyVar], [TyVar])]
-> Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
-> TcRnIf m n Class
buildClass Name
class_name [TyConBinder]
binders [Role]
roles [([TyVar], [TyVar])]
fds Maybe ([Type], [ClassATItem], [TcMethInfo], ClassMinimalDef)
body
       ; String -> SDoc -> TcRn ()
traceTc String
"tcClassDecl" (forall a. Outputable a => a -> SDoc
ppr [LHsFunDep GhcRn]
fundeps SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
binders SDoc -> SDoc -> SDoc
$$
                                forall a. Outputable a => a -> SDoc
ppr [([TyVar], [TyVar])]
fds)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return Class
clas }
  where
    skol_info :: SkolemInfo
skol_info = TyConFlavour -> Name -> SkolemInfo
TyConSkol TyConFlavour
ClassFlavour Name
class_name
    tc_fundep :: GHC.Hs.FunDep GhcRn -> TcM ([Var],[Var])
    tc_fundep :: FunDep GhcRn -> TcM ([TyVar], [TyVar])
tc_fundep (FunDep XCFunDep GhcRn
_ [LIdP GhcRn]
tvs1 [LIdP GhcRn]
tvs2)
                           = do { [TyVar]
tvs1' <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name -> TcM TyVar
tcLookupTyVar forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [LIdP GhcRn]
tvs1 ;
                                ; [TyVar]
tvs2' <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name -> TcM TyVar
tcLookupTyVar forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [LIdP GhcRn]
tvs2 ;
                                ; forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
tvs1',[TyVar]
tvs2') }


{- Note [Associated type defaults]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The following is an example of associated type defaults:
             class C a where
               data D a

               type F a b :: *
               type F a b = [a]        -- Default

Note that we can get default definitions only for type families, not data
families.
-}

tcClassATs :: Name                    -- The class name (not knot-tied)
           -> Class                   -- The class parent of this associated type
           -> [LFamilyDecl GhcRn]     -- Associated types.
           -> [LTyFamDefltDecl GhcRn] -- Associated type defaults.
           -> TcM [ClassATItem]
tcClassATs :: Name
-> Class
-> [LFamilyDecl GhcRn]
-> [LTyFamDefltDecl GhcRn]
-> TcM [ClassATItem]
tcClassATs Name
class_name Class
cls [LFamilyDecl GhcRn]
ats [LTyFamDefltDecl GhcRn]
at_defs
  = do {  -- Complain about associated type defaults for non associated-types
         forall (t :: * -> *) (m :: * -> *) a.
(Foldable t, Monad m) =>
t (m a) -> m ()
sequence_ [ forall a. SDoc -> TcM a
failWithTc (Name -> Name -> SDoc
badATErr Name
class_name Name
n)
                   | Name
n <- forall a b. (a -> b) -> [a] -> [b]
map LTyFamDefltDecl GhcRn -> Name
at_def_tycon [LTyFamDefltDecl GhcRn]
at_defs
                   , Bool -> Bool
not (Name
n Name -> NameSet -> Bool
`elemNameSet` NameSet
at_names) ]
       ; forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM GenLocated SrcSpanAnnA (FamilyDecl GhcRn)
-> IOEnv (Env TcGblEnv TcLclEnv) ClassATItem
tc_at [LFamilyDecl GhcRn]
ats }
  where
    at_def_tycon :: LTyFamDefltDecl GhcRn -> Name
    at_def_tycon :: LTyFamDefltDecl GhcRn -> Name
at_def_tycon = forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyFamInstDecl (GhcPass p) -> IdP (GhcPass p)
tyFamInstDeclName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc

    at_fam_name :: LFamilyDecl GhcRn -> Name
    at_fam_name :: LFamilyDecl GhcRn -> Name
at_fam_name = forall (p :: Pass). FamilyDecl (GhcPass p) -> IdP (GhcPass p)
familyDeclName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc

    at_names :: NameSet
at_names = [Name] -> NameSet
mkNameSet (forall a b. (a -> b) -> [a] -> [b]
map LFamilyDecl GhcRn -> Name
at_fam_name [LFamilyDecl GhcRn]
ats)

    at_defs_map :: NameEnv [LTyFamDefltDecl GhcRn]
    -- Maps an AT in 'ats' to a list of all its default defs in 'at_defs'
    at_defs_map :: NameEnv [LTyFamDefltDecl GhcRn]
at_defs_map = forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (\GenLocated SrcSpanAnnA (TyFamInstDecl GhcRn)
at_def NameEnv [GenLocated SrcSpanAnnA (TyFamInstDecl GhcRn)]
nenv -> forall a. (a -> a -> a) -> NameEnv a -> Name -> a -> NameEnv a
extendNameEnv_C forall a. [a] -> [a] -> [a]
(++) NameEnv [GenLocated SrcSpanAnnA (TyFamInstDecl GhcRn)]
nenv
                                          (LTyFamDefltDecl GhcRn -> Name
at_def_tycon GenLocated SrcSpanAnnA (TyFamInstDecl GhcRn)
at_def) [GenLocated SrcSpanAnnA (TyFamInstDecl GhcRn)
at_def])
                        forall a. NameEnv a
emptyNameEnv [LTyFamDefltDecl GhcRn]
at_defs

    tc_at :: GenLocated SrcSpanAnnA (FamilyDecl GhcRn)
-> IOEnv (Env TcGblEnv TcLclEnv) ClassATItem
tc_at GenLocated SrcSpanAnnA (FamilyDecl GhcRn)
at = do { TyCon
fam_tc <- forall a b ann.
(a -> TcM b) -> GenLocated (SrcSpanAnn' ann) a -> TcM b
addLocMA (Maybe Class -> FamilyDecl GhcRn -> TcM TyCon
tcFamDecl1 (forall a. a -> Maybe a
Just Class
cls)) GenLocated SrcSpanAnnA (FamilyDecl GhcRn)
at
                  ; let at_defs :: [GenLocated SrcSpanAnnA (TyFamInstDecl GhcRn)]
at_defs = forall a. NameEnv a -> Name -> Maybe a
lookupNameEnv NameEnv [LTyFamDefltDecl GhcRn]
at_defs_map (LFamilyDecl GhcRn -> Name
at_fam_name GenLocated SrcSpanAnnA (FamilyDecl GhcRn)
at)
                                  forall a. Maybe a -> a -> a
`orElse` []
                  ; Maybe (Type, ATValidityInfo)
atd <- TyCon
-> [LTyFamDefltDecl GhcRn] -> TcM (Maybe (Type, ATValidityInfo))
tcDefaultAssocDecl TyCon
fam_tc [GenLocated SrcSpanAnnA (TyFamInstDecl GhcRn)]
at_defs
                  ; forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Maybe (Type, ATValidityInfo) -> ClassATItem
ATI TyCon
fam_tc Maybe (Type, ATValidityInfo)
atd) }

-------------------------
tcDefaultAssocDecl ::
     TyCon                                       -- ^ Family TyCon (not knot-tied)
  -> [LTyFamDefltDecl GhcRn]                     -- ^ Defaults
  -> TcM (Maybe (KnotTied Type, ATValidityInfo)) -- ^ Type checked RHS
tcDefaultAssocDecl :: TyCon
-> [LTyFamDefltDecl GhcRn] -> TcM (Maybe (Type, ATValidityInfo))
tcDefaultAssocDecl TyCon
_ []
  = forall (m :: * -> *) a. Monad m => a -> m a
return forall a. Maybe a
Nothing  -- No default declaration

tcDefaultAssocDecl TyCon
_ (LTyFamDefltDecl GhcRn
d1:LTyFamDefltDecl GhcRn
_:[LTyFamDefltDecl GhcRn]
_)
  = forall a. SDoc -> TcM a
failWithTc (String -> SDoc
text String
"More than one default declaration for"
                SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyFamInstDecl (GhcPass p) -> IdP (GhcPass p)
tyFamInstDeclName (forall l e. GenLocated l e -> e
unLoc LTyFamDefltDecl GhcRn
d1)))

tcDefaultAssocDecl TyCon
fam_tc
  [L SrcSpanAnnA
loc (TyFamInstDecl { tfid_eqn :: forall pass. TyFamInstDecl pass -> TyFamInstEqn pass
tfid_eqn =
                            FamEqn { feqn_tycon :: forall pass rhs. FamEqn pass rhs -> LIdP pass
feqn_tycon = L SrcSpanAnnN
_ Name
tc_name
                                   , feqn_bndrs :: forall pass rhs. FamEqn pass rhs -> HsOuterFamEqnTyVarBndrs pass
feqn_bndrs = HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs
                                   , feqn_pats :: forall pass rhs. FamEqn pass rhs -> HsTyPats pass
feqn_pats  = HsTyPats GhcRn
hs_pats
                                   , feqn_rhs :: forall pass rhs. FamEqn pass rhs -> rhs
feqn_rhs   = LHsKind GhcRn
hs_rhs_ty }})]
  = -- See Note [Type-checking default assoc decls]
    forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc forall a b. (a -> b) -> a -> b
$
    forall a. SDoc -> Name -> TcM a -> TcM a
tcAddFamInstCtxt (String -> SDoc
text String
"default type instance") Name
tc_name forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcDefaultAssocDecl 1" (forall a. Outputable a => a -> SDoc
ppr Name
tc_name)
       ; let fam_tc_name :: Name
fam_tc_name = TyCon -> Name
tyConName TyCon
fam_tc
             vis_arity :: Arity
vis_arity = forall (t :: * -> *) a. Foldable t => t a -> Arity
length (TyCon -> [TyVar]
tyConVisibleTyVars TyCon
fam_tc)
             vis_pats :: Arity
vis_pats  = forall tm ty. [HsArg tm ty] -> Arity
numVisibleArgs HsTyPats GhcRn
hs_pats

       -- Kind of family check
       ; ASSERT( fam_tc_name == tc_name )
         Bool -> SDoc -> TcRn ()
checkTc (TyCon -> Bool
isTypeFamilyTyCon TyCon
fam_tc) (TyCon -> SDoc
wrongKindOfFamily TyCon
fam_tc)

       -- Arity check
       ; Bool -> SDoc -> TcRn ()
checkTc (Arity
vis_pats forall a. Eq a => a -> a -> Bool
== Arity
vis_arity)
                 (Arity -> SDoc
wrongNumberOfParmsErr Arity
vis_arity)

       -- Typecheck RHS
       --
       -- You might think we should pass in some AssocInstInfo, as we're looking
       -- at an associated type. But this would be wrong, because an associated
       -- type default LHS can mention *different* type variables than the
       -- enclosing class. So it's treated more as a freestanding beast.
       ; ([TyVar]
qtvs, [Type]
pats, Type
rhs_ty) <- TyCon
-> AssocInstInfo
-> HsOuterFamEqnTyVarBndrs GhcRn
-> HsTyPats GhcRn
-> LHsKind GhcRn
-> TcM ([TyVar], [Type], Type)
tcTyFamInstEqnGuts TyCon
fam_tc AssocInstInfo
NotAssociated
                                      HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs HsTyPats GhcRn
hs_pats LHsKind GhcRn
hs_rhs_ty

       ; let fam_tvs :: [TyVar]
fam_tvs = TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc
       ; String -> SDoc -> TcRn ()
traceTc String
"tcDefaultAssocDecl 2" ([SDoc] -> SDoc
vcat
           [ String -> SDoc
text String
"hs_pats"   SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr HsTyPats GhcRn
hs_pats
           , String -> SDoc
text String
"hs_rhs_ty" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr LHsKind GhcRn
hs_rhs_ty
           , String -> SDoc
text String
"fam_tvs" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [TyVar]
fam_tvs
           , String -> SDoc
text String
"qtvs"    SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [TyVar]
qtvs
             -- NB: Do *not* print `pats` or rhs_ty here, as they can mention
             -- knot-tied TyCons. See #18648.
           ])
       ; let subst :: TCvSubst
subst = case forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
traverse Type -> Maybe TyVar
getTyVar_maybe [Type]
pats of
                       Just [TyVar]
cpt_tvs -> HasDebugCallStack => [TyVar] -> [Type] -> TCvSubst
zipTvSubst [TyVar]
cpt_tvs ([TyVar] -> [Type]
mkTyVarTys [TyVar]
fam_tvs)
                       Maybe [TyVar]
Nothing      -> TCvSubst
emptyTCvSubst
                       -- The Nothing case can only be reached in invalid
                       -- associated type family defaults. In such cases, we
                       -- simply create an empty substitution and let GHC fall
                       -- over later, in GHC.Tc.Validity.checkValidAssocTyFamDeflt.
                       -- See Note [Type-checking default assoc decls].
       ; forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a b. (a -> b) -> a -> b
$ forall a. a -> Maybe a
Just (TCvSubst -> Type -> Type
substTyUnchecked TCvSubst
subst Type
rhs_ty, SrcSpan -> [Type] -> ATValidityInfo
ATVI (forall a. SrcSpanAnn' a -> SrcSpan
locA SrcSpanAnnA
loc) [Type]
pats)
           -- We perform checks for well-formedness and validity later, in
           -- GHC.Tc.Validity.checkValidAssocTyFamDeflt.
     }

{- Note [Type-checking default assoc decls]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this default declaration for an associated type

   class C a where
      type F (a :: k) b :: Type
      type F (x :: j) y = Proxy x -> y

Note that the class variable 'a' doesn't scope over the default assoc
decl, nor do the type variables `k` and `b`. Instead, the default decl is
treated more like a top-level type instance. However, we store the default rhs
(Proxy x -> y) in F's TyCon, using F's own type variables, so we need to
convert it to (Proxy a -> b). We do this in the tcDefaultAssocDecl function by
creating a substitution [j |-> k, x |-> a, b |-> y] and applying this
substitution to the RHS.

In order to create this substitution, we must first ensure that all of
the arguments in the default instance consist of distinct type variables.
Checking for this property proves surprisingly tricky. Three potential places
where GHC could check for this property include:

1. Before typechecking (in the parser or renamer)
2. During typechecking (in tcDefaultAssocDecl)
3. After typechecking (using GHC.Tc.Validity)

Currently, GHC picks option (3) and implements this check using
GHC.Tc.Validity.checkValidAssocTyFamDeflt. GHC previously used options (1) and
(2), but neither option quite worked out for reasons that we will explain
shortly.

The first thing that checkValidAssocTyFamDeflt does is check that all arguments
in an associated type family default are type variables. As a motivating
example, consider this erroneous program (inspired by #11361):

   class C a where
      type F (a :: k) b :: Type
      type F x        b = x

If you squint, you'll notice that the kind of `x` is actually Type. However,
we cannot substitute from [Type |-> k], so we reject this default. This also
explains why GHC no longer implements option (1) above, since figuring out that
`x`'s kind is Type would be much more difficult without the knowledge that the
typechecker provides.

Next, checkValidAssocTyFamDeflt checks that all arguments are distinct. Here is
another offending example, this time taken from #13971:

   class C2 (a :: j) where
      type F2 (a :: j) (b :: k)
      type F2 (x :: z) y = SameKind x y
   data SameKind :: k -> k -> Type

All of the arguments in the default equation for `F2` are type variables, so
that passes the first check. However, if we were to build this substitution,
then both `j` and `k` map to `z`! In terms of visible kind application, it's as
if we had written `type F2 @z @z x y = SameKind @z x y`, which makes it clear
that we have duplicated a use of `z` on the LHS. Therefore, `F2`'s default is
also rejected.

There is one more design consideration in play here: what error message should
checkValidAssocTyFamDeflt produce if one of its checks fails? Ideally, it would
be something like this:

  Illegal duplicate variable ‘z’ in:
    ‘type F2 @z @z x y = ...’
    The arguments to ‘F2’ must all be distinct type variables

This requires printing out the arguments to the associated type family. This
can be dangerous, however. Consider this example, adapted from #18648:

  class C3 a where
     type F3 a
     type F3 (F3 a) = a

F3's default is illegal, since its argument is not a bare type variable. But
note that when we typecheck F3's default, the F3 type constructor is knot-tied.
Therefore, if we print the type `F3 a` in an error message, GHC will diverge!
This is the reason why GHC no longer implements option (2) above and instead
waits until /after/ typechecking has finished, at which point the typechecker
knot has been worked out.

As one final point, one might worry that the typechecker knot could cause the
substitution that tcDefaultAssocDecl creates to diverge, but this is not the
case. Since the LHS of a valid associated type family default is always just
variables, it won't contain any tycons. Accordingly, the patterns used in the
substitution won't actually be knot-tied, even though we're in the knot. (This
is too delicate for my taste, but it works.) If we're dealing with /invalid/
default, such as F3's above, then we simply create an empty substitution and
rely on checkValidAssocTyFamDeflt throwing an error message afterwards before
any damage is done.
-}

{- *********************************************************************
*                                                                      *
          Type family declarations
*                                                                      *
********************************************************************* -}

tcFamDecl1 :: Maybe Class -> FamilyDecl GhcRn -> TcM TyCon
tcFamDecl1 :: Maybe Class -> FamilyDecl GhcRn -> TcM TyCon
tcFamDecl1 Maybe Class
parent (FamilyDecl { fdInfo :: forall pass. FamilyDecl pass -> FamilyInfo pass
fdInfo = FamilyInfo GhcRn
fam_info
                              , fdLName :: forall pass. FamilyDecl pass -> LIdP pass
fdLName = tc_lname :: LIdP GhcRn
tc_lname@(L SrcSpanAnnN
_ Name
tc_name)
                              , fdResultSig :: forall pass. FamilyDecl pass -> LFamilyResultSig pass
fdResultSig = L SrcSpan
_ FamilyResultSig GhcRn
sig
                              , fdInjectivityAnn :: forall pass. FamilyDecl pass -> Maybe (LInjectivityAnn pass)
fdInjectivityAnn = Maybe (LInjectivityAnn GhcRn)
inj })
  | FamilyInfo GhcRn
DataFamily <- FamilyInfo GhcRn
fam_info
  = forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tc_name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind -> do
  { String -> SDoc -> TcRn ()
traceTc String
"data family:" (forall a. Outputable a => a -> SDoc
ppr Name
tc_name)
  ; Name -> TcRn ()
checkFamFlag Name
tc_name

  -- Check that the result kind is OK
  -- We allow things like
  --   data family T (a :: Type) :: forall k. k -> Type
  -- We treat T as having arity 1, but result kind forall k. k -> Type
  -- But we want to check that the result kind finishes in
  --   Type or a kind-variable
  -- For the latter, consider
  --   data family D a :: forall k. Type -> k
  -- When UnliftedNewtypes is enabled, we loosen this restriction
  -- on the return kind. See Note [Implementation of UnliftedNewtypes], wrinkle (1).
  -- See also Note [Datatype return kinds]
  ; DataSort -> Type -> TcRn ()
checkDataKindSig DataSort
DataFamilySort Type
res_kind
  ; Name
tc_rep_name <- forall gbl lcl. Name -> TcRnIf gbl lcl Name
newTyConRepName Name
tc_name
  ; let inj :: Injectivity
inj   = [Bool] -> Injectivity
Injective forall a b. (a -> b) -> a -> b
$ forall a. Arity -> a -> [a]
replicate (forall (t :: * -> *) a. Foldable t => t a -> Arity
length [TyConBinder]
binders) Bool
True
        tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
tc_name [TyConBinder]
binders
                              Type
res_kind
                              (forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig)
                              (Name -> FamTyConFlav
DataFamilyTyCon Name
tc_rep_name)
                              Maybe Class
parent Injectivity
inj
  ; forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }

  | FamilyInfo GhcRn
OpenTypeFamily <- FamilyInfo GhcRn
fam_info
  = forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tc_name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind -> do
  { String -> SDoc -> TcRn ()
traceTc String
"open type family:" (forall a. Outputable a => a -> SDoc
ppr Name
tc_name)
  ; Name -> TcRn ()
checkFamFlag Name
tc_name
  ; Injectivity
inj' <- [TyConBinder] -> Maybe (LInjectivityAnn GhcRn) -> TcM Injectivity
tcInjectivity [TyConBinder]
binders Maybe (LInjectivityAnn GhcRn)
inj
  ; Name -> FamilyResultSig GhcRn -> TcRn ()
checkResultSigFlag Name
tc_name FamilyResultSig GhcRn
sig  -- check after injectivity for better errors
  ; let tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
tc_name [TyConBinder]
binders Type
res_kind
                               (forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig) FamTyConFlav
OpenSynFamilyTyCon
                               Maybe Class
parent Injectivity
inj'
  ; forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }

  | ClosedTypeFamily Maybe [LTyFamInstEqn GhcRn]
mb_eqns <- FamilyInfo GhcRn
fam_info
  = -- Closed type families are a little tricky, because they contain the definition
    -- of both the type family and the equations for a CoAxiom.
    do { String -> SDoc -> TcRn ()
traceTc String
"Closed type family:" (forall a. Outputable a => a -> SDoc
ppr Name
tc_name)
         -- the variables in the header scope only over the injectivity
         -- declaration but this is not involved here
       ; (Injectivity
inj', [TyConBinder]
binders, Type
res_kind)
            <- forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tc_name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind ->
               do { Injectivity
inj' <- [TyConBinder] -> Maybe (LInjectivityAnn GhcRn) -> TcM Injectivity
tcInjectivity [TyConBinder]
binders Maybe (LInjectivityAnn GhcRn)
inj
                  ; forall (m :: * -> *) a. Monad m => a -> m a
return (Injectivity
inj', [TyConBinder]
binders, Type
res_kind) }

       ; Name -> TcRn ()
checkFamFlag Name
tc_name -- make sure we have -XTypeFamilies
       ; Name -> FamilyResultSig GhcRn -> TcRn ()
checkResultSigFlag Name
tc_name FamilyResultSig GhcRn
sig

         -- If Nothing, this is an abstract family in a hs-boot file;
         -- but eqns might be empty in the Just case as well
       ; case Maybe [LTyFamInstEqn GhcRn]
mb_eqns of
           Maybe [LTyFamInstEqn GhcRn]
Nothing   ->
               forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
tc_name [TyConBinder]
binders Type
res_kind
                                      (forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig)
                                      FamTyConFlav
AbstractClosedSynFamilyTyCon Maybe Class
parent
                                      Injectivity
inj'
           Just [LTyFamInstEqn GhcRn]
eqns -> do {

         -- Process the equations, creating CoAxBranches
       ; let tc_fam_tc :: TyCon
tc_fam_tc = Name
-> [TyConBinder]
-> Type
-> [(Name, TyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
tc_name [TyConBinder]
binders Type
res_kind
                                   [(Name, TyVar)]
noTcTyConScopedTyVars
                                   Bool
False {- this doesn't matter here -}
                                   TyConFlavour
ClosedTypeFamilyFlavour

       ; [KnotTied CoAxBranch]
branches <- forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndReportM (TyCon
-> AssocInstInfo
-> LTyFamInstEqn GhcRn
-> TcM (KnotTied CoAxBranch)
tcTyFamInstEqn TyCon
tc_fam_tc AssocInstInfo
NotAssociated) [LTyFamInstEqn GhcRn]
eqns
         -- Do not attempt to drop equations dominated by earlier
         -- ones here; in the case of mutual recursion with a data
         -- type, we get a knot-tying failure.  Instead we check
         -- for this afterwards, in GHC.Tc.Validity.checkValidCoAxiom
         -- Example: tc265

         -- Create a CoAxiom, with the correct src location.
       ; Name
co_ax_name <- GenLocated SrcSpanAnnN Name -> [[Type]] -> TcM Name
newFamInstAxiomName LIdP GhcRn
tc_lname []

       ; let mb_co_ax :: Maybe (CoAxiom Branched)
mb_co_ax
              | forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LTyFamInstEqn GhcRn]
eqns = forall a. Maybe a
Nothing   -- mkBranchedCoAxiom fails on empty list
              | Bool
otherwise = forall a. a -> Maybe a
Just (Name -> TyCon -> [KnotTied CoAxBranch] -> CoAxiom Branched
mkBranchedCoAxiom Name
co_ax_name TyCon
fam_tc [KnotTied CoAxBranch]
branches)

             fam_tc :: TyCon
fam_tc = Name
-> [TyConBinder]
-> Type
-> Maybe Name
-> FamTyConFlav
-> Maybe Class
-> Injectivity
-> TyCon
mkFamilyTyCon Name
tc_name [TyConBinder]
binders Type
res_kind (forall (a :: Pass).
FamilyResultSig (GhcPass a) -> Maybe (IdP (GhcPass a))
resultVariableName FamilyResultSig GhcRn
sig)
                      (Maybe (CoAxiom Branched) -> FamTyConFlav
ClosedSynFamilyTyCon Maybe (CoAxiom Branched)
mb_co_ax) Maybe Class
parent Injectivity
inj'

         -- We check for instance validity later, when doing validity
         -- checking for the tycon. Exception: checking equations
         -- overlap done by dropDominatedAxioms
       ; forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
fam_tc } }

#if __GLASGOW_HASKELL__ <= 810
  | otherwise = panic "tcFamInst1"  -- Silence pattern-exhaustiveness checker
#endif

-- | Maybe return a list of Bools that say whether a type family was declared
-- injective in the corresponding type arguments. Length of the list is equal to
-- the number of arguments (including implicit kind/coercion arguments).
-- True on position
-- N means that a function is injective in its Nth argument. False means it is
-- not.
tcInjectivity :: [TyConBinder] -> Maybe (LInjectivityAnn GhcRn)
              -> TcM Injectivity
tcInjectivity :: [TyConBinder] -> Maybe (LInjectivityAnn GhcRn) -> TcM Injectivity
tcInjectivity [TyConBinder]
_ Maybe (LInjectivityAnn GhcRn)
Nothing
  = forall (m :: * -> *) a. Monad m => a -> m a
return Injectivity
NotInjective

  -- User provided an injectivity annotation, so for each tyvar argument we
  -- check whether a type family was declared injective in that argument. We
  -- return a list of Bools, where True means that corresponding type variable
  -- was mentioned in lInjNames (type family is injective in that argument) and
  -- False means that it was not mentioned in lInjNames (type family is not
  -- injective in that type variable). We also extend injectivity information to
  -- kind variables, so if a user declares:
  --
  --   type family F (a :: k1) (b :: k2) = (r :: k3) | r -> a
  --
  -- then we mark both `a` and `k1` as injective.
  -- NB: the return kind is considered to be *input* argument to a type family.
  -- Since injectivity allows to infer input arguments from the result in theory
  -- we should always mark the result kind variable (`k3` in this example) as
  -- injective.  The reason is that result type has always an assigned kind and
  -- therefore we can always infer the result kind if we know the result type.
  -- But this does not seem to be useful in any way so we don't do it.  (Another
  -- reason is that the implementation would not be straightforward.)
tcInjectivity [TyConBinder]
tcbs (Just (L SrcSpan
loc (InjectivityAnn XCInjectivityAnn GhcRn
_ LIdP GhcRn
_ [LIdP GhcRn]
lInjNames)))
  = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc forall a b. (a -> b) -> a -> b
$
    do { let tvs :: [TyVar]
tvs = forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tcbs
       ; DynFlags
dflags <- forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; Bool -> SDoc -> TcRn ()
checkTc (Extension -> DynFlags -> Bool
xopt Extension
LangExt.TypeFamilyDependencies DynFlags
dflags)
                 (String -> SDoc
text String
"Illegal injectivity annotation" SDoc -> SDoc -> SDoc
$$
                  String -> SDoc
text String
"Use TypeFamilyDependencies to allow this")
       ; [TyVar]
inj_tvs <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name -> TcM TyVar
tcLookupTyVar forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [LIdP GhcRn]
lInjNames
       ; [TyVar]
inj_tvs <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM HasDebugCallStack => TyVar -> TcM TyVar
zonkTcTyVarToTyVar [TyVar]
inj_tvs -- zonk the kinds
       ; let inj_ktvs :: VarSet
inj_ktvs = (TyVar -> Bool) -> VarSet -> VarSet
filterVarSet TyVar -> Bool
isTyVar forall a b. (a -> b) -> a -> b
$  -- no injective coercion vars
                        VarSet -> VarSet
closeOverKinds ([TyVar] -> VarSet
mkVarSet [TyVar]
inj_tvs)
       ; let inj_bools :: [Bool]
inj_bools = forall a b. (a -> b) -> [a] -> [b]
map (TyVar -> VarSet -> Bool
`elemVarSet` VarSet
inj_ktvs) [TyVar]
tvs
       ; String -> SDoc -> TcRn ()
traceTc String
"tcInjectivity" ([SDoc] -> SDoc
vcat [ forall a. Outputable a => a -> SDoc
ppr [TyVar]
tvs, forall a. Outputable a => a -> SDoc
ppr [LIdP GhcRn]
lInjNames, forall a. Outputable a => a -> SDoc
ppr [TyVar]
inj_tvs
                                       , forall a. Outputable a => a -> SDoc
ppr VarSet
inj_ktvs, forall a. Outputable a => a -> SDoc
ppr [Bool]
inj_bools ])
       ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ [Bool] -> Injectivity
Injective [Bool]
inj_bools }

tcTySynRhs :: RolesInfo -> Name
           -> LHsType GhcRn -> TcM TyCon
tcTySynRhs :: (Name -> [Role]) -> Name -> LHsKind GhcRn -> TcM TyCon
tcTySynRhs Name -> [Role]
roles_info Name
tc_name LHsKind GhcRn
hs_ty
  = forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tc_name forall a b. (a -> b) -> a -> b
$ \ TyCon
_ [TyConBinder]
binders Type
res_kind ->
    do { TcLclEnv
env <- forall gbl lcl. TcRnIf gbl lcl lcl
getLclEnv
       ; String -> SDoc -> TcRn ()
traceTc String
"tc-syn" (forall a. Outputable a => a -> SDoc
ppr Name
tc_name SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr (TcLclEnv -> TcTypeEnv
tcl_env TcLclEnv
env))
       ; Type
rhs_ty <- forall a. SkolemInfo -> [TyVar] -> TcM a -> TcM a
pushLevelAndSolveEqualities SkolemInfo
skol_info (forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
binders) forall a b. (a -> b) -> a -> b
$
                   LHsKind GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsKind GhcRn
hs_ty (Type -> ContextKind
TheKind Type
res_kind)

         -- See Note [Error on unconstrained meta-variables] in GHC.Tc.Utils.TcMType
         -- Example: (typecheck/should_fail/T17567)
         --   type T = forall a. Proxy a
         -- The kind of `a` is unconstrained.
       ; CandidatesQTvs
dvs <- Type -> TcM CandidatesQTvs
candidateQTyVarsOfType Type
rhs_ty
       ; let mk_doc :: TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc TidyEnv
tidy_env = do { (TidyEnv
tidy_env2, Type
rhs_ty) <- TidyEnv -> Type -> TcM (TidyEnv, Type)
zonkTidyTcType TidyEnv
tidy_env Type
rhs_ty
                                  ; forall (m :: * -> *) a. Monad m => a -> m a
return ( TidyEnv
tidy_env2
                                           , [SDoc] -> SDoc
sep [ String -> SDoc
text String
"the type synonym right-hand side:"
                                                 , forall a. Outputable a => a -> SDoc
ppr Type
rhs_ty ] ) }
       ; CandidatesQTvs
-> (TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc))
-> TcRn ()
doNotQuantifyTyVars CandidatesQTvs
dvs TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc

       ; ZonkEnv
ze <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; Type
rhs_ty <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
rhs_ty
       ; let roles :: [Role]
roles = Name -> [Role]
roles_info Name
tc_name
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (Name -> [TyConBinder] -> Type -> [Role] -> Type -> TyCon
buildSynTyCon Name
tc_name [TyConBinder]
binders Type
res_kind [Role]
roles Type
rhs_ty) }
  where
    skol_info :: SkolemInfo
skol_info = TyConFlavour -> Name -> SkolemInfo
TyConSkol TyConFlavour
TypeSynonymFlavour Name
tc_name

tcDataDefn :: SDoc -> RolesInfo -> Name
           -> HsDataDefn GhcRn -> TcM (TyCon, [DerivInfo])
  -- NB: not used for newtype/data instances (whether associated or not)
tcDataDefn :: SDoc
-> (Name -> [Role])
-> Name
-> HsDataDefn GhcRn
-> TcM (TyCon, [DerivInfo])
tcDataDefn SDoc
err_ctxt Name -> [Role]
roles_info Name
tc_name
           (HsDataDefn { dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND = NewOrData
new_or_data, dd_cType :: forall pass. HsDataDefn pass -> Maybe (XRec pass CType)
dd_cType = Maybe (XRec GhcRn CType)
cType
                       , dd_ctxt :: forall pass. HsDataDefn pass -> Maybe (LHsContext pass)
dd_ctxt = Maybe (LHsContext GhcRn)
ctxt
                       , dd_kindSig :: forall pass. HsDataDefn pass -> Maybe (LHsKind pass)
dd_kindSig = Maybe (LHsKind GhcRn)
mb_ksig  -- Already in tc's kind
                                               -- via inferInitialKinds
                       , dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons = [LConDecl GhcRn]
cons
                       , dd_derivs :: forall pass. HsDataDefn pass -> HsDeriving pass
dd_derivs = HsDeriving GhcRn
derivs })
  = forall a.
Name -> (TyCon -> [TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tc_name forall a b. (a -> b) -> a -> b
$ \ TyCon
tctc [TyConBinder]
tycon_binders Type
res_kind ->
       -- 'tctc' is a 'TcTyCon' and has the 'tcTyConScopedTyVars' that we need
       -- unlike the finalized 'tycon' defined above which is an 'AlgTyCon'
       --
       -- The TyCon tyvars must scope over
       --    - the stupid theta (dd_ctxt)
       --    - for H98 constructors only, the ConDecl
       -- But it does no harm to bring them into scope
       -- over GADT ConDecls as well; and it's awkward not to
    do { Bool
gadt_syntax <- Name
-> NewOrData
-> Maybe (LHsContext GhcRn)
-> [LConDecl GhcRn]
-> IOEnv (Env TcGblEnv TcLclEnv) Bool
dataDeclChecks Name
tc_name NewOrData
new_or_data Maybe (LHsContext GhcRn)
ctxt [LConDecl GhcRn]
cons
         -- see Note [Datatype return kinds]
       ; ([TyConBinder]
extra_bndrs, Type
final_res_kind) <- [TyConBinder] -> Type -> TcM ([TyConBinder], Type)
etaExpandAlgTyCon [TyConBinder]
tycon_binders Type
res_kind

       ; TcGblEnv
tcg_env <- forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv
       ; let hsc_src :: HscSource
hsc_src = TcGblEnv -> HscSource
tcg_src TcGblEnv
tcg_env
       ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (forall {a}. HscSource -> [a] -> Bool
mk_permissive_kind HscSource
hsc_src [LConDecl GhcRn]
cons) forall a b. (a -> b) -> a -> b
$
         DataSort -> Type -> TcRn ()
checkDataKindSig (NewOrData -> DataSort
DataDeclSort NewOrData
new_or_data) Type
final_res_kind

       ; let skol_tvs :: [TyVar]
skol_tvs = forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tycon_binders
       ; [Type]
stupid_tc_theta <- forall a. SkolemInfo -> [TyVar] -> TcM a -> TcM a
pushLevelAndSolveEqualities SkolemInfo
skol_info [TyVar]
skol_tvs forall a b. (a -> b) -> a -> b
$
                            Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
ctxt

       -- See Note [Error on unconstrained meta-variables] in GHC.Tc.Utils.TcMType
       -- Example: (typecheck/should_fail/T17567StupidTheta)
       --   data (forall a. a b ~ a c) => T b c
       -- The kind of 'a' is unconstrained.
       ; CandidatesQTvs
dvs <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfTypes [Type]
stupid_tc_theta
       ; let mk_doc :: TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc TidyEnv
tidy_env
               = do { (TidyEnv
tidy_env2, [Type]
theta) <- TidyEnv -> [Type] -> TcM (TidyEnv, [Type])
zonkTidyTcTypes TidyEnv
tidy_env [Type]
stupid_tc_theta
                    ; forall (m :: * -> *) a. Monad m => a -> m a
return ( TidyEnv
tidy_env2
                             , [SDoc] -> SDoc
sep [ String -> SDoc
text String
"the datatype context:"
                                   , [Type] -> SDoc
pprTheta [Type]
theta ] ) }
       ; CandidatesQTvs
-> (TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc))
-> TcRn ()
doNotQuantifyTyVars CandidatesQTvs
dvs TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc

       ; ZonkEnv
ze              <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; [Type]
stupid_theta    <- ZonkEnv -> [Type] -> TcM [Type]
zonkTcTypesToTypesX ZonkEnv
ze [Type]
stupid_tc_theta

             -- Check that we don't use kind signatures without the extension
       ; Bool
kind_signatures <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.KindSignatures
       ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (forall a. Maybe a -> Bool
isJust Maybe (LHsKind GhcRn)
mb_ksig) forall a b. (a -> b) -> a -> b
$
         Bool -> SDoc -> TcRn ()
checkTc (Bool
kind_signatures) (Name -> SDoc
badSigTyDecl Name
tc_name)

       ; TyCon
tycon <- forall a env. (a -> IOEnv env a) -> IOEnv env a
fixM forall a b. (a -> b) -> a -> b
$ \ TyCon
rec_tycon -> do
             { let final_bndrs :: [TyConBinder]
final_bndrs = [TyConBinder]
tycon_binders forall a. [a] -> [a] -> [a]
`chkAppend` [TyConBinder]
extra_bndrs
                   roles :: [Role]
roles       = Name -> [Role]
roles_info Name
tc_name
             ; [DataCon]
data_cons <- NewOrData
-> DataDeclInfo
-> TyCon
-> [TyConBinder]
-> Type
-> [LConDecl GhcRn]
-> TcM [DataCon]
tcConDecls
                              NewOrData
new_or_data DataDeclInfo
DDataType
                              TyCon
rec_tycon [TyConBinder]
final_bndrs Type
final_res_kind
                              [LConDecl GhcRn]
cons
             ; AlgTyConRhs
tc_rhs    <- HscSource
-> TyCon -> [DataCon] -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
mk_tc_rhs HscSource
hsc_src TyCon
rec_tycon [DataCon]
data_cons
             ; Name
tc_rep_nm <- forall gbl lcl. Name -> TcRnIf gbl lcl Name
newTyConRepName Name
tc_name
             ; forall (m :: * -> *) a. Monad m => a -> m a
return (Name
-> [TyConBinder]
-> Type
-> [Role]
-> Maybe CType
-> [Type]
-> AlgTyConRhs
-> AlgTyConFlav
-> Bool
-> TyCon
mkAlgTyCon Name
tc_name
                                  [TyConBinder]
final_bndrs
                                  Type
final_res_kind
                                  [Role]
roles
                                  (forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap forall l e. GenLocated l e -> e
unLoc Maybe (XRec GhcRn CType)
cType)
                                  [Type]
stupid_theta AlgTyConRhs
tc_rhs
                                  (Name -> AlgTyConFlav
VanillaAlgTyCon Name
tc_rep_nm)
                                  Bool
gadt_syntax) }
       ; let deriv_info :: DerivInfo
deriv_info = DerivInfo { di_rep_tc :: TyCon
di_rep_tc = TyCon
tycon
                                    , di_scoped_tvs :: [(Name, TyVar)]
di_scoped_tvs = TyCon -> [(Name, TyVar)]
tcTyConScopedTyVars TyCon
tctc
                                    , di_clauses :: HsDeriving GhcRn
di_clauses = HsDeriving GhcRn
derivs
                                    , di_ctxt :: SDoc
di_ctxt = SDoc
err_ctxt }
       ; String -> SDoc -> TcRn ()
traceTc String
"tcDataDefn" (forall a. Outputable a => a -> SDoc
ppr Name
tc_name SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
tycon_binders SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
extra_bndrs)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
tycon, [DerivInfo
deriv_info]) }
  where
    skol_info :: SkolemInfo
skol_info = TyConFlavour -> Name -> SkolemInfo
TyConSkol TyConFlavour
flav Name
tc_name
    flav :: TyConFlavour
flav = NewOrData -> TyConFlavour
newOrDataToFlavour NewOrData
new_or_data

    -- Abstract data types in hsig files can have arbitrary kinds,
    -- because they may be implemented by type synonyms
    -- (which themselves can have arbitrary kinds, not just *). See #13955.
    --
    -- Note that this is only a property that data type declarations possess,
    -- so one could not have, say, a data family instance in an hsig file that
    -- has kind `Bool`. Therefore, this check need only occur in the code that
    -- typechecks data type declarations.
    mk_permissive_kind :: HscSource -> [a] -> Bool
mk_permissive_kind HscSource
HsigFile [] = Bool
True
    mk_permissive_kind HscSource
_ [a]
_ = Bool
False

    -- In hs-boot, a 'data' declaration with no constructors
    -- indicates a nominally distinct abstract data type.
    mk_tc_rhs :: HscSource
-> TyCon -> [DataCon] -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
mk_tc_rhs HscSource
HsBootFile TyCon
_ []
      = forall (m :: * -> *) a. Monad m => a -> m a
return AlgTyConRhs
AbstractTyCon

    mk_tc_rhs HscSource
HsigFile TyCon
_ [] -- ditto
      = forall (m :: * -> *) a. Monad m => a -> m a
return AlgTyConRhs
AbstractTyCon

    mk_tc_rhs HscSource
_ TyCon
tycon [DataCon]
data_cons
      = case NewOrData
new_or_data of
          NewOrData
DataType -> forall (m :: * -> *) a. Monad m => a -> m a
return ([DataCon] -> AlgTyConRhs
mkDataTyConRhs [DataCon]
data_cons)
          NewOrData
NewType  -> ASSERT( not (null data_cons) )
                      forall m n. Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
mkNewTyConRhs Name
tc_name TyCon
tycon (forall a. [a] -> a
head [DataCon]
data_cons)


-------------------------
kcTyFamInstEqn :: TcTyCon -> LTyFamInstEqn GhcRn -> TcM ()
-- Used for the equations of a closed type family only
-- Not used for data/type instances
kcTyFamInstEqn :: TyCon -> LTyFamInstEqn GhcRn -> TcRn ()
kcTyFamInstEqn TyCon
tc_fam_tc
    (L SrcSpanAnnA
loc (FamEqn { feqn_tycon :: forall pass rhs. FamEqn pass rhs -> LIdP pass
feqn_tycon = L SrcSpanAnnN
_ Name
eqn_tc_name
                   , feqn_bndrs :: forall pass rhs. FamEqn pass rhs -> HsOuterFamEqnTyVarBndrs pass
feqn_bndrs = HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs
                   , feqn_pats :: forall pass rhs. FamEqn pass rhs -> HsTyPats pass
feqn_pats  = HsTyPats GhcRn
hs_pats
                   , feqn_rhs :: forall pass rhs. FamEqn pass rhs -> rhs
feqn_rhs   = GenLocated SrcSpanAnnA (HsType GhcRn)
hs_rhs_ty }))
  = forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"kcTyFamInstEqn" ([SDoc] -> SDoc
vcat
           [ String -> SDoc
text String
"tc_name ="    SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Name
eqn_tc_name
           , String -> SDoc
text String
"fam_tc ="     SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr TyCon
tc_fam_tc SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (TyCon -> Type
tyConKind TyCon
tc_fam_tc)
           , String -> SDoc
text String
"feqn_bndrs =" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs
           , String -> SDoc
text String
"feqn_pats ="  SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr HsTyPats GhcRn
hs_pats ])

       ; forall tm ty. TyCon -> Name -> [HsArg tm ty] -> TcRn ()
checkTyFamInstEqn TyCon
tc_fam_tc Name
eqn_tc_name HsTyPats GhcRn
hs_pats

       ; forall a. TcM a -> TcRn ()
discardResult forall a b. (a -> b) -> a -> b
$
         forall a.
HsOuterFamEqnTyVarBndrs GhcRn -> TcM a -> TcM ([TyVar], a)
bindOuterFamEqnTKBndrs_Q_Tv HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs forall a b. (a -> b) -> a -> b
$
         do { (Type
_fam_app, Type
res_kind) <- TyCon -> HsTyPats GhcRn -> TcM (Type, Type)
tcFamTyPats TyCon
tc_fam_tc HsTyPats GhcRn
hs_pats
            ; LHsKind GhcRn -> ContextKind -> TcM Type
tcCheckLHsType GenLocated SrcSpanAnnA (HsType GhcRn)
hs_rhs_ty (Type -> ContextKind
TheKind Type
res_kind) }
             -- Why "_Tv" here?  Consider (#14066)
             --  type family Bar x y where
             --      Bar (x :: a) (y :: b) = Int
             --      Bar (x :: c) (y :: d) = Bool
             -- During kind-checking, a,b,c,d should be TyVarTvs and unify appropriately
    }

--------------------------
tcTyFamInstEqn :: TcTyCon -> AssocInstInfo -> LTyFamInstEqn GhcRn
               -> TcM (KnotTied CoAxBranch)
-- Needs to be here, not in GHC.Tc.TyCl.Instance, because closed families
-- (typechecked here) have TyFamInstEqns

tcTyFamInstEqn :: TyCon
-> AssocInstInfo
-> LTyFamInstEqn GhcRn
-> TcM (KnotTied CoAxBranch)
tcTyFamInstEqn TyCon
fam_tc AssocInstInfo
mb_clsinfo
    (L SrcSpanAnnA
loc (FamEqn { feqn_tycon :: forall pass rhs. FamEqn pass rhs -> LIdP pass
feqn_tycon  = L SrcSpanAnnN
_ Name
eqn_tc_name
                   , feqn_bndrs :: forall pass rhs. FamEqn pass rhs -> HsOuterFamEqnTyVarBndrs pass
feqn_bndrs  = HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs
                   , feqn_pats :: forall pass rhs. FamEqn pass rhs -> HsTyPats pass
feqn_pats   = HsTyPats GhcRn
hs_pats
                   , feqn_rhs :: forall pass rhs. FamEqn pass rhs -> rhs
feqn_rhs    = GenLocated SrcSpanAnnA (HsType GhcRn)
hs_rhs_ty }))
  = forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqn" forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ forall a. Outputable a => a -> SDoc
ppr SrcSpanAnnA
loc, forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr HsTyPats GhcRn
hs_pats
              , String -> SDoc
text String
"fam tc bndrs" SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars (TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc)
              , case AssocInstInfo
mb_clsinfo of
                  NotAssociated {} -> SDoc
empty
                  InClsInst { ai_class :: AssocInstInfo -> Class
ai_class = Class
cls } -> String -> SDoc
text String
"class" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Class
cls SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars (Class -> [TyVar]
classTyVars Class
cls) ]

       ; forall tm ty. TyCon -> Name -> [HsArg tm ty] -> TcRn ()
checkTyFamInstEqn TyCon
fam_tc Name
eqn_tc_name HsTyPats GhcRn
hs_pats

       ; ([TyVar]
qtvs, [Type]
pats, Type
rhs_ty) <- TyCon
-> AssocInstInfo
-> HsOuterFamEqnTyVarBndrs GhcRn
-> HsTyPats GhcRn
-> LHsKind GhcRn
-> TcM ([TyVar], [Type], Type)
tcTyFamInstEqnGuts TyCon
fam_tc AssocInstInfo
mb_clsinfo
                                      HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs HsTyPats GhcRn
hs_pats GenLocated SrcSpanAnnA (HsType GhcRn)
hs_rhs_ty
       -- Don't print results they may be knot-tied
       -- (tcFamInstEqnGuts zonks to Type)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
-> [TyVar]
-> [TyVar]
-> [Type]
-> Type
-> [Role]
-> SrcSpan
-> KnotTied CoAxBranch
mkCoAxBranch [TyVar]
qtvs [] [] [Type]
pats Type
rhs_ty
                              (forall a b. (a -> b) -> [a] -> [b]
map (forall a b. a -> b -> a
const Role
Nominal) [TyVar]
qtvs)
                              (forall a. SrcSpanAnn' a -> SrcSpan
locA SrcSpanAnnA
loc)) }

checkTyFamInstEqn :: TcTyCon -> Name -> [HsArg tm ty] -> TcM ()
checkTyFamInstEqn :: forall tm ty. TyCon -> Name -> [HsArg tm ty] -> TcRn ()
checkTyFamInstEqn TyCon
tc_fam_tc Name
eqn_tc_name [HsArg tm ty]
hs_pats =
  do { -- Ensure that each equation's type constructor is for the right
       -- type family.  E.g. barf on
       --    type family F a where { G Int = Bool }
       let tc_fam_tc_name :: Name
tc_fam_tc_name = forall a. NamedThing a => a -> Name
getName TyCon
tc_fam_tc
     ; Bool -> SDoc -> TcRn ()
checkTc (Name
tc_fam_tc_name forall a. Eq a => a -> a -> Bool
== Name
eqn_tc_name) forall a b. (a -> b) -> a -> b
$
               Name -> Name -> SDoc
wrongTyFamName Name
tc_fam_tc_name Name
eqn_tc_name

       -- Check the arity of visible arguments
       -- If we wait until validity checking, we'll get kind errors
       -- below when an arity error will be much easier to understand.
     ; let vis_arity :: Arity
vis_arity = forall (t :: * -> *) a. Foldable t => t a -> Arity
length (TyCon -> [TyVar]
tyConVisibleTyVars TyCon
tc_fam_tc)
           vis_pats :: Arity
vis_pats  = forall tm ty. [HsArg tm ty] -> Arity
numVisibleArgs [HsArg tm ty]
hs_pats
     ; Bool -> SDoc -> TcRn ()
checkTc (Arity
vis_pats forall a. Eq a => a -> a -> Bool
== Arity
vis_arity) forall a b. (a -> b) -> a -> b
$
               Arity -> SDoc
wrongNumberOfParmsErr Arity
vis_arity
     }

{- Note [Instantiating a family tycon]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It's possible that kind-checking the result of a family tycon applied to
its patterns will instantiate the tycon further. For example, we might
have

  type family F :: k where
    F = Int
    F = Maybe

After checking (F :: forall k. k) (with no visible patterns), we still need
to instantiate the k. With data family instances, this problem can be even
more intricate, due to Note [Arity of data families] in GHC.Core.FamInstEnv. See
indexed-types/should_compile/T12369 for an example.

So, the kind-checker must return the new skolems and args (that is, Type
or (Type -> Type) for the equations above) and the instantiated kind.

Note [Generalising in tcTyFamInstEqnGuts]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have something like
  type instance forall (a::k) b. F (Proxy t1) _ = rhs

Then  imp_vars = [k], exp_bndrs = [a::k, b]

We want to quantify over all the free vars of the LHS including
  * any invisible kind variables arising from instantiating tycons,
    such as Proxy
  * wildcards such as '_' above

The wildcards are particularly awkward: they may need to be quantified
  - before the explicit variables k,a,b
  - after them
  - or even interleaved with them
  c.f. Note [Naughty quantification candidates] in GHC.Tc.Utils.TcMType

So, we use bindOuterFamEqnTKBndrs (which does not create an implication for
the telescope), and generalise over /all/ the variables in the LHS,
without treating the explicitly-quanfitifed ones specially. Wrinkles:

 - When generalising, include the explicit user-specified forall'd
   variables, so that we get an error from Validity.checkFamPatBinders
   if a forall'd variable is not bound on the LHS

 - We still want to complain about a bad telescope among the user-specified
   variables.  So in checkFamTelescope we emit an implication constraint
   quantifying only over them, purely so that we get a good telescope error.

  - Note that, unlike a type signature like
       f :: forall (a::k). blah
    we do /not/ care about the Inferred/Specified designation or order for
    the final quantified tyvars.  Type-family instances are not invoked
    directly in Haskell source code, so visible type application etc plays
    no role.

See also Note [Re-quantify type variables in rules] in
GHC.Tc.Gen.Rule, which explains a /very/ similar design when
generalising over the type of a rewrite rule.

-}

--------------------------
tcTyFamInstEqnGuts :: TyCon -> AssocInstInfo
                   -> HsOuterFamEqnTyVarBndrs GhcRn     -- Implicit and explicit binders
                   -> HsTyPats GhcRn                    -- Patterns
                   -> LHsType GhcRn                     -- RHS
                   -> TcM ([TyVar], [TcType], TcType)   -- (tyvars, pats, rhs)
-- Used only for type families, not data families
tcTyFamInstEqnGuts :: TyCon
-> AssocInstInfo
-> HsOuterFamEqnTyVarBndrs GhcRn
-> HsTyPats GhcRn
-> LHsKind GhcRn
-> TcM ([TyVar], [Type], Type)
tcTyFamInstEqnGuts TyCon
fam_tc AssocInstInfo
mb_clsinfo HsOuterFamEqnTyVarBndrs GhcRn
outer_hs_bndrs HsTyPats GhcRn
hs_pats LHsKind GhcRn
hs_rhs_ty
  = do { String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqnGuts {" (forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc)

       -- By now, for type families (but not data families) we should
       -- have checked that the number of patterns matches tyConArity

       -- This code is closely related to the code
       -- in GHC.Tc.Gen.HsType.kcCheckDeclHeader_cusk
       ; (TcLevel
tclvl, WantedConstraints
wanted, ([TyVar]
outer_tvs, (Type
lhs_ty, Type
rhs_ty)))
               <- forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"tcTyFamInstEqnGuts" forall a b. (a -> b) -> a -> b
$
                  forall a.
HsOuterFamEqnTyVarBndrs GhcRn -> TcM a -> TcM ([TyVar], a)
bindOuterFamEqnTKBndrs HsOuterFamEqnTyVarBndrs GhcRn
outer_hs_bndrs             forall a b. (a -> b) -> a -> b
$
                  do { (Type
lhs_ty, Type
rhs_kind) <- TyCon -> HsTyPats GhcRn -> TcM (Type, Type)
tcFamTyPats TyCon
fam_tc HsTyPats GhcRn
hs_pats
                       -- Ensure that the instance is consistent with its
                       -- parent class (#16008)
                     ; AssocInstInfo -> Type -> TcRn ()
addConsistencyConstraints AssocInstInfo
mb_clsinfo Type
lhs_ty
                     ; Type
rhs_ty <- LHsKind GhcRn -> ContextKind -> TcM Type
tcCheckLHsType LHsKind GhcRn
hs_rhs_ty (Type -> ContextKind
TheKind Type
rhs_kind)
                     ; forall (m :: * -> *) a. Monad m => a -> m a
return (Type
lhs_ty, Type
rhs_ty) }

       -- This code (and the stuff immediately above) is very similar
       -- to that in tcDataFamInstHeader.  Maybe we should abstract the
       -- common code; but for the moment I concluded that it's
       -- clearer to duplicate it.  Still, if you fix a bug here,
       -- check there too!

       -- See Note [Generalising in tcTyFamInstEqnGuts]
       ; CandidatesQTvs
dvs  <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfTypes (Type
lhs_ty forall a. a -> [a] -> [a]
: [TyVar] -> [Type]
mkTyVarTys [TyVar]
outer_tvs)
       ; [TyVar]
qtvs <- CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
dvs
       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcRn ()
reportUnsolvedEqualities SkolemInfo
FamInstSkol [TyVar]
qtvs TcLevel
tclvl WantedConstraints
wanted
       ; TcLevel -> HsOuterFamEqnTyVarBndrs GhcRn -> [TyVar] -> TcRn ()
checkFamTelescope TcLevel
tclvl HsOuterFamEqnTyVarBndrs GhcRn
outer_hs_bndrs [TyVar]
outer_tvs

       ; String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqnGuts 2" forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc
              , String -> SDoc
text String
"lhs_ty"     SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Type
lhs_ty
              , String -> SDoc
text String
"qtvs"       SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
qtvs ]

       -- See Note [Error on unconstrained meta-variables] in GHC.Tc.Utils.TcMType
       -- Example: typecheck/should_fail/T17301
       ; CandidatesQTvs
dvs_rhs <- Type -> TcM CandidatesQTvs
candidateQTyVarsOfType Type
rhs_ty
       ; let mk_doc :: TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc TidyEnv
tidy_env
               = do { (TidyEnv
tidy_env2, Type
rhs_ty) <- TidyEnv -> Type -> TcM (TidyEnv, Type)
zonkTidyTcType TidyEnv
tidy_env Type
rhs_ty
                    ; forall (m :: * -> *) a. Monad m => a -> m a
return ( TidyEnv
tidy_env2
                             , [SDoc] -> SDoc
sep [ String -> SDoc
text String
"type family equation right-hand side:"
                                   , forall a. Outputable a => a -> SDoc
ppr Type
rhs_ty ] ) }
       ; CandidatesQTvs
-> (TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc))
-> TcRn ()
doNotQuantifyTyVars CandidatesQTvs
dvs_rhs TidyEnv -> IOEnv (Env TcGblEnv TcLclEnv) (TidyEnv, SDoc)
mk_doc

       ; ZonkEnv
ze         <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; (ZonkEnv
ze, [TyVar]
qtvs) <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX      ZonkEnv
ze [TyVar]
qtvs
       ; Type
lhs_ty     <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
lhs_ty
       ; Type
rhs_ty     <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
rhs_ty

       ; let pats :: [Type]
pats = Type -> [Type]
unravelFamInstPats Type
lhs_ty
             -- Note that we do this after solveEqualities
             -- so that any strange coercions inside lhs_ty
             -- have been solved before we attempt to unravel it
       ; String -> SDoc -> TcRn ()
traceTc String
"tcTyFamInstEqnGuts }" (forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc SDoc -> SDoc -> SDoc
<+> [TyVar] -> SDoc
pprTyVars [TyVar]
qtvs)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
qtvs, [Type]
pats, Type
rhs_ty) }


checkFamTelescope :: TcLevel -> HsOuterFamEqnTyVarBndrs GhcRn
                  -> [TcTyVar] -> TcM ()
-- Emit a constraint (forall a b c. <empty>), so that
-- we will do telescope-checking on a,b,c
-- See Note [Generalising in tcTyFamInstEqnGuts]
checkFamTelescope :: TcLevel -> HsOuterFamEqnTyVarBndrs GhcRn -> [TyVar] -> TcRn ()
checkFamTelescope TcLevel
tclvl HsOuterFamEqnTyVarBndrs GhcRn
hs_outer_bndrs [TyVar]
outer_tvs
  | HsOuterExplicit { hso_bndrs :: forall flag pass.
HsOuterTyVarBndrs flag pass -> [LHsTyVarBndr flag (NoGhcTc pass)]
hso_bndrs = [LHsTyVarBndr () (NoGhcTc GhcRn)]
bndrs } <- HsOuterFamEqnTyVarBndrs GhcRn
hs_outer_bndrs
  , (LHsTyVarBndr () (NoGhcTc GhcRn)
b_first : [LHsTyVarBndr () (NoGhcTc GhcRn)]
_) <- [LHsTyVarBndr () (NoGhcTc GhcRn)]
bndrs
  , let b_last :: GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
b_last    = forall a. [a] -> a
last [LHsTyVarBndr () (NoGhcTc GhcRn)]
bndrs
        skol_info :: SkolemInfo
skol_info = SDoc -> SkolemInfo
ForAllSkol ([SDoc] -> SDoc
fsep (forall a b. (a -> b) -> [a] -> [b]
map forall a. Outputable a => a -> SDoc
ppr [LHsTyVarBndr () (NoGhcTc GhcRn)]
bndrs))
  = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (SrcSpan -> SrcSpan -> SrcSpan
combineSrcSpans (forall a e. GenLocated (SrcSpanAnn' a) e -> SrcSpan
getLocA LHsTyVarBndr () (NoGhcTc GhcRn)
b_first) (forall a e. GenLocated (SrcSpanAnn' a) e -> SrcSpan
getLocA GenLocated SrcSpanAnnA (HsTyVarBndr () GhcRn)
b_last)) forall a b. (a -> b) -> a -> b
$
    SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcRn ()
emitResidualTvConstraint SkolemInfo
skol_info [TyVar]
outer_tvs TcLevel
tclvl WantedConstraints
emptyWC
  | Bool
otherwise
  = forall (m :: * -> *) a. Monad m => a -> m a
return ()

-----------------
unravelFamInstPats :: TcType -> [TcType]
-- Decompose fam_app to get the argument patterns
--
-- We expect fam_app to look like (F t1 .. tn)
-- tcFamTyPats is capable of returning ((F ty1 |> co) ty2),
-- but that can't happen here because we already checked the
-- arity of F matches the number of pattern
unravelFamInstPats :: Type -> [Type]
unravelFamInstPats Type
fam_app
  = case HasDebugCallStack => Type -> Maybe (TyCon, [Type])
splitTyConApp_maybe Type
fam_app of
      Just (TyCon
_, [Type]
pats) -> [Type]
pats
      Maybe (TyCon, [Type])
Nothing -> forall a. String -> a
panic String
"unravelFamInstPats: Ill-typed LHS of family instance"
        -- The Nothing case cannot happen for type families, because
        -- we don't call unravelFamInstPats until we've solved the
        -- equalities. For data families, it shouldn't happen either,
        -- we need to fail hard and early if it does. See trac issue #15905
        -- for an example of this happening.

addConsistencyConstraints :: AssocInstInfo -> TcType -> TcM ()
-- In the corresponding positions of the class and type-family,
-- ensure the family argument is the same as the class argument
--   E.g    class C a b c d where
--             F c x y a :: Type
-- Here the first  arg of F should be the same as the third of C
--  and the fourth arg of F should be the same as the first of C
--
-- We emit /Derived/ constraints (a bit like fundeps) to encourage
-- unification to happen, but without actually reporting errors.
-- If, despite the efforts, corresponding positions do not match,
-- checkConsistentFamInst will complain
addConsistencyConstraints :: AssocInstInfo -> Type -> TcRn ()
addConsistencyConstraints AssocInstInfo
mb_clsinfo Type
fam_app
  | InClsInst { ai_inst_env :: AssocInstInfo -> VarEnv Type
ai_inst_env = VarEnv Type
inst_env } <- AssocInstInfo
mb_clsinfo
  , Just (TyCon
fam_tc, [Type]
pats) <- HasCallStack => Type -> Maybe (TyCon, [Type])
tcSplitTyConApp_maybe Type
fam_app
  = do { let eqs :: [(Type, Type)]
eqs = [ (Type
cls_ty, Type
pat)
                   | (TyVar
fam_tc_tv, Type
pat) <- TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc forall a b. [a] -> [b] -> [(a, b)]
`zip` [Type]
pats
                   , Just Type
cls_ty <- [forall a. VarEnv a -> TyVar -> Maybe a
lookupVarEnv VarEnv Type
inst_env TyVar
fam_tc_tv] ]
       ; String -> SDoc -> TcRn ()
traceTc String
"addConsistencyConstraints" (forall a. Outputable a => a -> SDoc
ppr [(Type, Type)]
eqs)
       ; CtOrigin -> [(Type, Type)] -> TcRn ()
emitDerivedEqs CtOrigin
AssocFamPatOrigin [(Type, Type)]
eqs }
    -- Improve inference
    -- Any mis-match is reports by checkConsistentFamInst
  | Bool
otherwise
  = forall (m :: * -> *) a. Monad m => a -> m a
return ()

{- Note [Constraints in patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NB: This isn't the whole story. See comment in tcFamTyPats.

At first glance, it seems there is a complicated story to tell in tcFamTyPats
around constraint solving. After all, type family patterns can now do
GADT pattern-matching, which is jolly complicated. But, there's a key fact
which makes this all simple: everything is at top level! There cannot
be untouchable type variables. There can't be weird interaction between
case branches. There can't be global skolems.

This means that the semantics of type-level GADT matching is a little
different than term level. If we have

  data G a where
    MkGBool :: G Bool

And then

  type family F (a :: G k) :: k
  type instance F MkGBool = True

we get

  axF : F Bool (MkGBool <Bool>) ~ True

Simple! No casting on the RHS, because we can affect the kind parameter
to F.

If we ever introduce local type families, this all gets a lot more
complicated, and will end up looking awfully like term-level GADT
pattern-matching.


** The new story **

Here is really what we want:

The matcher really can't deal with covars in arbitrary spots in coercions.
But it can deal with covars that are arguments to GADT data constructors.
So we somehow want to allow covars only in precisely those spots, then use
them as givens when checking the RHS. TODO (RAE): Implement plan.

Note [Quantified kind variables of a family pattern]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider   type family KindFam (p :: k1) (q :: k1)
           data T :: Maybe k1 -> k2 -> *
           type instance KindFam (a :: Maybe k) b = T a b -> Int
The HsBSig for the family patterns will be ([k], [a])

Then in the family instance we want to
  * Bring into scope [ "k" -> k:*, "a" -> a:k ]
  * Kind-check the RHS
  * Quantify the type instance over k and k', as well as a,b, thus
       type instance [k, k', a:Maybe k, b:k']
                     KindFam (Maybe k) k' a b = T k k' a b -> Int

Notice that in the third step we quantify over all the visibly-mentioned
type variables (a,b), but also over the implicitly mentioned kind variables
(k, k').  In this case one is bound explicitly but often there will be
none. The role of the kind signature (a :: Maybe k) is to add a constraint
that 'a' must have that kind, and to bring 'k' into scope.



************************************************************************
*                                                                      *
               Data types
*                                                                      *
************************************************************************
-}

dataDeclChecks :: Name -> NewOrData
               -> Maybe (LHsContext GhcRn) -> [LConDecl GhcRn]
               -> TcM Bool
dataDeclChecks :: Name
-> NewOrData
-> Maybe (LHsContext GhcRn)
-> [LConDecl GhcRn]
-> IOEnv (Env TcGblEnv TcLclEnv) Bool
dataDeclChecks Name
tc_name NewOrData
new_or_data Maybe (LHsContext GhcRn)
mctxt [LConDecl GhcRn]
cons
  = do { let stupid_theta :: HsContext GhcRn
stupid_theta = forall (p :: Pass).
Maybe (LHsContext (GhcPass p)) -> HsContext (GhcPass p)
fromMaybeContext Maybe (LHsContext GhcRn)
mctxt
         -- Check that we don't use GADT syntax in H98 world
       ;  Bool
gadtSyntax_ok <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.GADTSyntax
       ; let gadt_syntax :: Bool
gadt_syntax = [LConDecl GhcRn] -> Bool
consUseGadtSyntax [LConDecl GhcRn]
cons
       ; Bool -> SDoc -> TcRn ()
checkTc (Bool
gadtSyntax_ok Bool -> Bool -> Bool
|| Bool -> Bool
not Bool
gadt_syntax) (Name -> SDoc
badGadtDecl Name
tc_name)

           -- Check that the stupid theta is empty for a GADT-style declaration
       ; Bool -> SDoc -> TcRn ()
checkTc (forall (t :: * -> *) a. Foldable t => t a -> Bool
null HsContext GhcRn
stupid_theta Bool -> Bool -> Bool
|| Bool -> Bool
not Bool
gadt_syntax) (Name -> SDoc
badStupidTheta Name
tc_name)

         -- Check that a newtype has exactly one constructor
         -- Do this before checking for empty data decls, so that
         -- we don't suggest -XEmptyDataDecls for newtypes
       ; Bool -> SDoc -> TcRn ()
checkTc (NewOrData
new_or_data forall a. Eq a => a -> a -> Bool
== NewOrData
DataType Bool -> Bool -> Bool
|| forall a. [a] -> Bool
isSingleton [LConDecl GhcRn]
cons)
                (Name -> Arity -> SDoc
newtypeConError Name
tc_name (forall (t :: * -> *) a. Foldable t => t a -> Arity
length [LConDecl GhcRn]
cons))

         -- Check that there's at least one condecl,
         -- or else we're reading an hs-boot file, or -XEmptyDataDecls
       ; Bool
empty_data_decls <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.EmptyDataDecls
       ; Bool
is_boot <- IOEnv (Env TcGblEnv TcLclEnv) Bool
tcIsHsBootOrSig  -- Are we compiling an hs-boot file?
       ; Bool -> SDoc -> TcRn ()
checkTc (Bool -> Bool
not (forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LConDecl GhcRn]
cons) Bool -> Bool -> Bool
|| Bool
empty_data_decls Bool -> Bool -> Bool
|| Bool
is_boot)
                 (Name -> SDoc
emptyConDeclsErr Name
tc_name)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return Bool
gadt_syntax }


-----------------------------------
consUseGadtSyntax :: [LConDecl GhcRn] -> Bool
consUseGadtSyntax :: [LConDecl GhcRn] -> Bool
consUseGadtSyntax (L SrcSpanAnnA
_ (ConDeclGADT {}) : [LConDecl GhcRn]
_) = Bool
True
consUseGadtSyntax [LConDecl GhcRn]
_                          = Bool
False
                 -- All constructors have same shape

-----------------------------------
data DataDeclInfo
  = DDataType      -- data T a b = T1 a | T2 b
  | DDataInstance  -- data instance D [a] = D1 a | D2
       Type        --   The header D [a]

mkDDHeaderTy :: DataDeclInfo -> TyCon -> [TyConBinder] -> Type
mkDDHeaderTy :: DataDeclInfo -> TyCon -> [TyConBinder] -> Type
mkDDHeaderTy DataDeclInfo
dd_info TyCon
rep_tycon [TyConBinder]
tc_bndrs
  = case DataDeclInfo
dd_info of
      DataDeclInfo
DDataType -> TyCon -> [Type] -> Type
mkTyConApp TyCon
rep_tycon forall a b. (a -> b) -> a -> b
$
                   [TyVar] -> [Type]
mkTyVarTys (forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tc_bndrs)
      DDataInstance Type
header_ty -> Type
header_ty

tcConDecls :: NewOrData
           -> DataDeclInfo
           -> KnotTied TyCon            -- Representation TyCon
           -> [TyConBinder]             -- Binders of representation TyCon
           -> TcKind                    -- Result kind
           -> [LConDecl GhcRn] -> TcM [DataCon]
tcConDecls :: NewOrData
-> DataDeclInfo
-> TyCon
-> [TyConBinder]
-> Type
-> [LConDecl GhcRn]
-> TcM [DataCon]
tcConDecls NewOrData
new_or_data DataDeclInfo
dd_info TyCon
rep_tycon [TyConBinder]
tmpl_bndrs Type
res_kind
  = forall (m :: * -> *) a b. Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM forall a b. (a -> b) -> a -> b
$ forall a b ann.
(a -> TcM b) -> GenLocated (SrcSpanAnn' ann) a -> TcM b
addLocMA forall a b. (a -> b) -> a -> b
$
    NewOrData
-> DataDeclInfo
-> TyCon
-> [TyConBinder]
-> Type
-> NameEnv Arity
-> ConDecl GhcRn
-> TcM [DataCon]
tcConDecl NewOrData
new_or_data DataDeclInfo
dd_info TyCon
rep_tycon [TyConBinder]
tmpl_bndrs Type
res_kind
              (TyCon -> NameEnv Arity
mkTyConTagMap TyCon
rep_tycon)
    -- mkTyConTagMap: it's important that we pay for tag allocation here,
    -- once per TyCon. See Note [Constructor tag allocation], fixes #14657

tcConDecl :: NewOrData
          -> DataDeclInfo
          -> KnotTied TyCon   -- Representation tycon. Knot-tied!
          -> [TyConBinder]    -- Binders of representation TyCon
          -> TcKind           -- Result kind
          -> NameEnv ConTag
          -> ConDecl GhcRn
          -> TcM [DataCon]

tcConDecl :: NewOrData
-> DataDeclInfo
-> TyCon
-> [TyConBinder]
-> Type
-> NameEnv Arity
-> ConDecl GhcRn
-> TcM [DataCon]
tcConDecl NewOrData
new_or_data DataDeclInfo
dd_info TyCon
rep_tycon [TyConBinder]
tc_bndrs Type
res_kind NameEnv Arity
tag_map
          (ConDeclH98 { con_name :: forall pass. ConDecl pass -> LIdP pass
con_name = lname :: LIdP GhcRn
lname@(L SrcSpanAnnN
_ Name
name)
                      , con_ex_tvs :: forall pass. ConDecl pass -> [LHsTyVarBndr Specificity pass]
con_ex_tvs = [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms
                      , con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (LHsContext GhcRn)
hs_ctxt
                      , con_args :: forall pass. ConDecl pass -> HsConDeclH98Details pass
con_args = HsConDeclH98Details GhcRn
hs_args })
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([GenLocated SrcSpanAnnN Name] -> SDoc
dataConCtxt [LIdP GhcRn
lname]) forall a b. (a -> b) -> a -> b
$
    do { -- NB: the tyvars from the declaration header are in scope

         -- Get hold of the existential type variables
         -- e.g. data T a = forall k (b::k) f. MkT a (f b)
         -- Here tc_bndrs = {a}
         --      hs_qvars = HsQTvs { hsq_implicit = {k}
         --                        , hsq_explicit = {f,b} }

       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 1" ([SDoc] -> SDoc
vcat [ forall a. Outputable a => a -> SDoc
ppr Name
name, forall a. Outputable a => a -> SDoc
ppr [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms ])

       ; (TcLevel
tclvl, WantedConstraints
wanted, ([VarBndr TyVar Specificity]
exp_tvbndrs, ([Type]
ctxt, [Scaled Type]
arg_tys, [FieldLabel]
field_lbls, [HsSrcBang]
stricts)))
           <- forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"tcConDecl:H98"  forall a b. (a -> b) -> a -> b
$
              forall flag a.
OutputableBndrFlag flag 'Renamed =>
[LHsTyVarBndr flag GhcRn] -> TcM a -> TcM ([VarBndr TyVar flag], a)
tcExplicitTKBndrs [LHsTyVarBndr Specificity GhcRn]
explicit_tkv_nms            forall a b. (a -> b) -> a -> b
$
              do { [Type]
ctxt <- Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
hs_ctxt
                 ; let exp_kind :: ContextKind
exp_kind = NewOrData -> Type -> ContextKind
getArgExpKind NewOrData
new_or_data Type
res_kind
                 ; [(Scaled Type, HsSrcBang)]
btys <- ContextKind
-> HsConDeclH98Details GhcRn -> TcM [(Scaled Type, HsSrcBang)]
tcConH98Args ContextKind
exp_kind HsConDeclH98Details GhcRn
hs_args
                 ; [FieldLabel]
field_lbls <- Name -> RnM [FieldLabel]
lookupConstructorFields Name
name
                 ; let ([Scaled Type]
arg_tys, [HsSrcBang]
stricts) = forall a b. [(a, b)] -> ([a], [b])
unzip [(Scaled Type, HsSrcBang)]
btys
                 ; forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
ctxt, [Scaled Type]
arg_tys, [FieldLabel]
field_lbls, [HsSrcBang]
stricts)
                 }


       ; let tc_tvs :: [TyVar]
tc_tvs   = forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tc_bndrs
             fake_ty :: Type
fake_ty  = [TyVar] -> Type -> Type
mkSpecForAllTys  [TyVar]
tc_tvs      forall a b. (a -> b) -> a -> b
$
                        [VarBndr TyVar Specificity] -> Type -> Type
mkInvisForAllTys [VarBndr TyVar Specificity]
exp_tvbndrs forall a b. (a -> b) -> a -> b
$
                        [Type] -> Type -> Type
mkPhiTy [Type]
ctxt forall a b. (a -> b) -> a -> b
$
                        [Scaled Type] -> Type -> Type
mkVisFunTys [Scaled Type]
arg_tys forall a b. (a -> b) -> a -> b
$
                        Type
unitTy
             -- That type is a lie, of course. (It shouldn't end in ()!)
             -- And we could construct a proper result type from the info
             -- at hand. But the result would mention only the univ_tvs,
             -- and so it just creates more work to do it right. Really,
             -- we're only doing this to find the right kind variables to
             -- quantify over, and this type is fine for that purpose.

         -- exp_tvbndrs have explicit, user-written binding sites
         -- the kvs below are those kind variables entirely unmentioned by the user
         --   and discovered only by generalization

       ; [TyVar]
kvs <- Type -> TcM [TyVar]
kindGeneralizeAll Type
fake_ty

       ; let skol_tvs :: [TyVar]
skol_tvs = [TyVar]
tc_tvs forall a. [a] -> [a] -> [a]
++ [TyVar]
kvs forall a. [a] -> [a] -> [a]
++ forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TyVar Specificity]
exp_tvbndrs
       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcRn ()
reportUnsolvedEqualities SkolemInfo
skol_info [TyVar]
skol_tvs TcLevel
tclvl WantedConstraints
wanted
             -- The skol_info claims that all the variables are bound
             -- by the data constructor decl, whereas actually the
             -- univ_tvs are bound by the data type decl itself.  It
             -- would be better to have a doubly-nested implication.
             -- But that just doesn't seem worth it.
             -- See test dependent/should_fail/T13780a

       -- Zonk to Types
       ; ZonkEnv
ze                  <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; (ZonkEnv
ze, [TyVar]
qkvs)          <- ZonkEnv -> [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrsX              ZonkEnv
ze [TyVar]
kvs
       ; (ZonkEnv
ze, [VarBndr TyVar Specificity]
user_qtvbndrs) <- forall vis.
ZonkEnv
-> [VarBndr TyVar vis] -> TcM (ZonkEnv, [VarBndr TyVar vis])
zonkTyVarBindersX         ZonkEnv
ze [VarBndr TyVar Specificity]
exp_tvbndrs
       ; [Scaled Type]
arg_tys             <- ZonkEnv -> [Scaled Type] -> TcM [Scaled Type]
zonkScaledTcTypesToTypesX ZonkEnv
ze [Scaled Type]
arg_tys
       ; [Type]
ctxt                <- ZonkEnv -> [Type] -> TcM [Type]
zonkTcTypesToTypesX       ZonkEnv
ze [Type]
ctxt

       -- Can't print univ_tvs, arg_tys etc, because we are inside the knot here
       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 2" (forall a. Outputable a => a -> SDoc
ppr Name
name SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [FieldLabel]
field_lbls)
       ; let univ_tvbs :: [VarBndr TyVar Specificity]
univ_tvbs = [TyConBinder] -> [VarBndr TyVar Specificity]
tyConInvisTVBinders [TyConBinder]
tc_bndrs
             ex_tvbs :: [VarBndr TyVar Specificity]
ex_tvbs   = forall vis. vis -> [TyVar] -> [VarBndr TyVar vis]
mkTyVarBinders Specificity
InferredSpec [TyVar]
qkvs forall a. [a] -> [a] -> [a]
++ [VarBndr TyVar Specificity]
user_qtvbndrs
             ex_tvs :: [TyVar]
ex_tvs    = forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TyVar Specificity]
ex_tvbs
                -- For H98 datatypes, the user-written tyvar binders are precisely
                -- the universals followed by the existentials.
                -- See Note [DataCon user type variable binders] in GHC.Core.DataCon.
             user_tvbs :: [VarBndr TyVar Specificity]
user_tvbs = [VarBndr TyVar Specificity]
univ_tvbs forall a. [a] -> [a] -> [a]
++ [VarBndr TyVar Specificity]
ex_tvbs
             user_res_ty :: Type
user_res_ty = DataDeclInfo -> TyCon -> [TyConBinder] -> Type
mkDDHeaderTy DataDeclInfo
dd_info TyCon
rep_tycon [TyConBinder]
tc_bndrs

       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 2" (forall a. Outputable a => a -> SDoc
ppr Name
name)
       ; Bool
is_infix <- Name
-> HsConDeclH98Details GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) Bool
tcConIsInfixH98 Name
name HsConDeclH98Details GhcRn
hs_args
       ; Name
rep_nm   <- forall gbl lcl. Name -> TcRnIf gbl lcl Name
newTyConRepName Name
name
       ; FamInstEnvs
fam_envs <- TcM FamInstEnvs
tcGetFamInstEnvs
       ; DataCon
dc <- forall m n.
FamInstEnvs
-> Name
-> Bool
-> Name
-> [HsSrcBang]
-> Maybe [HsImplBang]
-> [FieldLabel]
-> [TyVar]
-> [TyVar]
-> [VarBndr TyVar Specificity]
-> [EqSpec]
-> [Type]
-> [Scaled Type]
-> Type
-> TyCon
-> NameEnv Arity
-> TcRnIf m n DataCon
buildDataCon FamInstEnvs
fam_envs Name
name Bool
is_infix Name
rep_nm
                            [HsSrcBang]
stricts forall a. Maybe a
Nothing [FieldLabel]
field_lbls
                            [TyVar]
tc_tvs [TyVar]
ex_tvs [VarBndr TyVar Specificity]
user_tvbs
                            [{- no eq_preds -}] [Type]
ctxt [Scaled Type]
arg_tys
                            Type
user_res_ty TyCon
rep_tycon NameEnv Arity
tag_map
                  -- NB:  we put data_tc, the type constructor gotten from the
                  --      constructor type signature into the data constructor;
                  --      that way checkValidDataCon can complain if it's wrong.

       ; forall (m :: * -> *) a. Monad m => a -> m a
return [DataCon
dc] }
  where
    skol_info :: SkolemInfo
skol_info = Name -> SkolemInfo
DataConSkol Name
name

tcConDecl NewOrData
new_or_data DataDeclInfo
dd_info TyCon
rep_tycon [TyConBinder]
tc_bndrs Type
_res_kind NameEnv Arity
tag_map
  -- NB: don't use res_kind here, as it's ill-scoped. Instead,
  -- we get the res_kind by typechecking the result type.
          (ConDeclGADT { con_names :: forall pass. ConDecl pass -> [LIdP pass]
con_names = [LIdP GhcRn]
names
                       , con_bndrs :: forall pass. ConDecl pass -> XRec pass (HsOuterSigTyVarBndrs pass)
con_bndrs = L SrcSpanAnnA
_ HsOuterSigTyVarBndrs GhcRn
outer_hs_bndrs
                       , con_mb_cxt :: forall pass. ConDecl pass -> Maybe (LHsContext pass)
con_mb_cxt = Maybe (LHsContext GhcRn)
cxt, con_g_args :: forall pass. ConDecl pass -> HsConDeclGADTDetails pass
con_g_args = HsConDeclGADTDetails GhcRn
hs_args
                       , con_res_ty :: forall pass. ConDecl pass -> LHsType pass
con_res_ty = LHsKind GhcRn
hs_res_ty })
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([GenLocated SrcSpanAnnN Name] -> SDoc
dataConCtxt [LIdP GhcRn]
names) forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 1 gadt" (forall a. Outputable a => a -> SDoc
ppr [LIdP GhcRn]
names)
       ; let (L SrcSpanAnnN
_ Name
name : [LIdP GhcRn]
_) = [LIdP GhcRn]
names

       ; (TcLevel
tclvl, WantedConstraints
wanted, (HsOuterSigTyVarBndrs GhcTc
outer_bndrs, ([Type]
ctxt, [Scaled Type]
arg_tys, Type
res_ty, [FieldLabel]
field_lbls, [HsSrcBang]
stricts)))
           <- forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"tcConDecl:GADT" forall a b. (a -> b) -> a -> b
$
              forall flag a.
OutputableBndrFlag flag 'Renamed =>
SkolemInfo
-> HsOuterTyVarBndrs flag GhcRn
-> TcM a
-> TcM (HsOuterTyVarBndrs flag GhcTc, a)
tcOuterTKBndrs SkolemInfo
skol_info HsOuterSigTyVarBndrs GhcRn
outer_hs_bndrs       forall a b. (a -> b) -> a -> b
$
              do { [Type]
ctxt <- Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsContext Maybe (LHsContext GhcRn)
cxt
                 ; (Type
res_ty, Type
res_kind) <- LHsKind GhcRn -> TcM (Type, Type)
tcInferLHsTypeKind LHsKind GhcRn
hs_res_ty
                         -- See Note [GADT return kinds]

                 -- For data instances (only), ensure that the return type,
                 -- res_ty, is a substitution instance of the header.
                 -- See Note [GADT return types]
                 ; case DataDeclInfo
dd_info of
                      DataDeclInfo
DDataType -> forall (m :: * -> *) a. Monad m => a -> m a
return ()
                      DDataInstance Type
hdr_ty ->
                        do { (TCvSubst
subst, [TyVar]
_meta_tvs) <- [TyVar] -> TcM (TCvSubst, [TyVar])
newMetaTyVars (forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tc_bndrs)
                           ; let head_shape :: Type
head_shape = HasCallStack => TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
hdr_ty
                           ; forall a. TcM a -> TcRn ()
discardResult forall a b. (a -> b) -> a -> b
$
                             forall r. TcM r -> TcM r
popErrCtxt forall a b. (a -> b) -> a -> b
$  -- Drop dataConCtxt
                             forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([GenLocated SrcSpanAnnN Name] -> SDoc
dataConResCtxt [LIdP GhcRn]
names) forall a b. (a -> b) -> a -> b
$
                             Maybe SDoc -> Type -> Type -> TcM Coercion
unifyType forall a. Maybe a
Nothing Type
res_ty Type
head_shape }

                   -- See Note [Datatype return kinds]
                 ; let exp_kind :: ContextKind
exp_kind = NewOrData -> Type -> ContextKind
getArgExpKind NewOrData
new_or_data Type
res_kind
                 ; [(Scaled Type, HsSrcBang)]
btys <- ContextKind
-> HsConDeclGADTDetails GhcRn -> TcM [(Scaled Type, HsSrcBang)]
tcConGADTArgs ContextKind
exp_kind HsConDeclGADTDetails GhcRn
hs_args

                 ; let ([Scaled Type]
arg_tys, [HsSrcBang]
stricts) = forall a b. [(a, b)] -> ([a], [b])
unzip [(Scaled Type, HsSrcBang)]
btys
                 ; [FieldLabel]
field_lbls <- Name -> RnM [FieldLabel]
lookupConstructorFields Name
name
                 ; forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
ctxt, [Scaled Type]
arg_tys, Type
res_ty, [FieldLabel]
field_lbls, [HsSrcBang]
stricts)
                 }

       ; [VarBndr TyVar Specificity]
outer_tv_bndrs <- HsOuterSigTyVarBndrs GhcTc -> TcM [VarBndr TyVar Specificity]
scopedSortOuter HsOuterSigTyVarBndrs GhcTc
outer_bndrs

       ; [TyVar]
tkvs <- Type -> TcM [TyVar]
kindGeneralizeAll ([VarBndr TyVar Specificity] -> Type -> Type
mkInvisForAllTys [VarBndr TyVar Specificity]
outer_tv_bndrs forall a b. (a -> b) -> a -> b
$
                                    [Type] -> Type -> Type
mkPhiTy [Type]
ctxt forall a b. (a -> b) -> a -> b
$
                                    [Scaled Type] -> Type -> Type
mkVisFunTys [Scaled Type]
arg_tys forall a b. (a -> b) -> a -> b
$
                                    Type
res_ty)
       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl:GADT" (forall a. Outputable a => a -> SDoc
ppr [LIdP GhcRn]
names SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr Type
res_ty SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [TyVar]
tkvs)
       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcRn ()
reportUnsolvedEqualities SkolemInfo
skol_info [TyVar]
tkvs TcLevel
tclvl WantedConstraints
wanted

       ; let tvbndrs :: [VarBndr TyVar Specificity]
tvbndrs =  forall vis. vis -> [TyVar] -> [VarBndr TyVar vis]
mkTyVarBinders Specificity
InferredSpec [TyVar]
tkvs forall a. [a] -> [a] -> [a]
++ [VarBndr TyVar Specificity]
outer_tv_bndrs

             -- Zonk to Types
       ; ZonkEnv
ze            <- ZonkFlexi -> TcM ZonkEnv
mkEmptyZonkEnv ZonkFlexi
NoFlexi
       ; (ZonkEnv
ze, [VarBndr TyVar Specificity]
tvbndrs) <- forall vis.
ZonkEnv
-> [VarBndr TyVar vis] -> TcM (ZonkEnv, [VarBndr TyVar vis])
zonkTyVarBindersX         ZonkEnv
ze [VarBndr TyVar Specificity]
tvbndrs
       ; [Scaled Type]
arg_tys       <- ZonkEnv -> [Scaled Type] -> TcM [Scaled Type]
zonkScaledTcTypesToTypesX ZonkEnv
ze [Scaled Type]
arg_tys
       ; [Type]
ctxt          <- ZonkEnv -> [Type] -> TcM [Type]
zonkTcTypesToTypesX       ZonkEnv
ze [Type]
ctxt
       ; Type
res_ty        <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX         ZonkEnv
ze Type
res_ty

       ; let res_tmpl :: Type
res_tmpl = DataDeclInfo -> TyCon -> [TyConBinder] -> Type
mkDDHeaderTy DataDeclInfo
dd_info TyCon
rep_tycon [TyConBinder]
tc_bndrs
             ([TyVar]
univ_tvs, [TyVar]
ex_tvs, [VarBndr TyVar Specificity]
tvbndrs', [EqSpec]
eq_preds, TCvSubst
arg_subst)
               = [TyConBinder]
-> Type
-> [VarBndr TyVar Specificity]
-> Type
-> ([TyVar], [TyVar], [VarBndr TyVar Specificity], [EqSpec],
    TCvSubst)
rejigConRes [TyConBinder]
tc_bndrs Type
res_tmpl [VarBndr TyVar Specificity]
tvbndrs Type
res_ty
             -- See Note [rejigConRes]

             ctxt' :: [Type]
ctxt'      = HasCallStack => TCvSubst -> [Type] -> [Type]
substTys TCvSubst
arg_subst [Type]
ctxt
             arg_tys' :: [Scaled Type]
arg_tys'   = HasCallStack => TCvSubst -> [Scaled Type] -> [Scaled Type]
substScaledTys TCvSubst
arg_subst [Scaled Type]
arg_tys
             res_ty' :: Type
res_ty'    = HasCallStack => TCvSubst -> Type -> Type
substTy  TCvSubst
arg_subst Type
res_ty

       -- Can't print univ_tvs, arg_tys etc, because we are inside the knot here
       ; String -> SDoc -> TcRn ()
traceTc String
"tcConDecl 2" (forall a. Outputable a => a -> SDoc
ppr [LIdP GhcRn]
names SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [FieldLabel]
field_lbls)
       ; FamInstEnvs
fam_envs <- TcM FamInstEnvs
tcGetFamInstEnvs
       ; let
           buildOneDataCon :: GenLocated SrcSpanAnnN Name
-> IOEnv (Env TcGblEnv TcLclEnv) DataCon
buildOneDataCon (L SrcSpanAnnN
_ Name
name) = do
             { Bool
is_infix <- Name
-> HsConDeclGADTDetails GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) Bool
tcConIsInfixGADT Name
name HsConDeclGADTDetails GhcRn
hs_args
             ; Name
rep_nm   <- forall gbl lcl. Name -> TcRnIf gbl lcl Name
newTyConRepName Name
name

             ; forall m n.
FamInstEnvs
-> Name
-> Bool
-> Name
-> [HsSrcBang]
-> Maybe [HsImplBang]
-> [FieldLabel]
-> [TyVar]
-> [TyVar]
-> [VarBndr TyVar Specificity]
-> [EqSpec]
-> [Type]
-> [Scaled Type]
-> Type
-> TyCon
-> NameEnv Arity
-> TcRnIf m n DataCon
buildDataCon FamInstEnvs
fam_envs Name
name Bool
is_infix
                            Name
rep_nm
                            [HsSrcBang]
stricts forall a. Maybe a
Nothing [FieldLabel]
field_lbls
                            [TyVar]
univ_tvs [TyVar]
ex_tvs [VarBndr TyVar Specificity]
tvbndrs' [EqSpec]
eq_preds
                            [Type]
ctxt' [Scaled Type]
arg_tys' Type
res_ty' TyCon
rep_tycon NameEnv Arity
tag_map
                  -- NB:  we put data_tc, the type constructor gotten from the
                  --      constructor type signature into the data constructor;
                  --      that way checkValidDataCon can complain if it's wrong.
             }
       ; forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM GenLocated SrcSpanAnnN Name
-> IOEnv (Env TcGblEnv TcLclEnv) DataCon
buildOneDataCon [LIdP GhcRn]
names }
  where
    skol_info :: SkolemInfo
skol_info = Name -> SkolemInfo
DataConSkol (forall l e. GenLocated l e -> e
unLoc (forall a. [a] -> a
head [LIdP GhcRn]
names))

{- Note [GADT return types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
  data family T :: forall k. k -> Type
  data instance T (a :: Type) where
    MkT :: forall b. T b

What kind does `b` have in the signature for MkT?
Since the return type must be an instance of the type in the header,
we must have (b :: Type), but you can't tell that by looking only at
the type of the data constructor; you have to look at the header too.
If you wrote it out fully, it'd look like
  data instance T @Type (a :: Type) where
    MkT :: forall (b::Type). T @Type b

We could reject the program, and expect the user to add kind
annotations to `MkT` to restrict the signature.  But an easy and
helpful alternative is this: simply instantiate the type from the
header with fresh unification variables, and unify with the return
type of `MkT`. That will force `b` to have kind `Type`.  See #8707
and #14111.

Wrikles
* At first sight it looks as though this would completely subsume the
  return-type check in checkValidDataCon.  But it does not. Suppose we
  have
     data instance T [a] where
        MkT :: T (F (Maybe a))

  where F is a type function.  Then maybe (F (Maybe a)) evaluates to
  [a], so unifyType will succeed.  But we discard the coercion
  returned by unifyType; and we really don't want to accept this
  program.  The check in checkValidDataCon will, however, reject it.
  TL;DR: keep the check in checkValidDataCon.

* Consider a data type, rather than a data instance, declaration
     data S a where { MkS :: b -> S [b]  }
  In tcConDecl, S is knot-tied, so we don't want to unify (S alpha)
  with (S [b]). To put it another way, unifyType should never see a
  TcTycon.  Simple solution: do *not* do the extra unifyType for
  data types (DDataType) only for data instances (DDataInstance); in
  the latter the family constructor is not knot-tied so there is no
  problem.

* Consider this (from an earlier form of GHC itself):

     data Pass = Parsed | ...
     data GhcPass (c :: Pass) where
       GhcPs :: GhcPs
       ...
     type GhcPs   = GhcPass 'Parsed

   Now GhcPs and GhcPass are mutually recursive. If we did unifyType
   for datatypes like GhcPass, we would not be able to expand the type
   synonym (it'd still be a TcTyCon).  So again, we don't do unifyType
   for data types; we leave it to checkValidDataCon.

   We /do/ perform the unifyType for data /instances/, but a data
   instance doesn't declare a new (user-visible) type constructor, so
   there is no mutual recursion with type synonyms to worry about.
   All good.

   TL;DR we do support mutual recursion between type synonyms and
   data type/instance declarations, as above.

Note [GADT return kinds]
~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   type family Star where Star = Type
   data T :: Type where
      MkT :: Int -> T

If, for some stupid reason, tcInferLHsTypeKind on the return type of
MkT returned (T |> ax, Star), then the return-type check in
checkValidDataCon would reject the decl (although of course there is
nothing wrong with it).  We are implicitly requiring tha
tcInferLHsTypeKind doesn't any gratuitous top-level casts.
-}

-- | Produce an "expected kind" for the arguments of a data/newtype.
-- If the declaration is indeed for a newtype,
-- then this expected kind will be the kind provided. Otherwise,
-- it is OpenKind for datatypes and liftedTypeKind.
-- Why do we not check for -XUnliftedNewtypes? See point <Error Messages>
-- in Note [Implementation of UnliftedNewtypes]
getArgExpKind :: NewOrData -> Kind -> ContextKind
getArgExpKind :: NewOrData -> Type -> ContextKind
getArgExpKind NewOrData
NewType Type
res_ki = Type -> ContextKind
TheKind Type
res_ki
getArgExpKind NewOrData
DataType Type
_     = ContextKind
OpenKind

tcConIsInfixH98 :: Name
             -> HsConDeclH98Details GhcRn
             -> TcM Bool
tcConIsInfixH98 :: Name
-> HsConDeclH98Details GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) Bool
tcConIsInfixH98 Name
_   HsConDeclH98Details GhcRn
details
  = case HsConDeclH98Details GhcRn
details of
           InfixCon{}  -> forall (m :: * -> *) a. Monad m => a -> m a
return Bool
True
           RecCon{}    -> forall (m :: * -> *) a. Monad m => a -> m a
return Bool
False
           PrefixCon{} -> forall (m :: * -> *) a. Monad m => a -> m a
return Bool
False

tcConIsInfixGADT :: Name
             -> HsConDeclGADTDetails GhcRn
             -> TcM Bool
tcConIsInfixGADT :: Name
-> HsConDeclGADTDetails GhcRn -> IOEnv (Env TcGblEnv TcLclEnv) Bool
tcConIsInfixGADT Name
con HsConDeclGADTDetails GhcRn
details
  = case HsConDeclGADTDetails GhcRn
details of
           RecConGADT{} -> forall (m :: * -> *) a. Monad m => a -> m a
return Bool
False
           PrefixConGADT [HsScaled GhcRn (LHsKind GhcRn)]
arg_tys       -- See Note [Infix GADT constructors]
               | OccName -> Bool
isSymOcc (forall a. NamedThing a => a -> OccName
getOccName Name
con)
               , [GenLocated SrcSpanAnnA (HsType GhcRn)
_ty1,GenLocated SrcSpanAnnA (HsType GhcRn)
_ty2] <- forall a b. (a -> b) -> [a] -> [b]
map forall pass a. HsScaled pass a -> a
hsScaledThing [HsScaled GhcRn (LHsKind GhcRn)]
arg_tys
                  -> do { FixityEnv
fix_env <- TcRn FixityEnv
getFixityEnv
                        ; forall (m :: * -> *) a. Monad m => a -> m a
return (Name
con forall a. Name -> NameEnv a -> Bool
`elemNameEnv` FixityEnv
fix_env) }
               | Bool
otherwise -> forall (m :: * -> *) a. Monad m => a -> m a
return Bool
False

tcConH98Args :: ContextKind  -- expected kind of arguments
                             -- always OpenKind for datatypes, but unlifted newtypes
                             -- might have a specific kind
             -> HsConDeclH98Details GhcRn
             -> TcM [(Scaled TcType, HsSrcBang)]
tcConH98Args :: ContextKind
-> HsConDeclH98Details GhcRn -> TcM [(Scaled Type, HsSrcBang)]
tcConH98Args ContextKind
exp_kind (PrefixCon [Void]
_ [HsScaled GhcRn (LHsKind GhcRn)]
btys)
  = forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (ContextKind
-> HsScaled GhcRn (LHsKind GhcRn) -> TcM (Scaled Type, HsSrcBang)
tcConArg ContextKind
exp_kind) [HsScaled GhcRn (LHsKind GhcRn)]
btys
tcConH98Args ContextKind
exp_kind (InfixCon HsScaled GhcRn (LHsKind GhcRn)
bty1 HsScaled GhcRn (LHsKind GhcRn)
bty2)
  = do { (Scaled Type, HsSrcBang)
bty1' <- ContextKind
-> HsScaled GhcRn (LHsKind GhcRn) -> TcM (Scaled Type, HsSrcBang)
tcConArg ContextKind
exp_kind HsScaled GhcRn (LHsKind GhcRn)
bty1
       ; (Scaled Type, HsSrcBang)
bty2' <- ContextKind
-> HsScaled GhcRn (LHsKind GhcRn) -> TcM (Scaled Type, HsSrcBang)
tcConArg ContextKind
exp_kind HsScaled GhcRn (LHsKind GhcRn)
bty2
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [(Scaled Type, HsSrcBang)
bty1', (Scaled Type, HsSrcBang)
bty2'] }
tcConH98Args ContextKind
exp_kind (RecCon XRec GhcRn [LConDeclField GhcRn]
fields)
  = ContextKind
-> LocatedL [LConDeclField GhcRn] -> TcM [(Scaled Type, HsSrcBang)]
tcRecConDeclFields ContextKind
exp_kind XRec GhcRn [LConDeclField GhcRn]
fields

tcConGADTArgs :: ContextKind  -- expected kind of arguments
                              -- always OpenKind for datatypes, but unlifted newtypes
                              -- might have a specific kind
              -> HsConDeclGADTDetails GhcRn
              -> TcM [(Scaled TcType, HsSrcBang)]
tcConGADTArgs :: ContextKind
-> HsConDeclGADTDetails GhcRn -> TcM [(Scaled Type, HsSrcBang)]
tcConGADTArgs ContextKind
exp_kind (PrefixConGADT [HsScaled GhcRn (LHsKind GhcRn)]
btys)
  = forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (ContextKind
-> HsScaled GhcRn (LHsKind GhcRn) -> TcM (Scaled Type, HsSrcBang)
tcConArg ContextKind
exp_kind) [HsScaled GhcRn (LHsKind GhcRn)]
btys
tcConGADTArgs ContextKind
exp_kind (RecConGADT XRec GhcRn [LConDeclField GhcRn]
fields)
  = ContextKind
-> LocatedL [LConDeclField GhcRn] -> TcM [(Scaled Type, HsSrcBang)]
tcRecConDeclFields ContextKind
exp_kind XRec GhcRn [LConDeclField GhcRn]
fields

tcConArg :: ContextKind  -- expected kind for args; always OpenKind for datatypes,
                         -- but might be an unlifted type with UnliftedNewtypes
         -> HsScaled GhcRn (LHsType GhcRn) -> TcM (Scaled TcType, HsSrcBang)
tcConArg :: ContextKind
-> HsScaled GhcRn (LHsKind GhcRn) -> TcM (Scaled Type, HsSrcBang)
tcConArg ContextKind
exp_kind (HsScaled HsArrow GhcRn
w LHsKind GhcRn
bty)
  = do  { String -> SDoc -> TcRn ()
traceTc String
"tcConArg 1" (forall a. Outputable a => a -> SDoc
ppr LHsKind GhcRn
bty)
        ; Type
arg_ty <- LHsKind GhcRn -> ContextKind -> TcM Type
tcCheckLHsType (forall (p :: Pass). LHsType (GhcPass p) -> LHsType (GhcPass p)
getBangType LHsKind GhcRn
bty) ContextKind
exp_kind
        ; Type
w' <- HsArrow GhcRn -> TcM Type
tcDataConMult HsArrow GhcRn
w
        ; String -> SDoc -> TcRn ()
traceTc String
"tcConArg 2" (forall a. Outputable a => a -> SDoc
ppr LHsKind GhcRn
bty)
        ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall a. Type -> a -> Scaled a
Scaled Type
w' Type
arg_ty, forall (p :: Pass). LHsType (GhcPass p) -> HsSrcBang
getBangStrictness LHsKind GhcRn
bty) }

tcRecConDeclFields :: ContextKind
                   -> LocatedL [LConDeclField GhcRn]
                   -> TcM [(Scaled TcType, HsSrcBang)]
tcRecConDeclFields :: ContextKind
-> LocatedL [LConDeclField GhcRn] -> TcM [(Scaled Type, HsSrcBang)]
tcRecConDeclFields ContextKind
exp_kind LocatedL [LConDeclField GhcRn]
fields
  = forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (ContextKind
-> HsScaled GhcRn (LHsKind GhcRn) -> TcM (Scaled Type, HsSrcBang)
tcConArg ContextKind
exp_kind) [HsScaled GhcRn (LHsKind GhcRn)]
btys
  where
    -- We need a one-to-one mapping from field_names to btys
    combined :: [([XRec GhcRn (FieldOcc GhcRn)], HsScaled GhcRn (LHsKind GhcRn))]
combined = forall a b. (a -> b) -> [a] -> [b]
map (\(L SrcSpanAnnA
_ ConDeclField GhcRn
f) -> (forall pass. ConDeclField pass -> [LFieldOcc pass]
cd_fld_names ConDeclField GhcRn
f,forall a pass. a -> HsScaled pass a
hsLinear (forall pass. ConDeclField pass -> LBangType pass
cd_fld_type ConDeclField GhcRn
f)))
                   (forall l e. GenLocated l e -> e
unLoc LocatedL [LConDeclField GhcRn]
fields)
    explode :: ([a], b) -> [(a, b)]
explode ([a]
ns,b
ty) = forall a b. [a] -> [b] -> [(a, b)]
zip [a]
ns (forall a. a -> [a]
repeat b
ty)
    exploded :: [(XRec GhcRn (FieldOcc GhcRn), HsScaled GhcRn (LHsKind GhcRn))]
exploded = forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
concatMap forall {a} {b}. ([a], b) -> [(a, b)]
explode [([XRec GhcRn (FieldOcc GhcRn)], HsScaled GhcRn (LHsKind GhcRn))]
combined
    ([XRec GhcRn (FieldOcc GhcRn)]
_,[HsScaled GhcRn (LHsKind GhcRn)]
btys) = forall a b. [(a, b)] -> ([a], [b])
unzip [(XRec GhcRn (FieldOcc GhcRn), HsScaled GhcRn (LHsKind GhcRn))]
exploded

tcDataConMult :: HsArrow GhcRn -> TcM Mult
tcDataConMult :: HsArrow GhcRn -> TcM Type
tcDataConMult arr :: HsArrow GhcRn
arr@(HsUnrestrictedArrow IsUnicodeSyntax
_) = do
  -- See Note [Function arrows in GADT constructors]
  Bool
linearEnabled <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.LinearTypes
  if Bool
linearEnabled then HsArrow GhcRn -> TcM Type
tcMult HsArrow GhcRn
arr else forall (m :: * -> *) a. Monad m => a -> m a
return Type
oneDataConTy
tcDataConMult HsArrow GhcRn
arr = HsArrow GhcRn -> TcM Type
tcMult HsArrow GhcRn
arr

{-
Note [Function arrows in GADT constructors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In the absence of -XLinearTypes, we always interpret function arrows
in GADT constructor types as linear, even if the user wrote an
unrestricted arrow. See the "Without -XLinearTypes" section of the
linear types GHC proposal (#111). We opt to do this in the
typechecker, and not in an earlier pass, to ensure that the AST
matches what the user wrote (#18791).

Note [Infix GADT constructors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We do not currently have syntax to declare an infix constructor in GADT syntax,
but it makes a (small) difference to the Show instance.  So as a slightly
ad-hoc solution, we regard a GADT data constructor as infix if
  a) it is an operator symbol
  b) it has two arguments
  c) there is a fixity declaration for it
For example:
   infix 6 (:--:)
   data T a where
     (:--:) :: t1 -> t2 -> T Int


Note [rejigConRes]
~~~~~~~~~~~~~~~~~~
There is a delicacy around checking the return types of a datacon. The
central problem is dealing with a declaration like

  data T a where
    MkT :: T a -> Q a

Note that the return type of MkT is totally bogus. When creating the T
tycon, we also need to create the MkT datacon, which must have a "rejigged"
return type. That is, the MkT datacon's type must be transformed to have
a uniform return type with explicit coercions for GADT-like type parameters.
This rejigging is what rejigConRes does. The problem is, though, that checking
that the return type is appropriate is much easier when done over *Type*,
not *HsType*, and doing a call to tcMatchTy will loop because T isn't fully
defined yet.

So, we want to make rejigConRes lazy and then check the validity of
the return type in checkValidDataCon.  To do this we /always/ return a
6-tuple from rejigConRes (so that we can compute the return type from it, which
checkValidDataCon needs), but the first three fields may be bogus if
the return type isn't valid (the last equation for rejigConRes).

This is better than an earlier solution which reduced the number of
errors reported in one pass.  See #7175, and #10836.
-}

-- Example
--   data instance T (b,c) where
--      TI :: forall e. e -> T (e,e)
--
-- The representation tycon looks like this:
--   data :R7T b c where
--      TI :: forall b1 c1. (b1 ~ c1) => b1 -> :R7T b1 c1
-- In this case orig_res_ty = T (e,e)

rejigConRes :: [KnotTied TyConBinder]  -- Template for result type; e.g.
            -> KnotTied Type           -- data instance T [a] b c ...
                                       --      gives template ([a,b,c], T [a] b c)
            -> [InvisTVBinder]    -- The constructor's type variables (both inferred and user-written)
            -> KnotTied Type      -- res_ty
            -> ([TyVar],          -- Universal
                [TyVar],          -- Existential (distinct OccNames from univs)
                [InvisTVBinder],  -- The constructor's rejigged, user-written
                                  -- type variables
                [EqSpec],         -- Equality predicates
                TCvSubst)         -- Substitution to apply to argument types
        -- We don't check that the TyCon given in the ResTy is
        -- the same as the parent tycon, because checkValidDataCon will do it
-- NB: All arguments may potentially be knot-tied
rejigConRes :: [TyConBinder]
-> Type
-> [VarBndr TyVar Specificity]
-> Type
-> ([TyVar], [TyVar], [VarBndr TyVar Specificity], [EqSpec],
    TCvSubst)
rejigConRes [TyConBinder]
tc_tvbndrs Type
res_tmpl [VarBndr TyVar Specificity]
dc_tvbndrs Type
res_ty
        -- E.g.  data T [a] b c where
        --         MkT :: forall x y z. T [(x,y)] z z
        -- The {a,b,c} are the tc_tvs, and the {x,y,z} are the dc_tvs
        --     (NB: unlike the H98 case, the dc_tvs are not all existential)
        -- Then we generate
        --      Univ tyvars     Eq-spec
        --          a              a~(x,y)
        --          b              b~z
        --          z
        -- Existentials are the leftover type vars: [x,y]
        -- The user-written type variables are what is listed in the forall:
        --   [x, y, z] (all specified). We must rejig these as well.
        --   See Note [DataCon user type variable binders] in GHC.Core.DataCon.
        -- So we return ( [a,b,z], [x,y]
        --              , [], [x,y,z]
        --              , [a~(x,y),b~z], <arg-subst> )
  | Just TCvSubst
subst <- Type -> Type -> Maybe TCvSubst
tcMatchTy Type
res_tmpl Type
res_ty
  = let ([TyVar]
univ_tvs, [EqSpec]
raw_eqs, TCvSubst
kind_subst) = [TyVar] -> [TyVar] -> TCvSubst -> ([TyVar], [EqSpec], TCvSubst)
mkGADTVars [TyVar]
tc_tvs [TyVar]
dc_tvs TCvSubst
subst
        raw_ex_tvs :: [TyVar]
raw_ex_tvs = [TyVar]
dc_tvs forall a. Ord a => [a] -> [a] -> [a]
`minusList` [TyVar]
univ_tvs
        (TCvSubst
arg_subst, [TyVar]
substed_ex_tvs) = HasCallStack => TCvSubst -> [TyVar] -> (TCvSubst, [TyVar])
substTyVarBndrs TCvSubst
kind_subst [TyVar]
raw_ex_tvs

        -- After rejigging the existential tyvars, the resulting substitution
        -- gives us exactly what we need to rejig the user-written tyvars,
        -- since the dcUserTyVarBinders invariant guarantees that the
        -- substitution has *all* the tyvars in its domain.
        -- See Note [DataCon user type variable binders] in GHC.Core.DataCon.
        subst_user_tvs :: [VarBndr TyVar Specificity] -> [VarBndr TyVar Specificity]
subst_user_tvs  = forall var var' flag.
(var -> var') -> [VarBndr var flag] -> [VarBndr var' flag]
mapVarBndrs (String -> Type -> TyVar
getTyVar String
"rejigConRes" forall b c a. (b -> c) -> (a -> b) -> a -> c
. TCvSubst -> TyVar -> Type
substTyVar TCvSubst
arg_subst)
        substed_tvbndrs :: [VarBndr TyVar Specificity]
substed_tvbndrs = [VarBndr TyVar Specificity] -> [VarBndr TyVar Specificity]
subst_user_tvs [VarBndr TyVar Specificity]
dc_tvbndrs

        substed_eqs :: [EqSpec]
substed_eqs = forall a b. (a -> b) -> [a] -> [b]
map (TCvSubst -> EqSpec -> EqSpec
substEqSpec TCvSubst
arg_subst) [EqSpec]
raw_eqs
    in
    ([TyVar]
univ_tvs, [TyVar]
substed_ex_tvs, [VarBndr TyVar Specificity]
substed_tvbndrs, [EqSpec]
substed_eqs, TCvSubst
arg_subst)

  | Bool
otherwise
        -- If the return type of the data constructor doesn't match the parent
        -- type constructor, or the arity is wrong, the tcMatchTy will fail
        --    e.g   data T a b where
        --            T1 :: Maybe a   -- Wrong tycon
        --            T2 :: T [a]     -- Wrong arity
        -- We are detect that later, in checkValidDataCon, but meanwhile
        -- we must do *something*, not just crash.  So we do something simple
        -- albeit bogus, relying on checkValidDataCon to check the
        --  bad-result-type error before seeing that the other fields look odd
        -- See Note [rejigConRes]
  = ([TyVar]
tc_tvs, [TyVar]
dc_tvs forall a. Ord a => [a] -> [a] -> [a]
`minusList` [TyVar]
tc_tvs, [VarBndr TyVar Specificity]
dc_tvbndrs, [], TCvSubst
emptyTCvSubst)
  where
    dc_tvs :: [TyVar]
dc_tvs = forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [VarBndr TyVar Specificity]
dc_tvbndrs
    tc_tvs :: [TyVar]
tc_tvs = forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [TyConBinder]
tc_tvbndrs

{- Note [mkGADTVars]
~~~~~~~~~~~~~~~~~~~~
Running example:

data T (k1 :: *) (k2 :: *) (a :: k2) (b :: k2) where
  MkT :: forall (x1 : *) (y :: x1) (z :: *).
         T x1 * (Proxy (y :: x1), z) z

We need the rejigged type to be

  MkT :: forall (x1 :: *) (k2 :: *) (a :: k2) (b :: k2).
         forall (y :: x1) (z :: *).
         (k2 ~ *, a ~ (Proxy x1 y, z), b ~ z)
      => T x1 k2 a b

You might naively expect that z should become a universal tyvar,
not an existential. (After all, x1 becomes a universal tyvar.)
But z has kind * while b has kind k2, so the return type
   T x1 k2 a z
is ill-kinded.  Another way to say it is this: the universal
tyvars must have exactly the same kinds as the tyConTyVars.

So we need an existential tyvar and a heterogeneous equality
constraint. (The b ~ z is a bit redundant with the k2 ~ * that
comes before in that b ~ z implies k2 ~ *. I'm sure we could do
some analysis that could eliminate k2 ~ *. But we don't do this
yet.)

The data con signature has already been fully kind-checked.
The return type

  T x1 * (Proxy (y :: x1), z) z
becomes
  qtkvs    = [x1 :: *, y :: x1, z :: *]
  res_tmpl = T x1 * (Proxy x1 y, z) z

We start off by matching (T k1 k2 a b) with (T x1 * (Proxy x1 y, z) z). We
know this match will succeed because of the validity check (actually done
later, but laziness saves us -- see Note [rejigConRes]).
Thus, we get

  subst := { k1 |-> x1, k2 |-> *, a |-> (Proxy x1 y, z), b |-> z }

Now, we need to figure out what the GADT equalities should be. In this case,
we *don't* want (k1 ~ x1) to be a GADT equality: it should just be a
renaming. The others should be GADT equalities. We also need to make
sure that the universally-quantified variables of the datacon match up
with the tyvars of the tycon, as required for Core context well-formedness.
(This last bit is why we have to rejig at all!)

`choose` walks down the tycon tyvars, figuring out what to do with each one.
It carries two substitutions:
  - t_sub's domain is *template* or *tycon* tyvars, mapping them to variables
    mentioned in the datacon signature.
  - r_sub's domain is *result* tyvars, names written by the programmer in
    the datacon signature. The final rejigged type will use these names, but
    the subst is still needed because sometimes the printed name of these variables
    is different. (See choose_tv_name, below.)

Before explaining the details of `choose`, let's just look at its operation
on our example:

  choose [] [] {} {} [k1, k2, a, b]
  -->          -- first branch of `case` statement
  choose
    univs:    [x1 :: *]
    eq_spec:  []
    t_sub:    {k1 |-> x1}
    r_sub:    {x1 |-> x1}
    t_tvs:    [k2, a, b]
  -->          -- second branch of `case` statement
  choose
    univs:    [k2 :: *, x1 :: *]
    eq_spec:  [k2 ~ *]
    t_sub:    {k1 |-> x1, k2 |-> k2}
    r_sub:    {x1 |-> x1}
    t_tvs:    [a, b]
  -->          -- second branch of `case` statement
  choose
    univs:    [a :: k2, k2 :: *, x1 :: *]
    eq_spec:  [ a ~ (Proxy x1 y, z)
              , k2 ~ * ]
    t_sub:    {k1 |-> x1, k2 |-> k2, a |-> a}
    r_sub:    {x1 |-> x1}
    t_tvs:    [b]
  -->          -- second branch of `case` statement
  choose
    univs:    [b :: k2, a :: k2, k2 :: *, x1 :: *]
    eq_spec:  [ b ~ z
              , a ~ (Proxy x1 y, z)
              , k2 ~ * ]
    t_sub:    {k1 |-> x1, k2 |-> k2, a |-> a, b |-> z}
    r_sub:    {x1 |-> x1}
    t_tvs:    []
  -->          -- end of recursion
  ( [x1 :: *, k2 :: *, a :: k2, b :: k2]
  , [k2 ~ *, a ~ (Proxy x1 y, z), b ~ z]
  , {x1 |-> x1} )

`choose` looks up each tycon tyvar in the matching (it *must* be matched!).

* If it finds a bare result tyvar (the first branch of the `case`
  statement), it checks to make sure that the result tyvar isn't yet
  in the list of univ_tvs.  If it is in that list, then we have a
  repeated variable in the return type, and we in fact need a GADT
  equality.

* It then checks to make sure that the kind of the result tyvar
  matches the kind of the template tyvar. This check is what forces
  `z` to be existential, as it should be, explained above.

* Assuming no repeated variables or kind-changing, we wish to use the
  variable name given in the datacon signature (that is, `x1` not
  `k1`), not the tycon signature (which may have been made up by
  GHC). So, we add a mapping from the tycon tyvar to the result tyvar
  to t_sub.

* If we discover that a mapping in `subst` gives us a non-tyvar (the
  second branch of the `case` statement), then we have a GADT equality
  to create.  We create a fresh equality, but we don't extend any
  substitutions. The template variable substitution is meant for use
  in universal tyvar kinds, and these shouldn't be affected by any
  GADT equalities.

This whole algorithm is quite delicate, indeed. I (Richard E.) see two ways
of simplifying it:

1) The first branch of the `case` statement is really an optimization, used
in order to get fewer GADT equalities. It might be possible to make a GADT
equality for *every* univ. tyvar, even if the equality is trivial, and then
either deal with the bigger type or somehow reduce it later.

2) This algorithm strives to use the names for type variables as specified
by the user in the datacon signature. If we always used the tycon tyvar
names, for example, this would be simplified. This change would almost
certainly degrade error messages a bit, though.
-}

-- ^ From information about a source datacon definition, extract out
-- what the universal variables and the GADT equalities should be.
-- See Note [mkGADTVars].
mkGADTVars :: [TyVar]    -- ^ The tycon vars
           -> [TyVar]    -- ^ The datacon vars
           -> TCvSubst   -- ^ The matching between the template result type
                         -- and the actual result type
           -> ( [TyVar]
              , [EqSpec]
              , TCvSubst ) -- ^ The univ. variables, the GADT equalities,
                           -- and a subst to apply to the GADT equalities
                           -- and existentials.
mkGADTVars :: [TyVar] -> [TyVar] -> TCvSubst -> ([TyVar], [EqSpec], TCvSubst)
mkGADTVars [TyVar]
tmpl_tvs [TyVar]
dc_tvs TCvSubst
subst
  = [TyVar]
-> [EqSpec]
-> TCvSubst
-> TCvSubst
-> [TyVar]
-> ([TyVar], [EqSpec], TCvSubst)
choose [] [] TCvSubst
empty_subst TCvSubst
empty_subst [TyVar]
tmpl_tvs
  where
    in_scope :: InScopeSet
in_scope = VarSet -> InScopeSet
mkInScopeSet ([TyVar] -> VarSet
mkVarSet [TyVar]
tmpl_tvs VarSet -> VarSet -> VarSet
`unionVarSet` [TyVar] -> VarSet
mkVarSet [TyVar]
dc_tvs)
               InScopeSet -> InScopeSet -> InScopeSet
`unionInScope` TCvSubst -> InScopeSet
getTCvInScope TCvSubst
subst
    empty_subst :: TCvSubst
empty_subst = InScopeSet -> TCvSubst
mkEmptyTCvSubst InScopeSet
in_scope

    choose :: [TyVar]           -- accumulator of univ tvs, reversed
           -> [EqSpec]          -- accumulator of GADT equalities, reversed
           -> TCvSubst          -- template substitution
           -> TCvSubst          -- res. substitution
           -> [TyVar]           -- template tvs (the univ tvs passed in)
           -> ( [TyVar]         -- the univ_tvs
              , [EqSpec]        -- GADT equalities
              , TCvSubst )       -- a substitution to fix kinds in ex_tvs

    choose :: [TyVar]
-> [EqSpec]
-> TCvSubst
-> TCvSubst
-> [TyVar]
-> ([TyVar], [EqSpec], TCvSubst)
choose [TyVar]
univs [EqSpec]
eqs TCvSubst
_t_sub TCvSubst
r_sub []
      = (forall a. [a] -> [a]
reverse [TyVar]
univs, forall a. [a] -> [a]
reverse [EqSpec]
eqs, TCvSubst
r_sub)
    choose [TyVar]
univs [EqSpec]
eqs TCvSubst
t_sub TCvSubst
r_sub (TyVar
t_tv:[TyVar]
t_tvs)
      | Just Type
r_ty <- TCvSubst -> TyVar -> Maybe Type
lookupTyVar TCvSubst
subst TyVar
t_tv
      = case Type -> Maybe TyVar
getTyVar_maybe Type
r_ty of
          Just TyVar
r_tv
            |  Bool -> Bool
not (TyVar
r_tv forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [TyVar]
univs)
            ,  TyVar -> Type
tyVarKind TyVar
r_tv Type -> Type -> Bool
`eqType` (HasCallStack => TCvSubst -> Type -> Type
substTy TCvSubst
t_sub (TyVar -> Type
tyVarKind TyVar
t_tv))
            -> -- simple, well-kinded variable substitution.
               [TyVar]
-> [EqSpec]
-> TCvSubst
-> TCvSubst
-> [TyVar]
-> ([TyVar], [EqSpec], TCvSubst)
choose (TyVar
r_tvforall a. a -> [a] -> [a]
:[TyVar]
univs) [EqSpec]
eqs
                      (TCvSubst -> TyVar -> Type -> TCvSubst
extendTvSubst TCvSubst
t_sub TyVar
t_tv Type
r_ty')
                      (TCvSubst -> TyVar -> Type -> TCvSubst
extendTvSubst TCvSubst
r_sub TyVar
r_tv Type
r_ty')
                      [TyVar]
t_tvs
            where
              r_tv1 :: TyVar
r_tv1  = TyVar -> Name -> TyVar
setTyVarName TyVar
r_tv (TyVar -> TyVar -> Name
choose_tv_name TyVar
r_tv TyVar
t_tv)
              r_ty' :: Type
r_ty'  = TyVar -> Type
mkTyVarTy TyVar
r_tv1

               -- Not a simple substitution: make an equality predicate
          Maybe TyVar
_ -> [TyVar]
-> [EqSpec]
-> TCvSubst
-> TCvSubst
-> [TyVar]
-> ([TyVar], [EqSpec], TCvSubst)
choose (TyVar
t_tv'forall a. a -> [a] -> [a]
:[TyVar]
univs) (TyVar -> Type -> EqSpec
mkEqSpec TyVar
t_tv' Type
r_ty forall a. a -> [a] -> [a]
: [EqSpec]
eqs)
                      (TCvSubst -> TyVar -> Type -> TCvSubst
extendTvSubst TCvSubst
t_sub TyVar
t_tv (TyVar -> Type
mkTyVarTy TyVar
t_tv'))
                         -- We've updated the kind of t_tv,
                         -- so add it to t_sub (#14162)
                      TCvSubst
r_sub [TyVar]
t_tvs
            where
              t_tv' :: TyVar
t_tv' = (Type -> Type) -> TyVar -> TyVar
updateTyVarKind (HasCallStack => TCvSubst -> Type -> Type
substTy TCvSubst
t_sub) TyVar
t_tv

      | Bool
otherwise
      = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"mkGADTVars" (forall a. Outputable a => a -> SDoc
ppr [TyVar]
tmpl_tvs SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr TCvSubst
subst)

      -- choose an appropriate name for a univ tyvar.
      -- This *must* preserve the Unique of the result tv, so that we
      -- can detect repeated variables. It prefers user-specified names
      -- over system names. A result variable with a system name can
      -- happen with GHC-generated implicit kind variables.
    choose_tv_name :: TyVar -> TyVar -> Name
    choose_tv_name :: TyVar -> TyVar -> Name
choose_tv_name TyVar
r_tv TyVar
t_tv
      | Name -> Bool
isSystemName Name
r_tv_name
      = Name -> Unique -> Name
setNameUnique Name
t_tv_name (forall a. Uniquable a => a -> Unique
getUnique Name
r_tv_name)

      | Bool
otherwise
      = Name
r_tv_name

      where
        r_tv_name :: Name
r_tv_name = forall a. NamedThing a => a -> Name
getName TyVar
r_tv
        t_tv_name :: Name
t_tv_name = forall a. NamedThing a => a -> Name
getName TyVar
t_tv

{-
Note [Substitution in template variables kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

data G (a :: Maybe k) where
  MkG :: G Nothing

With explicit kind variables

data G k (a :: Maybe k) where
  MkG :: G k1 (Nothing k1)

Note how k1 is distinct from k. So, when we match the template
`G k a` against `G k1 (Nothing k1)`, we get a subst
[ k |-> k1, a |-> Nothing k1 ]. Even though this subst has two
mappings, we surely don't want to add (k, k1) to the list of
GADT equalities -- that would be overly complex and would create
more untouchable variables than we need. So, when figuring out
which tyvars are GADT-like and which aren't (the fundamental
job of `choose`), we want to treat `k` as *not* GADT-like.
Instead, we wish to substitute in `a`'s kind, to get (a :: Maybe k1)
instead of (a :: Maybe k). This is the reason for dealing
with a substitution in here.

However, we do not *always* want to substitute. Consider

data H (a :: k) where
  MkH :: H Int

With explicit kind variables:

data H k (a :: k) where
  MkH :: H * Int

Here, we have a kind-indexed GADT. The subst in question is
[ k |-> *, a |-> Int ]. Now, we *don't* want to substitute in `a`'s
kind, because that would give a constructor with the type

MkH :: forall (k :: *) (a :: *). (k ~ *) -> (a ~ Int) -> H k a

The problem here is that a's kind is wrong -- it needs to be k, not *!
So, if the matching for a variable is anything but another bare variable,
we drop the mapping from the substitution before proceeding. This
was not an issue before kind-indexed GADTs because this case could
never happen.

************************************************************************
*                                                                      *
                Validity checking
*                                                                      *
************************************************************************

Validity checking is done once the mutually-recursive knot has been
tied, so we can look at things freely.
-}

checkValidTyCl :: TyCon -> TcM [TyCon]
-- The returned list is either a singleton (if valid)
-- or a list of "fake tycons" (if not); the fake tycons
-- include any implicits, like promoted data constructors
-- See Note [Recover from validity error]
checkValidTyCl :: TyCon -> TcM [TyCon]
checkValidTyCl TyCon
tc
  = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (forall a. NamedThing a => a -> SrcSpan
getSrcSpan TyCon
tc) forall a b. (a -> b) -> a -> b
$
    forall a. TyCon -> TcM a -> TcM a
addTyConCtxt TyCon
tc            forall a b. (a -> b) -> a -> b
$
    forall r. TcRn r -> TcRn r -> TcRn r
recoverM TcM [TyCon]
recovery_code     forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"Starting validity for tycon" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)
       ; TyCon -> TcRn ()
checkValidTyCon TyCon
tc
       ; String -> SDoc -> TcRn ()
traceTc String
"Done validity for tycon" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)
       ; forall (m :: * -> *) a. Monad m => a -> m a
return [TyCon
tc] }
  where
    recovery_code :: TcM [TyCon]
recovery_code -- See Note [Recover from validity error]
      = do { String -> SDoc -> TcRn ()
traceTc String
"Aborted validity for tycon" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)
           ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall a b. (a -> b) -> [a] -> [b]
map TyCon -> TyCon
mk_fake_tc forall a b. (a -> b) -> a -> b
$
                     TyCon
tc forall a. a -> [a] -> [a]
: TyCon -> [TyCon]
child_tycons TyCon
tc) }

    mk_fake_tc :: TyCon -> TyCon
mk_fake_tc TyCon
tc
      | TyCon -> Bool
isClassTyCon TyCon
tc = TyCon
tc   -- Ugh! Note [Recover from validity error]
      | Bool
otherwise       = TyCon -> TyCon
makeRecoveryTyCon TyCon
tc

    child_tycons :: TyCon -> [TyCon]
child_tycons TyCon
tc = TyCon -> [TyCon]
tyConATs TyCon
tc forall a. [a] -> [a] -> [a]
++ forall a b. (a -> b) -> [a] -> [b]
map DataCon -> TyCon
promoteDataCon (TyCon -> [DataCon]
tyConDataCons TyCon
tc)

{- Note [Recover from validity error]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We recover from a validity error in a type or class, which allows us
to report multiple validity errors. In the failure case we return a
TyCon of the right kind, but with no interesting behaviour
(makeRecoveryTyCon). Why?  Suppose we have
   type T a = Fun
where Fun is a type family of arity 1.  The RHS is invalid, but we
want to go on checking validity of subsequent type declarations.
So we replace T with an abstract TyCon which will do no harm.
See indexed-types/should_fail/BadSock and #10896

Some notes:

* We must make fakes for promoted DataCons too. Consider (#15215)
      data T a = MkT ...
      data S a = ...T...MkT....
  If there is an error in the definition of 'T' we add a "fake type
  constructor" to the type environment, so that we can continue to
  typecheck 'S'.  But we /were not/ adding a fake anything for 'MkT'
  and so there was an internal error when we met 'MkT' in the body of
  'S'.

  Similarly for associated types.

* Painfully, we *don't* want to do this for classes.
  Consider tcfail041:
     class (?x::Int) => C a where ...
     instance C Int
  The class is invalid because of the superclass constraint.  But
  we still want it to look like a /class/, else the instance bleats
  that the instance is mal-formed because it hasn't got a class in
  the head.

  This is really bogus; now we have in scope a Class that is invalid
  in some way, with unknown downstream consequences.  A better
  alternative might be to make a fake class TyCon.  A job for another day.

* Previously, we used implicitTyConThings to snaffle out the parts
  to add to the context. The problem is that this also grabs data con
  wrapper Ids. These could be filtered out. But, painfully, getting
  the wrapper Ids checks the DataConRep, and forcing the DataConRep
  can panic if there is a levity-polymorphic argument. This is #18534.
  We don't need the wrapper Ids here anyway. So the code just takes what
  it needs, via child_tycons.
-}

-------------------------
-- For data types declared with record syntax, we require
-- that each constructor that has a field 'f'
--      (a) has the same result type
--      (b) has the same type for 'f'
-- module alpha conversion of the quantified type variables
-- of the constructor.
--
-- Note that we allow existentials to match because the
-- fields can never meet. E.g
--      data T where
--        T1 { f1 :: b, f2 :: a, f3 ::Int } :: T
--        T2 { f1 :: c, f2 :: c, f3 ::Int } :: T
-- Here we do not complain about f1,f2 because they are existential

checkValidTyCon :: TyCon -> TcM ()
checkValidTyCon :: TyCon -> TcRn ()
checkValidTyCon TyCon
tc
  | TyCon -> Bool
isPrimTyCon TyCon
tc   -- Happens when Haddock'ing GHC.Prim
  = forall (m :: * -> *) a. Monad m => a -> m a
return ()

  | forall thing. NamedThing thing => thing -> Bool
isWiredIn TyCon
tc     -- validity-checking wired-in tycons is a waste of
                     -- time. More importantly, a wired-in tycon might
                     -- violate assumptions. Example: (~) has a superclass
                     -- mentioning (~#), which is ill-kinded in source Haskell
  = String -> SDoc -> TcRn ()
traceTc String
"Skipping validity check for wired-in" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)

  | Bool
otherwise
  = do { String -> SDoc -> TcRn ()
traceTc String
"checkValidTyCon" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr (TyCon -> Maybe Class
tyConClass_maybe TyCon
tc))
       ; if | Just Class
cl <- TyCon -> Maybe Class
tyConClass_maybe TyCon
tc
              -> Class -> TcRn ()
checkValidClass Class
cl

            | Just Type
syn_rhs <- TyCon -> Maybe Type
synTyConRhs_maybe TyCon
tc
              -> do { UserTypeCtxt -> Type -> TcRn ()
checkValidType UserTypeCtxt
syn_ctxt Type
syn_rhs
                    ; UserTypeCtxt -> Type -> TcRn ()
checkTySynRhs UserTypeCtxt
syn_ctxt Type
syn_rhs }

            | Just FamTyConFlav
fam_flav <- TyCon -> Maybe FamTyConFlav
famTyConFlav_maybe TyCon
tc
              -> case FamTyConFlav
fam_flav of
               { ClosedSynFamilyTyCon (Just CoAxiom Branched
ax)
                   -> forall a. TyCon -> TcM a -> TcM a
tcAddClosedTypeFamilyDeclCtxt TyCon
tc forall a b. (a -> b) -> a -> b
$
                      CoAxiom Branched -> TcRn ()
checkValidCoAxiom CoAxiom Branched
ax
               ; ClosedSynFamilyTyCon Maybe (CoAxiom Branched)
Nothing   -> forall (m :: * -> *) a. Monad m => a -> m a
return ()
               ; FamTyConFlav
AbstractClosedSynFamilyTyCon ->
                 do { Bool
hsBoot <- IOEnv (Env TcGblEnv TcLclEnv) Bool
tcIsHsBootOrSig
                    ; Bool -> SDoc -> TcRn ()
checkTc Bool
hsBoot forall a b. (a -> b) -> a -> b
$
                      String -> SDoc
text String
"You may define an abstract closed type family" SDoc -> SDoc -> SDoc
$$
                      String -> SDoc
text String
"only in a .hs-boot file" }
               ; DataFamilyTyCon {}           -> forall (m :: * -> *) a. Monad m => a -> m a
return ()
               ; FamTyConFlav
OpenSynFamilyTyCon           -> forall (m :: * -> *) a. Monad m => a -> m a
return ()
               ; BuiltInSynFamTyCon BuiltInSynFamily
_         -> forall (m :: * -> *) a. Monad m => a -> m a
return () }

             | Bool
otherwise -> do
               { -- Check the context on the data decl
                 String -> SDoc -> TcRn ()
traceTc String
"cvtc1" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)
               ; UserTypeCtxt -> [Type] -> TcRn ()
checkValidTheta (Name -> UserTypeCtxt
DataTyCtxt Name
name) (TyCon -> [Type]
tyConStupidTheta TyCon
tc)

               ; String -> SDoc -> TcRn ()
traceTc String
"cvtc2" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)

               ; DynFlags
dflags          <- forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
               ; Bool
existential_ok  <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.ExistentialQuantification
               ; Bool
gadt_ok         <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.GADTs
               ; let ex_ok :: Bool
ex_ok = Bool
existential_ok Bool -> Bool -> Bool
|| Bool
gadt_ok
                     -- Data cons can have existential context
               ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (DynFlags -> Bool -> TyCon -> DataCon -> TcRn ()
checkValidDataCon DynFlags
dflags Bool
ex_ok TyCon
tc) [DataCon]
data_cons
               ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ ([DataCon] -> FieldLabel -> TcRn ()
checkPartialRecordField [DataCon]
data_cons) (TyCon -> [FieldLabel]
tyConFieldLabels TyCon
tc)

                -- Check that fields with the same name share a type
               ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ NonEmpty (FieldLabel, DataCon) -> TcRn ()
check_fields [NonEmpty (FieldLabel, DataCon)]
groups }}
  where
    syn_ctxt :: UserTypeCtxt
syn_ctxt  = Name -> UserTypeCtxt
TySynCtxt Name
name
    name :: Name
name      = TyCon -> Name
tyConName TyCon
tc
    data_cons :: [DataCon]
data_cons = TyCon -> [DataCon]
tyConDataCons TyCon
tc

    groups :: [NonEmpty (FieldLabel, DataCon)]
groups = forall a. (a -> a -> Ordering) -> [a] -> [NonEmpty a]
equivClasses forall {b} {b}. (FieldLabel, b) -> (FieldLabel, b) -> Ordering
cmp_fld (forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
concatMap DataCon -> [(FieldLabel, DataCon)]
get_fields [DataCon]
data_cons)
    cmp_fld :: (FieldLabel, b) -> (FieldLabel, b) -> Ordering
cmp_fld (FieldLabel
f1,b
_) (FieldLabel
f2,b
_) = FieldLabel -> FieldLabelString
flLabel FieldLabel
f1 FieldLabelString -> FieldLabelString -> Ordering
`uniqCompareFS` FieldLabel -> FieldLabelString
flLabel FieldLabel
f2
    get_fields :: DataCon -> [(FieldLabel, DataCon)]
get_fields DataCon
con = DataCon -> [FieldLabel]
dataConFieldLabels DataCon
con forall a b. [a] -> [b] -> [(a, b)]
`zip` forall a. a -> [a]
repeat DataCon
con
        -- dataConFieldLabels may return the empty list, which is fine

    -- See Note [GADT record selectors] in GHC.Tc.TyCl.Utils
    -- We must check (a) that the named field has the same
    --                   type in each constructor
    --               (b) that those constructors have the same result type
    --
    -- However, the constructors may have differently named type variable
    -- and (worse) we don't know how the correspond to each other.  E.g.
    --     C1 :: forall a b. { f :: a, g :: b } -> T a b
    --     C2 :: forall d c. { f :: c, g :: c } -> T c d
    --
    -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
    -- result type against other candidates' types BOTH WAYS ROUND.
    -- If they magically agrees, take the substitution and
    -- apply them to the latter ones, and see if they match perfectly.
    check_fields :: NonEmpty (FieldLabel, DataCon) -> TcRn ()
check_fields ((FieldLabel
label, DataCon
con1) :| [(FieldLabel, DataCon)]
other_fields)
        -- These fields all have the same name, but are from
        -- different constructors in the data type
        = forall r. TcRn r -> TcRn r -> TcRn r
recoverM (forall (m :: * -> *) a. Monad m => a -> m a
return ()) forall a b. (a -> b) -> a -> b
$ forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (FieldLabel, DataCon) -> TcRn ()
checkOne [(FieldLabel, DataCon)]
other_fields
                -- Check that all the fields in the group have the same type
                -- NB: this check assumes that all the constructors of a given
                -- data type use the same type variables
        where
        res1 :: Type
res1 = DataCon -> Type
dataConOrigResTy DataCon
con1
        fty1 :: Type
fty1 = DataCon -> FieldLabelString -> Type
dataConFieldType DataCon
con1 FieldLabelString
lbl
        lbl :: FieldLabelString
lbl = FieldLabel -> FieldLabelString
flLabel FieldLabel
label

        checkOne :: (FieldLabel, DataCon) -> TcRn ()
checkOne (FieldLabel
_, DataCon
con2)    -- Do it both ways to ensure they are structurally identical
            = do { FieldLabelString
-> DataCon -> DataCon -> Type -> Type -> Type -> Type -> TcRn ()
checkFieldCompat FieldLabelString
lbl DataCon
con1 DataCon
con2 Type
res1 Type
res2 Type
fty1 Type
fty2
                 ; FieldLabelString
-> DataCon -> DataCon -> Type -> Type -> Type -> Type -> TcRn ()
checkFieldCompat FieldLabelString
lbl DataCon
con2 DataCon
con1 Type
res2 Type
res1 Type
fty2 Type
fty1 }
            where
                res2 :: Type
res2 = DataCon -> Type
dataConOrigResTy DataCon
con2
                fty2 :: Type
fty2 = DataCon -> FieldLabelString -> Type
dataConFieldType DataCon
con2 FieldLabelString
lbl

checkPartialRecordField :: [DataCon] -> FieldLabel -> TcM ()
-- Checks the partial record field selector, and warns.
-- See Note [Checking partial record field]
checkPartialRecordField :: [DataCon] -> FieldLabel -> TcRn ()
checkPartialRecordField [DataCon]
all_cons FieldLabel
fld
  = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc forall a b. (a -> b) -> a -> b
$
      WarningFlag -> Bool -> SDoc -> TcRn ()
warnIfFlag WarningFlag
Opt_WarnPartialFields
        (Bool -> Bool
not Bool
is_exhaustive Bool -> Bool -> Bool
&& Bool -> Bool
not (OccName -> Bool
startsWithUnderscore OccName
occ_name))
        ([SDoc] -> SDoc
sep [String -> SDoc
text String
"Use of partial record field selector" SDoc -> SDoc -> SDoc
<> SDoc
colon,
              Arity -> SDoc -> SDoc
nest Arity
2 forall a b. (a -> b) -> a -> b
$ SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr OccName
occ_name)])
  where
    loc :: SrcSpan
loc = forall a. NamedThing a => a -> SrcSpan
getSrcSpan (FieldLabel -> Name
flSelector FieldLabel
fld)
    occ_name :: OccName
occ_name = forall name. HasOccName name => name -> OccName
occName FieldLabel
fld

    ([DataCon]
cons_with_field, [DataCon]
cons_without_field) = forall a. (a -> Bool) -> [a] -> ([a], [a])
partition DataCon -> Bool
has_field [DataCon]
all_cons
    has_field :: DataCon -> Bool
has_field DataCon
con = FieldLabel
fld forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` (DataCon -> [FieldLabel]
dataConFieldLabels DataCon
con)
    is_exhaustive :: Bool
is_exhaustive = forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all ([Type] -> DataCon -> Bool
dataConCannotMatch [Type]
inst_tys) [DataCon]
cons_without_field

    con1 :: DataCon
con1 = ASSERT( not (null cons_with_field) ) head cons_with_field
    ([TyVar]
univ_tvs, [TyVar]
_, [EqSpec]
eq_spec, [Type]
_, [Scaled Type]
_, Type
_) = DataCon
-> ([TyVar], [TyVar], [EqSpec], [Type], [Scaled Type], Type)
dataConFullSig DataCon
con1
    eq_subst :: TCvSubst
eq_subst = [(TyVar, Type)] -> TCvSubst
mkTvSubstPrs (forall a b. (a -> b) -> [a] -> [b]
map EqSpec -> (TyVar, Type)
eqSpecPair [EqSpec]
eq_spec)
    inst_tys :: [Type]
inst_tys = TCvSubst -> [TyVar] -> [Type]
substTyVars TCvSubst
eq_subst [TyVar]
univ_tvs

checkFieldCompat :: FieldLabelString -> DataCon -> DataCon
                 -> Type -> Type -> Type -> Type -> TcM ()
checkFieldCompat :: FieldLabelString
-> DataCon -> DataCon -> Type -> Type -> Type -> Type -> TcRn ()
checkFieldCompat FieldLabelString
fld DataCon
con1 DataCon
con2 Type
res1 Type
res2 Type
fty1 Type
fty2
  = do  { Bool -> SDoc -> TcRn ()
checkTc (forall a. Maybe a -> Bool
isJust Maybe TCvSubst
mb_subst1) (FieldLabelString -> DataCon -> DataCon -> SDoc
resultTypeMisMatch FieldLabelString
fld DataCon
con1 DataCon
con2)
        ; Bool -> SDoc -> TcRn ()
checkTc (forall a. Maybe a -> Bool
isJust Maybe TCvSubst
mb_subst2) (FieldLabelString -> DataCon -> DataCon -> SDoc
fieldTypeMisMatch FieldLabelString
fld DataCon
con1 DataCon
con2) }
  where
    mb_subst1 :: Maybe TCvSubst
mb_subst1 = Type -> Type -> Maybe TCvSubst
tcMatchTy Type
res1 Type
res2
    mb_subst2 :: Maybe TCvSubst
mb_subst2 = TCvSubst -> Type -> Type -> Maybe TCvSubst
tcMatchTyX (forall a. HasCallStack => String -> Maybe a -> a
expectJust String
"checkFieldCompat" Maybe TCvSubst
mb_subst1) Type
fty1 Type
fty2

-------------------------------
checkValidDataCon :: DynFlags -> Bool -> TyCon -> DataCon -> TcM ()
checkValidDataCon :: DynFlags -> Bool -> TyCon -> DataCon -> TcRn ()
checkValidDataCon DynFlags
dflags Bool
existential_ok TyCon
tc DataCon
con
  = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
con_loc forall a b. (a -> b) -> a -> b
$
    forall a. SDoc -> TcM a -> TcM a
addErrCtxt ([GenLocated SrcSpanAnnN Name] -> SDoc
dataConCtxt [forall l e. l -> e -> GenLocated l e
L (forall ann. SrcSpan -> SrcAnn ann
noAnnSrcSpan SrcSpan
con_loc) Name
con_name]) forall a b. (a -> b) -> a -> b
$
    do  { let tc_tvs :: [TyVar]
tc_tvs      = TyCon -> [TyVar]
tyConTyVars TyCon
tc
              res_ty_tmpl :: Type
res_ty_tmpl = TyCon -> [Type] -> Type
mkFamilyTyConApp TyCon
tc ([TyVar] -> [Type]
mkTyVarTys [TyVar]
tc_tvs)
              orig_res_ty :: Type
orig_res_ty = DataCon -> Type
dataConOrigResTy DataCon
con
        ; String -> SDoc -> TcRn ()
traceTc String
"checkValidDataCon" ([SDoc] -> SDoc
vcat
              [ forall a. Outputable a => a -> SDoc
ppr DataCon
con, forall a. Outputable a => a -> SDoc
ppr TyCon
tc, forall a. Outputable a => a -> SDoc
ppr [TyVar]
tc_tvs
              , forall a. Outputable a => a -> SDoc
ppr Type
res_ty_tmpl SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (HasDebugCallStack => Type -> Type
tcTypeKind Type
res_ty_tmpl)
              , forall a. Outputable a => a -> SDoc
ppr Type
orig_res_ty SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (HasDebugCallStack => Type -> Type
tcTypeKind Type
orig_res_ty)])


        -- Check that the return type of the data constructor
        -- matches the type constructor; eg reject this:
        --   data T a where { MkT :: Bogus a }
        -- It's important to do this first:
        --  see Note [rejigCon
        --  and c.f. Note [Check role annotations in a second pass]

        -- Check that the return type of the data constructor is an instance
        -- of the header of the header of data decl.  This checks for
        --      data T a where { MkT :: S a }
        --      data instance D [a] where { MkD :: D (Maybe b) }
        -- see Note [GADT return types]
        ; Bool -> SDoc -> TcRn ()
checkTc (forall a. Maybe a -> Bool
isJust (Type -> Type -> Maybe TCvSubst
tcMatchTyKi Type
res_ty_tmpl Type
orig_res_ty))
                  (DataCon -> Type -> SDoc
badDataConTyCon DataCon
con Type
res_ty_tmpl)
            -- Note that checkTc aborts if it finds an error. This is
            -- critical to avoid panicking when we call dataConDisplayType
            -- on an un-rejiggable datacon!
            -- Also NB that we match the *kind* as well as the *type* (#18357)
            -- However, if the kind is the only thing that doesn't match, the
            -- error message is terrible.  E.g. test T18357b
            --    type family Star where Star = Type
            --    newtype T :: Type where MkT :: Int -> (T :: Star)

        ; String -> SDoc -> TcRn ()
traceTc String
"checkValidDataCon 2" (forall a. Outputable a => a -> SDoc
ppr Type
data_con_display_type)

          -- Check that the result type is a *monotype*
          --  e.g. reject this:   MkT :: T (forall a. a->a)
          -- Reason: it's really the argument of an equality constraint
        ; Type -> TcRn ()
checkValidMonoType Type
orig_res_ty

          -- If we are dealing with a newtype, we allow levity polymorphism
          -- regardless of whether or not UnliftedNewtypes is enabled. A
          -- later check in checkNewDataCon handles this, producing a
          -- better error message than checkForLevPoly would.
        ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (TyCon -> Bool
isNewTyCon TyCon
tc) forall a b. (a -> b) -> a -> b
$
            forall r. TcM r -> TcM r
checkNoErrs forall a b. (a -> b) -> a -> b
$
            forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (SDoc -> Type -> TcRn ()
checkForLevPoly SDoc
empty) (forall a b. (a -> b) -> [a] -> [b]
map forall a. Scaled a -> a
scaledThing forall a b. (a -> b) -> a -> b
$ DataCon -> [Scaled Type]
dataConOrigArgTys DataCon
con)
            -- the checkNoErrs is to prevent a panic in isVanillaDataCon
            -- (called a a few lines down), which can fall over if there is a
            -- bang on a levity-polymorphic argument. This is #18534,
            -- typecheck/should_fail/T18534

          -- Extra checks for newtype data constructors. Importantly, these
          -- checks /must/ come before the call to checkValidType below. This
          -- is because checkValidType invokes the constraint solver, and
          -- invoking the solver on an ill formed newtype constructor can
          -- confuse GHC to the point of panicking. See #17955 for an example.
        ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (TyCon -> Bool
isNewTyCon TyCon
tc) (DataCon -> TcRn ()
checkNewDataCon DataCon
con)

          -- Check all argument types for validity
        ; UserTypeCtxt -> Type -> TcRn ()
checkValidType UserTypeCtxt
ctxt Type
data_con_display_type

          -- Check that existentials are allowed if they are used
        ; Bool -> SDoc -> TcRn ()
checkTc (Bool
existential_ok Bool -> Bool -> Bool
|| DataCon -> Bool
isVanillaDataCon DataCon
con)
                  (DataCon -> SDoc
badExistential DataCon
con)

          -- Check that UNPACK pragmas and bangs work out
          -- E.g.  reject   data T = MkT {-# UNPACK #-} Int     -- No "!"
          --                data T = MkT {-# UNPACK #-} !a      -- Can't unpack
        ; HscEnv
hsc_env <- forall gbl lcl. TcRnIf gbl lcl HscEnv
getTopEnv
        ; let check_bang :: HsSrcBang -> HsImplBang -> Int -> TcM ()
              check_bang :: HsSrcBang -> HsImplBang -> Arity -> TcRn ()
check_bang HsSrcBang
bang HsImplBang
rep_bang Arity
n
               | HsSrcBang SourceText
_ SrcUnpackedness
_ SrcStrictness
SrcLazy <- HsSrcBang
bang
               , Bool -> Bool
not (Extension -> DynFlags -> Bool
xopt Extension
LangExt.StrictData DynFlags
dflags)
               = SDoc -> TcRn ()
addErrTc (Arity -> SDoc -> SDoc
bad_bang Arity
n (String -> SDoc
text String
"Lazy annotation (~) without StrictData"))

               | HsSrcBang SourceText
_ SrcUnpackedness
want_unpack SrcStrictness
strict_mark <- HsSrcBang
bang
               , SrcUnpackedness -> Bool
isSrcUnpacked SrcUnpackedness
want_unpack, Bool -> Bool
not (SrcStrictness -> Bool
is_strict SrcStrictness
strict_mark)
               = WarnReason -> SDoc -> TcRn ()
addWarnTc WarnReason
NoReason (Arity -> SDoc -> SDoc
bad_bang Arity
n (String -> SDoc
text String
"UNPACK pragma lacks '!'"))

               | HsSrcBang SourceText
_ SrcUnpackedness
want_unpack SrcStrictness
_ <- HsSrcBang
bang
               , SrcUnpackedness -> Bool
isSrcUnpacked SrcUnpackedness
want_unpack
               , case HsImplBang
rep_bang of { HsUnpack {} -> Bool
False; HsImplBang
_ -> Bool
True }
               -- If not optimising, we don't unpack (rep_bang is never
               -- HsUnpack), so don't complain!  This happens, e.g., in Haddock.
               -- See dataConSrcToImplBang.
               , Bool -> Bool
not (GeneralFlag -> DynFlags -> Bool
gopt GeneralFlag
Opt_OmitInterfacePragmas DynFlags
dflags)
               -- When typechecking an indefinite package in Backpack, we
               -- may attempt to UNPACK an abstract type.  The test here will
               -- conclude that this is unusable, but it might become usable
               -- when we actually fill in the abstract type.  As such, don't
               -- warn in this case (it gives users the wrong idea about whether
               -- or not UNPACK on abstract types is supported; it is!)
               , forall u. GenHomeUnit u -> Bool
isHomeUnitDefinite (HscEnv -> HomeUnit
hsc_home_unit HscEnv
hsc_env)
               = WarnReason -> SDoc -> TcRn ()
addWarnTc WarnReason
NoReason (Arity -> SDoc -> SDoc
bad_bang Arity
n (String -> SDoc
text String
"Ignoring unusable UNPACK pragma"))

               | Bool
otherwise
               = forall (m :: * -> *) a. Monad m => a -> m a
return ()

        ; forall (m :: * -> *) a b c d.
Monad m =>
(a -> b -> c -> m d) -> [a] -> [b] -> [c] -> m ()
zipWith3M_ HsSrcBang -> HsImplBang -> Arity -> TcRn ()
check_bang (DataCon -> [HsSrcBang]
dataConSrcBangs DataCon
con) (DataCon -> [HsImplBang]
dataConImplBangs DataCon
con) [Arity
1..]

          -- Check the dcUserTyVarBinders invariant
          -- See Note [DataCon user type variable binders] in GHC.Core.DataCon
          -- checked here because we sometimes build invalid DataCons before
          -- erroring above here
        ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
debugIsOn forall a b. (a -> b) -> a -> b
$
          do { let ([TyVar]
univs, [TyVar]
exs, [EqSpec]
eq_spec, [Type]
_, [Scaled Type]
_, Type
_) = DataCon
-> ([TyVar], [TyVar], [EqSpec], [Type], [Scaled Type], Type)
dataConFullSig DataCon
con
                   user_tvs :: [TyVar]
user_tvs                       = DataCon -> [TyVar]
dataConUserTyVars DataCon
con
                   user_tvbs_invariant :: Bool
user_tvbs_invariant
                     =    forall a. Ord a => [a] -> Set a
Set.fromList ([EqSpec] -> [TyVar] -> [TyVar]
filterEqSpec [EqSpec]
eq_spec [TyVar]
univs forall a. [a] -> [a] -> [a]
++ [TyVar]
exs)
                       forall a. Eq a => a -> a -> Bool
== forall a. Ord a => [a] -> Set a
Set.fromList [TyVar]
user_tvs
             ; MASSERT2( user_tvbs_invariant
                       , vcat ([ ppr con
                               , ppr univs
                               , ppr exs
                               , ppr eq_spec
                               , ppr user_tvs ])) }

        ; String -> SDoc -> TcRn ()
traceTc String
"Done validity of data con" forall a b. (a -> b) -> a -> b
$
          [SDoc] -> SDoc
vcat [ forall a. Outputable a => a -> SDoc
ppr DataCon
con
               , String -> SDoc
text String
"Datacon wrapper type:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (DataCon -> Type
dataConWrapperType DataCon
con)
               , String -> SDoc
text String
"Datacon rep type:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (DataCon -> Type
dataConRepType DataCon
con)
               , String -> SDoc
text String
"Datacon display type:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Type
data_con_display_type
               , String -> SDoc
text String
"Rep typcon binders:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyConBinder]
tyConBinders (DataCon -> TyCon
dataConTyCon DataCon
con))
               , case TyCon -> Maybe (TyCon, [Type])
tyConFamInst_maybe (DataCon -> TyCon
dataConTyCon DataCon
con) of
                   Maybe (TyCon, [Type])
Nothing -> String -> SDoc
text String
"not family"
                   Just (TyCon
f, [Type]
_) -> forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyConBinder]
tyConBinders TyCon
f) ]
    }
  where
    con_name :: Name
con_name = DataCon -> Name
dataConName DataCon
con
    con_loc :: SrcSpan
con_loc  = Name -> SrcSpan
nameSrcSpan Name
con_name
    ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
ConArgCtxt Name
con_name
    is_strict :: SrcStrictness -> Bool
is_strict = \case
      SrcStrictness
NoSrcStrict -> Extension -> DynFlags -> Bool
xopt Extension
LangExt.StrictData DynFlags
dflags
      SrcStrictness
bang        -> SrcStrictness -> Bool
isSrcStrict SrcStrictness
bang

    bad_bang :: Arity -> SDoc -> SDoc
bad_bang Arity
n SDoc
herald
      = SDoc -> Arity -> SDoc -> SDoc
hang SDoc
herald Arity
2 (String -> SDoc
text String
"on the" SDoc -> SDoc -> SDoc
<+> Arity -> SDoc
speakNth Arity
n
                       SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"argument of" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr DataCon
con))

    show_linear_types :: Bool
show_linear_types     = Extension -> DynFlags -> Bool
xopt Extension
LangExt.LinearTypes DynFlags
dflags
    data_con_display_type :: Type
data_con_display_type = Bool -> DataCon -> Type
dataConDisplayType Bool
show_linear_types DataCon
con

-------------------------------
checkNewDataCon :: DataCon -> TcM ()
-- Further checks for the data constructor of a newtype
checkNewDataCon :: DataCon -> TcRn ()
checkNewDataCon DataCon
con
  = do  { Bool -> SDoc -> TcRn ()
checkTc (forall a. [a] -> Bool
isSingleton [Scaled Type]
arg_tys) (DataCon -> Arity -> SDoc
newtypeFieldErr DataCon
con (forall (t :: * -> *) a. Foldable t => t a -> Arity
length [Scaled Type]
arg_tys))
              -- One argument

        ; Bool
unlifted_newtypes <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.UnliftedNewtypes
        ; let allowedArgType :: Bool
allowedArgType =
                Bool
unlifted_newtypes Bool -> Bool -> Bool
|| HasDebugCallStack => Type -> Maybe Bool
isLiftedType_maybe (forall a. Scaled a -> a
scaledThing Scaled Type
arg_ty1) forall a. Eq a => a -> a -> Bool
== forall a. a -> Maybe a
Just Bool
True
        ; Bool -> SDoc -> TcRn ()
checkTc Bool
allowedArgType forall a b. (a -> b) -> a -> b
$ [SDoc] -> SDoc
vcat
          [ String -> SDoc
text String
"A newtype cannot have an unlifted argument type"
          , String -> SDoc
text String
"Perhaps you intended to use UnliftedNewtypes"
          ]
        ; Bool
show_linear_types <- Extension -> DynFlags -> Bool
xopt Extension
LangExt.LinearTypes forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags

        ; let check_con :: Bool -> SDoc -> TcRn ()
check_con Bool
what SDoc
msg =
               Bool -> SDoc -> TcRn ()
checkTc Bool
what (SDoc
msg SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr DataCon
con SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (Bool -> DataCon -> Type
dataConDisplayType Bool
show_linear_types DataCon
con))

        ; Bool -> SDoc -> TcRn ()
checkTc (Type -> Bool
ok_mult (forall a. Scaled a -> Type
scaledMult Scaled Type
arg_ty1)) forall a b. (a -> b) -> a -> b
$
          String -> SDoc
text String
"A newtype constructor must be linear"

        ; Bool -> SDoc -> TcRn ()
check_con (forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EqSpec]
eq_spec) forall a b. (a -> b) -> a -> b
$
          String -> SDoc
text String
"A newtype constructor must have a return type of form T a1 ... an"
                -- Return type is (T a b c)

        ; Bool -> SDoc -> TcRn ()
check_con (forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Type]
theta) forall a b. (a -> b) -> a -> b
$
          String -> SDoc
text String
"A newtype constructor cannot have a context in its type"

        ; Bool -> SDoc -> TcRn ()
check_con (forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TyVar]
ex_tvs) forall a b. (a -> b) -> a -> b
$
          String -> SDoc
text String
"A newtype constructor cannot have existential type variables"
                -- No existentials

        ; Bool -> SDoc -> TcRn ()
checkTc (forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all HsSrcBang -> Bool
ok_bang (DataCon -> [HsSrcBang]
dataConSrcBangs DataCon
con))
                  (DataCon -> SDoc
newtypeStrictError DataCon
con)
                -- No strictness annotations
    }
  where
    ([TyVar]
_univ_tvs, [TyVar]
ex_tvs, [EqSpec]
eq_spec, [Type]
theta, [Scaled Type]
arg_tys, Type
_res_ty)
      = DataCon
-> ([TyVar], [TyVar], [EqSpec], [Type], [Scaled Type], Type)
dataConFullSig DataCon
con

    (Scaled Type
arg_ty1 : [Scaled Type]
_) = [Scaled Type]
arg_tys

    ok_bang :: HsSrcBang -> Bool
ok_bang (HsSrcBang SourceText
_ SrcUnpackedness
_ SrcStrictness
SrcStrict) = Bool
False
    ok_bang (HsSrcBang SourceText
_ SrcUnpackedness
_ SrcStrictness
SrcLazy)   = Bool
False
    ok_bang HsSrcBang
_                         = Bool
True

    ok_mult :: Type -> Bool
ok_mult Type
One = Bool
True
    ok_mult Type
_   = Bool
False

-------------------------------
checkValidClass :: Class -> TcM ()
checkValidClass :: Class -> TcRn ()
checkValidClass Class
cls
  = do  { Bool
constrained_class_methods <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.ConstrainedClassMethods
        ; Bool
multi_param_type_classes  <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.MultiParamTypeClasses
        ; Bool
nullary_type_classes      <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.NullaryTypeClasses
        ; Bool
fundep_classes            <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.FunctionalDependencies
        ; Bool
undecidable_super_classes <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.UndecidableSuperClasses

        -- Check that the class is unary, unless multiparameter type classes
        -- are enabled; also recognize deprecated nullary type classes
        -- extension (subsumed by multiparameter type classes, #8993)
        ; Bool -> SDoc -> TcRn ()
checkTc (Bool
multi_param_type_classes Bool -> Bool -> Bool
|| Arity
cls_arity forall a. Eq a => a -> a -> Bool
== Arity
1 Bool -> Bool -> Bool
||
                    (Bool
nullary_type_classes Bool -> Bool -> Bool
&& Arity
cls_arity forall a. Eq a => a -> a -> Bool
== Arity
0))
                  (Arity -> Class -> SDoc
classArityErr Arity
cls_arity Class
cls)
        ; Bool -> SDoc -> TcRn ()
checkTc (Bool
fundep_classes Bool -> Bool -> Bool
|| forall (t :: * -> *) a. Foldable t => t a -> Bool
null [([TyVar], [TyVar])]
fundeps) (Class -> SDoc
classFunDepsErr Class
cls)

        -- Check the super-classes
        ; UserTypeCtxt -> [Type] -> TcRn ()
checkValidTheta (Name -> UserTypeCtxt
ClassSCCtxt (Class -> Name
className Class
cls)) [Type]
theta

          -- Now check for cyclic superclasses
          -- If there are superclass cycles, checkClassCycleErrs bails.
        ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless Bool
undecidable_super_classes forall a b. (a -> b) -> a -> b
$
          case Class -> Maybe SDoc
checkClassCycles Class
cls of
             Just SDoc
err -> forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (forall a. NamedThing a => a -> SrcSpan
getSrcSpan Class
cls) forall a b. (a -> b) -> a -> b
$
                         SDoc -> TcRn ()
addErrTc SDoc
err
             Maybe SDoc
Nothing  -> forall (m :: * -> *) a. Monad m => a -> m a
return ()

        -- Check the class operations.
        -- But only if there have been no earlier errors
        -- See Note [Abort when superclass cycle is detected]
        ; TcRn () -> TcRn ()
whenNoErrs forall a b. (a -> b) -> a -> b
$
          forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (Bool -> (TyVar, DefMethInfo) -> TcRn ()
check_op Bool
constrained_class_methods) [(TyVar, DefMethInfo)]
op_stuff

        -- Check the associated type defaults are well-formed and instantiated
        ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ ClassATItem -> TcRn ()
check_at [ClassATItem]
at_stuff  }
  where
    ([TyVar]
tyvars, [([TyVar], [TyVar])]
fundeps, [Type]
theta, [TyVar]
_, [ClassATItem]
at_stuff, [(TyVar, DefMethInfo)]
op_stuff) = Class
-> ([TyVar], [([TyVar], [TyVar])], [Type], [TyVar], [ClassATItem],
    [(TyVar, DefMethInfo)])
classExtraBigSig Class
cls
    cls_arity :: Arity
cls_arity = forall (t :: * -> *) a. Foldable t => t a -> Arity
length (TyCon -> [TyVar]
tyConVisibleTyVars (Class -> TyCon
classTyCon Class
cls))
       -- Ignore invisible variables
    cls_tv_set :: VarSet
cls_tv_set = [TyVar] -> VarSet
mkVarSet [TyVar]
tyvars

    check_op :: Bool -> (TyVar, DefMethInfo) -> TcRn ()
check_op Bool
constrained_class_methods (TyVar
sel_id, DefMethInfo
dm)
      = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (forall a. NamedThing a => a -> SrcSpan
getSrcSpan TyVar
sel_id) forall a b. (a -> b) -> a -> b
$
        forall a. SDoc -> TcM a -> TcM a
addErrCtxt (TyVar -> Type -> SDoc
classOpCtxt TyVar
sel_id Type
op_ty) forall a b. (a -> b) -> a -> b
$ do
        { String -> SDoc -> TcRn ()
traceTc String
"class op type" (forall a. Outputable a => a -> SDoc
ppr Type
op_ty)
        ; UserTypeCtxt -> Type -> TcRn ()
checkValidType UserTypeCtxt
ctxt Type
op_ty
                -- This implements the ambiguity check, among other things
                -- Example: tc223
                --   class Error e => Game b mv e | b -> mv e where
                --      newBoard :: MonadState b m => m ()
                -- Here, MonadState has a fundep m->b, so newBoard is fine

           -- a method cannot be levity polymorphic, as we have to store the
           -- method in a dictionary
           -- example of what this prevents:
           --   class BoundedX (a :: TYPE r) where minBound :: a
           -- See Note [Levity polymorphism checking] in GHC.HsToCore.Monad
        ; SDoc -> Type -> TcRn ()
checkForLevPoly SDoc
empty Type
tau1

        ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless Bool
constrained_class_methods forall a b. (a -> b) -> a -> b
$
          forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ Type -> TcRn ()
check_constraint (forall a. [a] -> [a]
tail (Type
cls_predforall a. a -> [a] -> [a]
:[Type]
op_theta))

        ; UserTypeCtxt -> TyVar -> Type -> Type -> DefMethInfo -> TcRn ()
check_dm UserTypeCtxt
ctxt TyVar
sel_id Type
cls_pred Type
tau2 DefMethInfo
dm
        }
        where
          ctxt :: UserTypeCtxt
ctxt    = Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
op_name Bool
True -- Report redundant class constraints
          op_name :: Name
op_name = TyVar -> Name
idName TyVar
sel_id
          op_ty :: Type
op_ty   = TyVar -> Type
idType TyVar
sel_id
          ([TyVar]
_,Type
cls_pred,Type
tau1) = Type -> ([TyVar], Type, Type)
tcSplitMethodTy Type
op_ty
          -- See Note [Splitting nested sigma types in class type signatures]
          ([TyVar]
_,[Type]
op_theta,Type
tau2) = Type -> ([TyVar], [Type], Type)
tcSplitNestedSigmaTys Type
tau1

          check_constraint :: TcPredType -> TcM ()
          check_constraint :: Type -> TcRn ()
check_constraint Type
pred -- See Note [Class method constraints]
            = forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Bool -> Bool
not (VarSet -> Bool
isEmptyVarSet VarSet
pred_tvs) Bool -> Bool -> Bool
&&
                    VarSet
pred_tvs VarSet -> VarSet -> Bool
`subVarSet` VarSet
cls_tv_set)
                   (SDoc -> TcRn ()
addErrTc (TyVar -> Type -> SDoc
badMethPred TyVar
sel_id Type
pred))
            where
              pred_tvs :: VarSet
pred_tvs = Type -> VarSet
tyCoVarsOfType Type
pred

    check_at :: ClassATItem -> TcRn ()
check_at (ATI TyCon
fam_tc Maybe (Type, ATValidityInfo)
m_dflt_rhs)
      = do { Bool -> SDoc -> TcRn ()
checkTc (Arity
cls_arity forall a. Eq a => a -> a -> Bool
== Arity
0 Bool -> Bool -> Bool
|| forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (TyVar -> VarSet -> Bool
`elemVarSet` VarSet
cls_tv_set) [TyVar]
fam_tvs)
                     (Class -> TyCon -> SDoc
noClassTyVarErr Class
cls TyCon
fam_tc)
                        -- Check that the associated type mentions at least
                        -- one of the class type variables
                        -- The check is disabled for nullary type classes,
                        -- since there is no possible ambiguity (#10020)

             -- Check that any default declarations for associated types are valid
           ; forall (m :: * -> *) a. Monad m => Maybe a -> (a -> m ()) -> m ()
whenIsJust Maybe (Type, ATValidityInfo)
m_dflt_rhs forall a b. (a -> b) -> a -> b
$ \ (Type
rhs, ATValidityInfo
at_validity_info) ->
             case ATValidityInfo
at_validity_info of
               ATValidityInfo
NoATVI -> forall (f :: * -> *) a. Applicative f => a -> f a
pure ()
               ATVI SrcSpan
loc [Type]
pats ->
                 forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc forall a b. (a -> b) -> a -> b
$
                 forall a. SDoc -> Name -> TcM a -> TcM a
tcAddFamInstCtxt (String -> SDoc
text String
"default type instance") (forall a. NamedThing a => a -> Name
getName TyCon
fam_tc) forall a b. (a -> b) -> a -> b
$
                 do { TyCon -> [Type] -> TcRn ()
checkValidAssocTyFamDeflt TyCon
fam_tc [Type]
pats
                    ; TyCon -> [TyVar] -> [Type] -> Type -> TcRn ()
checkValidTyFamEqn TyCon
fam_tc [TyVar]
fam_tvs ([TyVar] -> [Type]
mkTyVarTys [TyVar]
fam_tvs) Type
rhs }}
        where
          fam_tvs :: [TyVar]
fam_tvs = TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc

    check_dm :: UserTypeCtxt -> Id -> PredType -> Type -> DefMethInfo -> TcM ()
    -- Check validity of the /top-level/ generic-default type
    -- E.g for   class C a where
    --             default op :: forall b. (a~b) => blah
    -- we do not want to do an ambiguity check on a type with
    -- a free TyVar 'a' (#11608).  See TcType
    -- Note [TyVars and TcTyVars during type checking] in GHC.Tc.Utils.TcType
    -- Hence the mkDefaultMethodType to close the type.
    check_dm :: UserTypeCtxt -> TyVar -> Type -> Type -> DefMethInfo -> TcRn ()
check_dm UserTypeCtxt
ctxt TyVar
sel_id Type
vanilla_cls_pred Type
vanilla_tau
             (Just (Name
dm_name, dm_spec :: DefMethSpec Type
dm_spec@(GenericDM Type
dm_ty)))
      = forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (forall a. NamedThing a => a -> SrcSpan
getSrcSpan Name
dm_name) forall a b. (a -> b) -> a -> b
$ do
            -- We have carefully set the SrcSpan on the generic
            -- default-method Name to be that of the generic
            -- default type signature

          -- First, we check that the method's default type signature
          -- aligns with the non-default type signature.
          -- See Note [Default method type signatures must align]
          let cls_pred :: Type
cls_pred = Class -> [Type] -> Type
mkClassPred Class
cls forall a b. (a -> b) -> a -> b
$ [TyVar] -> [Type]
mkTyVarTys forall a b. (a -> b) -> a -> b
$ Class -> [TyVar]
classTyVars Class
cls
              -- Note that the second field of this tuple contains the context
              -- of the default type signature, making it apparent that we
              -- ignore method contexts completely when validity-checking
              -- default type signatures. See the end of
              -- Note [Default method type signatures must align]
              -- to learn why this is OK.
              --
              -- See also
              -- Note [Splitting nested sigma types in class type signatures]
              -- for an explanation of why we don't use tcSplitSigmaTy here.
              ([TyVar]
_, [Type]
_, Type
dm_tau) = Type -> ([TyVar], [Type], Type)
tcSplitNestedSigmaTys Type
dm_ty

              -- Given this class definition:
              --
              --  class C a b where
              --    op         :: forall p q. (Ord a, D p q)
              --               => a -> b -> p -> (a, b)
              --    default op :: forall r s. E r
              --               => a -> b -> s -> (a, b)
              --
              -- We want to match up two types of the form:
              --
              --   Vanilla type sig: C aa bb => aa -> bb -> p -> (aa, bb)
              --   Default type sig: C a  b  => a  -> b  -> s -> (a,  b)
              --
              -- Notice that the two type signatures can be quantified over
              -- different class type variables! Therefore, it's important that
              -- we include the class predicate parts to match up a with aa and
              -- b with bb.
              vanilla_phi_ty :: Type
vanilla_phi_ty = [Type] -> Type -> Type
mkPhiTy [Type
vanilla_cls_pred] Type
vanilla_tau
              dm_phi_ty :: Type
dm_phi_ty      = [Type] -> Type -> Type
mkPhiTy [Type
cls_pred] Type
dm_tau

          String -> SDoc -> TcRn ()
traceTc String
"check_dm" forall a b. (a -> b) -> a -> b
$ [SDoc] -> SDoc
vcat
              [ String -> SDoc
text String
"vanilla_phi_ty" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Type
vanilla_phi_ty
              , String -> SDoc
text String
"dm_phi_ty"      SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Type
dm_phi_ty ]

          -- Actually checking that the types align is done with a call to
          -- tcMatchTys. We need to get a match in both directions to rule
          -- out degenerate cases like these:
          --
          --  class Foo a where
          --    foo1         :: a -> b
          --    default foo1 :: a -> Int
          --
          --    foo2         :: a -> Int
          --    default foo2 :: a -> b
          forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (forall a. Maybe a -> Bool
isJust forall a b. (a -> b) -> a -> b
$ [Type] -> [Type] -> Maybe TCvSubst
tcMatchTys [Type
dm_phi_ty, Type
vanilla_phi_ty]
                                      [Type
vanilla_phi_ty, Type
dm_phi_ty]) forall a b. (a -> b) -> a -> b
$ SDoc -> TcRn ()
addErrTc forall a b. (a -> b) -> a -> b
$
               SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"The default type signature for"
                     SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id SDoc -> SDoc -> SDoc
<> SDoc
colon)
                 Arity
2 (forall a. Outputable a => a -> SDoc
ppr Type
dm_ty)
            SDoc -> SDoc -> SDoc
$$ (String -> SDoc
text String
"does not match its corresponding"
                SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"non-default type signature")

          -- Now do an ambiguity check on the default type signature.
          UserTypeCtxt -> Type -> TcRn ()
checkValidType UserTypeCtxt
ctxt (Class -> TyVar -> DefMethSpec Type -> Type
mkDefaultMethodType Class
cls TyVar
sel_id DefMethSpec Type
dm_spec)
    check_dm UserTypeCtxt
_ TyVar
_ Type
_ Type
_ DefMethInfo
_ = forall (m :: * -> *) a. Monad m => a -> m a
return ()

checkFamFlag :: Name -> TcM ()
-- Check that we don't use families without -XTypeFamilies
-- The parser won't even parse them, but I suppose a GHC API
-- client might have a go!
checkFamFlag :: Name -> TcRn ()
checkFamFlag Name
tc_name
  = do { Bool
idx_tys <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.TypeFamilies
       ; Bool -> SDoc -> TcRn ()
checkTc Bool
idx_tys SDoc
err_msg }
  where
    err_msg :: SDoc
err_msg = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Illegal family declaration for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tc_name))
                 Arity
2 (String -> SDoc
text String
"Enable TypeFamilies to allow indexed type families")

checkResultSigFlag :: Name -> FamilyResultSig GhcRn -> TcM ()
checkResultSigFlag :: Name -> FamilyResultSig GhcRn -> TcRn ()
checkResultSigFlag Name
tc_name (TyVarSig XTyVarSig GhcRn
_ LHsTyVarBndr () GhcRn
tvb)
  = do { Bool
ty_fam_deps <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.TypeFamilyDependencies
       ; Bool -> SDoc -> TcRn ()
checkTc Bool
ty_fam_deps forall a b. (a -> b) -> a -> b
$
         SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Illegal result type variable" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr LHsTyVarBndr () GhcRn
tvb SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tc_name))
            Arity
2 (String -> SDoc
text String
"Enable TypeFamilyDependencies to allow result variable names") }
checkResultSigFlag Name
_ FamilyResultSig GhcRn
_ = forall (m :: * -> *) a. Monad m => a -> m a
return ()  -- other cases OK

{- Note [Class method constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Haskell 2010 is supposed to reject
  class C a where
    op :: Eq a => a -> a
where the method type constrains only the class variable(s).  (The extension
-XConstrainedClassMethods switches off this check.)  But regardless
we should not reject
  class C a where
    op :: (?x::Int) => a -> a
as pointed out in #11793. So the test here rejects the program if
  * -XConstrainedClassMethods is off
  * the tyvars of the constraint are non-empty
  * all the tyvars are class tyvars, none are locally quantified

Note [Abort when superclass cycle is detected]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We must avoid doing the ambiguity check for the methods (in
checkValidClass.check_op) when there are already errors accumulated.
This is because one of the errors may be a superclass cycle, and
superclass cycles cause canonicalization to loop. Here is a
representative example:

  class D a => C a where
    meth :: D a => ()
  class C a => D a

This fixes #9415, #9739

Note [Default method type signatures must align]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GHC enforces the invariant that a class method's default type signature
must "align" with that of the method's non-default type signature, as per
GHC #12918. For instance, if you have:

  class Foo a where
    bar :: forall b. Context => a -> b

Then a default type signature for bar must be alpha equivalent to
(forall b. a -> b). That is, the types must be the same modulo differences in
contexts. So the following would be acceptable default type signatures:

    default bar :: forall b. Context1 => a -> b
    default bar :: forall x. Context2 => a -> x

But the following are NOT acceptable default type signatures:

    default bar :: forall b. b -> a
    default bar :: forall x. x
    default bar :: a -> Int

Note that a is bound by the class declaration for Foo itself, so it is
not allowed to differ in the default type signature.

The default type signature (default bar :: a -> Int) deserves special mention,
since (a -> Int) is a straightforward instantiation of (forall b. a -> b). To
write this, you need to declare the default type signature like so:

    default bar :: forall b. (b ~ Int). a -> b

As noted in #12918, there are several reasons to do this:

1. It would make no sense to have a type that was flat-out incompatible with
   the non-default type signature. For instance, if you had:

     class Foo a where
       bar :: a -> Int
       default bar :: a -> Bool

   Then that would always fail in an instance declaration. So this check
   nips such cases in the bud before they have the chance to produce
   confusing error messages.

2. Internally, GHC uses TypeApplications to instantiate the default method in
   an instance. See Note [Default methods in instances] in GHC.Tc.TyCl.Instance.
   Thus, GHC needs to know exactly what the universally quantified type
   variables are, and when instantiated that way, the default method's type
   must match the expected type.

3. Aesthetically, by only allowing the default type signature to differ in its
   context, we are making it more explicit the ways in which the default type
   signature is less polymorphic than the non-default type signature.

You might be wondering: why are the contexts allowed to be different, but not
the rest of the type signature? That's because default implementations often
rely on assumptions that the more general, non-default type signatures do not.
For instance, in the Enum class declaration:

    class Enum a where
      enum :: [a]
      default enum :: (Generic a, GEnum (Rep a)) => [a]
      enum = map to genum

    class GEnum f where
      genum :: [f a]

The default implementation for enum only works for types that are instances of
Generic, and for which their generic Rep type is an instance of GEnum. But
clearly enum doesn't _have_ to use this implementation, so naturally, the
context for enum is allowed to be different to accommodate this. As a result,
when we validity-check default type signatures, we ignore contexts completely.

Note that when checking whether two type signatures match, we must take care to
split as many foralls as it takes to retrieve the tau types we which to check.
See Note [Splitting nested sigma types in class type signatures].

Note [Splitting nested sigma types in class type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this type synonym and class definition:

  type Traversal s t a b = forall f. Applicative f => (a -> f b) -> s -> f t

  class Each s t a b where
    each         ::                                      Traversal s t a b
    default each :: (Traversable g, s ~ g a, t ~ g b) => Traversal s t a b

It might seem obvious that the tau types in both type signatures for `each`
are the same, but actually getting GHC to conclude this is surprisingly tricky.
That is because in general, the form of a class method's non-default type
signature is:

  forall a. C a => forall d. D d => E a b

And the general form of a default type signature is:

  forall f. F f => E a f -- The variable `a` comes from the class

So it you want to get the tau types in each type signature, you might find it
reasonable to call tcSplitSigmaTy twice on the non-default type signature, and
call it once on the default type signature. For most classes and methods, this
will work, but Each is a bit of an exceptional case. The way `each` is written,
it doesn't quantify any additional type variables besides those of the Each
class itself, so the non-default type signature for `each` is actually this:

  forall s t a b. Each s t a b => Traversal s t a b

Notice that there _appears_ to only be one forall. But there's actually another
forall lurking in the Traversal type synonym, so if you call tcSplitSigmaTy
twice, you'll also go under the forall in Traversal! That is, you'll end up
with:

  (a -> f b) -> s -> f t

A problem arises because you only call tcSplitSigmaTy once on the default type
signature for `each`, which gives you

  Traversal s t a b

Or, equivalently:

  forall f. Applicative f => (a -> f b) -> s -> f t

This is _not_ the same thing as (a -> f b) -> s -> f t! So now tcMatchTy will
say that the tau types for `each` are not equal.

A solution to this problem is to use tcSplitNestedSigmaTys instead of
tcSplitSigmaTy. tcSplitNestedSigmaTys will always split any foralls that it
sees until it can't go any further, so if you called it on the default type
signature for `each`, it would return (a -> f b) -> s -> f t like we desired.

Note [Checking partial record field]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This check checks the partial record field selector, and warns (#7169).

For example:

  data T a = A { m1 :: a, m2 :: a } | B { m1 :: a }

The function 'm2' is partial record field, and will fail when it is applied to
'B'. The warning identifies such partial fields. The check is performed at the
declaration of T, not at the call-sites of m2.

The warning can be suppressed by prefixing the field-name with an underscore.
For example:

  data T a = A { m1 :: a, _m2 :: a } | B { m1 :: a }

************************************************************************
*                                                                      *
                Checking role validity
*                                                                      *
************************************************************************
-}

checkValidRoleAnnots :: RoleAnnotEnv -> TyCon -> TcM ()
checkValidRoleAnnots :: RoleAnnotEnv -> TyCon -> TcRn ()
checkValidRoleAnnots RoleAnnotEnv
role_annots TyCon
tc
  | TyCon -> Bool
isTypeSynonymTyCon TyCon
tc = TcRn ()
check_no_roles
  | TyCon -> Bool
isFamilyTyCon TyCon
tc      = TcRn ()
check_no_roles
  | TyCon -> Bool
isAlgTyCon TyCon
tc         = TcRn ()
check_roles
  | Bool
otherwise             = forall (m :: * -> *) a. Monad m => a -> m a
return ()
  where
    -- Role annotations are given only on *explicit* variables,
    -- but a tycon stores roles for all variables.
    -- So, we drop the implicit roles (which are all Nominal, anyway).
    name :: Name
name                   = TyCon -> Name
tyConName TyCon
tc
    roles :: [Role]
roles                  = TyCon -> [Role]
tyConRoles TyCon
tc
    ([Role]
vis_roles, [TyVar]
vis_vars)  = forall a b. [(a, b)] -> ([a], [b])
unzip forall a b. (a -> b) -> a -> b
$ forall a b. (a -> Maybe b) -> [a] -> [b]
mapMaybe (Role, TyConBinder) -> Maybe (Role, TyVar)
pick_vis forall a b. (a -> b) -> a -> b
$
                             forall a b. [a] -> [b] -> [(a, b)]
zip [Role]
roles (TyCon -> [TyConBinder]
tyConBinders TyCon
tc)
    role_annot_decl_maybe :: Maybe (LRoleAnnotDecl GhcRn)
role_annot_decl_maybe  = RoleAnnotEnv -> Name -> Maybe (LRoleAnnotDecl GhcRn)
lookupRoleAnnot RoleAnnotEnv
role_annots Name
name

    pick_vis :: (Role, TyConBinder) -> Maybe (Role, TyVar)
    pick_vis :: (Role, TyConBinder) -> Maybe (Role, TyVar)
pick_vis (Role
role, TyConBinder
tvb)
      | forall tv. VarBndr tv TyConBndrVis -> Bool
isVisibleTyConBinder TyConBinder
tvb = forall a. a -> Maybe a
Just (Role
role, forall tv argf. VarBndr tv argf -> tv
binderVar TyConBinder
tvb)
      | Bool
otherwise                = forall a. Maybe a
Nothing

    check_roles :: TcRn ()
check_roles
      = forall (m :: * -> *) a. Monad m => Maybe a -> (a -> m ()) -> m ()
whenIsJust Maybe (LRoleAnnotDecl GhcRn)
role_annot_decl_maybe forall a b. (a -> b) -> a -> b
$
          \decl :: GenLocated SrcSpanAnnA (RoleAnnotDecl GhcRn)
decl@(L SrcSpanAnnA
loc (RoleAnnotDecl XCRoleAnnotDecl GhcRn
_ LIdP GhcRn
_ [XRec GhcRn (Maybe Role)]
the_role_annots)) ->
          forall a. Name -> TcM a -> TcM a
addRoleAnnotCtxt Name
name forall a b. (a -> b) -> a -> b
$
          forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc forall a b. (a -> b) -> a -> b
$ do
          { Bool
role_annots_ok <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.RoleAnnotations
          ; Bool -> SDoc -> TcRn ()
checkTc Bool
role_annots_ok forall a b. (a -> b) -> a -> b
$ TyCon -> SDoc
needXRoleAnnotations TyCon
tc
          ; Bool -> SDoc -> TcRn ()
checkTc ([TyVar]
vis_vars forall a b. [a] -> [b] -> Bool
`equalLength` [XRec GhcRn (Maybe Role)]
the_role_annots)
                    (forall a. [a] -> LRoleAnnotDecl GhcRn -> SDoc
wrongNumberOfRoles [TyVar]
vis_vars GenLocated SrcSpanAnnA (RoleAnnotDecl GhcRn)
decl)
          ; [()]
_ <- forall (m :: * -> *) a b c d.
Monad m =>
(a -> b -> c -> m d) -> [a] -> [b] -> [c] -> m [d]
zipWith3M TyVar -> Located (Maybe Role) -> Role -> TcRn ()
checkRoleAnnot [TyVar]
vis_vars [XRec GhcRn (Maybe Role)]
the_role_annots [Role]
vis_roles
          -- Representational or phantom roles for class parameters
          -- quickly lead to incoherence. So, we require
          -- IncoherentInstances to have them. See #8773, #14292
          ; Bool
incoherent_roles_ok <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.IncoherentInstances
          ; Bool -> SDoc -> TcRn ()
checkTc (  Bool
incoherent_roles_ok
                    Bool -> Bool -> Bool
|| (Bool -> Bool
not forall a b. (a -> b) -> a -> b
$ TyCon -> Bool
isClassTyCon TyCon
tc)
                    Bool -> Bool -> Bool
|| (forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all (forall a. Eq a => a -> a -> Bool
== Role
Nominal) [Role]
vis_roles))
                    SDoc
incoherentRoles

          ; Bool
lint <- forall gbl lcl. GeneralFlag -> TcRnIf gbl lcl Bool
goptM GeneralFlag
Opt_DoCoreLinting
          ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
lint forall a b. (a -> b) -> a -> b
$ TyCon -> TcRn ()
checkValidRoles TyCon
tc }

    check_no_roles :: TcRn ()
check_no_roles
      = forall (m :: * -> *) a. Monad m => Maybe a -> (a -> m ()) -> m ()
whenIsJust Maybe (LRoleAnnotDecl GhcRn)
role_annot_decl_maybe LRoleAnnotDecl GhcRn -> TcRn ()
illegalRoleAnnotDecl

checkRoleAnnot :: TyVar -> Located (Maybe Role) -> Role -> TcM ()
checkRoleAnnot :: TyVar -> Located (Maybe Role) -> Role -> TcRn ()
checkRoleAnnot TyVar
_  (L SrcSpan
_ Maybe Role
Nothing)   Role
_  = forall (m :: * -> *) a. Monad m => a -> m a
return ()
checkRoleAnnot TyVar
tv (L SrcSpan
_ (Just Role
r1)) Role
r2
  = forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Role
r1 forall a. Eq a => a -> a -> Bool
/= Role
r2) forall a b. (a -> b) -> a -> b
$
    SDoc -> TcRn ()
addErrTc forall a b. (a -> b) -> a -> b
$ Name -> Role -> Role -> SDoc
badRoleAnnot (TyVar -> Name
tyVarName TyVar
tv) Role
r1 Role
r2

-- This is a double-check on the role inference algorithm. It is only run when
-- -dcore-lint is enabled. See Note [Role inference] in GHC.Tc.TyCl.Utils
checkValidRoles :: TyCon -> TcM ()
-- If you edit this function, you may need to update the GHC formalism
-- See Note [GHC Formalism] in GHC.Core.Lint
checkValidRoles :: TyCon -> TcRn ()
checkValidRoles TyCon
tc
  | TyCon -> Bool
isAlgTyCon TyCon
tc
    -- tyConDataCons returns an empty list for data families
  = forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ DataCon -> TcRn ()
check_dc_roles (TyCon -> [DataCon]
tyConDataCons TyCon
tc)
  | Just Type
rhs <- TyCon -> Maybe Type
synTyConRhs_maybe TyCon
tc
  = UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles (forall a. [TyVar] -> [a] -> VarEnv a
zipVarEnv (TyCon -> [TyVar]
tyConTyVars TyCon
tc) (TyCon -> [Role]
tyConRoles TyCon
tc)) Role
Representational Type
rhs
  | Bool
otherwise
  = forall (m :: * -> *) a. Monad m => a -> m a
return ()
  where
    check_dc_roles :: DataCon -> TcRn ()
check_dc_roles DataCon
datacon
      = do { String -> SDoc -> TcRn ()
traceTc String
"check_dc_roles" (forall a. Outputable a => a -> SDoc
ppr DataCon
datacon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (TyCon -> [Role]
tyConRoles TyCon
tc))
           ; forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
role_env Role
Representational) forall a b. (a -> b) -> a -> b
$
                    [EqSpec] -> [Type]
eqSpecPreds [EqSpec]
eq_spec forall a. [a] -> [a] -> [a]
++ [Type]
theta forall a. [a] -> [a] -> [a]
++ (forall a b. (a -> b) -> [a] -> [b]
map forall a. Scaled a -> a
scaledThing [Scaled Type]
arg_tys) }
                    -- See Note [Role-checking data constructor arguments] in GHC.Tc.TyCl.Utils
      where
        ([TyVar]
univ_tvs, [TyVar]
ex_tvs, [EqSpec]
eq_spec, [Type]
theta, [Scaled Type]
arg_tys, Type
_res_ty)
          = DataCon
-> ([TyVar], [TyVar], [EqSpec], [Type], [Scaled Type], Type)
dataConFullSig DataCon
datacon
        univ_roles :: UniqFM TyVar Role
univ_roles = forall a. [TyVar] -> [a] -> VarEnv a
zipVarEnv [TyVar]
univ_tvs (TyCon -> [Role]
tyConRoles TyCon
tc)
              -- zipVarEnv uses zipEqual, but we don't want that for ex_tvs
        ex_roles :: UniqFM TyVar Role
ex_roles   = forall a. [(TyVar, a)] -> VarEnv a
mkVarEnv (forall a b. (a -> b) -> [a] -> [b]
map (, Role
Nominal) [TyVar]
ex_tvs)
        role_env :: UniqFM TyVar Role
role_env   = UniqFM TyVar Role
univ_roles forall a. VarEnv a -> VarEnv a -> VarEnv a
`plusVarEnv` UniqFM TyVar Role
ex_roles

    check_ty_roles :: UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
role Type
ty
      | Just Type
ty' <- Type -> Maybe Type
coreView Type
ty -- #14101
      = UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
role Type
ty'

    check_ty_roles UniqFM TyVar Role
env Role
role (TyVarTy TyVar
tv)
      = case forall a. VarEnv a -> TyVar -> Maybe a
lookupVarEnv UniqFM TyVar Role
env TyVar
tv of
          Just Role
role' -> forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Role
role' Role -> Role -> Bool
`ltRole` Role
role Bool -> Bool -> Bool
|| Role
role' forall a. Eq a => a -> a -> Bool
== Role
role) forall a b. (a -> b) -> a -> b
$
                        SDoc -> TcRn ()
report_error forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"type variable" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr TyVar
tv) SDoc -> SDoc -> SDoc
<+>
                                       String -> SDoc
text String
"cannot have role" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Role
role SDoc -> SDoc -> SDoc
<+>
                                       String -> SDoc
text String
"because it was assigned role" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Role
role'
          Maybe Role
Nothing    -> SDoc -> TcRn ()
report_error forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"type variable" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr TyVar
tv) SDoc -> SDoc -> SDoc
<+>
                                       String -> SDoc
text String
"missing in environment"

    check_ty_roles UniqFM TyVar Role
env Role
Representational (TyConApp TyCon
tc [Type]
tys)
      = let roles' :: [Role]
roles' = TyCon -> [Role]
tyConRoles TyCon
tc in
        forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m ()
zipWithM_ (UniqFM TyVar Role -> Role -> Type -> TcRn ()
maybe_check_ty_roles UniqFM TyVar Role
env) [Role]
roles' [Type]
tys

    check_ty_roles UniqFM TyVar Role
env Role
Nominal (TyConApp TyCon
_ [Type]
tys)
      = forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
Nominal) [Type]
tys

    check_ty_roles UniqFM TyVar Role
_   Role
Phantom ty :: Type
ty@(TyConApp {})
      = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"check_ty_roles" (forall a. Outputable a => a -> SDoc
ppr Type
ty)

    check_ty_roles UniqFM TyVar Role
env Role
role (AppTy Type
ty1 Type
ty2)
      =  UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
role    Type
ty1
      forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
Nominal Type
ty2

    check_ty_roles UniqFM TyVar Role
env Role
role (FunTy AnonArgFlag
_ Type
w Type
ty1 Type
ty2)
      =  UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
Nominal Type
w
      forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
role Type
ty1
      forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
role Type
ty2

    check_ty_roles UniqFM TyVar Role
env Role
role (ForAllTy (Bndr TyVar
tv ArgFlag
_) Type
ty)
      =  UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
Nominal (TyVar -> Type
tyVarKind TyVar
tv)
      forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles (forall a. VarEnv a -> TyVar -> a -> VarEnv a
extendVarEnv UniqFM TyVar Role
env TyVar
tv Role
Nominal) Role
role Type
ty

    check_ty_roles UniqFM TyVar Role
_   Role
_    (LitTy {}) = forall (m :: * -> *) a. Monad m => a -> m a
return ()

    check_ty_roles UniqFM TyVar Role
env Role
role (CastTy Type
t Coercion
_)
      = UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
role Type
t

    check_ty_roles UniqFM TyVar Role
_   Role
role (CoercionTy Coercion
co)
      = forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Role
role forall a. Eq a => a -> a -> Bool
== Role
Phantom) forall a b. (a -> b) -> a -> b
$
        SDoc -> TcRn ()
report_error forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"coercion" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Coercion
co SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"has bad role" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Role
role

    maybe_check_ty_roles :: UniqFM TyVar Role -> Role -> Type -> TcRn ()
maybe_check_ty_roles UniqFM TyVar Role
env Role
role Type
ty
      = forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Role
role forall a. Eq a => a -> a -> Bool
== Role
Nominal Bool -> Bool -> Bool
|| Role
role forall a. Eq a => a -> a -> Bool
== Role
Representational) forall a b. (a -> b) -> a -> b
$
        UniqFM TyVar Role -> Role -> Type -> TcRn ()
check_ty_roles UniqFM TyVar Role
env Role
role Type
ty

    report_error :: SDoc -> TcRn ()
report_error SDoc
doc
      = SDoc -> TcRn ()
addErrTc forall a b. (a -> b) -> a -> b
$ [SDoc] -> SDoc
vcat [String -> SDoc
text String
"Internal error in role inference:",
                         SDoc
doc,
                         String -> SDoc
text String
"Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug"]

{-
************************************************************************
*                                                                      *
                Error messages
*                                                                      *
************************************************************************
-}

tcMkDeclCtxt :: TyClDecl GhcRn -> SDoc
tcMkDeclCtxt :: TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl = [SDoc] -> SDoc
hsep [String -> SDoc
text String
"In the", forall (p :: Pass). TyClDecl (GhcPass p) -> SDoc
pprTyClDeclFlavour TyClDecl GhcRn
decl,
                      String -> SDoc
text String
"declaration for", SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyClDecl (GhcPass p) -> IdP (GhcPass p)
tcdName TyClDecl GhcRn
decl))]

addVDQNote :: TcTyCon -> TcM a -> TcM a
-- See Note [Inferring visible dependent quantification]
-- Only types without a signature (CUSK or SAK) here
addVDQNote :: forall a. TyCon -> TcM a -> TcM a
addVDQNote TyCon
tycon TcM a
thing_inside
  | ASSERT2( isTcTyCon tycon, ppr tycon )
    ASSERT2( not (tcTyConIsPoly tycon), ppr tycon $$ ppr tc_kind )
    Bool
has_vdq
  = forall a. SDoc -> TcM a -> TcM a
addLandmarkErrCtxt SDoc
vdq_warning TcM a
thing_inside
  | Bool
otherwise
  = TcM a
thing_inside
  where
      -- Check whether a tycon has visible dependent quantification.
      -- This will *always* be a TcTyCon. Furthermore, it will *always*
      -- be an ungeneralised TcTyCon, straight out of kcInferDeclHeader.
      -- Thus, all the TyConBinders will be anonymous. Thus, the
      -- free variables of the tycon's kind will be the same as the free
      -- variables from all the binders.
    has_vdq :: Bool
has_vdq  = forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any TyConBinder -> Bool
is_vdq_tcb (TyCon -> [TyConBinder]
tyConBinders TyCon
tycon)
    tc_kind :: Type
tc_kind  = TyCon -> Type
tyConKind TyCon
tycon
    kind_fvs :: VarSet
kind_fvs = Type -> VarSet
tyCoVarsOfType Type
tc_kind

    is_vdq_tcb :: TyConBinder -> Bool
is_vdq_tcb TyConBinder
tcb = (forall tv argf. VarBndr tv argf -> tv
binderVar TyConBinder
tcb TyVar -> VarSet -> Bool
`elemVarSet` VarSet
kind_fvs) Bool -> Bool -> Bool
&&
                     forall tv. VarBndr tv TyConBndrVis -> Bool
isVisibleTyConBinder TyConBinder
tcb

    vdq_warning :: SDoc
vdq_warning = [SDoc] -> SDoc
vcat
      [ String -> SDoc
text String
"NB: Type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr TyCon
tycon) SDoc -> SDoc -> SDoc
<+>
        String -> SDoc
text String
"was inferred to use visible dependent quantification."
      , String -> SDoc
text String
"Most types with visible dependent quantification are"
      , String -> SDoc
text String
"polymorphically recursive and need a standalone kind"
      , String -> SDoc
text String
"signature. Perhaps supply one, with StandaloneKindSignatures."
      ]

tcAddDeclCtxt :: TyClDecl GhcRn -> TcM a -> TcM a
tcAddDeclCtxt :: forall a. TyClDecl GhcRn -> TcM a -> TcM a
tcAddDeclCtxt TyClDecl GhcRn
decl TcM a
thing_inside
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt (TyClDecl GhcRn -> SDoc
tcMkDeclCtxt TyClDecl GhcRn
decl) TcM a
thing_inside

tcAddTyFamInstCtxt :: TyFamInstDecl GhcRn -> TcM a -> TcM a
tcAddTyFamInstCtxt :: forall a. TyFamInstDecl GhcRn -> TcM a -> TcM a
tcAddTyFamInstCtxt TyFamInstDecl GhcRn
decl
  = forall a. SDoc -> Name -> TcM a -> TcM a
tcAddFamInstCtxt (String -> SDoc
text String
"type instance") (forall (p :: Pass).
(Anno (IdGhcP p) ~ SrcSpanAnnN) =>
TyFamInstDecl (GhcPass p) -> IdP (GhcPass p)
tyFamInstDeclName TyFamInstDecl GhcRn
decl)

tcMkDataFamInstCtxt :: DataFamInstDecl GhcRn -> SDoc
tcMkDataFamInstCtxt :: DataFamInstDecl GhcRn -> SDoc
tcMkDataFamInstCtxt decl :: DataFamInstDecl GhcRn
decl@(DataFamInstDecl { dfid_eqn :: forall pass. DataFamInstDecl pass -> FamEqn pass (HsDataDefn pass)
dfid_eqn = FamEqn GhcRn (HsDataDefn GhcRn)
eqn })
  = SDoc -> Name -> SDoc
tcMkFamInstCtxt (forall (p :: Pass). DataFamInstDecl (GhcPass p) -> SDoc
pprDataFamInstFlavour DataFamInstDecl GhcRn
decl SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"instance")
                    (forall l e. GenLocated l e -> e
unLoc (forall pass rhs. FamEqn pass rhs -> LIdP pass
feqn_tycon FamEqn GhcRn (HsDataDefn GhcRn)
eqn))

tcAddDataFamInstCtxt :: DataFamInstDecl GhcRn -> TcM a -> TcM a
tcAddDataFamInstCtxt :: forall a. DataFamInstDecl GhcRn -> TcM a -> TcM a
tcAddDataFamInstCtxt DataFamInstDecl GhcRn
decl
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt (DataFamInstDecl GhcRn -> SDoc
tcMkDataFamInstCtxt DataFamInstDecl GhcRn
decl)

tcMkFamInstCtxt :: SDoc -> Name -> SDoc
tcMkFamInstCtxt :: SDoc -> Name -> SDoc
tcMkFamInstCtxt SDoc
flavour Name
tycon
  = [SDoc] -> SDoc
hsep [ String -> SDoc
text String
"In the" SDoc -> SDoc -> SDoc
<+> SDoc
flavour SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"declaration for"
         , SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tycon) ]

tcAddFamInstCtxt :: SDoc -> Name -> TcM a -> TcM a
tcAddFamInstCtxt :: forall a. SDoc -> Name -> TcM a -> TcM a
tcAddFamInstCtxt SDoc
flavour Name
tycon TcM a
thing_inside
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt (SDoc -> Name -> SDoc
tcMkFamInstCtxt SDoc
flavour Name
tycon) TcM a
thing_inside

tcAddClosedTypeFamilyDeclCtxt :: TyCon -> TcM a -> TcM a
tcAddClosedTypeFamilyDeclCtxt :: forall a. TyCon -> TcM a -> TcM a
tcAddClosedTypeFamilyDeclCtxt TyCon
tc
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt SDoc
ctxt
  where
    ctxt :: SDoc
ctxt = String -> SDoc
text String
"In the equations for closed type family" SDoc -> SDoc -> SDoc
<+>
           SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)

resultTypeMisMatch :: FieldLabelString -> DataCon -> DataCon -> SDoc
resultTypeMisMatch :: FieldLabelString -> DataCon -> DataCon -> SDoc
resultTypeMisMatch FieldLabelString
field_name DataCon
con1 DataCon
con2
  = [SDoc] -> SDoc
vcat [[SDoc] -> SDoc
sep [String -> SDoc
text String
"Constructors" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr DataCon
con1 SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"and" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr DataCon
con2,
                String -> SDoc
text String
"have a common field" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr FieldLabelString
field_name) SDoc -> SDoc -> SDoc
<> SDoc
comma],
          Arity -> SDoc -> SDoc
nest Arity
2 forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"but have different result types"]

fieldTypeMisMatch :: FieldLabelString -> DataCon -> DataCon -> SDoc
fieldTypeMisMatch :: FieldLabelString -> DataCon -> DataCon -> SDoc
fieldTypeMisMatch FieldLabelString
field_name DataCon
con1 DataCon
con2
  = [SDoc] -> SDoc
sep [String -> SDoc
text String
"Constructors" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr DataCon
con1 SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"and" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr DataCon
con2,
         String -> SDoc
text String
"give different types for field", SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr FieldLabelString
field_name)]

dataConCtxt :: [LocatedN Name] -> SDoc
dataConCtxt :: [GenLocated SrcSpanAnnN Name] -> SDoc
dataConCtxt [GenLocated SrcSpanAnnN Name]
cons = String -> SDoc
text String
"In the definition of data constructor" SDoc -> SDoc -> SDoc
<> forall a. [a] -> SDoc
plural [GenLocated SrcSpanAnnN Name]
cons
                   SDoc -> SDoc -> SDoc
<+> [GenLocated SrcSpanAnnN Name] -> SDoc
ppr_cons [GenLocated SrcSpanAnnN Name]
cons

dataConResCtxt :: [LocatedN Name] -> SDoc
dataConResCtxt :: [GenLocated SrcSpanAnnN Name] -> SDoc
dataConResCtxt [GenLocated SrcSpanAnnN Name]
cons = String -> SDoc
text String
"In the result type of data constructor" SDoc -> SDoc -> SDoc
<> forall a. [a] -> SDoc
plural [GenLocated SrcSpanAnnN Name]
cons
                      SDoc -> SDoc -> SDoc
<+> [GenLocated SrcSpanAnnN Name] -> SDoc
ppr_cons [GenLocated SrcSpanAnnN Name]
cons

ppr_cons :: [LocatedN Name] -> SDoc
ppr_cons :: [GenLocated SrcSpanAnnN Name] -> SDoc
ppr_cons [GenLocated SrcSpanAnnN Name
con] = SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnN Name
con)
ppr_cons [GenLocated SrcSpanAnnN Name]
cons  = forall a. Outputable a => [a] -> SDoc
interpp'SP [GenLocated SrcSpanAnnN Name]
cons

classOpCtxt :: Var -> Type -> SDoc
classOpCtxt :: TyVar -> Type -> SDoc
classOpCtxt TyVar
sel_id Type
tau = [SDoc] -> SDoc
sep [String -> SDoc
text String
"When checking the class method:",
                              Arity -> SDoc -> SDoc
nest Arity
2 (forall a. OutputableBndr a => a -> SDoc
pprPrefixOcc TyVar
sel_id SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Type
tau)]

classArityErr :: Int -> Class -> SDoc
classArityErr :: Arity -> Class -> SDoc
classArityErr Arity
n Class
cls
    | Arity
n forall a. Eq a => a -> a -> Bool
== Arity
0 = String -> String -> SDoc
mkErr String
"No" String
"no-parameter"
    | Bool
otherwise = String -> String -> SDoc
mkErr String
"Too many" String
"multi-parameter"
  where
    mkErr :: String -> String -> SDoc
mkErr String
howMany String
allowWhat =
        [SDoc] -> SDoc
vcat [String -> SDoc
text (String
howMany forall a. [a] -> [a] -> [a]
++ String
" parameters for class") SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Class
cls),
              SDoc -> SDoc
parens (String -> SDoc
text (String
"Enable MultiParamTypeClasses to allow "
                                    forall a. [a] -> [a] -> [a]
++ String
allowWhat forall a. [a] -> [a] -> [a]
++ String
" classes"))]

classFunDepsErr :: Class -> SDoc
classFunDepsErr :: Class -> SDoc
classFunDepsErr Class
cls
  = [SDoc] -> SDoc
vcat [String -> SDoc
text String
"Fundeps in class" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Class
cls),
          SDoc -> SDoc
parens (String -> SDoc
text String
"Enable FunctionalDependencies to allow fundeps")]

badMethPred :: Id -> TcPredType -> SDoc
badMethPred :: TyVar -> Type -> SDoc
badMethPred TyVar
sel_id Type
pred
  = [SDoc] -> SDoc
vcat [ SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Constraint" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Type
pred)
                 SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"in the type of" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id))
              Arity
2 (String -> SDoc
text String
"constrains only the class type variables")
         , String -> SDoc
text String
"Enable ConstrainedClassMethods to allow it" ]

noClassTyVarErr :: Class -> TyCon -> SDoc
noClassTyVarErr :: Class -> TyCon -> SDoc
noClassTyVarErr Class
clas TyCon
fam_tc
  = [SDoc] -> SDoc
sep [ String -> SDoc
text String
"The associated type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc SDoc -> SDoc -> SDoc
<+> [SDoc] -> SDoc
hsep (forall a b. (a -> b) -> [a] -> [b]
map forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyVar]
tyConTyVars TyCon
fam_tc)))
        , String -> SDoc
text String
"mentions none of the type or kind variables of the class" SDoc -> SDoc -> SDoc
<+>
                SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Class
clas SDoc -> SDoc -> SDoc
<+> [SDoc] -> SDoc
hsep (forall a b. (a -> b) -> [a] -> [b]
map forall a. Outputable a => a -> SDoc
ppr (Class -> [TyVar]
classTyVars Class
clas)))]

badDataConTyCon :: DataCon -> Type -> SDoc
badDataConTyCon :: DataCon -> Type -> SDoc
badDataConTyCon DataCon
data_con Type
res_ty_tmpl
  = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Data constructor" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr DataCon
data_con) SDoc -> SDoc -> SDoc
<+>
                String -> SDoc
text String
"returns type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Type
actual_res_ty))
       Arity
2 (String -> SDoc
text String
"instead of an instance of its parent type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Type
res_ty_tmpl))
  where
    actual_res_ty :: Type
actual_res_ty = DataCon -> Type
dataConOrigResTy DataCon
data_con

badGadtDecl :: Name -> SDoc
badGadtDecl :: Name -> SDoc
badGadtDecl Name
tc_name
  = [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Illegal generalised algebraic data declaration for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tc_name)
         , Arity -> SDoc -> SDoc
nest Arity
2 (SDoc -> SDoc
parens forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"Enable the GADTs extension to allow this") ]

badExistential :: DataCon -> SDoc
badExistential :: DataCon -> SDoc
badExistential DataCon
con
  = forall a. (SDocContext -> a) -> (a -> SDoc) -> SDoc
sdocOption SDocContext -> Bool
sdocLinearTypes (\Bool
show_linear_types ->
      SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Data constructor" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr DataCon
con) SDoc -> SDoc -> SDoc
<+>
                  String -> SDoc
text String
"has existential type variables, a context, or a specialised result type")
         Arity
2 ([SDoc] -> SDoc
vcat [ forall a. Outputable a => a -> SDoc
ppr DataCon
con SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr (Bool -> DataCon -> Type
dataConDisplayType Bool
show_linear_types DataCon
con)
                 , SDoc -> SDoc
parens forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"Enable ExistentialQuantification or GADTs to allow this" ]))

badStupidTheta :: Name -> SDoc
badStupidTheta :: Name -> SDoc
badStupidTheta Name
tc_name
  = String -> SDoc
text String
"A data type declared in GADT style cannot have a context:" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tc_name)

newtypeConError :: Name -> Int -> SDoc
newtypeConError :: Name -> Arity -> SDoc
newtypeConError Name
tycon Arity
n
  = [SDoc] -> SDoc
sep [String -> SDoc
text String
"A newtype must have exactly one constructor,",
         Arity -> SDoc -> SDoc
nest Arity
2 forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"but" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tycon) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"has" SDoc -> SDoc -> SDoc
<+> Arity -> SDoc
speakN Arity
n ]

newtypeStrictError :: DataCon -> SDoc
newtypeStrictError :: DataCon -> SDoc
newtypeStrictError DataCon
con
  = [SDoc] -> SDoc
sep [String -> SDoc
text String
"A newtype constructor cannot have a strictness annotation,",
         Arity -> SDoc -> SDoc
nest Arity
2 forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"but" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr DataCon
con) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"does"]

newtypeFieldErr :: DataCon -> Int -> SDoc
newtypeFieldErr :: DataCon -> Arity -> SDoc
newtypeFieldErr DataCon
con_name Arity
n_flds
  = [SDoc] -> SDoc
sep [String -> SDoc
text String
"The constructor of a newtype must have exactly one field",
         Arity -> SDoc -> SDoc
nest Arity
2 forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"but" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr DataCon
con_name) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"has" SDoc -> SDoc -> SDoc
<+> Arity -> SDoc
speakN Arity
n_flds]

badSigTyDecl :: Name -> SDoc
badSigTyDecl :: Name -> SDoc
badSigTyDecl Name
tc_name
  = [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Illegal kind signature" SDoc -> SDoc -> SDoc
<+>
           SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tc_name)
         , Arity -> SDoc -> SDoc
nest Arity
2 (SDoc -> SDoc
parens forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"Use KindSignatures to allow kind signatures") ]

emptyConDeclsErr :: Name -> SDoc
emptyConDeclsErr :: Name -> SDoc
emptyConDeclsErr Name
tycon
  = [SDoc] -> SDoc
sep [SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
tycon) SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"has no constructors",
         Arity -> SDoc -> SDoc
nest Arity
2 forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"(EmptyDataDecls permits this)"]

wrongKindOfFamily :: TyCon -> SDoc
wrongKindOfFamily :: TyCon -> SDoc
wrongKindOfFamily TyCon
family
  = String -> SDoc
text String
"Wrong category of family instance; declaration was for a"
    SDoc -> SDoc -> SDoc
<+> SDoc
kindOfFamily
  where
    kindOfFamily :: SDoc
kindOfFamily | TyCon -> Bool
isTypeFamilyTyCon TyCon
family = String -> SDoc
text String
"type family"
                 | TyCon -> Bool
isDataFamilyTyCon TyCon
family = String -> SDoc
text String
"data family"
                 | Bool
otherwise = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"wrongKindOfFamily" (forall a. Outputable a => a -> SDoc
ppr TyCon
family)

-- | Produce an error for oversaturated type family equations with too many
-- required arguments.
-- See Note [Oversaturated type family equations] in "GHC.Tc.Validity".
wrongNumberOfParmsErr :: Arity -> SDoc
wrongNumberOfParmsErr :: Arity -> SDoc
wrongNumberOfParmsErr Arity
max_args
  = String -> SDoc
text String
"Number of parameters must match family declaration; expected"
    SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Arity
max_args

badRoleAnnot :: Name -> Role -> Role -> SDoc
badRoleAnnot :: Name -> Role -> Role -> SDoc
badRoleAnnot Name
var Role
annot Role
inferred
  = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Role mismatch on variable" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Name
var SDoc -> SDoc -> SDoc
<> SDoc
colon)
       Arity
2 ([SDoc] -> SDoc
sep [ String -> SDoc
text String
"Annotation says", forall a. Outputable a => a -> SDoc
ppr Role
annot
              , String -> SDoc
text String
"but role", forall a. Outputable a => a -> SDoc
ppr Role
inferred
              , String -> SDoc
text String
"is required" ])

wrongNumberOfRoles :: [a] -> LRoleAnnotDecl GhcRn -> SDoc
wrongNumberOfRoles :: forall a. [a] -> LRoleAnnotDecl GhcRn -> SDoc
wrongNumberOfRoles [a]
tyvars d :: LRoleAnnotDecl GhcRn
d@(L SrcSpanAnnA
_ (RoleAnnotDecl XCRoleAnnotDecl GhcRn
_ LIdP GhcRn
_ [XRec GhcRn (Maybe Role)]
annots))
  = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Wrong number of roles listed in role annotation;" SDoc -> SDoc -> SDoc
$$
          String -> SDoc
text String
"Expected" SDoc -> SDoc -> SDoc
<+> (forall a. Outputable a => a -> SDoc
ppr forall a b. (a -> b) -> a -> b
$ forall (t :: * -> *) a. Foldable t => t a -> Arity
length [a]
tyvars) SDoc -> SDoc -> SDoc
<> SDoc
comma SDoc -> SDoc -> SDoc
<+>
          String -> SDoc
text String
"got" SDoc -> SDoc -> SDoc
<+> (forall a. Outputable a => a -> SDoc
ppr forall a b. (a -> b) -> a -> b
$ forall (t :: * -> *) a. Foldable t => t a -> Arity
length [XRec GhcRn (Maybe Role)]
annots) SDoc -> SDoc -> SDoc
<> SDoc
colon)
       Arity
2 (forall a. Outputable a => a -> SDoc
ppr LRoleAnnotDecl GhcRn
d)


illegalRoleAnnotDecl :: LRoleAnnotDecl GhcRn -> TcM ()
illegalRoleAnnotDecl :: LRoleAnnotDecl GhcRn -> TcRn ()
illegalRoleAnnotDecl (L SrcSpanAnnA
loc (RoleAnnotDecl XCRoleAnnotDecl GhcRn
_ LIdP GhcRn
tycon [XRec GhcRn (Maybe Role)]
_))
  = forall a. [ErrCtxt] -> TcM a -> TcM a
setErrCtxt [] forall a b. (a -> b) -> a -> b
$
    forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
loc forall a b. (a -> b) -> a -> b
$
    SDoc -> TcRn ()
addErrTc (String -> SDoc
text String
"Illegal role annotation for" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr LIdP GhcRn
tycon SDoc -> SDoc -> SDoc
<> Char -> SDoc
char Char
';' SDoc -> SDoc -> SDoc
$$
              String -> SDoc
text String
"they are allowed only for datatypes and classes.")

needXRoleAnnotations :: TyCon -> SDoc
needXRoleAnnotations :: TyCon -> SDoc
needXRoleAnnotations TyCon
tc
  = String -> SDoc
text String
"Illegal role annotation for" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr TyCon
tc SDoc -> SDoc -> SDoc
<> Char -> SDoc
char Char
';' SDoc -> SDoc -> SDoc
$$
    String -> SDoc
text String
"did you intend to use RoleAnnotations?"

incoherentRoles :: SDoc
incoherentRoles :: SDoc
incoherentRoles = (String -> SDoc
text String
"Roles other than" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (String -> SDoc
text String
"nominal") SDoc -> SDoc -> SDoc
<+>
                   String -> SDoc
text String
"for class parameters can lead to incoherence.") SDoc -> SDoc -> SDoc
$$
                  (String -> SDoc
text String
"Use IncoherentInstances to allow this; bad role found")

wrongTyFamName :: Name -> Name -> SDoc
wrongTyFamName :: Name -> Name -> SDoc
wrongTyFamName Name
fam_tc_name Name
eqn_tc_name
  = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Mismatched type name in type family instance.")
       Arity
2 ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Expected:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Name
fam_tc_name
               , String -> SDoc
text String
"  Actual:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr Name
eqn_tc_name ])

addTyConCtxt :: TyCon -> TcM a -> TcM a
addTyConCtxt :: forall a. TyCon -> TcM a -> TcM a
addTyConCtxt TyCon
tc = forall a. Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav
  where
    name :: Name
name = forall a. NamedThing a => a -> Name
getName TyCon
tc
    flav :: TyConFlavour
flav = TyCon -> TyConFlavour
tyConFlavour TyCon
tc

addRoleAnnotCtxt :: Name -> TcM a -> TcM a
addRoleAnnotCtxt :: forall a. Name -> TcM a -> TcM a
addRoleAnnotCtxt Name
name
  = forall a. SDoc -> TcM a -> TcM a
addErrCtxt forall a b. (a -> b) -> a -> b
$
    String -> SDoc
text String
"while checking a role annotation for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr Name
name)