{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998

\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
-}

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

module TcHsType (
        -- Type signatures
        kcClassSigType, tcClassSigType,
        tcHsSigType, tcHsSigWcType,
        tcHsPartialSigType,
        tcStandaloneKindSig,
        funsSigCtxt, addSigCtxt, pprSigCtxt,

        tcHsClsInstType,
        tcHsDeriv, tcDerivStrategy,
        tcHsTypeApp,
        UserTypeCtxt(..),
        bindImplicitTKBndrs_Tv, bindImplicitTKBndrs_Skol,
            bindImplicitTKBndrs_Q_Tv, bindImplicitTKBndrs_Q_Skol,
        bindExplicitTKBndrs_Tv, bindExplicitTKBndrs_Skol,
            bindExplicitTKBndrs_Q_Tv, bindExplicitTKBndrs_Q_Skol,
        ContextKind(..),

                -- Type checking type and class decls
        kcLookupTcTyCon, bindTyClTyVars,
        etaExpandAlgTyCon, tcbVisibilities,

          -- tyvars
        zonkAndScopedSort,

        -- Kind-checking types
        -- No kind generalisation, no checkValidType
        InitialKindStrategy(..),
        SAKS_or_CUSK(..),
        kcDeclHeader,
        tcNamedWildCardBinders,
        tcHsLiftedType,   tcHsOpenType,
        tcHsLiftedTypeNC, tcHsOpenTypeNC,
        tcLHsType, tcLHsTypeUnsaturated, tcCheckLHsType,
        tcHsMbContext, tcHsContext, tcLHsPredType, tcInferApps,
        failIfEmitsConstraints,
        solveEqualities, -- useful re-export

        typeLevelMode, kindLevelMode,

        kindGeneralizeAll, kindGeneralizeSome, kindGeneralizeNone,
        checkExpectedKind_pp,

        -- Sort-checking kinds
        tcLHsKindSig, checkDataKindSig, DataSort(..),
        checkClassKindSig,

        -- Pattern type signatures
        tcHsPatSigType, tcPatSig,

        -- Error messages
        funAppCtxt, addTyConFlavCtxt
   ) where

#include "HsVersions.h"

import GhcPrelude

import GHC.Hs
import TcRnMonad
import TcOrigin
import Predicate
import Constraint
import TcEvidence
import TcEnv
import TcMType
import TcValidity
import TcUnify
import TcIface
import TcSimplify
import TcHsSyn
import TyCoRep
import TyCoPpr
import TcErrors ( reportAllUnsolved )
import TcType
import Inst   ( tcInstInvisibleTyBinders, tcInstInvisibleTyBinder )
import Type
import TysPrim
import RdrName( lookupLocalRdrOcc )
import Var
import VarSet
import TyCon
import ConLike
import DataCon
import Class
import Name
-- import NameSet
import VarEnv
import TysWiredIn
import BasicTypes
import SrcLoc
import Constants ( mAX_CTUPLE_SIZE )
import ErrUtils( MsgDoc )
import Unique
import UniqSet
import Util
import UniqSupply
import Outputable
import FastString
import PrelNames hiding ( wildCardName )
import DynFlags
import qualified GHC.LanguageExtensions as LangExt

import Maybes
import Data.List ( find )
import Control.Monad

{-
        ----------------------------
                General notes
        ----------------------------

Unlike with expressions, type-checking types both does some checking and
desugars at the same time. This is necessary because we often want to perform
equality checks on the types right away, and it would be incredibly painful
to do this on un-desugared types. Luckily, desugared types are close enough
to HsTypes to make the error messages sane.

During type-checking, we perform as little validity checking as possible.
Generally, after type-checking, you will want to do validity checking, say
with TcValidity.checkValidType.

Validity checking
~~~~~~~~~~~~~~~~~
Some of the validity check could in principle be done by the kind checker,
but not all:

- During desugaring, we normalise by expanding type synonyms.  Only
  after this step can we check things like type-synonym saturation
  e.g.  type T k = k Int
        type S a = a
  Then (T S) is ok, because T is saturated; (T S) expands to (S Int);
  and then S is saturated.  This is a GHC extension.

- Similarly, also a GHC extension, we look through synonyms before complaining
  about the form of a class or instance declaration

- Ambiguity checks involve functional dependencies

Also, in a mutually recursive group of types, we can't look at the TyCon until we've
finished building the loop.  So to keep things simple, we postpone most validity
checking until step (3).

%************************************************************************
%*                                                                      *
              Check types AND do validity checking
*                                                                      *
************************************************************************
-}

funsSigCtxt :: [Located Name] -> UserTypeCtxt
-- Returns FunSigCtxt, with no redundant-context-reporting,
-- form a list of located names
funsSigCtxt :: [Located Name] -> UserTypeCtxt
funsSigCtxt (L SrcSpan
_ Name
name1 : [Located Name]
_) = Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
name1 Bool
False
funsSigCtxt []              = String -> UserTypeCtxt
forall a. String -> a
panic String
"funSigCtxt"

addSigCtxt :: UserTypeCtxt -> LHsType GhcRn -> TcM a -> TcM a
addSigCtxt :: UserTypeCtxt -> LHsType GhcRn -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt LHsType GhcRn
hs_ty TcM a
thing_inside
  = SrcSpan -> TcM a -> TcM a
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (LHsType GhcRn -> SrcSpan
forall a. HasSrcSpan a => a -> SrcSpan
getLoc LHsType GhcRn
hs_ty) (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    MsgDoc -> TcM a -> TcM a
forall a. MsgDoc -> TcM a -> TcM a
addErrCtxt (UserTypeCtxt -> LHsType GhcRn -> MsgDoc
pprSigCtxt UserTypeCtxt
ctxt LHsType GhcRn
hs_ty) (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    TcM a
thing_inside

pprSigCtxt :: UserTypeCtxt -> LHsType GhcRn -> SDoc
-- (pprSigCtxt ctxt <extra> <type>)
-- prints    In the type signature for 'f':
--              f :: <type>
-- The <extra> is either empty or "the ambiguity check for"
pprSigCtxt :: UserTypeCtxt -> LHsType GhcRn -> MsgDoc
pprSigCtxt UserTypeCtxt
ctxt LHsType GhcRn
hs_ty
  | Just Name
n <- UserTypeCtxt -> Maybe Name
isSigMaybe UserTypeCtxt
ctxt
  = MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"In the type signature:")
       Int
2 (Name -> MsgDoc
forall a. OutputableBndr a => a -> MsgDoc
pprPrefixOcc Name
n MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc
dcolon MsgDoc -> MsgDoc -> MsgDoc
<+> LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
hs_ty)

  | Bool
otherwise
  = MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"In" MsgDoc -> MsgDoc -> MsgDoc
<+> UserTypeCtxt -> MsgDoc
pprUserTypeCtxt UserTypeCtxt
ctxt MsgDoc -> MsgDoc -> MsgDoc
<> MsgDoc
colon)
       Int
2 (LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
hs_ty)

tcHsSigWcType :: UserTypeCtxt -> LHsSigWcType GhcRn -> TcM Type
-- This one is used when we have a LHsSigWcType, but in
-- a place where wildcards aren't allowed. The renamer has
-- already checked this, so we can simply ignore it.
tcHsSigWcType :: UserTypeCtxt -> LHsSigWcType GhcRn -> TcM Type
tcHsSigWcType UserTypeCtxt
ctxt LHsSigWcType GhcRn
sig_ty = UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsSigType UserTypeCtxt
ctxt (LHsSigWcType GhcRn -> LHsSigType GhcRn
forall pass. LHsSigWcType pass -> LHsSigType pass
dropWildCards LHsSigWcType GhcRn
sig_ty)

kcClassSigType :: SkolemInfo -> [Located Name] -> LHsSigType GhcRn -> TcM ()
kcClassSigType :: SkolemInfo -> [Located Name] -> LHsSigType GhcRn -> TcM ()
kcClassSigType SkolemInfo
skol_info [Located Name]
names LHsSigType GhcRn
sig_ty
  = TcM Type -> TcM ()
forall a. TcM a -> TcM ()
discardResult (TcM Type -> TcM ()) -> TcM Type -> TcM ()
forall a b. (a -> b) -> a -> b
$
    SkolemInfo -> [Located Name] -> LHsSigType GhcRn -> TcM Type
tcClassSigType SkolemInfo
skol_info [Located Name]
names LHsSigType GhcRn
sig_ty
  -- tcClassSigType does a fair amount of extra work that we don't need,
  -- such as ordering quantified variables. But we absolutely do need
  -- to push the level when checking method types and solve local equalities,
  -- and so it seems easier just to call tcClassSigType than selectively
  -- extract the lines of code from tc_hs_sig_type that we really need.
  -- If we don't push the level, we get #16517, where GHC accepts
  --   class C a where
  --     meth :: forall k. Proxy (a :: k) -> ()
  -- Note that k is local to meth -- this is hogwash.

tcClassSigType :: SkolemInfo -> [Located Name] -> LHsSigType GhcRn -> TcM Type
-- Does not do validity checking
tcClassSigType :: SkolemInfo -> [Located Name] -> LHsSigType GhcRn -> TcM Type
tcClassSigType SkolemInfo
skol_info [Located Name]
names LHsSigType GhcRn
sig_ty
  = UserTypeCtxt -> LHsType GhcRn -> TcM Type -> TcM Type
forall a. UserTypeCtxt -> LHsType GhcRn -> TcM a -> TcM a
addSigCtxt ([Located Name] -> UserTypeCtxt
funsSigCtxt [Located Name]
names) (LHsSigType GhcRn -> LHsType GhcRn
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
hsSigType LHsSigType GhcRn
sig_ty) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    (Bool, Type) -> Type
forall a b. (a, b) -> b
snd ((Bool, Type) -> Type)
-> IOEnv (Env TcGblEnv TcLclEnv) (Bool, Type) -> TcM Type
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> SkolemInfo
-> LHsSigType GhcRn
-> ContextKind
-> IOEnv (Env TcGblEnv TcLclEnv) (Bool, Type)
tc_hs_sig_type SkolemInfo
skol_info LHsSigType GhcRn
sig_ty (Type -> ContextKind
TheKind Type
liftedTypeKind)
       -- Do not zonk-to-Type, nor perform a validity check
       -- We are in a knot with the class and associated types
       -- Zonking and validity checking is done by tcClassDecl
       -- No need to fail here if the type has an error:
       --   If we're in the kind-checking phase, the solveEqualities
       --     in kcTyClGroup catches the error
       --   If we're in the type-checking phase, the solveEqualities
       --     in tcClassDecl1 gets it
       -- Failing fast here degrades the error message in, e.g., tcfail135:
       --   class Foo f where
       --     baa :: f a -> f
       -- If we fail fast, we're told that f has kind `k1` when we wanted `*`.
       -- It should be that f has kind `k2 -> *`, but we never get a chance
       -- to run the solver where the kind of f is touchable. This is
       -- painfully delicate.

tcHsSigType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
-- Does validity checking
-- See Note [Recipe for checking a signature]
tcHsSigType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsSigType UserTypeCtxt
ctxt LHsSigType GhcRn
sig_ty
  = UserTypeCtxt -> LHsType GhcRn -> TcM Type -> TcM Type
forall a. UserTypeCtxt -> LHsType GhcRn -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt (LHsSigType GhcRn -> LHsType GhcRn
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
hsSigType LHsSigType GhcRn
sig_ty) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { String -> MsgDoc -> TcM ()
traceTc String
"tcHsSigType {" (LHsSigType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsSigType GhcRn
sig_ty)

          -- Generalise here: see Note [Kind generalisation]
       ; (Bool
insol, Type
ty) <- SkolemInfo
-> LHsSigType GhcRn
-> ContextKind
-> IOEnv (Env TcGblEnv TcLclEnv) (Bool, Type)
tc_hs_sig_type SkolemInfo
skol_info LHsSigType GhcRn
sig_ty
                                       (UserTypeCtxt -> ContextKind
expectedKindInCtxt UserTypeCtxt
ctxt)
       ; Type
ty <- Type -> TcM Type
zonkTcType Type
ty

       ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
insol TcM ()
forall env a. IOEnv env a
failM
       -- See Note [Fail fast if there are insoluble kind equalities] in TcSimplify

       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
ty
       ; String -> MsgDoc -> TcM ()
traceTc String
"end tcHsSigType }" (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
ty)
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
ty }
  where
    skol_info :: SkolemInfo
skol_info = UserTypeCtxt -> SkolemInfo
SigTypeSkol UserTypeCtxt
ctxt

-- Does validity checking and zonking.
tcStandaloneKindSig :: LStandaloneKindSig GhcRn -> TcM (Name, Kind)
tcStandaloneKindSig :: LStandaloneKindSig GhcRn -> TcM (Name, Type)
tcStandaloneKindSig (L SrcSpan
_ StandaloneKindSig GhcRn
kisig) = case StandaloneKindSig GhcRn
kisig of
  StandaloneKindSig XStandaloneKindSig GhcRn
_ (L SrcSpan
_ IdP GhcRn
name) LHsSigType GhcRn
ksig ->
    let ctxt :: UserTypeCtxt
ctxt = Name -> UserTypeCtxt
StandaloneKindSigCtxt Name
IdP GhcRn
name in
    UserTypeCtxt
-> LHsType GhcRn -> TcM (Name, Type) -> TcM (Name, Type)
forall a. UserTypeCtxt -> LHsType GhcRn -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt (LHsSigType GhcRn -> LHsType GhcRn
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
hsSigType LHsSigType GhcRn
ksig) (TcM (Name, Type) -> TcM (Name, Type))
-> TcM (Name, Type) -> TcM (Name, Type)
forall a b. (a -> b) -> a -> b
$
    do { Type
kind <- TcTyMode -> LHsSigType GhcRn -> ContextKind -> TcM Type
tcTopLHsType TcTyMode
kindLevelMode LHsSigType GhcRn
ksig (UserTypeCtxt -> ContextKind
expectedKindInCtxt UserTypeCtxt
ctxt)
       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
kind
       ; (Name, Type) -> TcM (Name, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Name
IdP GhcRn
name, Type
kind) }
  XStandaloneKindSig XXStandaloneKindSig GhcRn
nec -> NoExtCon -> TcM (Name, Type)
forall a. NoExtCon -> a
noExtCon XXStandaloneKindSig GhcRn
NoExtCon
nec

tc_hs_sig_type :: SkolemInfo -> LHsSigType GhcRn
               -> ContextKind -> TcM (Bool, TcType)
-- Kind-checks/desugars an 'LHsSigType',
--   solve equalities,
--   and then kind-generalizes.
-- This will never emit constraints, as it uses solveEqualities interally.
-- No validity checking or zonking
-- Returns also a Bool indicating whether the type induced an insoluble constraint;
-- True <=> constraint is insoluble
tc_hs_sig_type :: SkolemInfo
-> LHsSigType GhcRn
-> ContextKind
-> IOEnv (Env TcGblEnv TcLclEnv) (Bool, Type)
tc_hs_sig_type SkolemInfo
skol_info LHsSigType GhcRn
hs_sig_type ContextKind
ctxt_kind
  | HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext = XHsIB GhcRn (LHsType GhcRn)
sig_vars, hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body = LHsType GhcRn
hs_ty } <- LHsSigType GhcRn
hs_sig_type
  = do { (TcLevel
tc_lvl, (WantedConstraints
wanted, ([TcTyVar]
spec_tkvs, Type
ty)))
              <- TcM (WantedConstraints, ([TcTyVar], Type))
-> TcM (TcLevel, (WantedConstraints, ([TcTyVar], Type)))
forall a. TcM a -> TcM (TcLevel, a)
pushTcLevelM                           (TcM (WantedConstraints, ([TcTyVar], Type))
 -> TcM (TcLevel, (WantedConstraints, ([TcTyVar], Type))))
-> TcM (WantedConstraints, ([TcTyVar], Type))
-> TcM (TcLevel, (WantedConstraints, ([TcTyVar], Type)))
forall a b. (a -> b) -> a -> b
$
                 String
-> TcM ([TcTyVar], Type)
-> TcM (WantedConstraints, ([TcTyVar], Type))
forall a. String -> TcM a -> TcM (WantedConstraints, a)
solveLocalEqualitiesX String
"tc_hs_sig_type" (TcM ([TcTyVar], Type)
 -> TcM (WantedConstraints, ([TcTyVar], Type)))
-> TcM ([TcTyVar], Type)
-> TcM (WantedConstraints, ([TcTyVar], Type))
forall a b. (a -> b) -> a -> b
$
                 [Name] -> TcM Type -> TcM ([TcTyVar], Type)
forall a. [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Skol [Name]
XHsIB GhcRn (LHsType GhcRn)
sig_vars      (TcM Type -> TcM ([TcTyVar], Type))
-> TcM Type -> TcM ([TcTyVar], Type)
forall a b. (a -> b) -> a -> b
$
                 do { Type
kind <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
                    ; TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
typeLevelMode LHsType GhcRn
hs_ty Type
kind }
       -- Any remaining variables (unsolved in the solveLocalEqualities)
       -- should be in the global tyvars, and therefore won't be quantified

       ; [TcTyVar]
spec_tkvs <- [TcTyVar] -> TcM [TcTyVar]
zonkAndScopedSort [TcTyVar]
spec_tkvs
       ; let ty1 :: Type
ty1 = [TcTyVar] -> Type -> Type
mkSpecForAllTys [TcTyVar]
spec_tkvs Type
ty

       -- This bit is very much like decideMonoTyVars in TcSimplify,
       -- but constraints are so much simpler in kinds, it is much
       -- easier here. (In particular, we never quantify over a
       -- constraint in a type.)
       ; TyCoVarSet
constrained <- TyCoVarSet -> TcM TyCoVarSet
zonkTyCoVarsAndFV (WantedConstraints -> TyCoVarSet
tyCoVarsOfWC WantedConstraints
wanted)
       ; let should_gen :: TcTyVar -> Bool
should_gen = Bool -> Bool
not (Bool -> Bool) -> (TcTyVar -> Bool) -> TcTyVar -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (TcTyVar -> TyCoVarSet -> Bool
`elemVarSet` TyCoVarSet
constrained)

       ; [TcTyVar]
kvs <- (TcTyVar -> Bool) -> Type -> TcM [TcTyVar]
kindGeneralizeSome TcTyVar -> Bool
should_gen Type
ty1
       ; SkolemInfo
-> Maybe MsgDoc
-> [TcTyVar]
-> TcLevel
-> WantedConstraints
-> TcM ()
emitResidualTvConstraint SkolemInfo
skol_info Maybe MsgDoc
forall a. Maybe a
Nothing ([TcTyVar]
kvs [TcTyVar] -> [TcTyVar] -> [TcTyVar]
forall a. [a] -> [a] -> [a]
++ [TcTyVar]
spec_tkvs)
                                  TcLevel
tc_lvl WantedConstraints
wanted

       ; (Bool, Type) -> IOEnv (Env TcGblEnv TcLclEnv) (Bool, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (WantedConstraints -> Bool
insolubleWC WantedConstraints
wanted, [TcTyVar] -> Type -> Type
mkInvForAllTys [TcTyVar]
kvs Type
ty1) }

tc_hs_sig_type SkolemInfo
_ (XHsImplicitBndrs XXHsImplicitBndrs GhcRn (LHsType GhcRn)
nec) ContextKind
_ = NoExtCon -> IOEnv (Env TcGblEnv TcLclEnv) (Bool, Type)
forall a. NoExtCon -> a
noExtCon XXHsImplicitBndrs GhcRn (LHsType GhcRn)
NoExtCon
nec

tcTopLHsType :: TcTyMode -> LHsSigType GhcRn -> ContextKind -> TcM Type
-- tcTopLHsType is used for kind-checking top-level HsType where
--   we want to fully solve /all/ equalities, and report errors
-- Does zonking, but not validity checking because it's used
--   for things (like deriving and instances) that aren't
--   ordinary types
tcTopLHsType :: TcTyMode -> LHsSigType GhcRn -> ContextKind -> TcM Type
tcTopLHsType TcTyMode
mode LHsSigType GhcRn
hs_sig_type ContextKind
ctxt_kind
  | HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext = XHsIB GhcRn (LHsType GhcRn)
sig_vars, hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body = LHsType GhcRn
hs_ty } <- LHsSigType GhcRn
hs_sig_type
  = do { String -> MsgDoc -> TcM ()
traceTc String
"tcTopLHsType {" (LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
hs_ty)
       ; ([TcTyVar]
spec_tkvs, Type
ty)
              <- TcM ([TcTyVar], Type) -> TcM ([TcTyVar], Type)
forall a. TcM a -> TcM a
pushTcLevelM_                     (TcM ([TcTyVar], Type) -> TcM ([TcTyVar], Type))
-> TcM ([TcTyVar], Type) -> TcM ([TcTyVar], Type)
forall a b. (a -> b) -> a -> b
$
                 TcM ([TcTyVar], Type) -> TcM ([TcTyVar], Type)
forall a. TcM a -> TcM a
solveEqualities                   (TcM ([TcTyVar], Type) -> TcM ([TcTyVar], Type))
-> TcM ([TcTyVar], Type) -> TcM ([TcTyVar], Type)
forall a b. (a -> b) -> a -> b
$
                 [Name] -> TcM Type -> TcM ([TcTyVar], Type)
forall a. [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Skol [Name]
XHsIB GhcRn (LHsType GhcRn)
sig_vars (TcM Type -> TcM ([TcTyVar], Type))
-> TcM Type -> TcM ([TcTyVar], Type)
forall a b. (a -> b) -> a -> b
$
                 do { Type
kind <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
                    ; TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
hs_ty Type
kind }

       ; [TcTyVar]
spec_tkvs <- [TcTyVar] -> TcM [TcTyVar]
zonkAndScopedSort [TcTyVar]
spec_tkvs
       ; let ty1 :: Type
ty1 = [TcTyVar] -> Type -> Type
mkSpecForAllTys [TcTyVar]
spec_tkvs Type
ty
       ; [TcTyVar]
kvs <- Type -> TcM [TcTyVar]
kindGeneralizeAll Type
ty1  -- "All" because it's a top-level type
       ; Type
final_ty <- Type -> TcM Type
zonkTcTypeToType ([TcTyVar] -> Type -> Type
mkInvForAllTys [TcTyVar]
kvs Type
ty1)
       ; String -> MsgDoc -> TcM ()
traceTc String
"End tcTopLHsType }" ([MsgDoc] -> MsgDoc
vcat [LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
hs_ty, Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
final_ty])
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
final_ty}

tcTopLHsType TcTyMode
_ (XHsImplicitBndrs XXHsImplicitBndrs GhcRn (LHsType GhcRn)
nec) ContextKind
_ = NoExtCon -> TcM Type
forall a. NoExtCon -> a
noExtCon XXHsImplicitBndrs GhcRn (LHsType GhcRn)
NoExtCon
nec

-----------------
tcHsDeriv :: LHsSigType GhcRn -> TcM ([TyVar], Class, [Type], [Kind])
-- Like tcHsSigType, but for the ...deriving( C t1 ty2 ) clause
-- Returns the C, [ty1, ty2, and the kinds of C's remaining arguments
-- E.g.    class C (a::*) (b::k->k)
--         data T a b = ... deriving( C Int )
--    returns ([k], C, [k, Int], [k->k])
-- Return values are fully zonked
tcHsDeriv :: LHsSigType GhcRn -> TcM ([TcTyVar], Class, [Type], [Type])
tcHsDeriv LHsSigType GhcRn
hs_ty
  = do { Type
ty <- TcM Type -> TcM Type
forall a. TcM a -> TcM a
checkNoErrs (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$  -- Avoid redundant error report
                              -- with "illegal deriving", below
               TcTyMode -> LHsSigType GhcRn -> ContextKind -> TcM Type
tcTopLHsType TcTyMode
typeLevelMode LHsSigType GhcRn
hs_ty ContextKind
AnyKind
       ; let ([TcTyVar]
tvs, Type
pred)    = Type -> ([TcTyVar], Type)
splitForAllTys Type
ty
             ([Type]
kind_args, Type
_) = Type -> ([Type], Type)
splitFunTys (HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
pred)
       ; case Type -> Maybe (Class, [Type])
getClassPredTys_maybe Type
pred of
           Just (Class
cls, [Type]
tys) -> ([TcTyVar], Class, [Type], [Type])
-> TcM ([TcTyVar], Class, [Type], [Type])
forall (m :: * -> *) a. Monad m => a -> m a
return ([TcTyVar]
tvs, Class
cls, [Type]
tys, [Type]
kind_args)
           Maybe (Class, [Type])
Nothing -> MsgDoc -> TcM ([TcTyVar], Class, [Type], [Type])
forall a. MsgDoc -> TcM a
failWithTc (String -> MsgDoc
text String
"Illegal deriving item" MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (LHsSigType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsSigType GhcRn
hs_ty)) }

-- | Typecheck a deriving strategy. For most deriving strategies, this is a
-- no-op, but for the @via@ strategy, this requires typechecking the @via@ type.
tcDerivStrategy ::
     Maybe (LDerivStrategy GhcRn)
     -- ^ The deriving strategy
  -> TcM (Maybe (LDerivStrategy GhcTc), [TyVar])
     -- ^ The typechecked deriving strategy and the tyvars that it binds
     -- (if using 'ViaStrategy').
tcDerivStrategy :: Maybe (LDerivStrategy GhcRn)
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
tcDerivStrategy Maybe (LDerivStrategy GhcRn)
mb_lds
  = case Maybe (LDerivStrategy GhcRn)
mb_lds of
      Maybe (LDerivStrategy GhcRn)
Nothing -> Maybe (LDerivStrategy GhcTc)
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
forall ds. ds -> TcM (ds, [TcTyVar])
boring_case Maybe (LDerivStrategy GhcTc)
forall a. Maybe a
Nothing
      Just (LDerivStrategy GhcRn
-> Located (SrcSpanLess (LDerivStrategy GhcRn))
forall a. HasSrcSpan a => a -> Located (SrcSpanLess a)
dL->L SrcSpan
loc SrcSpanLess (LDerivStrategy GhcRn)
ds) ->
        SrcSpan
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
 -> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar]))
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
forall a b. (a -> b) -> a -> b
$ do
          (DerivStrategy GhcTc
ds', [TcTyVar]
tvs) <- DerivStrategy GhcRn -> TcM (DerivStrategy GhcTc, [TcTyVar])
tc_deriv_strategy SrcSpanLess (LDerivStrategy GhcRn)
DerivStrategy GhcRn
ds
          (Maybe (LDerivStrategy GhcTc), [TcTyVar])
-> TcM (Maybe (LDerivStrategy GhcTc), [TcTyVar])
forall (f :: * -> *) a. Applicative f => a -> f a
pure (LDerivStrategy GhcTc -> Maybe (LDerivStrategy GhcTc)
forall a. a -> Maybe a
Just (SrcSpan
-> SrcSpanLess (LDerivStrategy GhcTc) -> LDerivStrategy GhcTc
forall a. HasSrcSpan a => SrcSpan -> SrcSpanLess a -> a
cL SrcSpan
loc SrcSpanLess (LDerivStrategy GhcTc)
DerivStrategy GhcTc
ds'), [TcTyVar]
tvs)
  where
    tc_deriv_strategy :: DerivStrategy GhcRn
                      -> TcM (DerivStrategy GhcTc, [TyVar])
    tc_deriv_strategy :: DerivStrategy GhcRn -> TcM (DerivStrategy GhcTc, [TcTyVar])
tc_deriv_strategy DerivStrategy GhcRn
StockStrategy    = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TcTyVar])
forall ds. ds -> TcM (ds, [TcTyVar])
boring_case DerivStrategy GhcTc
forall pass. DerivStrategy pass
StockStrategy
    tc_deriv_strategy DerivStrategy GhcRn
AnyclassStrategy = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TcTyVar])
forall ds. ds -> TcM (ds, [TcTyVar])
boring_case DerivStrategy GhcTc
forall pass. DerivStrategy pass
AnyclassStrategy
    tc_deriv_strategy DerivStrategy GhcRn
NewtypeStrategy  = DerivStrategy GhcTc -> TcM (DerivStrategy GhcTc, [TcTyVar])
forall ds. ds -> TcM (ds, [TcTyVar])
boring_case DerivStrategy GhcTc
forall pass. DerivStrategy pass
NewtypeStrategy
    tc_deriv_strategy (ViaStrategy XViaStrategy GhcRn
ty) = do
      Type
ty' <- TcM Type -> TcM Type
forall a. TcM a -> TcM a
checkNoErrs (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$ TcTyMode -> LHsSigType GhcRn -> ContextKind -> TcM Type
tcTopLHsType TcTyMode
typeLevelMode XViaStrategy GhcRn
LHsSigType GhcRn
ty ContextKind
AnyKind
      let ([TcTyVar]
via_tvs, Type
via_pred) = Type -> ([TcTyVar], Type)
splitForAllTys Type
ty'
      (DerivStrategy GhcTc, [TcTyVar])
-> TcM (DerivStrategy GhcTc, [TcTyVar])
forall (f :: * -> *) a. Applicative f => a -> f a
pure (XViaStrategy GhcTc -> DerivStrategy GhcTc
forall pass. XViaStrategy pass -> DerivStrategy pass
ViaStrategy Type
XViaStrategy GhcTc
via_pred, [TcTyVar]
via_tvs)

    boring_case :: ds -> TcM (ds, [TyVar])
    boring_case :: ds -> TcM (ds, [TcTyVar])
boring_case ds
ds = (ds, [TcTyVar]) -> TcM (ds, [TcTyVar])
forall (f :: * -> *) a. Applicative f => a -> f a
pure (ds
ds, [])

tcHsClsInstType :: UserTypeCtxt    -- InstDeclCtxt or SpecInstCtxt
                -> LHsSigType GhcRn
                -> TcM Type
-- Like tcHsSigType, but for a class instance declaration
tcHsClsInstType :: UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsClsInstType UserTypeCtxt
user_ctxt LHsSigType GhcRn
hs_inst_ty
  = SrcSpan -> TcM Type -> TcM Type
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (LHsType GhcRn -> SrcSpan
forall a. HasSrcSpan a => a -> SrcSpan
getLoc (LHsSigType GhcRn -> LHsType GhcRn
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
hsSigType LHsSigType GhcRn
hs_inst_ty)) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    do { -- Fail eagerly if tcTopLHsType fails.  We are at top level so
         -- these constraints will never be solved later. And failing
         -- eagerly avoids follow-on errors when checkValidInstance
         -- sees an unsolved coercion hole
         Type
inst_ty <- TcM Type -> TcM Type
forall a. TcM a -> TcM a
checkNoErrs (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                    TcTyMode -> LHsSigType GhcRn -> ContextKind -> TcM Type
tcTopLHsType TcTyMode
typeLevelMode LHsSigType GhcRn
hs_inst_ty (Type -> ContextKind
TheKind Type
constraintKind)
       ; UserTypeCtxt -> LHsSigType GhcRn -> Type -> TcM ()
checkValidInstance UserTypeCtxt
user_ctxt LHsSigType GhcRn
hs_inst_ty Type
inst_ty
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
inst_ty }

----------------------------------------------
-- | Type-check a visible type application
tcHsTypeApp :: LHsWcType GhcRn -> Kind -> TcM Type
-- See Note [Recipe for checking a signature] in TcHsType
tcHsTypeApp :: LHsWcType GhcRn -> Type -> TcM Type
tcHsTypeApp LHsWcType GhcRn
wc_ty Type
kind
  | HsWC { hswc_ext :: forall pass thing. HsWildCardBndrs pass thing -> XHsWC pass thing
hswc_ext = XHsWC GhcRn (LHsType GhcRn)
sig_wcs, hswc_body :: forall pass thing. HsWildCardBndrs pass thing -> thing
hswc_body = LHsType GhcRn
hs_ty } <- LHsWcType GhcRn
wc_ty
  = do { Type
ty <- String -> TcM Type -> TcM Type
forall a. String -> TcM a -> TcM a
solveLocalEqualities String
"tcHsTypeApp" (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
               -- We are looking at a user-written type, very like a
               -- signature so we want to solve its equalities right now
               WarningFlag -> TcM Type -> TcM Type
forall gbl lcl a.
WarningFlag -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
unsetWOptM WarningFlag
Opt_WarnPartialTypeSignatures (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
               Extension -> TcM Type -> TcM Type
forall gbl lcl a. Extension -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setXOptM Extension
LangExt.PartialTypeSignatures (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
               -- See Note [Wildcards in visible type application]
               [Name] -> ([(Name, TcTyVar)] -> TcM Type) -> TcM Type
forall a. [Name] -> ([(Name, TcTyVar)] -> TcM a) -> TcM a
tcNamedWildCardBinders [Name]
XHsWC GhcRn (LHsType GhcRn)
sig_wcs (([(Name, TcTyVar)] -> TcM Type) -> TcM Type)
-> ([(Name, TcTyVar)] -> TcM Type) -> TcM Type
forall a b. (a -> b) -> a -> b
$ \ [(Name, TcTyVar)]
_ ->
               LHsType GhcRn -> Type -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_ty Type
kind
       -- We do not kind-generalize type applications: we just
       -- instantiate with exactly what the user says.
       -- See Note [No generalization in type application]
       -- We still must call kindGeneralizeNone, though, according
       -- to Note [Recipe for checking a signature]
       ; Type -> TcM ()
kindGeneralizeNone Type
ty
       ; Type
ty <- Type -> TcM Type
zonkTcType Type
ty
       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
TypeAppCtxt Type
ty
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
ty }
tcHsTypeApp (XHsWildCardBndrs XXHsWildCardBndrs GhcRn (LHsType GhcRn)
nec) Type
_ = NoExtCon -> TcM Type
forall a. NoExtCon -> a
noExtCon XXHsWildCardBndrs GhcRn (LHsType GhcRn)
NoExtCon
nec

{- Note [Wildcards in visible type application]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A HsWildCardBndrs's hswc_ext now only includes /named/ wildcards, so
any unnamed wildcards stay unchanged in hswc_body.  When called in
tcHsTypeApp, tcCheckLHsType will call emitAnonWildCardHoleConstraint
on these anonymous wildcards. However, this would trigger
error/warning when an anonymous wildcard is passed in as a visible type
argument, which we do not want because users should be able to write
@_ to skip a instantiating a type variable variable without fuss. The
solution is to switch the PartialTypeSignatures flags here to let the
typechecker know that it's checking a '@_' and do not emit hole
constraints on it.  See related Note [Wildcards in visible kind
application] and Note [The wildcard story for types] in GHC.Hs.Types

Ugh!

Note [No generalization in type application]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We do not kind-generalize type applications. Imagine

  id @(Proxy Nothing)

If we kind-generalized, we would get

  id @(forall {k}. Proxy @(Maybe k) (Nothing @k))

which is very sneakily impredicative instantiation.

There is also the possibility of mentioning a wildcard
(`id @(Proxy _)`), which definitely should not be kind-generalized.

-}

{-
************************************************************************
*                                                                      *
            The main kind checker: no validity checks here
*                                                                      *
************************************************************************
-}

---------------------------
tcHsOpenType, tcHsLiftedType,
  tcHsOpenTypeNC, tcHsLiftedTypeNC :: LHsType GhcRn -> TcM TcType
-- Used for type signatures
-- Do not do validity checking
tcHsOpenType :: LHsType GhcRn -> TcM Type
tcHsOpenType LHsType GhcRn
ty   = LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$ LHsType GhcRn -> TcM Type
tcHsOpenTypeNC LHsType GhcRn
ty
tcHsLiftedType :: LHsType GhcRn -> TcM Type
tcHsLiftedType LHsType GhcRn
ty = LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$ LHsType GhcRn -> TcM Type
tcHsLiftedTypeNC LHsType GhcRn
ty

tcHsOpenTypeNC :: LHsType GhcRn -> TcM Type
tcHsOpenTypeNC   LHsType GhcRn
ty = do { Type
ek <- TcM Type
newOpenTypeKind
                         ; TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
typeLevelMode LHsType GhcRn
ty Type
ek }
tcHsLiftedTypeNC :: LHsType GhcRn -> TcM Type
tcHsLiftedTypeNC LHsType GhcRn
ty = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
typeLevelMode LHsType GhcRn
ty Type
liftedTypeKind

-- Like tcHsType, but takes an expected kind
tcCheckLHsType :: LHsType GhcRn -> Kind -> TcM TcType
tcCheckLHsType :: LHsType GhcRn -> Type -> TcM Type
tcCheckLHsType LHsType GhcRn
hs_ty Type
exp_kind
  = LHsType GhcRn -> TcM Type -> TcM Type
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
typeLevelMode LHsType GhcRn
hs_ty Type
exp_kind

tcLHsType :: LHsType GhcRn -> TcM (TcType, TcKind)
-- Called from outside: set the context
tcLHsType :: LHsType GhcRn -> TcM (Type, Type)
tcLHsType LHsType GhcRn
ty = LHsType GhcRn -> TcM (Type, Type) -> TcM (Type, Type)
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
ty (TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
typeLevelMode LHsType GhcRn
ty)

-- Like tcLHsType, but use it in a context where type synonyms and type families
-- do not need to be saturated, like in a GHCi :kind call
tcLHsTypeUnsaturated :: LHsType GhcRn -> TcM (TcType, TcKind)
tcLHsTypeUnsaturated :: LHsType GhcRn -> TcM (Type, Type)
tcLHsTypeUnsaturated LHsType GhcRn
hs_ty
  | Just (LHsType GhcRn
hs_fun_ty, [LHsTypeArg GhcRn]
hs_args) <- HsType GhcRn -> Maybe (LHsType GhcRn, [LHsTypeArg GhcRn])
splitHsAppTys (LHsType GhcRn -> SrcSpanLess (LHsType GhcRn)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc LHsType GhcRn
hs_ty)
  = LHsType GhcRn -> TcM (Type, Type) -> TcM (Type, Type)
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
    do { (Type
fun_ty, Type
_ki) <- TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tcInferAppHead TcTyMode
mode LHsType GhcRn
hs_fun_ty
       ; TcTyMode
-> LHsType GhcRn -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
tcInferApps_nosat TcTyMode
mode LHsType GhcRn
hs_fun_ty Type
fun_ty [LHsTypeArg GhcRn]
hs_args }
         -- Notice the 'nosat'; do not instantiate trailing
         -- invisible arguments of a type family.
         -- See Note [Dealing with :kind]

  | Bool
otherwise
  = LHsType GhcRn -> TcM (Type, Type) -> TcM (Type, Type)
forall a. LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt LHsType GhcRn
hs_ty (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
hs_ty

  where
    mode :: TcTyMode
mode = TcTyMode
typeLevelMode

{- Note [Dealing with :kind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this GHCi command
  ghci> type family F :: Either j k
  ghci> :kind F
  F :: forall {j,k}. Either j k

We will only get the 'forall' if we /refrain/ from saturating those
invisible binders. But generally we /do/ saturate those invisible
binders (see tcInferApps), and we want to do so for nested application
even in GHCi.  Consider for example (#16287)
  ghci> type family F :: k
  ghci> data T :: (forall k. k) -> Type
  ghci> :kind T F
We want to reject this. It's just at the very top level that we want
to switch off saturation.

So tcLHsTypeUnsaturated does a little special case for top level
applications.  Actually the common case is a bare variable, as above.


************************************************************************
*                                                                      *
      Type-checking modes
*                                                                      *
************************************************************************

The kind-checker is parameterised by a TcTyMode, which contains some
information about where we're checking a type.

The renamer issues errors about what it can. All errors issued here must
concern things that the renamer can't handle.

-}

-- | Info about the context in which we're checking a type. Currently,
-- differentiates only between types and kinds, but this will likely
-- grow, at least to include the distinction between patterns and
-- not-patterns.
--
-- To find out where the mode is used, search for 'mode_level'
data TcTyMode = TcTyMode { TcTyMode -> TypeOrKind
mode_level :: TypeOrKind }

typeLevelMode :: TcTyMode
typeLevelMode :: TcTyMode
typeLevelMode = TcTyMode :: TypeOrKind -> TcTyMode
TcTyMode { mode_level :: TypeOrKind
mode_level = TypeOrKind
TypeLevel }

kindLevelMode :: TcTyMode
kindLevelMode :: TcTyMode
kindLevelMode = TcTyMode :: TypeOrKind -> TcTyMode
TcTyMode { mode_level :: TypeOrKind
mode_level = TypeOrKind
KindLevel }

-- switch to kind level
kindLevel :: TcTyMode -> TcTyMode
kindLevel :: TcTyMode -> TcTyMode
kindLevel TcTyMode
mode = TcTyMode
mode { mode_level :: TypeOrKind
mode_level = TypeOrKind
KindLevel }

instance Outputable TcTyMode where
  ppr :: TcTyMode -> MsgDoc
ppr = TypeOrKind -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr (TypeOrKind -> MsgDoc)
-> (TcTyMode -> TypeOrKind) -> TcTyMode -> MsgDoc
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcTyMode -> TypeOrKind
mode_level

{-
Note [Bidirectional type checking]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In expressions, whenever we see a polymorphic identifier, say `id`, we are
free to instantiate it with metavariables, knowing that we can always
re-generalize with type-lambdas when necessary. For example:

  rank2 :: (forall a. a -> a) -> ()
  x = rank2 id

When checking the body of `x`, we can instantiate `id` with a metavariable.
Then, when we're checking the application of `rank2`, we notice that we really
need a polymorphic `id`, and then re-generalize over the unconstrained
metavariable.

In types, however, we're not so lucky, because *we cannot re-generalize*!
There is no lambda. So, we must be careful only to instantiate at the last
possible moment, when we're sure we're never going to want the lost polymorphism
again. This is done in calls to tcInstInvisibleTyBinders.

To implement this behavior, we use bidirectional type checking, where we
explicitly think about whether we know the kind of the type we're checking
or not. Note that there is a difference between not knowing a kind and
knowing a metavariable kind: the metavariables are TauTvs, and cannot become
forall-quantified kinds. Previously (before dependent types), there were
no higher-rank kinds, and so we could instantiate early and be sure that
no types would have polymorphic kinds, and so we could always assume that
the kind of a type was a fresh metavariable. Not so anymore, thus the
need for two algorithms.

For HsType forms that can never be kind-polymorphic, we implement only the
"down" direction, where we safely assume a metavariable kind. For HsType forms
that *can* be kind-polymorphic, we implement just the "up" (functions with
"infer" in their name) version, as we gain nothing by also implementing the
"down" version.

Note [Future-proofing the type checker]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As discussed in Note [Bidirectional type checking], each HsType form is
handled in *either* tc_infer_hs_type *or* tc_hs_type. These functions
are mutually recursive, so that either one can work for any type former.
But, we want to make sure that our pattern-matches are complete. So,
we have a bunch of repetitive code just so that we get warnings if we're
missing any patterns.

-}

------------------------------------------
-- | Check and desugar a type, returning the core type and its
-- possibly-polymorphic kind. Much like 'tcInferRho' at the expression
-- level.
tc_infer_lhs_type :: TcTyMode -> LHsType GhcRn -> TcM (TcType, TcKind)
tc_infer_lhs_type :: TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode (L SrcSpan
span HsType GhcRn
ty)
  = SrcSpan -> TcM (Type, Type) -> TcM (Type, Type)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
span (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode HsType GhcRn
ty

---------------------------
-- | Call 'tc_infer_hs_type' and check its result against an expected kind.
tc_infer_hs_type_ek :: HasDebugCallStack => TcTyMode -> HsType GhcRn -> TcKind -> TcM TcType
tc_infer_hs_type_ek :: TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
hs_ty Type
ek
  = do { (Type
ty, Type
k) <- TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode HsType GhcRn
hs_ty
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
hs_ty Type
ty Type
k Type
ek }

---------------------------
-- | Infer the kind of a type and desugar. This is the "up" type-checker,
-- as described in Note [Bidirectional type checking]
tc_infer_hs_type :: TcTyMode -> HsType GhcRn -> TcM (TcType, TcKind)

tc_infer_hs_type :: TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode (HsParTy XParTy GhcRn
_ LHsType GhcRn
t)
  = TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
t

tc_infer_hs_type TcTyMode
mode HsType GhcRn
ty
  | Just (LHsType GhcRn
hs_fun_ty, [LHsTypeArg GhcRn]
hs_args) <- HsType GhcRn -> Maybe (LHsType GhcRn, [LHsTypeArg GhcRn])
splitHsAppTys HsType GhcRn
ty
  = do { (Type
fun_ty, Type
_ki) <- TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tcInferAppHead TcTyMode
mode LHsType GhcRn
hs_fun_ty
       ; TcTyMode
-> LHsType GhcRn -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
tcInferApps TcTyMode
mode LHsType GhcRn
hs_fun_ty Type
fun_ty [LHsTypeArg GhcRn]
hs_args }

tc_infer_hs_type TcTyMode
mode (HsKindSig XKindSig GhcRn
_ LHsType GhcRn
ty LHsType GhcRn
sig)
  = do { Type
sig' <- UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
KindSigCtxt LHsType GhcRn
sig
                 -- We must typecheck the kind signature, and solve all
                 -- its equalities etc; from this point on we may do
                 -- things like instantiate its foralls, so it needs
                 -- to be fully determined (#14904)
       ; String -> MsgDoc -> TcM ()
traceTc String
"tc_infer_hs_type:sig" (LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
ty MsgDoc -> MsgDoc -> MsgDoc
$$ Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
sig')
       ; Type
ty' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
sig'
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty', Type
sig') }

-- HsSpliced is an annotation produced by 'RnSplice.rnSpliceType' to communicate
-- the splice location to the typechecker. Here we skip over it in order to have
-- the same kind inferred for a given expression whether it was produced from
-- splices or not.
--
-- See Note [Delaying modFinalizers in untyped splices].
tc_infer_hs_type TcTyMode
mode (HsSpliceTy XSpliceTy GhcRn
_ (HsSpliced XSpliced GhcRn
_ ThModFinalizers
_ (HsSplicedTy HsType GhcRn
ty)))
  = TcTyMode -> HsType GhcRn -> TcM (Type, Type)
tc_infer_hs_type TcTyMode
mode HsType GhcRn
ty

tc_infer_hs_type TcTyMode
mode (HsDocTy XDocTy GhcRn
_ LHsType GhcRn
ty LHsDocString
_) = TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
ty
tc_infer_hs_type TcTyMode
_    (XHsType (NHsCoreTy ty))
  = (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty, HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
ty)

tc_infer_hs_type TcTyMode
_ (HsExplicitListTy XExplicitListTy GhcRn
_ PromotionFlag
_ [LHsType GhcRn]
tys)
  | [LHsType GhcRn] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LHsType GhcRn]
tys  -- this is so that we can use visible kind application with '[]
              -- e.g ... '[] @Bool
  = (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Type
mkTyConTy TyCon
promotedNilDataCon,
            [TcTyVar] -> Type -> Type
mkSpecForAllTys [TcTyVar
alphaTyVar] (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ Type -> Type
mkListTy Type
alphaTy)

tc_infer_hs_type TcTyMode
mode HsType GhcRn
other_ty
  = do { Type
kv <- TcM Type
newMetaKindVar
       ; Type
ty' <- TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode HsType GhcRn
other_ty Type
kv
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty', Type
kv) }

------------------------------------------
tc_lhs_type :: TcTyMode -> LHsType GhcRn -> TcKind -> TcM TcType
tc_lhs_type :: TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode (L SrcSpan
span HsType GhcRn
ty) Type
exp_kind
  = SrcSpan -> TcM Type -> TcM Type
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
span (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode HsType GhcRn
ty Type
exp_kind

tc_hs_type :: TcTyMode -> HsType GhcRn -> TcKind -> TcM TcType
-- See Note [Bidirectional type checking]

tc_hs_type :: TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode (HsParTy XParTy GhcRn
_ LHsType GhcRn
ty)   Type
exp_kind = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
exp_kind
tc_hs_type TcTyMode
mode (HsDocTy XDocTy GhcRn
_ LHsType GhcRn
ty LHsDocString
_) Type
exp_kind = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
exp_kind
tc_hs_type TcTyMode
_ ty :: HsType GhcRn
ty@(HsBangTy XBangTy GhcRn
_ HsSrcBang
bang LHsType GhcRn
_) Type
_
    -- While top-level bangs at this point are eliminated (eg !(Maybe Int)),
    -- other kinds of bangs are not (eg ((!Maybe) Int)). These kinds of
    -- bangs are invalid, so fail. (#7210, #14761)
    = do { let bangError :: String -> TcM Type
bangError String
err = MsgDoc -> TcM Type
forall a. MsgDoc -> TcM a
failWith (MsgDoc -> TcM Type) -> MsgDoc -> TcM Type
forall a b. (a -> b) -> a -> b
$
                 String -> MsgDoc
text String
"Unexpected" MsgDoc -> MsgDoc -> MsgDoc
<+> String -> MsgDoc
text String
err MsgDoc -> MsgDoc -> MsgDoc
<+> String -> MsgDoc
text String
"annotation:" MsgDoc -> MsgDoc -> MsgDoc
<+> HsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr HsType GhcRn
ty MsgDoc -> MsgDoc -> MsgDoc
$$
                 String -> MsgDoc
text String
err MsgDoc -> MsgDoc -> MsgDoc
<+> String -> MsgDoc
text String
"annotation cannot appear nested inside a type"
         ; case HsSrcBang
bang of
             HsSrcBang SourceText
_ SrcUnpackedness
SrcUnpack SrcStrictness
_           -> String -> TcM Type
bangError String
"UNPACK"
             HsSrcBang SourceText
_ SrcUnpackedness
SrcNoUnpack SrcStrictness
_         -> String -> TcM Type
bangError String
"NOUNPACK"
             HsSrcBang SourceText
_ SrcUnpackedness
NoSrcUnpack SrcStrictness
SrcLazy   -> String -> TcM Type
bangError String
"laziness"
             HsSrcBang SourceText
_ SrcUnpackedness
_ SrcStrictness
_                   -> String -> TcM Type
bangError String
"strictness" }
tc_hs_type TcTyMode
_ ty :: HsType GhcRn
ty@(HsRecTy {})      Type
_
      -- Record types (which only show up temporarily in constructor
      -- signatures) should have been removed by now
    = MsgDoc -> TcM Type
forall a. MsgDoc -> TcM a
failWithTc (String -> MsgDoc
text String
"Record syntax is illegal here:" MsgDoc -> MsgDoc -> MsgDoc
<+> HsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr HsType GhcRn
ty)

-- HsSpliced is an annotation produced by 'RnSplice.rnSpliceType'.
-- Here we get rid of it and add the finalizers to the global environment
-- while capturing the local environment.
--
-- See Note [Delaying modFinalizers in untyped splices].
tc_hs_type TcTyMode
mode (HsSpliceTy XSpliceTy GhcRn
_ (HsSpliced XSpliced GhcRn
_ ThModFinalizers
mod_finalizers (HsSplicedTy HsType GhcRn
ty)))
           Type
exp_kind
  = do ThModFinalizers -> TcM ()
addModFinalizersWithLclEnv ThModFinalizers
mod_finalizers
       TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_hs_type TcTyMode
mode HsType GhcRn
ty Type
exp_kind

-- This should never happen; type splices are expanded by the renamer
tc_hs_type TcTyMode
_ ty :: HsType GhcRn
ty@(HsSpliceTy {}) Type
_exp_kind
  = MsgDoc -> TcM Type
forall a. MsgDoc -> TcM a
failWithTc (String -> MsgDoc
text String
"Unexpected type splice:" MsgDoc -> MsgDoc -> MsgDoc
<+> HsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr HsType GhcRn
ty)

---------- Functions and applications
tc_hs_type TcTyMode
mode (HsFunTy XFunTy GhcRn
_ LHsType GhcRn
ty1 LHsType GhcRn
ty2) Type
exp_kind
  = TcTyMode -> LHsType GhcRn -> LHsType GhcRn -> Type -> TcM Type
tc_fun_type TcTyMode
mode LHsType GhcRn
ty1 LHsType GhcRn
ty2 Type
exp_kind

tc_hs_type TcTyMode
mode (HsOpTy XOpTy GhcRn
_ LHsType GhcRn
ty1 (L SrcSpan
_ IdP GhcRn
op) LHsType GhcRn
ty2) Type
exp_kind
  | Name
IdP GhcRn
op Name -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
funTyConKey
  = TcTyMode -> LHsType GhcRn -> LHsType GhcRn -> Type -> TcM Type
tc_fun_type TcTyMode
mode LHsType GhcRn
ty1 LHsType GhcRn
ty2 Type
exp_kind

--------- Foralls
tc_hs_type TcTyMode
mode forall :: HsType GhcRn
forall@(HsForAllTy { hst_fvf :: forall pass. HsType pass -> ForallVisFlag
hst_fvf = ForallVisFlag
fvf, hst_bndrs :: forall pass. HsType pass -> [LHsTyVarBndr pass]
hst_bndrs = [LHsTyVarBndr GhcRn]
hs_tvs
                                   , hst_body :: forall pass. HsType pass -> LHsType pass
hst_body = LHsType GhcRn
ty }) Type
exp_kind
  = do { (TcLevel
tclvl, WantedConstraints
wanted, ([TcTyVar]
tvs', Type
ty'))
            <- TcM ([TcTyVar], Type)
-> TcM (TcLevel, WantedConstraints, ([TcTyVar], Type))
forall a. TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndCaptureConstraints (TcM ([TcTyVar], Type)
 -> TcM (TcLevel, WantedConstraints, ([TcTyVar], Type)))
-> TcM ([TcTyVar], Type)
-> TcM (TcLevel, WantedConstraints, ([TcTyVar], Type))
forall a b. (a -> b) -> a -> b
$
               [LHsTyVarBndr GhcRn] -> TcM Type -> TcM ([TcTyVar], Type)
forall a. [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Skol [LHsTyVarBndr GhcRn]
hs_tvs (TcM Type -> TcM ([TcTyVar], Type))
-> TcM Type -> TcM ([TcTyVar], Type)
forall a b. (a -> b) -> a -> b
$
               TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
exp_kind
    -- Do not kind-generalise here!  See Note [Kind generalisation]
    -- Why exp_kind?  See Note [Body kind of HsForAllTy]
       ; let argf :: ArgFlag
argf        = case ForallVisFlag
fvf of
                             ForallVisFlag
ForallVis   -> ArgFlag
Required
                             ForallVisFlag
ForallInvis -> ArgFlag
Specified
             bndrs :: [TyVarBinder]
bndrs       = ArgFlag -> [TcTyVar] -> [TyVarBinder]
mkTyVarBinders ArgFlag
argf [TcTyVar]
tvs'
             skol_info :: SkolemInfo
skol_info   = MsgDoc -> SkolemInfo
ForAllSkol (HsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr HsType GhcRn
forall)
             m_telescope :: Maybe MsgDoc
m_telescope = MsgDoc -> Maybe MsgDoc
forall a. a -> Maybe a
Just ([MsgDoc] -> MsgDoc
sep ((LHsTyVarBndr GhcRn -> MsgDoc) -> [LHsTyVarBndr GhcRn] -> [MsgDoc]
forall a b. (a -> b) -> [a] -> [b]
map LHsTyVarBndr GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsTyVarBndr GhcRn]
hs_tvs))

       ; SkolemInfo
-> Maybe MsgDoc
-> [TcTyVar]
-> TcLevel
-> WantedConstraints
-> TcM ()
emitResidualTvConstraint SkolemInfo
skol_info Maybe MsgDoc
m_telescope [TcTyVar]
tvs' TcLevel
tclvl WantedConstraints
wanted

       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVarBinder] -> Type -> Type
mkForAllTys [TyVarBinder]
bndrs Type
ty') }

tc_hs_type TcTyMode
mode (HsQualTy { hst_ctxt :: forall pass. HsType pass -> LHsContext pass
hst_ctxt = LHsContext GhcRn
ctxt, hst_body :: forall pass. HsType pass -> LHsType pass
hst_body = LHsType GhcRn
rn_ty }) Type
exp_kind
  | [LHsType GhcRn] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null (LHsContext GhcRn -> SrcSpanLess (LHsContext GhcRn)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc LHsContext GhcRn
ctxt)
  = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
rn_ty Type
exp_kind

  -- See Note [Body kind of a HsQualTy]
  | Type -> Bool
tcIsConstraintKind Type
exp_kind
  = do { [Type]
ctxt' <- TcTyMode -> LHsContext GhcRn -> TcM [Type]
tc_hs_context TcTyMode
mode LHsContext GhcRn
ctxt
       ; Type
ty'   <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
rn_ty Type
constraintKind
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type] -> Type -> Type
mkPhiTy [Type]
ctxt' Type
ty') }

  | Bool
otherwise
  = do { [Type]
ctxt' <- TcTyMode -> LHsContext GhcRn -> TcM [Type]
tc_hs_context TcTyMode
mode LHsContext GhcRn
ctxt

       ; Type
ek <- TcM Type
newOpenTypeKind  -- The body kind (result of the function) can
                                -- be TYPE r, for any r, hence newOpenTypeKind
       ; Type
ty' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
rn_ty Type
ek
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (LHsType GhcRn -> SrcSpanLess (LHsType GhcRn)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc LHsType GhcRn
rn_ty) ([Type] -> Type -> Type
mkPhiTy [Type]
ctxt' Type
ty')
                           Type
liftedTypeKind Type
exp_kind }

--------- Lists, arrays, and tuples
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsListTy XListTy GhcRn
_ LHsType GhcRn
elt_ty) Type
exp_kind
  = do { Type
tau_ty <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
elt_ty Type
liftedTypeKind
       ; TyCon -> TcM ()
checkWiredInTyCon TyCon
listTyCon
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (Type -> Type
mkListTy Type
tau_ty) Type
liftedTypeKind Type
exp_kind }

-- See Note [Distinguishing tuple kinds] in GHC.Hs.Types
-- See Note [Inferring tuple kinds]
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsTupleTy XTupleTy GhcRn
_ HsTupleSort
HsBoxedOrConstraintTuple [LHsType GhcRn]
hs_tys) Type
exp_kind
     -- (NB: not zonking before looking at exp_k, to avoid left-right bias)
  | Just TupleSort
tup_sort <- Type -> Maybe TupleSort
tupKindSort_maybe Type
exp_kind
  = String -> MsgDoc -> TcM ()
traceTc String
"tc_hs_type tuple" ([LHsType GhcRn] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsType GhcRn]
hs_tys) TcM () -> TcM Type -> TcM Type
forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>>
    HsType GhcRn
-> TcTyMode -> TupleSort -> [LHsType GhcRn] -> Type -> TcM Type
tc_tuple HsType GhcRn
rn_ty TcTyMode
mode TupleSort
tup_sort [LHsType GhcRn]
hs_tys Type
exp_kind
  | Bool
otherwise
  = do { String -> MsgDoc -> TcM ()
traceTc String
"tc_hs_type tuple 2" ([LHsType GhcRn] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsType GhcRn]
hs_tys)
       ; ([Type]
tys, [Type]
kinds) <- (LHsType GhcRn -> TcM (Type, Type))
-> [LHsType GhcRn]
-> IOEnv (Env TcGblEnv TcLclEnv) ([Type], [Type])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode) [LHsType GhcRn]
hs_tys
       ; [Type]
kinds <- (Type -> TcM Type) -> [Type] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Type -> TcM Type
zonkTcType [Type]
kinds
           -- Infer each arg type separately, because errors can be
           -- confusing if we give them a shared kind.  Eg #7410
           -- (Either Int, Int), we do not want to get an error saying
           -- "the second argument of a tuple should have kind *->*"

       ; let (Type
arg_kind, TupleSort
tup_sort)
               = case [ (Type
k,TupleSort
s) | Type
k <- [Type]
kinds
                              , Just TupleSort
s <- [Type -> Maybe TupleSort
tupKindSort_maybe Type
k] ] of
                    ((Type
k,TupleSort
s) : [(Type, TupleSort)]
_) -> (Type
k,TupleSort
s)
                    [] -> (Type
liftedTypeKind, TupleSort
BoxedTuple)
         -- In the [] case, it's not clear what the kind is, so guess *

       ; [Type]
tys' <- [TcM Type] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a.
(Traversable t, Monad m) =>
t (m a) -> m (t a)
sequence [ SrcSpan -> TcM Type -> TcM Type
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                            HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
hs_ty Type
ty Type
kind Type
arg_kind
                          | ((L SrcSpan
loc HsType GhcRn
hs_ty),Type
ty,Type
kind) <- [LHsType GhcRn]
-> [Type] -> [Type] -> [(LHsType GhcRn, Type, Type)]
forall a b c. [a] -> [b] -> [c] -> [(a, b, c)]
zip3 [LHsType GhcRn]
hs_tys [Type]
tys [Type]
kinds ]

       ; HsType GhcRn -> TupleSort -> [Type] -> [Type] -> Type -> TcM Type
finish_tuple HsType GhcRn
rn_ty TupleSort
tup_sort [Type]
tys' ((Type -> Type) -> [Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map (Type -> Type -> Type
forall a b. a -> b -> a
const Type
arg_kind) [Type]
tys') Type
exp_kind }


tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsTupleTy XTupleTy GhcRn
_ HsTupleSort
hs_tup_sort [LHsType GhcRn]
tys) Type
exp_kind
  = HsType GhcRn
-> TcTyMode -> TupleSort -> [LHsType GhcRn] -> Type -> TcM Type
tc_tuple HsType GhcRn
rn_ty TcTyMode
mode TupleSort
tup_sort [LHsType GhcRn]
tys Type
exp_kind
  where
    tup_sort :: TupleSort
tup_sort = case HsTupleSort
hs_tup_sort of  -- Fourth case dealt with above
                  HsTupleSort
HsUnboxedTuple    -> TupleSort
UnboxedTuple
                  HsTupleSort
HsBoxedTuple      -> TupleSort
BoxedTuple
                  HsTupleSort
HsConstraintTuple -> TupleSort
ConstraintTuple
                  HsTupleSort
_                 -> String -> TupleSort
forall a. String -> a
panic String
"tc_hs_type HsTupleTy"

tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsSumTy XSumTy GhcRn
_ [LHsType GhcRn]
hs_tys) Type
exp_kind
  = do { let arity :: Int
arity = [LHsType GhcRn] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [LHsType GhcRn]
hs_tys
       ; [Type]
arg_kinds <- (LHsType GhcRn -> TcM Type) -> [LHsType GhcRn] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (\LHsType GhcRn
_ -> TcM Type
newOpenTypeKind) [LHsType GhcRn]
hs_tys
       ; [Type]
tau_tys   <- (LHsType GhcRn -> Type -> TcM Type)
-> [LHsType GhcRn] -> [Type] -> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode) [LHsType GhcRn]
hs_tys [Type]
arg_kinds
       ; let arg_reps :: [Type]
arg_reps = (Type -> Type) -> [Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map HasDebugCallStack => Type -> Type
Type -> Type
kindRep [Type]
arg_kinds
             arg_tys :: [Type]
arg_tys  = [Type]
arg_reps [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
tau_tys
             sum_ty :: Type
sum_ty   = TyCon -> [Type] -> Type
mkTyConApp (Int -> TyCon
sumTyCon Int
arity) [Type]
arg_tys
             sum_kind :: Type
sum_kind = [Type] -> Type
unboxedSumKind [Type]
arg_reps
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
sum_ty Type
sum_kind Type
exp_kind
       }

--------- Promoted lists and tuples
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsExplicitListTy XExplicitListTy GhcRn
_ PromotionFlag
_ [LHsType GhcRn]
tys) Type
exp_kind
  = do { [(Type, Type)]
tks <- (LHsType GhcRn -> TcM (Type, Type))
-> [LHsType GhcRn] -> IOEnv (Env TcGblEnv TcLclEnv) [(Type, Type)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode) [LHsType GhcRn]
tys
       ; ([Type]
taus', Type
kind) <- [LHsType GhcRn] -> [(Type, Type)] -> TcM ([Type], Type)
unifyKinds [LHsType GhcRn]
tys [(Type, Type)]
tks
       ; let ty :: Type
ty = ((Type -> Type -> Type) -> Type -> [Type] -> Type
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (Type -> Type -> Type -> Type
mk_cons Type
kind) (Type -> Type
mk_nil Type
kind) [Type]
taus')
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
ty (Type -> Type
mkListTy Type
kind) Type
exp_kind }
  where
    mk_cons :: Type -> Type -> Type -> Type
mk_cons Type
k Type
a Type
b = TyCon -> [Type] -> Type
mkTyConApp (DataCon -> TyCon
promoteDataCon DataCon
consDataCon) [Type
k, Type
a, Type
b]
    mk_nil :: Type -> Type
mk_nil  Type
k     = TyCon -> [Type] -> Type
mkTyConApp (DataCon -> TyCon
promoteDataCon DataCon
nilDataCon) [Type
k]

tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsExplicitTupleTy XExplicitTupleTy GhcRn
_ [LHsType GhcRn]
tys) Type
exp_kind
  -- using newMetaKindVar means that we force instantiations of any polykinded
  -- types. At first, I just used tc_infer_lhs_type, but that led to #11255.
  = do { [Type]
ks   <- Int -> TcM Type -> TcM [Type]
forall (m :: * -> *) a. Applicative m => Int -> m a -> m [a]
replicateM Int
arity TcM Type
newMetaKindVar
       ; [Type]
taus <- (LHsType GhcRn -> Type -> TcM Type)
-> [LHsType GhcRn] -> [Type] -> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode) [LHsType GhcRn]
tys [Type]
ks
       ; let kind_con :: TyCon
kind_con   = Boxity -> Int -> TyCon
tupleTyCon           Boxity
Boxed Int
arity
             ty_con :: TyCon
ty_con     = Boxity -> Int -> TyCon
promotedTupleDataCon Boxity
Boxed Int
arity
             tup_k :: Type
tup_k      = TyCon -> [Type] -> Type
mkTyConApp TyCon
kind_con [Type]
ks
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (TyCon -> [Type] -> Type
mkTyConApp TyCon
ty_con ([Type]
ks [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
taus)) Type
tup_k Type
exp_kind }
  where
    arity :: Int
arity = [LHsType GhcRn] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [LHsType GhcRn]
tys

--------- Constraint types
tc_hs_type TcTyMode
mode rn_ty :: HsType GhcRn
rn_ty@(HsIParamTy XIParamTy GhcRn
_ (L SrcSpan
_ HsIPName
n) LHsType GhcRn
ty) Type
exp_kind
  = do { MASSERT( isTypeLevel (mode_level mode) )
       ; Type
ty' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty Type
liftedTypeKind
       ; let n' :: Type
n' = FastString -> Type
mkStrLitTy (FastString -> Type) -> FastString -> Type
forall a b. (a -> b) -> a -> b
$ HsIPName -> FastString
hsIPNameFS HsIPName
n
       ; Class
ipClass <- Name -> TcM Class
tcLookupClass Name
ipClassName
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (Class -> [Type] -> Type
mkClassPred Class
ipClass [Type
n',Type
ty'])
                           Type
constraintKind Type
exp_kind }

tc_hs_type TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsStarTy XStarTy GhcRn
_ Bool
_) Type
exp_kind
  -- Desugaring 'HsStarTy' to 'Data.Kind.Type' here means that we don't have to
  -- handle it in 'coreView' and 'tcView'.
  = HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
liftedTypeKind Type
liftedTypeKind Type
exp_kind

--------- Literals
tc_hs_type TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsNumTy SourceText
_ Integer
n)) Type
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
typeNatKindCon
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (Integer -> Type
mkNumLitTy Integer
n) Type
typeNatKind Type
exp_kind }

tc_hs_type TcTyMode
_ rn_ty :: HsType GhcRn
rn_ty@(HsTyLit XTyLit GhcRn
_ (HsStrTy SourceText
_ FastString
s)) Type
exp_kind
  = do { TyCon -> TcM ()
checkWiredInTyCon TyCon
typeSymbolKindCon
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty (FastString -> Type
mkStrLitTy FastString
s) Type
typeSymbolKind Type
exp_kind }

--------- Potentially kind-polymorphic types: call the "up" checker
-- See Note [Future-proofing the type checker]
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsTyVar {})            Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsAppTy {})            Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsAppKindTy{})         Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsOpTy {})             Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(HsKindSig {})          Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
mode ty :: HsType GhcRn
ty@(XHsType (NHsCoreTy{})) Type
ek = HasDebugCallStack => TcTyMode -> HsType GhcRn -> Type -> TcM Type
TcTyMode -> HsType GhcRn -> Type -> TcM Type
tc_infer_hs_type_ek TcTyMode
mode HsType GhcRn
ty Type
ek
tc_hs_type TcTyMode
_    wc :: HsType GhcRn
wc@(HsWildCardTy XWildCardTy GhcRn
_)        Type
ek = HsType GhcRn -> Type -> TcM Type
tcAnonWildCardOcc HsType GhcRn
wc Type
ek

------------------------------------------
tc_fun_type :: TcTyMode -> LHsType GhcRn -> LHsType GhcRn -> TcKind
            -> TcM TcType
tc_fun_type :: TcTyMode -> LHsType GhcRn -> LHsType GhcRn -> Type -> TcM Type
tc_fun_type TcTyMode
mode LHsType GhcRn
ty1 LHsType GhcRn
ty2 Type
exp_kind = case TcTyMode -> TypeOrKind
mode_level TcTyMode
mode of
  TypeOrKind
TypeLevel ->
    do { Type
arg_k <- TcM Type
newOpenTypeKind
       ; Type
res_k <- TcM Type
newOpenTypeKind
       ; Type
ty1' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty1 Type
arg_k
       ; Type
ty2' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty2 Type
res_k
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (XFunTy GhcRn -> LHsType GhcRn -> LHsType GhcRn -> HsType GhcRn
forall pass.
XFunTy pass -> LHsType pass -> LHsType pass -> HsType pass
HsFunTy XFunTy GhcRn
NoExtField
noExtField LHsType GhcRn
ty1 LHsType GhcRn
ty2) (Type -> Type -> Type
mkVisFunTy Type
ty1' Type
ty2')
                           Type
liftedTypeKind Type
exp_kind }
  TypeOrKind
KindLevel ->  -- no representation polymorphism in kinds. yet.
    do { Type
ty1' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty1 Type
liftedTypeKind
       ; Type
ty2' <- TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
ty2 Type
liftedTypeKind
       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (XFunTy GhcRn -> LHsType GhcRn -> LHsType GhcRn -> HsType GhcRn
forall pass.
XFunTy pass -> LHsType pass -> LHsType pass -> HsType pass
HsFunTy XFunTy GhcRn
NoExtField
noExtField LHsType GhcRn
ty1 LHsType GhcRn
ty2) (Type -> Type -> Type
mkVisFunTy Type
ty1' Type
ty2')
                           Type
liftedTypeKind Type
exp_kind }

---------------------------
tcAnonWildCardOcc :: HsType GhcRn -> Kind -> TcM TcType
tcAnonWildCardOcc :: HsType GhcRn -> Type -> TcM Type
tcAnonWildCardOcc HsType GhcRn
wc Type
exp_kind
  = do { TcTyVar
wc_tv <- TcM TcTyVar
newWildTyVar  -- The wildcard's kind will be an un-filled-in meta tyvar

       ; Bool
part_tysig <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.PartialTypeSignatures
       ; Bool
warning <- WarningFlag -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. WarningFlag -> TcRnIf gbl lcl Bool
woptM WarningFlag
Opt_WarnPartialTypeSignatures

       ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Bool
part_tysig Bool -> Bool -> Bool
&& Bool -> Bool
not Bool
warning) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
         TcTyVar -> TcM ()
emitAnonWildCardHoleConstraint TcTyVar
wc_tv
         -- Why the 'unless' guard?
         -- See Note [Wildcards in visible kind application]

       ; HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
wc (TcTyVar -> Type
mkTyVarTy TcTyVar
wc_tv)
                           (TcTyVar -> Type
tyVarKind TcTyVar
wc_tv) Type
exp_kind }

{- Note [Wildcards in visible kind application]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are cases where users might want to pass in a wildcard as a visible kind
argument, for instance:

data T :: forall k1 k2. k1 → k2 → Type where
  MkT :: T a b
x :: T @_ @Nat False n
x = MkT

So we should allow '@_' without emitting any hole constraints, and
regardless of whether PartialTypeSignatures is enabled or not. But how would
the typechecker know which '_' is being used in VKA and which is not when it
calls emitNamedWildCardHoleConstraints in tcHsPartialSigType on all HsWildCardBndrs?
The solution then is to neither rename nor include unnamed wildcards in HsWildCardBndrs,
but instead give every anonymous wildcard a fresh wild tyvar in tcAnonWildCardOcc.
And whenever we see a '@', we automatically turn on PartialTypeSignatures and
turn off hole constraint warnings, and do not call emitAnonWildCardHoleConstraint
under these conditions.
See related Note [Wildcards in visible type application] here and
Note [The wildcard story for types] in GHC.Hs.Types

-}

{- *********************************************************************
*                                                                      *
                Tuples
*                                                                      *
********************************************************************* -}

---------------------------
tupKindSort_maybe :: TcKind -> Maybe TupleSort
tupKindSort_maybe :: Type -> Maybe TupleSort
tupKindSort_maybe Type
k
  | Just (Type
k', Coercion
_) <- Type -> Maybe (Type, Coercion)
splitCastTy_maybe Type
k = Type -> Maybe TupleSort
tupKindSort_maybe Type
k'
  | Just Type
k'      <- Type -> Maybe Type
tcView Type
k            = Type -> Maybe TupleSort
tupKindSort_maybe Type
k'
  | Type -> Bool
tcIsConstraintKind Type
k = TupleSort -> Maybe TupleSort
forall a. a -> Maybe a
Just TupleSort
ConstraintTuple
  | Type -> Bool
tcIsLiftedTypeKind Type
k   = TupleSort -> Maybe TupleSort
forall a. a -> Maybe a
Just TupleSort
BoxedTuple
  | Bool
otherwise            = Maybe TupleSort
forall a. Maybe a
Nothing

tc_tuple :: HsType GhcRn -> TcTyMode -> TupleSort -> [LHsType GhcRn] -> TcKind -> TcM TcType
tc_tuple :: HsType GhcRn
-> TcTyMode -> TupleSort -> [LHsType GhcRn] -> Type -> TcM Type
tc_tuple HsType GhcRn
rn_ty TcTyMode
mode TupleSort
tup_sort [LHsType GhcRn]
tys Type
exp_kind
  = do { [Type]
arg_kinds <- case TupleSort
tup_sort of
           TupleSort
BoxedTuple      -> [Type] -> TcM [Type]
forall (m :: * -> *) a. Monad m => a -> m a
return (Int -> Type -> [Type]
forall a. Int -> a -> [a]
replicate Int
arity Type
liftedTypeKind)
           TupleSort
UnboxedTuple    -> Int -> TcM Type -> TcM [Type]
forall (m :: * -> *) a. Applicative m => Int -> m a -> m [a]
replicateM Int
arity TcM Type
newOpenTypeKind
           TupleSort
ConstraintTuple -> [Type] -> TcM [Type]
forall (m :: * -> *) a. Monad m => a -> m a
return (Int -> Type -> [Type]
forall a. Int -> a -> [a]
replicate Int
arity Type
constraintKind)
       ; [Type]
tau_tys <- (LHsType GhcRn -> Type -> TcM Type)
-> [LHsType GhcRn] -> [Type] -> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode) [LHsType GhcRn]
tys [Type]
arg_kinds
       ; HsType GhcRn -> TupleSort -> [Type] -> [Type] -> Type -> TcM Type
finish_tuple HsType GhcRn
rn_ty TupleSort
tup_sort [Type]
tau_tys [Type]
arg_kinds Type
exp_kind }
  where
    arity :: Int
arity   = [LHsType GhcRn] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [LHsType GhcRn]
tys

finish_tuple :: HsType GhcRn
             -> TupleSort
             -> [TcType]    -- ^ argument types
             -> [TcKind]    -- ^ of these kinds
             -> TcKind      -- ^ expected kind of the whole tuple
             -> TcM TcType
finish_tuple :: HsType GhcRn -> TupleSort -> [Type] -> [Type] -> Type -> TcM Type
finish_tuple HsType GhcRn
rn_ty TupleSort
tup_sort [Type]
tau_tys [Type]
tau_kinds Type
exp_kind = do
  String -> MsgDoc -> TcM ()
traceTc String
"finish_tuple" (TupleSort -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TupleSort
tup_sort MsgDoc -> MsgDoc -> MsgDoc
$$ [Type] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [Type]
tau_kinds MsgDoc -> MsgDoc -> MsgDoc
$$ Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
exp_kind)
  case TupleSort
tup_sort of
    TupleSort
ConstraintTuple
      |  [Type
tau_ty] <- [Type]
tau_tys
         -- Drop any uses of 1-tuple constraints here.
         -- See Note [Ignore unary constraint tuples]
      -> Type -> Type -> TcM Type
check_expected_kind Type
tau_ty Type
constraintKind
      |  Int
arity Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
mAX_CTUPLE_SIZE
      -> MsgDoc -> TcM Type
forall a. MsgDoc -> TcM a
failWith (Int -> MsgDoc
bigConstraintTuple Int
arity)
      |  Bool
otherwise
      -> do TyCon
tycon <- Name -> TcM TyCon
tcLookupTyCon (Int -> Name
cTupleTyConName Int
arity)
            Type -> Type -> TcM Type
check_expected_kind (TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon [Type]
tau_tys) Type
constraintKind
    TupleSort
BoxedTuple -> do
      let tycon :: TyCon
tycon = Boxity -> Int -> TyCon
tupleTyCon Boxity
Boxed Int
arity
      TyCon -> TcM ()
checkWiredInTyCon TyCon
tycon
      Type -> Type -> TcM Type
check_expected_kind (TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon [Type]
tau_tys) Type
liftedTypeKind
    TupleSort
UnboxedTuple ->
      let tycon :: TyCon
tycon    = Boxity -> Int -> TyCon
tupleTyCon Boxity
Unboxed Int
arity
          tau_reps :: [Type]
tau_reps = (Type -> Type) -> [Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map HasDebugCallStack => Type -> Type
Type -> Type
kindRep [Type]
tau_kinds
          -- See also Note [Unboxed tuple RuntimeRep vars] in TyCon
          arg_tys :: [Type]
arg_tys  = [Type]
tau_reps [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
tau_tys
          res_kind :: Type
res_kind = [Type] -> Type
unboxedTupleKind [Type]
tau_reps in
      Type -> Type -> TcM Type
check_expected_kind (TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon [Type]
arg_tys) Type
res_kind
  where
    arity :: Int
arity = [Type] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Type]
tau_tys
    check_expected_kind :: Type -> Type -> TcM Type
check_expected_kind Type
ty Type
act_kind =
      HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
rn_ty Type
ty Type
act_kind Type
exp_kind

bigConstraintTuple :: Arity -> MsgDoc
bigConstraintTuple :: Int -> MsgDoc
bigConstraintTuple Int
arity
  = MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"Constraint tuple arity too large:" MsgDoc -> MsgDoc -> MsgDoc
<+> Int -> MsgDoc
int Int
arity
          MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
parens (String -> MsgDoc
text String
"max arity =" MsgDoc -> MsgDoc -> MsgDoc
<+> Int -> MsgDoc
int Int
mAX_CTUPLE_SIZE))
       Int
2 (String -> MsgDoc
text String
"Instead, use a nested tuple")

{-
Note [Ignore unary constraint tuples]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GHC provides unary tuples and unboxed tuples (see Note [One-tuples] in
TysWiredIn) but does *not* provide unary constraint tuples. Why? First,
recall the definition of a unary tuple data type:

  data Unit a = Unit a

Note that `Unit a` is *not* the same thing as `a`, since Unit is boxed and
lazy. Therefore, the presence of `Unit` matters semantically. On the other
hand, suppose we had a unary constraint tuple:

  class a => Unit% a

This compiles down a newtype (i.e., a cast) in Core, so `Unit% a` is
semantically equivalent to `a`. Therefore, a 1-tuple constraint would have
no user-visible impact, nor would it allow you to express anything that
you couldn't otherwise.

We could simply add Unit% for consistency with tuples (Unit) and unboxed
tuples (Unit#), but that would require even more magic to wire in another
magical class, so we opt not to do so. We must be careful, however, since
one can try to sneak in uses of unary constraint tuples through Template
Haskell, such as in this program (from #17511):

  f :: $(pure (ForallT [] [TupleT 1 `AppT` (ConT ''Show `AppT` ConT ''Int)]
                       (ConT ''String)))
  -- f :: Unit% (Show Int) => String
  f = "abc"

This use of `TupleT 1` will produce an HsBoxedOrConstraintTuple of arity 1,
and since it is used in a Constraint position, GHC will attempt to treat
it as thought it were a constraint tuple, which can potentially lead to
trouble if one attempts to look up the name of a constraint tuple of arity
1 (as it won't exist). To avoid this trouble, we simply take any unary
constraint tuples discovered when typechecking and drop them—i.e., treat
"Unit% a" as though the user had written "a". This is always safe to do
since the two constraints should be semantically equivalent.
-}

{- *********************************************************************
*                                                                      *
                Type applications
*                                                                      *
********************************************************************* -}

splitHsAppTys :: HsType GhcRn -> Maybe (LHsType GhcRn, [LHsTypeArg GhcRn])
splitHsAppTys :: HsType GhcRn -> Maybe (LHsType GhcRn, [LHsTypeArg GhcRn])
splitHsAppTys HsType GhcRn
hs_ty
  | HsType GhcRn -> Bool
is_app HsType GhcRn
hs_ty = (LHsType GhcRn, [LHsTypeArg GhcRn])
-> Maybe (LHsType GhcRn, [LHsTypeArg GhcRn])
forall a. a -> Maybe a
Just (LHsType GhcRn
-> [LHsTypeArg GhcRn] -> (LHsType GhcRn, [LHsTypeArg GhcRn])
forall pass.
(XTyVar pass ~ NoExtField, XAppKindTy pass ~ SrcSpan) =>
LHsType pass
-> [HsArg (LHsType pass) (LHsType pass)]
-> (LHsType pass, [HsArg (LHsType pass) (LHsType pass)])
go (SrcSpanLess (LHsType GhcRn) -> LHsType GhcRn
forall a. HasSrcSpan a => SrcSpanLess a -> a
noLoc SrcSpanLess (LHsType GhcRn)
HsType GhcRn
hs_ty) [])
  | Bool
otherwise    = Maybe (LHsType GhcRn, [LHsTypeArg GhcRn])
forall a. Maybe a
Nothing
  where
    is_app :: HsType GhcRn -> Bool
    is_app :: HsType GhcRn -> Bool
is_app (HsAppKindTy {})        = Bool
True
    is_app (HsAppTy {})            = Bool
True
    is_app (HsOpTy XOpTy GhcRn
_ LHsType GhcRn
_ (L SrcSpan
_ IdP GhcRn
op) LHsType GhcRn
_) = Bool -> Bool
not (Name
IdP GhcRn
op Name -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
funTyConKey)
      -- I'm not sure why this funTyConKey test is necessary
      -- Can it even happen?  Perhaps for   t1 `(->)` t2
      -- but then maybe it's ok to treat that like a normal
      -- application rather than using the special rule for HsFunTy
    is_app (HsTyVar {})            = Bool
True
    is_app (HsParTy XParTy GhcRn
_ (L SrcSpan
_ HsType GhcRn
ty))    = HsType GhcRn -> Bool
is_app HsType GhcRn
ty
    is_app HsType GhcRn
_                       = Bool
False

    go :: LHsType pass
-> [HsArg (LHsType pass) (LHsType pass)]
-> (LHsType pass, [HsArg (LHsType pass) (LHsType pass)])
go (L SrcSpan
_  (HsAppTy XAppTy pass
_ LHsType pass
f LHsType pass
a))      [HsArg (LHsType pass) (LHsType pass)]
as = LHsType pass
-> [HsArg (LHsType pass) (LHsType pass)]
-> (LHsType pass, [HsArg (LHsType pass) (LHsType pass)])
go LHsType pass
f (LHsType pass -> HsArg (LHsType pass) (LHsType pass)
forall tm ty. tm -> HsArg tm ty
HsValArg LHsType pass
a HsArg (LHsType pass) (LHsType pass)
-> [HsArg (LHsType pass) (LHsType pass)]
-> [HsArg (LHsType pass) (LHsType pass)]
forall a. a -> [a] -> [a]
: [HsArg (LHsType pass) (LHsType pass)]
as)
    go (L SrcSpan
_  (HsAppKindTy XAppKindTy pass
l LHsType pass
ty LHsType pass
k)) [HsArg (LHsType pass) (LHsType pass)]
as = LHsType pass
-> [HsArg (LHsType pass) (LHsType pass)]
-> (LHsType pass, [HsArg (LHsType pass) (LHsType pass)])
go LHsType pass
ty (SrcSpan -> LHsType pass -> HsArg (LHsType pass) (LHsType pass)
forall tm ty. SrcSpan -> ty -> HsArg tm ty
HsTypeArg SrcSpan
XAppKindTy pass
l LHsType pass
k HsArg (LHsType pass) (LHsType pass)
-> [HsArg (LHsType pass) (LHsType pass)]
-> [HsArg (LHsType pass) (LHsType pass)]
forall a. a -> [a] -> [a]
: [HsArg (LHsType pass) (LHsType pass)]
as)
    go (L SrcSpan
sp (HsParTy XParTy pass
_ LHsType pass
f))        [HsArg (LHsType pass) (LHsType pass)]
as = LHsType pass
-> [HsArg (LHsType pass) (LHsType pass)]
-> (LHsType pass, [HsArg (LHsType pass) (LHsType pass)])
go LHsType pass
f (SrcSpan -> HsArg (LHsType pass) (LHsType pass)
forall tm ty. SrcSpan -> HsArg tm ty
HsArgPar SrcSpan
sp HsArg (LHsType pass) (LHsType pass)
-> [HsArg (LHsType pass) (LHsType pass)]
-> [HsArg (LHsType pass) (LHsType pass)]
forall a. a -> [a] -> [a]
: [HsArg (LHsType pass) (LHsType pass)]
as)
    go (L SrcSpan
_  (HsOpTy XOpTy pass
_ LHsType pass
l op :: Located (IdP pass)
op@(L SrcSpan
sp IdP pass
_) LHsType pass
r)) [HsArg (LHsType pass) (LHsType pass)]
as
      = ( SrcSpan -> HsType pass -> LHsType pass
forall l e. l -> e -> GenLocated l e
L SrcSpan
sp (XTyVar pass -> PromotionFlag -> Located (IdP pass) -> HsType pass
forall pass.
XTyVar pass -> PromotionFlag -> Located (IdP pass) -> HsType pass
HsTyVar XTyVar pass
NoExtField
noExtField PromotionFlag
NotPromoted Located (IdP pass)
op)
        , LHsType pass -> HsArg (LHsType pass) (LHsType pass)
forall tm ty. tm -> HsArg tm ty
HsValArg LHsType pass
l HsArg (LHsType pass) (LHsType pass)
-> [HsArg (LHsType pass) (LHsType pass)]
-> [HsArg (LHsType pass) (LHsType pass)]
forall a. a -> [a] -> [a]
: LHsType pass -> HsArg (LHsType pass) (LHsType pass)
forall tm ty. tm -> HsArg tm ty
HsValArg LHsType pass
r HsArg (LHsType pass) (LHsType pass)
-> [HsArg (LHsType pass) (LHsType pass)]
-> [HsArg (LHsType pass) (LHsType pass)]
forall a. a -> [a] -> [a]
: [HsArg (LHsType pass) (LHsType pass)]
as )
    go LHsType pass
f [HsArg (LHsType pass) (LHsType pass)]
as = (LHsType pass
f, [HsArg (LHsType pass) (LHsType pass)]
as)

---------------------------
tcInferAppHead :: TcTyMode -> LHsType GhcRn -> TcM (TcType, TcKind)
-- Version of tc_infer_lhs_type specialised for the head of an
-- application. In particular, for a HsTyVar (which includes type
-- constructors, it does not zoom off into tcInferApps and family
-- saturation
tcInferAppHead :: TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tcInferAppHead TcTyMode
mode (L SrcSpan
_ (HsTyVar XTyVar GhcRn
_ PromotionFlag
_ (L SrcSpan
_ IdP GhcRn
tv)))
  = TcTyMode -> Name -> TcM (Type, Type)
tcTyVar TcTyMode
mode Name
IdP GhcRn
tv
tcInferAppHead TcTyMode
mode LHsType GhcRn
ty
  = TcTyMode -> LHsType GhcRn -> TcM (Type, Type)
tc_infer_lhs_type TcTyMode
mode LHsType GhcRn
ty

---------------------------
-- | Apply a type of a given kind to a list of arguments. This instantiates
-- invisible parameters as necessary. Always consumes all the arguments,
-- using matchExpectedFunKind as necessary.
-- This takes an optional @VarEnv Kind@ which maps kind variables to kinds.-
-- These kinds should be used to instantiate invisible kind variables;
-- they come from an enclosing class for an associated type/data family.
--
-- tcInferApps also arranges to saturate any trailing invisible arguments
--   of a type-family application, which is usually the right thing to do
-- tcInferApps_nosat does not do this saturation; it is used only
--   by ":kind" in GHCi
tcInferApps, tcInferApps_nosat
    :: TcTyMode
    -> LHsType GhcRn        -- ^ Function (for printing only)
    -> TcType               -- ^ Function
    -> [LHsTypeArg GhcRn]   -- ^ Args
    -> TcM (TcType, TcKind) -- ^ (f args, args, result kind)
tcInferApps :: TcTyMode
-> LHsType GhcRn -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
tcInferApps TcTyMode
mode LHsType GhcRn
hs_ty Type
fun [LHsTypeArg GhcRn]
hs_args
  = do { (Type
f_args, Type
res_k) <- TcTyMode
-> LHsType GhcRn -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
tcInferApps_nosat TcTyMode
mode LHsType GhcRn
hs_ty Type
fun [LHsTypeArg GhcRn]
hs_args
       ; Type -> Type -> TcM (Type, Type)
saturateFamApp Type
f_args Type
res_k }

tcInferApps_nosat :: TcTyMode
-> LHsType GhcRn -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
tcInferApps_nosat TcTyMode
mode LHsType GhcRn
orig_hs_ty Type
fun [LHsTypeArg GhcRn]
orig_hs_args
  = do { String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps {" (LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
orig_hs_ty MsgDoc -> MsgDoc -> MsgDoc
$$ [LHsTypeArg GhcRn] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsTypeArg GhcRn]
orig_hs_args)
       ; (Type
f_args, Type
res_k) <- Int -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
go_init Int
1 Type
fun [LHsTypeArg GhcRn]
orig_hs_args
       ; String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps }" (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
f_args MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc
dcolon MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
res_k)
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
f_args, Type
res_k) }
  where

    -- go_init just initialises the auxiliary
    -- arguments of the 'go' loop
    go_init :: Int -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
go_init Int
n Type
fun [LHsTypeArg GhcRn]
all_args
      = Int
-> Type
-> TCvSubst
-> Type
-> [LHsTypeArg GhcRn]
-> TcM (Type, Type)
go Int
n Type
fun TCvSubst
empty_subst Type
fun_ki [LHsTypeArg GhcRn]
all_args
      where
        fun_ki :: Type
fun_ki = HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
fun
           -- We do (tcTypeKind fun) here, even though the caller
           -- knows the function kind, to absolutely guarantee
           -- INVARIANT for 'go'
           -- Note that in a typical application (F t1 t2 t3),
           -- the 'fun' is just a TyCon, so tcTypeKind is fast

        empty_subst :: TCvSubst
empty_subst = InScopeSet -> TCvSubst
mkEmptyTCvSubst (InScopeSet -> TCvSubst) -> InScopeSet -> TCvSubst
forall a b. (a -> b) -> a -> b
$ TyCoVarSet -> InScopeSet
mkInScopeSet (TyCoVarSet -> InScopeSet) -> TyCoVarSet -> InScopeSet
forall a b. (a -> b) -> a -> b
$
                      Type -> TyCoVarSet
tyCoVarsOfType Type
fun_ki

    go :: Int             -- The # of the next argument
       -> TcType          -- Function applied to some args
       -> TCvSubst        -- Applies to function kind
       -> TcKind          -- Function kind
       -> [LHsTypeArg GhcRn]    -- Un-type-checked args
       -> TcM (TcType, TcKind)  -- Result type and its kind
    -- INVARIANT: in any call (go n fun subst fun_ki args)
    --               tcTypeKind fun  =  subst(fun_ki)
    -- So the 'subst' and 'fun_ki' arguments are simply
    -- there to avoid repeatedly calling tcTypeKind.
    --
    -- Reason for INVARIANT: to support the Purely Kinded Type Invariant
    -- it's important that if fun_ki has a forall, then so does
    -- (tcTypeKind fun), because the next thing we are going to do
    -- is apply 'fun' to an argument type.

    -- Dispatch on all_args first, for performance reasons
    go :: Int
-> Type
-> TCvSubst
-> Type
-> [LHsTypeArg GhcRn]
-> TcM (Type, Type)
go Int
n Type
fun TCvSubst
subst Type
fun_ki [LHsTypeArg GhcRn]
all_args = case ([LHsTypeArg GhcRn]
all_args, Type -> Maybe (TyBinder, Type)
tcSplitPiTy_maybe Type
fun_ki) of

      ---------------- No user-written args left. We're done!
      ([], Maybe (TyBinder, Type)
_) -> (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
fun, HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_ki)

      ---------------- HsArgPar: We don't care about parens here
      (HsArgPar SrcSpan
_ : [LHsTypeArg GhcRn]
args, Maybe (TyBinder, Type)
_) -> Int
-> Type
-> TCvSubst
-> Type
-> [LHsTypeArg GhcRn]
-> TcM (Type, Type)
go Int
n Type
fun TCvSubst
subst Type
fun_ki [LHsTypeArg GhcRn]
args

      ---------------- HsTypeArg: a kind application (fun @ki)
      (HsTypeArg SrcSpan
_ LHsType GhcRn
hs_ki_arg : [LHsTypeArg GhcRn]
hs_args, Just (TyBinder
ki_binder, Type
inner_ki)) ->
        case TyBinder
ki_binder of

        -- FunTy with PredTy on LHS, or ForAllTy with Inferred
        Named (Bndr TcTyVar
_ ArgFlag
Inferred) -> TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki
        Anon AnonArgFlag
InvisArg Type
_         -> TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki

        Named (Bndr TcTyVar
_ ArgFlag
Specified) ->  -- Visible kind application
          do { String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps (vis kind app)"
                       ([MsgDoc] -> MsgDoc
vcat [ TyBinder -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TyBinder
ki_binder, LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
hs_ki_arg
                             , Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr (TyBinder -> Type
tyBinderType TyBinder
ki_binder)
                             , TCvSubst -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TCvSubst
subst ])

             ; let exp_kind :: Type
exp_kind = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ TyBinder -> Type
tyBinderType TyBinder
ki_binder

             ; Type
ki_arg <- MsgDoc -> TcM Type -> TcM Type
forall a. MsgDoc -> TcM a -> TcM a
addErrCtxt (LHsType GhcRn -> LHsType GhcRn -> Int -> MsgDoc
forall fun arg.
(Outputable fun, Outputable arg) =>
fun -> arg -> Int -> MsgDoc
funAppCtxt LHsType GhcRn
orig_hs_ty LHsType GhcRn
hs_ki_arg Int
n) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                         WarningFlag -> TcM Type -> TcM Type
forall gbl lcl a.
WarningFlag -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
unsetWOptM WarningFlag
Opt_WarnPartialTypeSignatures (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                         Extension -> TcM Type -> TcM Type
forall gbl lcl a. Extension -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setXOptM Extension
LangExt.PartialTypeSignatures (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                             -- Urgh!  see Note [Wildcards in visible kind application]
                             -- ToDo: must kill this ridiculous messing with DynFlags
                         TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type (TcTyMode -> TcTyMode
kindLevel TcTyMode
mode) LHsType GhcRn
hs_ki_arg Type
exp_kind

             ; String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps (vis kind app)" (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
exp_kind)
             ; (TCvSubst
subst', Type
fun') <- TCvSubst -> Type -> TyBinder -> Type -> TcM (TCvSubst, Type)
mkAppTyM TCvSubst
subst Type
fun TyBinder
ki_binder Type
ki_arg
             ; Int
-> Type
-> TCvSubst
-> Type
-> [LHsTypeArg GhcRn]
-> TcM (Type, Type)
go (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1) Type
fun' TCvSubst
subst' Type
inner_ki [LHsTypeArg GhcRn]
hs_args }

        -- Attempted visible kind application (fun @ki), but fun_ki is
        --   forall k -> blah   or   k1 -> k2
        -- So we need a normal application.  Error.
        TyBinder
_ -> LHsType GhcRn -> Type -> TcM (Type, Type)
forall a a a. (Outputable a, Outputable a) => a -> a -> TcRn a
ty_app_err LHsType GhcRn
hs_ki_arg (Type -> TcM (Type, Type)) -> Type -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$ HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_ki

      -- No binder; try applying the substitution, or fail if that's not possible
      (HsTypeArg SrcSpan
_ LHsType GhcRn
ki_arg : [LHsTypeArg GhcRn]
_, Maybe (TyBinder, Type)
Nothing) -> TcM (Type, Type) -> TcM (Type, Type)
try_again_after_substing_or (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
                                           LHsType GhcRn -> Type -> TcM (Type, Type)
forall a a a. (Outputable a, Outputable a) => a -> a -> TcRn a
ty_app_err LHsType GhcRn
ki_arg Type
substed_fun_ki

      ---------------- HsValArg: a nomal argument (fun ty)
      (HsValArg LHsType GhcRn
arg : [LHsTypeArg GhcRn]
args, Just (TyBinder
ki_binder, Type
inner_ki))
        -- next binder is invisible; need to instantiate it
        | TyBinder -> Bool
isInvisibleBinder TyBinder
ki_binder   -- FunTy with InvisArg on LHS;
                                        -- or ForAllTy with Inferred or Specified
         -> TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki

        -- "normal" case
        | Bool
otherwise
         -> do { String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps (vis normal app)"
                          ([MsgDoc] -> MsgDoc
vcat [ TyBinder -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TyBinder
ki_binder
                                , LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
arg
                                , Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr (TyBinder -> Type
tyBinderType TyBinder
ki_binder)
                                , TCvSubst -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TCvSubst
subst ])
                ; let exp_kind :: Type
exp_kind = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$ TyBinder -> Type
tyBinderType TyBinder
ki_binder
                ; Type
arg' <- MsgDoc -> TcM Type -> TcM Type
forall a. MsgDoc -> TcM a -> TcM a
addErrCtxt (LHsType GhcRn -> LHsType GhcRn -> Int -> MsgDoc
forall fun arg.
(Outputable fun, Outputable arg) =>
fun -> arg -> Int -> MsgDoc
funAppCtxt LHsType GhcRn
orig_hs_ty LHsType GhcRn
arg Int
n) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                          TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
arg Type
exp_kind
                ; String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps (vis normal app) 2" (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
exp_kind)
                ; (TCvSubst
subst', Type
fun') <- TCvSubst -> Type -> TyBinder -> Type -> TcM (TCvSubst, Type)
mkAppTyM TCvSubst
subst Type
fun TyBinder
ki_binder Type
arg'
                ; Int
-> Type
-> TCvSubst
-> Type
-> [LHsTypeArg GhcRn]
-> TcM (Type, Type)
go (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1) Type
fun' TCvSubst
subst' Type
inner_ki [LHsTypeArg GhcRn]
args }

          -- no binder; try applying the substitution, or infer another arrow in fun kind
      (HsValArg LHsType GhcRn
_ : [LHsTypeArg GhcRn]
_, Maybe (TyBinder, Type)
Nothing)
        -> TcM (Type, Type) -> TcM (Type, Type)
try_again_after_substing_or (TcM (Type, Type) -> TcM (Type, Type))
-> TcM (Type, Type) -> TcM (Type, Type)
forall a b. (a -> b) -> a -> b
$
           do { let arrows_needed :: Int
arrows_needed = [LHsTypeArg GhcRn] -> Int
forall tm ty. [HsArg tm ty] -> Int
n_initial_val_args [LHsTypeArg GhcRn]
all_args
              ; Coercion
co <- LHsType GhcRn -> Int -> Type -> TcM Coercion
forall fun. Outputable fun => fun -> Int -> Type -> TcM Coercion
matchExpectedFunKind LHsType GhcRn
hs_ty Int
arrows_needed Type
substed_fun_ki

              ; Type
fun' <- Type -> TcM Type
zonkTcType (Type
fun Type -> Coercion -> Type
`mkTcCastTy` Coercion
co)
                     -- This zonk is essential, to expose the fruits
                     -- of matchExpectedFunKind to the 'go' loop

              ; String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps (no binder)" (MsgDoc -> TcM ()) -> MsgDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
                   [MsgDoc] -> MsgDoc
vcat [ Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
fun MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc
dcolon MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
fun_ki
                        , Int -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Int
arrows_needed
                        , Coercion -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Coercion
co
                        , Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
fun' MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc
dcolon MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr (HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
fun')]
              ; Int -> Type -> [LHsTypeArg GhcRn] -> TcM (Type, Type)
go_init Int
n Type
fun' [LHsTypeArg GhcRn]
all_args }
                -- Use go_init to establish go's INVARIANT
      where
        instantiate :: TyBinder -> Type -> TcM (Type, Type)
instantiate TyBinder
ki_binder Type
inner_ki
          = do { String -> MsgDoc -> TcM ()
traceTc String
"tcInferApps (need to instantiate)"
                         ([MsgDoc] -> MsgDoc
vcat [ TyBinder -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TyBinder
ki_binder, TCvSubst -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TCvSubst
subst])
               ; (TCvSubst
subst', Type
arg') <- TCvSubst -> TyBinder -> TcM (TCvSubst, Type)
tcInstInvisibleTyBinder TCvSubst
subst TyBinder
ki_binder
               ; Int
-> Type
-> TCvSubst
-> Type
-> [LHsTypeArg GhcRn]
-> TcM (Type, Type)
go Int
n (Type -> Type -> Type
mkAppTy Type
fun Type
arg') TCvSubst
subst' Type
inner_ki [LHsTypeArg GhcRn]
all_args }
                 -- Because tcInvisibleTyBinder instantiate ki_binder,
                 -- the kind of arg' will have the same shape as the kind
                 -- of ki_binder.  So we don't need mkAppTyM here.

        try_again_after_substing_or :: TcM (Type, Type) -> TcM (Type, Type)
try_again_after_substing_or TcM (Type, Type)
fallthrough
          | Bool -> Bool
not (TCvSubst -> Bool
isEmptyTCvSubst TCvSubst
subst)
          = Int
-> Type
-> TCvSubst
-> Type
-> [LHsTypeArg GhcRn]
-> TcM (Type, Type)
go Int
n Type
fun TCvSubst
zapped_subst Type
substed_fun_ki [LHsTypeArg GhcRn]
all_args
          | Bool
otherwise
          = TcM (Type, Type)
fallthrough

        zapped_subst :: TCvSubst
zapped_subst   = TCvSubst -> TCvSubst
zapTCvSubst TCvSubst
subst
        substed_fun_ki :: Type
substed_fun_ki = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_ki
        hs_ty :: LHsType GhcRn
hs_ty          = LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg LHsType GhcRn
orig_hs_ty (Int -> [LHsTypeArg GhcRn] -> [LHsTypeArg GhcRn]
forall a. Int -> [a] -> [a]
take (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) [LHsTypeArg GhcRn]
orig_hs_args)

    n_initial_val_args :: [HsArg tm ty] -> Arity
    -- Count how many leading HsValArgs we have
    n_initial_val_args :: [HsArg tm ty] -> Int
n_initial_val_args (HsValArg {} : [HsArg tm ty]
args) = Int
1 Int -> Int -> Int
forall a. Num a => a -> a -> a
+ [HsArg tm ty] -> Int
forall tm ty. [HsArg tm ty] -> Int
n_initial_val_args [HsArg tm ty]
args
    n_initial_val_args (HsArgPar {} : [HsArg tm ty]
args) = [HsArg tm ty] -> Int
forall tm ty. [HsArg tm ty] -> Int
n_initial_val_args [HsArg tm ty]
args
    n_initial_val_args [HsArg tm ty]
_                    = Int
0

    ty_app_err :: a -> a -> TcRn a
ty_app_err a
arg a
ty
      = MsgDoc -> TcRn a
forall a. MsgDoc -> TcM a
failWith (MsgDoc -> TcRn a) -> MsgDoc -> TcRn a
forall a b. (a -> b) -> a -> b
$ String -> MsgDoc
text String
"Cannot apply function of kind" MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (a -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr a
ty)
                MsgDoc -> MsgDoc -> MsgDoc
$$ String -> MsgDoc
text String
"to visible kind argument" MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (a -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr a
arg)


mkAppTyM :: TCvSubst
         -> TcType -> TyCoBinder    -- fun, plus its top-level binder
         -> TcType                  -- arg
         -> TcM (TCvSubst, TcType)  -- Extended subst, plus (fun arg)
-- Precondition: the application (fun arg) is well-kinded after zonking
--               That is, the application makes sense
--
-- Precondition: for (mkAppTyM subst fun bndr arg)
--       tcTypeKind fun  =  Pi bndr. body
--  That is, fun always has a ForAllTy or FunTy at the top
--           and 'bndr' is fun's pi-binder
--
-- Postcondition: if fun and arg satisfy (PKTI), the purely-kinded type
--                invariant, then so does the result type (fun arg)
--
-- We do not require that
--    tcTypeKind arg = tyVarKind (binderVar bndr)
-- This must be true after zonking (precondition 1), but it's not
-- required for the (PKTI).
mkAppTyM :: TCvSubst -> Type -> TyBinder -> Type -> TcM (TCvSubst, Type)
mkAppTyM TCvSubst
subst Type
fun TyBinder
ki_binder Type
arg
  | -- See Note [mkAppTyM]: Nasty case 2
    TyConApp TyCon
tc [Type]
args <- Type
fun
  , TyCon -> Bool
isTypeSynonymTyCon TyCon
tc
  , [Type]
args [Type] -> Int -> Bool
forall a. [a] -> Int -> Bool
`lengthIs` (TyCon -> Int
tyConArity TyCon
tc Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1)
  , (TcTyVar -> Bool) -> [TcTyVar] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any TcTyVar -> Bool
isTrickyTvBinder (TyCon -> [TcTyVar]
tyConTyVars TyCon
tc) -- We could cache this in the synonym
  = do { Type
arg'  <- Type -> TcM Type
zonkTcType  Type
arg
       ; [Type]
args' <- [Type] -> TcM [Type]
zonkTcTypes [Type]
args
       ; let subst' :: TCvSubst
subst' = case TyBinder
ki_binder of
                        Anon {}           -> TCvSubst
subst
                        Named (Bndr TcTyVar
tv ArgFlag
_) -> TCvSubst -> TcTyVar -> Type -> TCvSubst
extendTvSubstAndInScope TCvSubst
subst TcTyVar
tv Type
arg'
       ; (TCvSubst, Type) -> TcM (TCvSubst, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TCvSubst
subst', TyCon -> [Type] -> Type
mkTyConApp TyCon
tc ([Type]
args' [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type
arg'])) }


mkAppTyM TCvSubst
subst Type
fun (Anon {}) Type
arg
   = (TCvSubst, Type) -> TcM (TCvSubst, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TCvSubst
subst, Type -> Type -> Type
mk_app_ty Type
fun Type
arg)

mkAppTyM TCvSubst
subst Type
fun (Named (Bndr TcTyVar
tv ArgFlag
_)) Type
arg
  = do { Type
arg' <- if TcTyVar -> Bool
isTrickyTvBinder TcTyVar
tv
                 then -- See Note [mkAppTyM]: Nasty case 1
                      Type -> TcM Type
zonkTcType Type
arg
                 else Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return     Type
arg
       ; (TCvSubst, Type) -> TcM (TCvSubst, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ( TCvSubst -> TcTyVar -> Type -> TCvSubst
extendTvSubstAndInScope TCvSubst
subst TcTyVar
tv Type
arg'
                , Type -> Type -> Type
mk_app_ty Type
fun Type
arg' ) }

mk_app_ty :: TcType -> TcType -> TcType
-- This function just adds an ASSERT for mkAppTyM's precondition
mk_app_ty :: Type -> Type -> Type
mk_app_ty Type
fun Type
arg
  = ASSERT2( isPiTy fun_kind
           ,  ppr fun <+> dcolon <+> ppr fun_kind $$ ppr arg )
    Type -> Type -> Type
mkAppTy Type
fun Type
arg
  where
    fun_kind :: Type
fun_kind = HasDebugCallStack => Type -> Type
Type -> Type
tcTypeKind Type
fun

isTrickyTvBinder :: TcTyVar -> Bool
-- NB: isTrickyTvBinder is just an optimisation
-- It would be absolutely sound to return True always
isTrickyTvBinder :: TcTyVar -> Bool
isTrickyTvBinder TcTyVar
tv = Type -> Bool
isPiTy (TcTyVar -> Type
tyVarKind TcTyVar
tv)

{- Note [The Purely Kinded Type Invariant (PKTI)]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
During type inference, we maintain this invariant

 (PKTI) It is legal to call 'tcTypeKind' on any Type ty,
        on any sub-term of ty, /without/ zonking ty

        Moreover, any such returned kind
        will itself satisfy (PKTI)

By "legal to call tcTypeKind" we mean "tcTypeKind will not crash".
The way in which tcTypeKind can crash is in applications
    (a t1 t2 .. tn)
if 'a' is a type variable whose kind doesn't have enough arrows
or foralls.  (The crash is in piResultTys.)

The loop in tcInferApps has to be very careful to maintain the (PKTI).
For example, suppose
    kappa is a unification variable
    We have already unified kappa := Type
      yielding    co :: Refl (Type -> Type)
    a :: kappa
then consider the type
    (a Int)
If we call tcTypeKind on that, we'll crash, because the (un-zonked)
kind of 'a' is just kappa, not an arrow kind.  So we must zonk first.

So the type inference engine is very careful when building applications.
This happens in tcInferApps. Suppose we are kind-checking the type (a Int),
where (a :: kappa).  Then in tcInferApps we'll run out of binders on
a's kind, so we'll call matchExpectedFunKind, and unify
   kappa := kappa1 -> kappa2,  with evidence co :: kappa ~ (kappa1 ~ kappa2)
At this point we must zonk the function type to expose the arrrow, so
that (a Int) will satisfy (PKTI).

The absence of this caused #14174 and #14520.

The calls to mkAppTyM is the other place we are very careful.

Note [mkAppTyM]
~~~~~~~~~~~~~~~
mkAppTyM is trying to guarantee the Purely Kinded Type Invariant
(PKTI) for its result type (fun arg).  There are two ways it can go wrong:

* Nasty case 1: forall types (polykinds/T14174a)
    T :: forall (p :: *->*). p Int -> p Bool
  Now kind-check (T x), where x::kappa.
  Well, T and x both satisfy the PKTI, but
     T x :: x Int -> x Bool
  and (x Int) does /not/ satisfy the PKTI.

* Nasty case 2: type synonyms
    type S f a = f a
  Even though (S ff aa) would satisfy the (PKTI) if S was a data type
  (i.e. nasty case 1 is dealt with), it might still not satisfy (PKTI)
  if S is a type synonym, because the /expansion/ of (S ff aa) is
  (ff aa), and /that/ does not satisfy (PKTI).  E.g. perhaps
  (ff :: kappa), where 'kappa' has already been unified with (*->*).

  We check for nasty case 2 on the final argument of a type synonym.

Notice that in both cases the trickiness only happens if the
bound variable has a pi-type.  Hence isTrickyTvBinder.
-}


saturateFamApp :: TcType -> TcKind -> TcM (TcType, TcKind)
-- Precondition for (saturateFamApp ty kind):
--     tcTypeKind ty = kind
--
-- If 'ty' is an unsaturated family application wtih trailing
-- invisible arguments, instanttiate them.
-- See Note [saturateFamApp]

saturateFamApp :: Type -> Type -> TcM (Type, Type)
saturateFamApp Type
ty Type
kind
  | Just (TyCon
tc, [Type]
args) <- HasCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
tcSplitTyConApp_maybe Type
ty
  , TyCon -> Bool
mustBeSaturated TyCon
tc
  , let n_to_inst :: Int
n_to_inst = TyCon -> Int
tyConArity TyCon
tc Int -> Int -> Int
forall a. Num a => a -> a -> a
- [Type] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Type]
args
  = do { ([Type]
extra_args, Type
ki') <- Int -> Type -> TcM ([Type], Type)
tcInstInvisibleTyBinders Int
n_to_inst Type
kind
       ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty Type -> [Type] -> Type
`mkTcAppTys` [Type]
extra_args, Type
ki') }
  | Bool
otherwise
  = (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
ty, Type
kind)

{- Note [saturateFamApp]
~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   type family F :: Either j k
   type instance F @Type = Right Maybe
   type instance F @Type = Right Either```

Then F :: forall {j,k}. Either j k

The two type instances do a visible kind application that instantiates
'j' but not 'k'.  But we want to end up with instances that look like
  type instance F @Type @(*->*) = Right @Type @(*->*) Maybe

so that F has arity 2.  We must instantiate that trailing invisible
binder. In general, Invisible binders precede Specified and Required,
so this is only going to bite for apparently-nullary families.

Note that
  type family F2 :: forall k. k -> *
is quite different and really does have arity 0.

It's not just type instances where we need to saturate those
unsaturated arguments: see #11246.  Hence doing this in tcInferApps.
-}

appTypeToArg :: LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg :: LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg LHsType GhcRn
f []                       = LHsType GhcRn
f
appTypeToArg LHsType GhcRn
f (HsValArg LHsType GhcRn
arg    : [LHsTypeArg GhcRn]
args) = LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg (LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass).
LHsType (GhcPass p) -> LHsType (GhcPass p) -> LHsType (GhcPass p)
mkHsAppTy LHsType GhcRn
f LHsType GhcRn
arg) [LHsTypeArg GhcRn]
args
appTypeToArg LHsType GhcRn
f (HsArgPar SrcSpan
_      : [LHsTypeArg GhcRn]
args) = LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg LHsType GhcRn
f                 [LHsTypeArg GhcRn]
args
appTypeToArg LHsType GhcRn
f (HsTypeArg SrcSpan
l LHsType GhcRn
arg : [LHsTypeArg GhcRn]
args)
  = LHsType GhcRn -> [LHsTypeArg GhcRn] -> LHsType GhcRn
appTypeToArg (XAppKindTy GhcRn -> LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass).
XAppKindTy (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
mkHsAppKindTy SrcSpan
XAppKindTy GhcRn
l LHsType GhcRn
f LHsType GhcRn
arg) [LHsTypeArg GhcRn]
args


{- *********************************************************************
*                                                                      *
                checkExpectedKind
*                                                                      *
********************************************************************* -}

-- | This instantiates invisible arguments for the type being checked if it must
-- be saturated and is not yet saturated. It then calls and uses the result
-- from checkExpectedKindX to build the final type
checkExpectedKind :: HasDebugCallStack
                  => HsType GhcRn       -- ^ type we're checking (for printing)
                  -> TcType             -- ^ type we're checking
                  -> TcKind             -- ^ the known kind of that type
                  -> TcKind             -- ^ the expected kind
                  -> TcM TcType
-- Just a convenience wrapper to save calls to 'ppr'
checkExpectedKind :: HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind HsType GhcRn
hs_ty Type
ty Type
act Type
exp
  = HasDebugCallStack => MsgDoc -> Type -> Type -> Type -> TcM Type
MsgDoc -> Type -> Type -> Type -> TcM Type
checkExpectedKind_pp (HsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr HsType GhcRn
hs_ty) Type
ty Type
act Type
exp

checkExpectedKind_pp :: HasDebugCallStack
                     => SDoc               -- ^ The thing we are checking
                     -> TcType             -- ^ type we're checking
                     -> TcKind             -- ^ the known kind of that type
                     -> TcKind             -- ^ the expected kind
                     -> TcM TcType
checkExpectedKind_pp :: MsgDoc -> Type -> Type -> Type -> TcM Type
checkExpectedKind_pp MsgDoc
pp_hs_ty Type
ty Type
act_kind Type
exp_kind
  = do { String -> MsgDoc -> TcM ()
traceTc String
"checkExpectedKind" (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
ty MsgDoc -> MsgDoc -> MsgDoc
$$ Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
act_kind)

       ; ([Type]
new_args, Type
act_kind') <- Int -> Type -> TcM ([Type], Type)
tcInstInvisibleTyBinders Int
n_to_inst Type
act_kind

       ; let origin :: CtOrigin
origin = TypeEqOrigin :: Type -> Type -> Maybe MsgDoc -> Bool -> CtOrigin
TypeEqOrigin { uo_actual :: Type
uo_actual   = Type
act_kind'
                                   , uo_expected :: Type
uo_expected = Type
exp_kind
                                   , uo_thing :: Maybe MsgDoc
uo_thing    = MsgDoc -> Maybe MsgDoc
forall a. a -> Maybe a
Just MsgDoc
pp_hs_ty
                                   , uo_visible :: Bool
uo_visible  = Bool
True } -- the hs_ty is visible

       ; String -> MsgDoc -> TcM ()
traceTc String
"checkExpectedKindX" (MsgDoc -> TcM ()) -> MsgDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [MsgDoc] -> MsgDoc
vcat [ MsgDoc
pp_hs_ty
              , String -> MsgDoc
text String
"act_kind':" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
act_kind'
              , String -> MsgDoc
text String
"exp_kind:" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
exp_kind ]

       ; let res_ty :: Type
res_ty = Type
ty Type -> [Type] -> Type
`mkTcAppTys` [Type]
new_args

       ; if Type
act_kind' HasDebugCallStack => Type -> Type -> Bool
Type -> Type -> Bool
`tcEqType` Type
exp_kind
         then Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
res_ty  -- This is very common
         else do { Coercion
co_k <- TypeOrKind -> CtOrigin -> Type -> Type -> TcM Coercion
uType TypeOrKind
KindLevel CtOrigin
origin Type
act_kind' Type
exp_kind
                 ; String -> MsgDoc -> TcM ()
traceTc String
"checkExpectedKind" ([MsgDoc] -> MsgDoc
vcat [ Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
act_kind
                                                     , Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
exp_kind
                                                     , Coercion -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Coercion
co_k ])
                ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
res_ty Type -> Coercion -> Type
`mkTcCastTy` Coercion
co_k) } }
    where
      -- We need to make sure that both kinds have the same number of implicit
      -- foralls out front. If the actual kind has more, instantiate accordingly.
      -- Otherwise, just pass the type & kind through: the errors are caught
      -- in unifyType.
      n_exp_invis_bndrs :: Int
n_exp_invis_bndrs = Type -> Int
invisibleTyBndrCount Type
exp_kind
      n_act_invis_bndrs :: Int
n_act_invis_bndrs = Type -> Int
invisibleTyBndrCount Type
act_kind
      n_to_inst :: Int
n_to_inst         = Int
n_act_invis_bndrs Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
n_exp_invis_bndrs


---------------------------
tcHsMbContext :: Maybe (LHsContext GhcRn) -> TcM [PredType]
tcHsMbContext :: Maybe (LHsContext GhcRn) -> TcM [Type]
tcHsMbContext Maybe (LHsContext GhcRn)
Nothing    = [Type] -> TcM [Type]
forall (m :: * -> *) a. Monad m => a -> m a
return []
tcHsMbContext (Just LHsContext GhcRn
cxt) = LHsContext GhcRn -> TcM [Type]
tcHsContext LHsContext GhcRn
cxt

tcHsContext :: LHsContext GhcRn -> TcM [PredType]
tcHsContext :: LHsContext GhcRn -> TcM [Type]
tcHsContext = TcTyMode -> LHsContext GhcRn -> TcM [Type]
tc_hs_context TcTyMode
typeLevelMode

tcLHsPredType :: LHsType GhcRn -> TcM PredType
tcLHsPredType :: LHsType GhcRn -> TcM Type
tcLHsPredType = TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
typeLevelMode

tc_hs_context :: TcTyMode -> LHsContext GhcRn -> TcM [PredType]
tc_hs_context :: TcTyMode -> LHsContext GhcRn -> TcM [Type]
tc_hs_context TcTyMode
mode LHsContext GhcRn
ctxt = (LHsType GhcRn -> TcM Type) -> [LHsType GhcRn] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
mode) (LHsContext GhcRn -> SrcSpanLess (LHsContext GhcRn)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc LHsContext GhcRn
ctxt)

tc_lhs_pred :: TcTyMode -> LHsType GhcRn -> TcM PredType
tc_lhs_pred :: TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_pred TcTyMode
mode LHsType GhcRn
pred = TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type TcTyMode
mode LHsType GhcRn
pred Type
constraintKind

---------------------------
tcTyVar :: TcTyMode -> Name -> TcM (TcType, TcKind)
-- See Note [Type checking recursive type and class declarations]
-- in TcTyClsDecls
tcTyVar :: TcTyMode -> Name -> TcM (Type, Type)
tcTyVar TcTyMode
mode Name
name         -- Could be a tyvar, a tycon, or a datacon
  = do { String -> MsgDoc -> TcM ()
traceTc String
"lk1" (Name -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Name
name)
       ; TcTyThing
thing <- Name -> TcM TcTyThing
tcLookup Name
name
       ; case TcTyThing
thing of
           ATyVar Name
_ TcTyVar
tv -> (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcTyVar -> Type
mkTyVarTy TcTyVar
tv, TcTyVar -> Type
tyVarKind TcTyVar
tv)

           ATcTyCon TyCon
tc_tc
             -> do { -- See Note [GADT kind self-reference]
                     Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (TypeOrKind -> Bool
isTypeLevel (TcTyMode -> TypeOrKind
mode_level TcTyMode
mode))
                            (Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
TyConPE)
                   ; TyCon -> TcM ()
check_tc TyCon
tc_tc
                   ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Type
mkTyConTy TyCon
tc_tc, TyCon -> Type
tyConKind TyCon
tc_tc) }

           AGlobal (ATyCon TyCon
tc)
             -> do { TyCon -> TcM ()
check_tc TyCon
tc
                   ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> Type
mkTyConTy TyCon
tc, TyCon -> Type
tyConKind TyCon
tc) }

           AGlobal (AConLike (RealDataCon DataCon
dc))
             -> do { Bool
data_kinds <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.DataKinds
                   ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Bool
data_kinds Bool -> Bool -> Bool
|| DataCon -> Bool
specialPromotedDc DataCon
dc) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                       Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
NoDataKindsDC
                   ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (TyCon -> Bool
isFamInstTyCon (DataCon -> TyCon
dataConTyCon DataCon
dc)) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                       -- see #15245
                       Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
FamDataConPE
                   ; let ([TcTyVar]
_, [TcTyVar]
_, [EqSpec]
_, [Type]
theta, [Type]
_, Type
_) = DataCon -> ([TcTyVar], [TcTyVar], [EqSpec], [Type], [Type], Type)
dataConFullSig DataCon
dc
                   ; String -> MsgDoc -> TcM ()
traceTc String
"tcTyVar" (DataCon -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr DataCon
dc MsgDoc -> MsgDoc -> MsgDoc
<+> [Type] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [Type]
theta MsgDoc -> MsgDoc -> MsgDoc
$$ Maybe Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr ([Type] -> Maybe Type
dc_theta_illegal_constraint [Type]
theta))
                   ; case [Type] -> Maybe Type
dc_theta_illegal_constraint [Type]
theta of
                       Just Type
pred -> Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name (PromotionErr -> TcM ()) -> PromotionErr -> TcM ()
forall a b. (a -> b) -> a -> b
$
                                    Type -> PromotionErr
ConstrainedDataConPE Type
pred
                       Maybe Type
Nothing   -> () -> TcM ()
forall (f :: * -> *) a. Applicative f => a -> f a
pure ()
                   ; let tc :: TyCon
tc = DataCon -> TyCon
promoteDataCon DataCon
dc
                   ; (Type, Type) -> TcM (Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> [Type] -> Type
mkTyConApp TyCon
tc [], TyCon -> Type
tyConKind TyCon
tc) }

           APromotionErr PromotionErr
err -> Name -> PromotionErr -> TcM (Type, Type)
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
err

           TcTyThing
_  -> String -> TcTyThing -> Name -> TcM (Type, Type)
forall a. String -> TcTyThing -> Name -> TcM a
wrongThingErr String
"type" TcTyThing
thing Name
name }
  where
    check_tc :: TyCon -> TcM ()
    check_tc :: TyCon -> TcM ()
check_tc TyCon
tc = do { Bool
data_kinds   <- Extension -> TcRnIf TcGblEnv TcLclEnv Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.DataKinds
                     ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (TypeOrKind -> Bool
isTypeLevel (TcTyMode -> TypeOrKind
mode_level TcTyMode
mode) Bool -> Bool -> Bool
||
                               Bool
data_kinds Bool -> Bool -> Bool
||
                               TyCon -> Bool
isKindTyCon TyCon
tc) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
                       Name -> PromotionErr -> TcM ()
forall a. Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
NoDataKindsTC }

    -- We cannot promote a data constructor with a context that contains
    -- constraints other than equalities, so error if we find one.
    -- See Note [Constraints in kinds] in TyCoRep
    dc_theta_illegal_constraint :: ThetaType -> Maybe PredType
    dc_theta_illegal_constraint :: [Type] -> Maybe Type
dc_theta_illegal_constraint = (Type -> Bool) -> [Type] -> Maybe Type
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Maybe a
find (Bool -> Bool
not (Bool -> Bool) -> (Type -> Bool) -> Type -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Type -> Bool
isEqPred)

{-
Note [GADT kind self-reference]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

A promoted type cannot be used in the body of that type's declaration.
#11554 shows this example, which made GHC loop:

  import Data.Kind
  data P (x :: k) = Q
  data A :: Type where
    B :: forall (a :: A). P a -> A

In order to check the constructor B, we need to have the promoted type A, but in
order to get that promoted type, B must first be checked. To prevent looping, a
TyConPE promotion error is given when tcTyVar checks an ATcTyCon in kind mode.
Any ATcTyCon is a TyCon being defined in the current recursive group (see data
type decl for TcTyThing), and all such TyCons are illegal in kinds.

#11962 proposes checking the head of a data declaration separately from
its constructors. This would allow the example above to pass.

Note [Body kind of a HsForAllTy]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The body of a forall is usually a type, but in principle
there's no reason to prohibit *unlifted* types.
In fact, GHC can itself construct a function with an
unboxed tuple inside a for-all (via CPR analysis; see
typecheck/should_compile/tc170).

Moreover in instance heads we get forall-types with
kind Constraint.

It's tempting to check that the body kind is either * or #. But this is
wrong. For example:

  class C a b
  newtype N = Mk Foo deriving (C a)

We're doing newtype-deriving for C. But notice how `a` isn't in scope in
the predicate `C a`. So we quantify, yielding `forall a. C a` even though
`C a` has kind `* -> Constraint`. The `forall a. C a` is a bit cheeky, but
convenient. Bottom line: don't check for * or # here.

Note [Body kind of a HsQualTy]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If ctxt is non-empty, the HsQualTy really is a /function/, so the
kind of the result really is '*', and in that case the kind of the
body-type can be lifted or unlifted.

However, consider
    instance Eq a => Eq [a] where ...
or
    f :: (Eq a => Eq [a]) => blah
Here both body-kind of the HsQualTy is Constraint rather than *.
Rather crudely we tell the difference by looking at exp_kind. It's
very convenient to typecheck instance types like any other HsSigType.

Admittedly the '(Eq a => Eq [a]) => blah' case is erroneous, but it's
better to reject in checkValidType.  If we say that the body kind
should be '*' we risk getting TWO error messages, one saying that Eq
[a] doens't have kind '*', and one saying that we need a Constraint to
the left of the outer (=>).

How do we figure out the right body kind?  Well, it's a bit of a
kludge: I just look at the expected kind.  If it's Constraint, we
must be in this instance situation context. It's a kludge because it
wouldn't work if any unification was involved to compute that result
kind -- but it isn't.  (The true way might be to use the 'mode'
parameter, but that seemed like a sledgehammer to crack a nut.)

Note [Inferring tuple kinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Give a tuple type (a,b,c), which the parser labels as HsBoxedOrConstraintTuple,
we try to figure out whether it's a tuple of kind * or Constraint.
  Step 1: look at the expected kind
  Step 2: infer argument kinds

If after Step 2 it's not clear from the arguments that it's
Constraint, then it must be *.  Once having decided that we re-check
the arguments to give good error messages in
  e.g.  (Maybe, Maybe)

Note that we will still fail to infer the correct kind in this case:

  type T a = ((a,a), D a)
  type family D :: Constraint -> Constraint

While kind checking T, we do not yet know the kind of D, so we will default the
kind of T to * -> *. It works if we annotate `a` with kind `Constraint`.

Note [Desugaring types]
~~~~~~~~~~~~~~~~~~~~~~~
The type desugarer is phase 2 of dealing with HsTypes.  Specifically:

  * It transforms from HsType to Type

  * It zonks any kinds.  The returned type should have no mutable kind
    or type variables (hence returning Type not TcType):
      - any unconstrained kind variables are defaulted to (Any *) just
        as in TcHsSyn.
      - there are no mutable type variables because we are
        kind-checking a type
    Reason: the returned type may be put in a TyCon or DataCon where
    it will never subsequently be zonked.

You might worry about nested scopes:
        ..a:kappa in scope..
            let f :: forall b. T '[a,b] -> Int
In this case, f's type could have a mutable kind variable kappa in it;
and we might then default it to (Any *) when dealing with f's type
signature.  But we don't expect this to happen because we can't get a
lexically scoped type variable with a mutable kind variable in it.  A
delicate point, this.  If it becomes an issue we might need to
distinguish top-level from nested uses.

Moreover
  * it cannot fail,
  * it does no unifications
  * it does no validity checking, except for structural matters, such as
        (a) spurious ! annotations.
        (b) a class used as a type

Note [Kind of a type splice]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider these terms, each with TH type splice inside:
     [| e1 :: Maybe $(..blah..) |]
     [| e2 :: $(..blah..) |]
When kind-checking the type signature, we'll kind-check the splice
$(..blah..); we want to give it a kind that can fit in any context,
as if $(..blah..) :: forall k. k.

In the e1 example, the context of the splice fixes kappa to *.  But
in the e2 example, we'll desugar the type, zonking the kind unification
variables as we go.  When we encounter the unconstrained kappa, we
want to default it to '*', not to (Any *).

Help functions for type applications
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-}

addTypeCtxt :: LHsType GhcRn -> TcM a -> TcM a
        -- Wrap a context around only if we want to show that contexts.
        -- Omit invisible ones and ones user's won't grok
addTypeCtxt :: LHsType GhcRn -> TcM a -> TcM a
addTypeCtxt (L SrcSpan
_ (HsWildCardTy XWildCardTy GhcRn
_)) TcM a
thing = TcM a
thing   -- "In the type '_'" just isn't helpful.
addTypeCtxt (L SrcSpan
_ HsType GhcRn
ty) TcM a
thing
  = MsgDoc -> TcM a -> TcM a
forall a. MsgDoc -> TcM a -> TcM a
addErrCtxt MsgDoc
doc TcM a
thing
  where
    doc :: MsgDoc
doc = String -> MsgDoc
text String
"In the type" MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (HsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr HsType GhcRn
ty)

{-
************************************************************************
*                                                                      *
                Type-variable binders
%*                                                                      *
%************************************************************************

Note [Keeping scoped variables in order: Explicit]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When the user writes `forall a b c. blah`, we bring a, b, and c into
scope and then check blah. In the process of checking blah, we might
learn the kinds of a, b, and c, and these kinds might indicate that
b depends on c, and thus that we should reject the user-written type.

One approach to doing this would be to bring each of a, b, and c into
scope, one at a time, creating an implication constraint and
bumping the TcLevel for each one. This would work, because the kind
of, say, b would be untouchable when c is in scope (and the constraint
couldn't float out because c blocks it). However, it leads to terrible
error messages, complaining about skolem escape. While it is indeed
a problem of skolem escape, we can do better.

Instead, our approach is to bring the block of variables into scope
all at once, creating one implication constraint for the lot. The
user-written variables are skolems in the implication constraint. In
TcSimplify.setImplicationStatus, we check to make sure that the ordering
is correct, choosing ImplicationStatus IC_BadTelescope if they aren't.
Then, in TcErrors, we report if there is a bad telescope. This way,
we can report a suggested ordering to the user if there is a problem.

See also Note [Checking telescopes] in Constraint

Note [Keeping scoped variables in order: Implicit]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When the user implicitly quantifies over variables (say, in a type
signature), we need to come up with some ordering on these variables.
This is done by bumping the TcLevel, bringing the tyvars into scope,
and then type-checking the thing_inside. The constraints are all
wrapped in an implication, which is then solved. Finally, we can
zonk all the binders and then order them with scopedSort.

It's critical to solve before zonking and ordering in order to uncover
any unifications. You might worry that this eager solving could cause
trouble elsewhere. I don't think it will. Because it will solve only
in an increased TcLevel, it can't unify anything that was mentioned
elsewhere. Additionally, we require that the order of implicitly
quantified variables is manifest by the scope of these variables, so
we're not going to learn more information later that will help order
these variables.

Note [Recipe for checking a signature]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Checking a user-written signature requires several steps:

 1. Generate constraints.
 2. Solve constraints.
 3. Promote tyvars and/or kind-generalize.
 4. Zonk.
 5. Check validity.

There may be some surprises in here:

Step 2 is necessary for two reasons: most signatures also bring
implicitly quantified variables into scope, and solving is necessary
to get these in the right order (see Note [Keeping scoped variables in
order: Implicit]). Additionally, solving is necessary in order to
kind-generalize correctly: otherwise, we do not know which metavariables
are left unsolved.

Step 3 is done by a call to candidateQTyVarsOfType, followed by a call to
kindGeneralize{All,Some,None}. Here, we have to deal with the fact that
metatyvars generated in the type may have a bumped TcLevel, because explicit
foralls raise the TcLevel. To avoid these variables from ever being visible in
the surrounding context, we must obey the following dictum:

  Every metavariable in a type must either be
    (A) generalized, or
    (B) promoted, or        See Note [Promotion in signatures]
    (C) zapped to Any       See Note [Naughty quantification candidates] in TcMType

The kindGeneralize functions do not require pre-zonking; they zonk as they
go.

If you are actually doing kind-generalization, you need to bump the level
before generating constraints, as we will only generalize variables with
a TcLevel higher than the ambient one.

After promoting/generalizing, we need to zonk again because both
promoting and generalizing fill in metavariables.

Note [Promotion in signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If an unsolved metavariable in a signature is not generalized
(because we're not generalizing the construct -- e.g., pattern
sig -- or because the metavars are constrained -- see kindGeneralizeSome)
we need to promote to maintain (MetaTvInv) of Note [TcLevel and untouchable type variables]
in TcType. Note that promotion is identical in effect to generalizing
and the reinstantiating with a fresh metavariable at the current level.
So in some sense, we generalize *all* variables, but then re-instantiate
some of them.

Here is an example of why we must promote:
  foo (x :: forall a. a -> Proxy b) = ...

In the pattern signature, `b` is unbound, and will thus be brought into
scope. We do not know its kind: it will be assigned kappa[2]. Note that
kappa is at TcLevel 2, because it is invented under a forall. (A priori,
the kind kappa might depend on `a`, so kappa rightly has a higher TcLevel
than the surrounding context.) This kappa cannot be solved for while checking
the pattern signature (which is not kind-generalized). When we are checking
the *body* of foo, though, we need to unify the type of x with the argument
type of bar. At this point, the ambient TcLevel is 1, and spotting a
matavariable with level 2 would violate the (MetaTvInv) invariant of
Note [TcLevel and untouchable type variables]. So, instead of kind-generalizing,
we promote the metavariable to level 1. This is all done in kindGeneralizeNone.

-}

tcNamedWildCardBinders :: [Name]
                       -> ([(Name, TcTyVar)] -> TcM a)
                       -> TcM a
-- Bring into scope the /named/ wildcard binders.  Remember that
-- plain wildcards _ are anonymous and dealt with by HsWildCardTy
-- Soe Note [The wildcard story for types] in GHC.Hs.Types
tcNamedWildCardBinders :: [Name] -> ([(Name, TcTyVar)] -> TcM a) -> TcM a
tcNamedWildCardBinders [Name]
wc_names [(Name, TcTyVar)] -> TcM a
thing_inside
  = do { [TcTyVar]
wcs <- (Name -> TcM TcTyVar) -> [Name] -> TcM [TcTyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (TcM TcTyVar -> Name -> TcM TcTyVar
forall a b. a -> b -> a
const TcM TcTyVar
newWildTyVar) [Name]
wc_names
       ; let wc_prs :: [(Name, TcTyVar)]
wc_prs = [Name]
wc_names [Name] -> [TcTyVar] -> [(Name, TcTyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcTyVar]
wcs
       ; [(Name, TcTyVar)] -> TcM a -> TcM a
forall r. [(Name, TcTyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TcTyVar)]
wc_prs (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
         [(Name, TcTyVar)] -> TcM a
thing_inside [(Name, TcTyVar)]
wc_prs }

newWildTyVar :: TcM TcTyVar
-- ^ New unification variable '_' for a wildcard
newWildTyVar :: TcM TcTyVar
newWildTyVar
  = do { Type
kind <- TcM Type
newMetaKindVar
       ; Unique
uniq <- TcRnIf TcGblEnv TcLclEnv Unique
forall gbl lcl. TcRnIf gbl lcl Unique
newUnique
       ; TcTyVarDetails
details <- MetaInfo -> TcM TcTyVarDetails
newMetaDetails MetaInfo
TauTv
       ; let name :: Name
name  = Unique -> FastString -> Name
mkSysTvName Unique
uniq (String -> FastString
fsLit String
"_")
             tyvar :: TcTyVar
tyvar = Name -> Type -> TcTyVarDetails -> TcTyVar
mkTcTyVar Name
name Type
kind TcTyVarDetails
details
       ; String -> MsgDoc -> TcM ()
traceTc String
"newWildTyVar" (TcTyVar -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TcTyVar
tyvar)
       ; TcTyVar -> TcM TcTyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TcTyVar
tyvar }

{- *********************************************************************
*                                                                      *
             Kind inference for type declarations
*                                                                      *
********************************************************************* -}

-- See Note [kcCheckDeclHeader vs kcInferDeclHeader]
data InitialKindStrategy
  = InitialKindCheck SAKS_or_CUSK
  | InitialKindInfer

-- Does the declaration have a standalone kind signature (SAKS) or a complete
-- user-specified kind (CUSK)?
data SAKS_or_CUSK
  = SAKS Kind  -- Standalone kind signature, fully zonked! (zonkTcTypeToType)
  | CUSK       -- Complete user-specified kind (CUSK)

instance Outputable SAKS_or_CUSK where
  ppr :: SAKS_or_CUSK -> MsgDoc
ppr (SAKS Type
k) = String -> MsgDoc
text String
"SAKS" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
k
  ppr SAKS_or_CUSK
CUSK = String -> MsgDoc
text String
"CUSK"

-- See Note [kcCheckDeclHeader vs kcInferDeclHeader]
kcDeclHeader
  :: InitialKindStrategy
  -> Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind
  -> TcM TcTyCon       -- ^ A suitably-kinded TcTyCon
kcDeclHeader :: InitialKindStrategy
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcDeclHeader (InitialKindCheck SAKS_or_CUSK
msig) = SAKS_or_CUSK
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader SAKS_or_CUSK
msig
kcDeclHeader InitialKindStrategy
InitialKindInfer = Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcInferDeclHeader

{- Note [kcCheckDeclHeader vs kcInferDeclHeader]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kcCheckDeclHeader and kcInferDeclHeader are responsible for getting the initial kind
of a type constructor.

* kcCheckDeclHeader: the TyCon has a standalone kind signature or a CUSK. In that
  case, find the full, final, poly-kinded kind of the TyCon.  It's very like a
  term-level binding where we have a complete type signature for the function.

* kcInferDeclHeader: the TyCon has neither a standalone kind signature nor a
  CUSK. Find a monomorphic kind, with unification variables in it; they will be
  generalised later.  It's very like a term-level binding where we do not have a
  type signature (or, more accurately, where we have a partial type signature),
  so we infer the type and generalise.
-}

------------------------------
kcCheckDeclHeader
  :: SAKS_or_CUSK
  -> Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind. AnyKind == no result signature
  -> TcM TcTyCon       -- ^ A suitably-kinded generalized TcTyCon
kcCheckDeclHeader :: SAKS_or_CUSK
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader (SAKS Type
sig) = Type
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader_sig Type
sig
kcCheckDeclHeader SAKS_or_CUSK
CUSK       = Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcCheckDeclHeader_cusk

kcCheckDeclHeader_cusk
  :: Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind
  -> TcM TcTyCon       -- ^ A suitably-kinded generalized TcTyCon
kcCheckDeclHeader_cusk :: Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcCheckDeclHeader_cusk Name
name TyConFlavour
flav
              (HsQTvs { hsq_ext :: forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext = XHsQTvs GhcRn
kv_ns
                      , hsq_explicit :: forall pass. LHsQTyVars pass -> [LHsTyVarBndr pass]
hsq_explicit = [LHsTyVarBndr GhcRn]
hs_tvs }) TcM ContextKind
kc_res_ki
  -- CUSK case
  -- See note [Required, Specified, and Inferred for types] in TcTyClsDecls
  = Name -> TyConFlavour -> TcM TyCon -> TcM TyCon
forall a. Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    do { ([TcTyVar]
scoped_kvs, ([TcTyVar]
tc_tvs, Type
res_kind))
           <- TcM ([TcTyVar], ([TcTyVar], Type))
-> TcM ([TcTyVar], ([TcTyVar], Type))
forall a. TcM a -> TcM a
pushTcLevelM_                               (TcM ([TcTyVar], ([TcTyVar], Type))
 -> TcM ([TcTyVar], ([TcTyVar], Type)))
-> TcM ([TcTyVar], ([TcTyVar], Type))
-> TcM ([TcTyVar], ([TcTyVar], Type))
forall a b. (a -> b) -> a -> b
$
              TcM ([TcTyVar], ([TcTyVar], Type))
-> TcM ([TcTyVar], ([TcTyVar], Type))
forall a. TcM a -> TcM a
solveEqualities                             (TcM ([TcTyVar], ([TcTyVar], Type))
 -> TcM ([TcTyVar], ([TcTyVar], Type)))
-> TcM ([TcTyVar], ([TcTyVar], Type))
-> TcM ([TcTyVar], ([TcTyVar], Type))
forall a b. (a -> b) -> a -> b
$
              [Name]
-> TcM ([TcTyVar], Type) -> TcM ([TcTyVar], ([TcTyVar], Type))
forall a. [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Q_Skol [Name]
XHsQTvs GhcRn
kv_ns            (TcM ([TcTyVar], Type) -> TcM ([TcTyVar], ([TcTyVar], Type)))
-> TcM ([TcTyVar], Type) -> TcM ([TcTyVar], ([TcTyVar], Type))
forall a b. (a -> b) -> a -> b
$
              ContextKind
-> [LHsTyVarBndr GhcRn] -> TcM Type -> TcM ([TcTyVar], Type)
forall a.
ContextKind -> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Q_Skol ContextKind
ctxt_kind [LHsTyVarBndr GhcRn]
hs_tvs (TcM Type -> TcM ([TcTyVar], Type))
-> TcM Type -> TcM ([TcTyVar], Type)
forall a b. (a -> b) -> a -> b
$
              ContextKind -> TcM Type
newExpectedKind (ContextKind -> TcM Type) -> TcM ContextKind -> TcM Type
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< TcM ContextKind
kc_res_ki

           -- Now, because we're in a CUSK,
           -- we quantify over the mentioned kind vars
       ; let spec_req_tkvs :: [TcTyVar]
spec_req_tkvs = [TcTyVar]
scoped_kvs [TcTyVar] -> [TcTyVar] -> [TcTyVar]
forall a. [a] -> [a] -> [a]
++ [TcTyVar]
tc_tvs
             all_kinds :: [Type]
all_kinds     = Type
res_kind Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: (TcTyVar -> Type) -> [TcTyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TcTyVar -> Type
tyVarKind [TcTyVar]
spec_req_tkvs

       ; CandidatesQTvs
candidates' <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfKinds [Type]
all_kinds
             -- 'candidates' are all the variables that we are going to
             -- skolemise and then quantify over.  We do not include spec_req_tvs
             -- because they are /already/ skolems

       ; let non_tc_candidates :: [TcTyVar]
non_tc_candidates = (TcTyVar -> Bool) -> [TcTyVar] -> [TcTyVar]
forall a. (a -> Bool) -> [a] -> [a]
filter (Bool -> Bool
not (Bool -> Bool) -> (TcTyVar -> Bool) -> TcTyVar -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcTyVar -> Bool
isTcTyVar) (TyCoVarSet -> [TcTyVar]
forall elt. UniqSet elt -> [elt]
nonDetEltsUniqSet ([Type] -> TyCoVarSet
tyCoVarsOfTypes [Type]
all_kinds))
             candidates :: CandidatesQTvs
candidates = CandidatesQTvs
candidates' { dv_kvs :: DTyVarSet
dv_kvs = CandidatesQTvs -> DTyVarSet
dv_kvs CandidatesQTvs
candidates' DTyVarSet -> [TcTyVar] -> DTyVarSet
`extendDVarSetList` [TcTyVar]
non_tc_candidates }
             inf_candidates :: CandidatesQTvs
inf_candidates = CandidatesQTvs
candidates CandidatesQTvs -> [TcTyVar] -> CandidatesQTvs
`delCandidates` [TcTyVar]
spec_req_tkvs

       ; [TcTyVar]
inferred <- CandidatesQTvs -> TcM [TcTyVar]
quantifyTyVars CandidatesQTvs
inf_candidates
                     -- NB: 'inferred' comes back sorted in dependency order

       ; [TcTyVar]
scoped_kvs <- (TcTyVar -> TcM TcTyVar) -> [TcTyVar] -> TcM [TcTyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM TcTyVar -> TcM TcTyVar
zonkTyCoVarKind [TcTyVar]
scoped_kvs
       ; [TcTyVar]
tc_tvs     <- (TcTyVar -> TcM TcTyVar) -> [TcTyVar] -> TcM [TcTyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM TcTyVar -> TcM TcTyVar
zonkTyCoVarKind [TcTyVar]
tc_tvs
       ; Type
res_kind   <- Type -> TcM Type
zonkTcType           Type
res_kind

       ; let mentioned_kv_set :: TyCoVarSet
mentioned_kv_set = CandidatesQTvs -> TyCoVarSet
candidateKindVars CandidatesQTvs
candidates
             specified :: [TcTyVar]
specified        = [TcTyVar] -> [TcTyVar]
scopedSort [TcTyVar]
scoped_kvs
                                -- NB: maintain the L-R order of scoped_kvs

             final_tc_binders :: [TyConBinder]
final_tc_binders =  ArgFlag -> [TcTyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Inferred  [TcTyVar]
inferred
                              [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ ArgFlag -> [TcTyVar] -> [TyConBinder]
mkNamedTyConBinders ArgFlag
Specified [TcTyVar]
specified
                              [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ (TcTyVar -> TyConBinder) -> [TcTyVar] -> [TyConBinder]
forall a b. (a -> b) -> [a] -> [b]
map (TyCoVarSet -> TcTyVar -> TyConBinder
mkRequiredTyConBinder TyCoVarSet
mentioned_kv_set) [TcTyVar]
tc_tvs

             all_tv_prs :: [(Name, TcTyVar)]
all_tv_prs = [TcTyVar] -> [(Name, TcTyVar)]
mkTyVarNamePairs ([TcTyVar]
scoped_kvs [TcTyVar] -> [TcTyVar] -> [TcTyVar]
forall a. [a] -> [a] -> [a]
++ [TcTyVar]
tc_tvs)
             tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TcTyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
name [TyConBinder]
final_tc_binders Type
res_kind [(Name, TcTyVar)]
all_tv_prs
                               Bool
True -- it is generalised
                               TyConFlavour
flav
         -- If the ordering from
         -- Note [Required, Specified, and Inferred for types] in TcTyClsDecls
         -- doesn't work, we catch it here, before an error cascade
       ; TyCon -> TcM ()
checkTyConTelescope TyCon
tycon

       ; String -> MsgDoc -> TcM ()
traceTc String
"kcCheckDeclHeader_cusk " (MsgDoc -> TcM ()) -> MsgDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [MsgDoc] -> MsgDoc
vcat [ String -> MsgDoc
text String
"name" MsgDoc -> MsgDoc -> MsgDoc
<+> Name -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Name
name
              , String -> MsgDoc
text String
"kv_ns" MsgDoc -> MsgDoc -> MsgDoc
<+> [Name] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [Name]
XHsQTvs GhcRn
kv_ns
              , String -> MsgDoc
text String
"hs_tvs" MsgDoc -> MsgDoc -> MsgDoc
<+> [LHsTyVarBndr GhcRn] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsTyVarBndr GhcRn]
hs_tvs
              , String -> MsgDoc
text String
"scoped_kvs" MsgDoc -> MsgDoc -> MsgDoc
<+> [TcTyVar] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TcTyVar]
scoped_kvs
              , String -> MsgDoc
text String
"tc_tvs" MsgDoc -> MsgDoc -> MsgDoc
<+> [TcTyVar] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TcTyVar]
tc_tvs
              , String -> MsgDoc
text String
"res_kind" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
res_kind
              , String -> MsgDoc
text String
"candidates" MsgDoc -> MsgDoc -> MsgDoc
<+> CandidatesQTvs -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr CandidatesQTvs
candidates
              , String -> MsgDoc
text String
"inferred" MsgDoc -> MsgDoc -> MsgDoc
<+> [TcTyVar] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TcTyVar]
inferred
              , String -> MsgDoc
text String
"specified" MsgDoc -> MsgDoc -> MsgDoc
<+> [TcTyVar] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TcTyVar]
specified
              , String -> MsgDoc
text String
"final_tc_binders" MsgDoc -> MsgDoc -> MsgDoc
<+> [TyConBinder] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TyConBinder]
final_tc_binders
              , String -> MsgDoc
text String
"mkTyConKind final_tc_bndrs res_kind"
                MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr ([TyConBinder] -> Type -> Type
mkTyConKind [TyConBinder]
final_tc_binders Type
res_kind)
              , String -> MsgDoc
text String
"all_tv_prs" MsgDoc -> MsgDoc -> MsgDoc
<+> [(Name, TcTyVar)] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [(Name, TcTyVar)]
all_tv_prs ]

       ; TyCon -> TcM TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }
  where
    ctxt_kind :: ContextKind
ctxt_kind | TyConFlavour -> Bool
tcFlavourIsOpen TyConFlavour
flav = Type -> ContextKind
TheKind Type
liftedTypeKind
              | Bool
otherwise            = ContextKind
AnyKind
kcCheckDeclHeader_cusk Name
_ TyConFlavour
_ (XLHsQTyVars XXLHsQTyVars GhcRn
nec) TcM ContextKind
_ = NoExtCon -> TcM TyCon
forall a. NoExtCon -> a
noExtCon XXLHsQTyVars GhcRn
NoExtCon
nec

-- | Kind-check a 'LHsQTyVars'. Used in 'inferInitialKind' (for tycon kinds and
-- other kinds).
--
-- This function does not do telescope checking.
kcInferDeclHeader
  :: Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn
  -> TcM ContextKind   -- ^ The result kind
  -> TcM TcTyCon       -- ^ A suitably-kinded non-generalized TcTyCon
kcInferDeclHeader :: Name
-> TyConFlavour -> LHsQTyVars GhcRn -> TcM ContextKind -> TcM TyCon
kcInferDeclHeader Name
name TyConFlavour
flav
              (HsQTvs { hsq_ext :: forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext = XHsQTvs GhcRn
kv_ns
                      , hsq_explicit :: forall pass. LHsQTyVars pass -> [LHsTyVarBndr pass]
hsq_explicit = [LHsTyVarBndr GhcRn]
hs_tvs }) TcM ContextKind
kc_res_ki
  -- No standalane kind signature and no CUSK.
  -- See note [Required, Specified, and Inferred for types] in TcTyClsDecls
  = do { ([TcTyVar]
scoped_kvs, ([TcTyVar]
tc_tvs, Type
res_kind))
           -- Why bindImplicitTKBndrs_Q_Tv which uses newTyVarTyVar?
           -- See Note [Inferring kinds for type declarations] in TcTyClsDecls
           <- [Name]
-> TcM ([TcTyVar], Type) -> TcM ([TcTyVar], ([TcTyVar], Type))
forall a. [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Q_Tv [Name]
XHsQTvs GhcRn
kv_ns            (TcM ([TcTyVar], Type) -> TcM ([TcTyVar], ([TcTyVar], Type)))
-> TcM ([TcTyVar], Type) -> TcM ([TcTyVar], ([TcTyVar], Type))
forall a b. (a -> b) -> a -> b
$
              ContextKind
-> [LHsTyVarBndr GhcRn] -> TcM Type -> TcM ([TcTyVar], Type)
forall a.
ContextKind -> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Q_Tv ContextKind
ctxt_kind [LHsTyVarBndr GhcRn]
hs_tvs (TcM Type -> TcM ([TcTyVar], Type))
-> TcM Type -> TcM ([TcTyVar], Type)
forall a b. (a -> b) -> a -> b
$
              ContextKind -> TcM Type
newExpectedKind (ContextKind -> TcM Type) -> TcM ContextKind -> TcM Type
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< TcM ContextKind
kc_res_ki
              -- Why "_Tv" not "_Skol"? See third wrinkle in
              -- Note [Inferring kinds for type declarations] in TcTyClsDecls,

       ; let   -- NB: Don't add scoped_kvs to tyConTyVars, because they
               -- might unify with kind vars in other types in a mutually
               -- recursive group.
               -- See Note [Inferring kinds for type declarations] in TcTyClsDecls

             tc_binders :: [TyConBinder]
tc_binders = AnonArgFlag -> [TcTyVar] -> [TyConBinder]
mkAnonTyConBinders AnonArgFlag
VisArg [TcTyVar]
tc_tvs
               -- Also, note that tc_binders has the tyvars from only the
               -- user-written tyvarbinders. See S1 in Note [How TcTyCons work]
               -- in TcTyClsDecls
               --
               -- mkAnonTyConBinder: see Note [No polymorphic recursion]

             all_tv_prs :: [(Name, TcTyVar)]
all_tv_prs = ([Name]
XHsQTvs GhcRn
kv_ns                [Name] -> [TcTyVar] -> [(Name, TcTyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcTyVar]
scoped_kvs) [(Name, TcTyVar)] -> [(Name, TcTyVar)] -> [(Name, TcTyVar)]
forall a. [a] -> [a] -> [a]
++
                          ([LHsTyVarBndr GhcRn] -> [IdP GhcRn]
forall (p :: Pass). [LHsTyVarBndr (GhcPass p)] -> [IdP (GhcPass p)]
hsLTyVarNames [LHsTyVarBndr GhcRn]
hs_tvs [Name] -> [TcTyVar] -> [(Name, TcTyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcTyVar]
tc_tvs)
               -- NB: bindIplicitTKBndrs_Q_Tv makes /freshly-named/ unification
               --     variables, hence the need to zip here.  Ditto bindExplicit..
               -- See TcMType Note [Unification variables need fresh Names]

             tycon :: TyCon
tycon = Name
-> [TyConBinder]
-> Type
-> [(Name, TcTyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
name [TyConBinder]
tc_binders Type
res_kind [(Name, TcTyVar)]
all_tv_prs
                               Bool
False -- not yet generalised
                               TyConFlavour
flav

       ; String -> MsgDoc -> TcM ()
traceTc String
"kcInferDeclHeader: not-cusk" (MsgDoc -> TcM ()) -> MsgDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [MsgDoc] -> MsgDoc
vcat [ Name -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Name
name, [Name] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [Name]
XHsQTvs GhcRn
kv_ns, [LHsTyVarBndr GhcRn] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsTyVarBndr GhcRn]
hs_tvs
              , [TcTyVar] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TcTyVar]
scoped_kvs
              , [TcTyVar] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TcTyVar]
tc_tvs, Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr ([TyConBinder] -> Type -> Type
mkTyConKind [TyConBinder]
tc_binders Type
res_kind) ]
       ; TyCon -> TcM TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tycon }
  where
    ctxt_kind :: ContextKind
ctxt_kind | TyConFlavour -> Bool
tcFlavourIsOpen TyConFlavour
flav = Type -> ContextKind
TheKind Type
liftedTypeKind
              | Bool
otherwise            = ContextKind
AnyKind

kcInferDeclHeader Name
_ TyConFlavour
_ (XLHsQTyVars XXLHsQTyVars GhcRn
nec) TcM ContextKind
_ = NoExtCon -> TcM TyCon
forall a. NoExtCon -> a
noExtCon XXLHsQTyVars GhcRn
NoExtCon
nec

-- | Kind-check a declaration header against a standalone kind signature.
-- See Note [Arity inference in kcCheckDeclHeader_sig]
kcCheckDeclHeader_sig
  :: Kind              -- ^ Standalone kind signature, fully zonked! (zonkTcTypeToType)
  -> Name              -- ^ of the thing being checked
  -> TyConFlavour      -- ^ What sort of 'TyCon' is being checked
  -> LHsQTyVars GhcRn  -- ^ Binders in the header
  -> TcM ContextKind   -- ^ The result kind. AnyKind == no result signature
  -> TcM TcTyCon       -- ^ A suitably-kinded TcTyCon
kcCheckDeclHeader_sig :: Type
-> Name
-> TyConFlavour
-> LHsQTyVars GhcRn
-> TcM ContextKind
-> TcM TyCon
kcCheckDeclHeader_sig Type
kisig Name
name TyConFlavour
flav LHsQTyVars GhcRn
ktvs TcM ContextKind
kc_res_ki =
  Name -> TyConFlavour -> TcM TyCon -> TcM TyCon
forall a. Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    TcM TyCon -> TcM TyCon
forall a. TcM a -> TcM a
pushTcLevelM_ (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$
    TcM TyCon -> TcM TyCon
forall a. TcM a -> TcM a
solveEqualities (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$  -- #16687
    [Name] -> ([(Name, TcTyVar)] -> TcM TyCon) -> TcM TyCon
forall a. [Name] -> ([(Name, TcTyVar)] -> TcM a) -> TcM a
bind_implicit (LHsQTyVars GhcRn -> XHsQTvs GhcRn
forall pass. LHsQTyVars pass -> XHsQTvs pass
hsq_ext LHsQTyVars GhcRn
ktvs) (([(Name, TcTyVar)] -> TcM TyCon) -> TcM TyCon)
-> ([(Name, TcTyVar)] -> TcM TyCon) -> TcM TyCon
forall a b. (a -> b) -> a -> b
$ \[(Name, TcTyVar)]
implicit_tcv_prs -> do

      -- Step 1: zip user-written binders with quantifiers from the kind signature.
      -- For example:
      --
      --   type F :: forall k -> k -> forall j. j -> Type
      --   data F i a b = ...
      --
      -- Results in the following 'zipped_binders':
      --
      --                   TyBinder      LHsTyVarBndr
      --    ---------------------------------------
      --    ZippedBinder   forall k ->   i
      --    ZippedBinder   k ->          a
      --    ZippedBinder   forall j.
      --    ZippedBinder   j ->          b
      --
      let ([ZippedBinder]
zipped_binders, [LHsTyVarBndr GhcRn]
excess_bndrs, Type
kisig') = Type
-> [LHsTyVarBndr GhcRn]
-> ([ZippedBinder], [LHsTyVarBndr GhcRn], Type)
zipBinders Type
kisig (LHsQTyVars GhcRn -> [LHsTyVarBndr GhcRn]
forall pass. LHsQTyVars pass -> [LHsTyVarBndr pass]
hsq_explicit LHsQTyVars GhcRn
ktvs)

      -- Report binders that don't have a corresponding quantifier.
      -- For example:
      --
      --   type T :: Type -> Type
      --   data T b1 b2 b3 = ...
      --
      -- Here, b1 is zipped with Type->, while b2 and b3 are excess binders.
      --
      Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless ([LHsTyVarBndr GhcRn] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LHsTyVarBndr GhcRn]
excess_bndrs) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$ MsgDoc -> TcM ()
forall a. MsgDoc -> TcM a
failWithTc (Type -> [LHsTyVarBndr GhcRn] -> MsgDoc
tooManyBindersErr Type
kisig' [LHsTyVarBndr GhcRn]
excess_bndrs)

      -- Convert each ZippedBinder to TyConBinder        for  tyConBinders
      --                       and to [(Name, TcTyVar)]  for  tcTyConScopedTyVars
      ([TyConBinder]
vis_tcbs, [[(Name, TcTyVar)]] -> [(Name, TcTyVar)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat -> [(Name, TcTyVar)]
explicit_tv_prs) <- (ZippedBinder
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)]))
-> [ZippedBinder]
-> IOEnv
     (Env TcGblEnv TcLclEnv) ([TyConBinder], [[(Name, TcTyVar)]])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM ZippedBinder
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
zipped_to_tcb [ZippedBinder]
zipped_binders

      [(Name, TcTyVar)] -> TcM TyCon -> TcM TyCon
forall r. [(Name, TcTyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TcTyVar)]
explicit_tv_prs (TcM TyCon -> TcM TyCon) -> TcM TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$ do

        -- Check that inline kind annotations on binders are valid.
        -- For example:
        --
        --   type T :: Maybe k -> Type
        --   data T (a :: Maybe j) = ...
        --
        -- Here we unify   Maybe k ~ Maybe j
        (ZippedBinder -> TcM ()) -> [ZippedBinder] -> TcM ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ ZippedBinder -> TcM ()
check_zipped_binder [ZippedBinder]
zipped_binders

        -- Kind-check the result kind annotation, if present:
        --
        --    data T a b :: res_ki where
        --               ^^^^^^^^^
        -- We do it here because at this point the environment has been
        -- extended with both 'implicit_tcv_prs' and 'explicit_tv_prs'.
        Maybe Type
m_res_ki <- TcM ContextKind
kc_res_ki TcM ContextKind
-> (ContextKind -> IOEnv (Env TcGblEnv TcLclEnv) (Maybe Type))
-> IOEnv (Env TcGblEnv TcLclEnv) (Maybe Type)
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \ContextKind
ctx_k ->
          case ContextKind
ctx_k of
            ContextKind
AnyKind -> Maybe Type -> IOEnv (Env TcGblEnv TcLclEnv) (Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Type
forall a. Maybe a
Nothing
            ContextKind
_ -> Type -> Maybe Type
forall a. a -> Maybe a
Just (Type -> Maybe Type)
-> TcM Type -> IOEnv (Env TcGblEnv TcLclEnv) (Maybe Type)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> ContextKind -> TcM Type
newExpectedKind ContextKind
ctx_k

        -- Step 2: split off invisible binders.
        -- For example:
        --
        --   type F :: forall k1 k2. (k1, k2) -> Type
        --   type family F
        --
        -- Does 'forall k1 k2' become a part of 'tyConBinders' or 'tyConResKind'?
        -- See Note [Arity inference in kcCheckDeclHeader_sig]
        let ([TyBinder]
invis_binders, Type
r_ki) = Type -> Maybe Type -> ([TyBinder], Type)
split_invis Type
kisig' Maybe Type
m_res_ki

        -- Convert each invisible TyCoBinder to TyConBinder for tyConBinders.
        [TyConBinder]
invis_tcbs <- (TyBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder)
-> [TyBinder] -> IOEnv (Env TcGblEnv TcLclEnv) [TyConBinder]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM TyBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder
invis_to_tcb [TyBinder]
invis_binders

        -- Check that the inline result kind annotation is valid.
        -- For example:
        --
        --   type T :: Type -> Maybe k
        --   type family T a :: Maybe j where
        --
        -- Here we unify   Maybe k ~ Maybe j
        Maybe Type -> (Type -> TcM ()) -> TcM ()
forall (m :: * -> *) a. Monad m => Maybe a -> (a -> m ()) -> m ()
whenIsJust Maybe Type
m_res_ki ((Type -> TcM ()) -> TcM ()) -> (Type -> TcM ()) -> TcM ()
forall a b. (a -> b) -> a -> b
$ \Type
res_ki ->
          TcM Coercion -> TcM ()
forall a. TcM a -> TcM ()
discardResult (TcM Coercion -> TcM ()) -> TcM Coercion -> TcM ()
forall a b. (a -> b) -> a -> b
$ -- See Note [discardResult in kcCheckDeclHeader_sig]
          Maybe (HsType GhcRn) -> Type -> Type -> TcM Coercion
unifyKind Maybe (HsType GhcRn)
forall a. Maybe a
Nothing Type
r_ki Type
res_ki

        -- Zonk the implicitly quantified variables.
        [(Name, TcTyVar)]
implicit_tv_prs <- (TcTyVar -> TcM TcTyVar)
-> [(Name, TcTyVar)]
-> IOEnv (Env TcGblEnv TcLclEnv) [(Name, TcTyVar)]
forall (m :: * -> *) b c a.
Monad m =>
(b -> m c) -> [(a, b)] -> m [(a, c)]
mapSndM HasDebugCallStack => TcTyVar -> TcM TcTyVar
TcTyVar -> TcM TcTyVar
zonkTcTyVarToTyVar [(Name, TcTyVar)]
implicit_tcv_prs

        -- Build the final, generalized TcTyCon
        let tcbs :: [TyConBinder]
tcbs       = [TyConBinder]
vis_tcbs [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ [TyConBinder]
invis_tcbs
            all_tv_prs :: [(Name, TcTyVar)]
all_tv_prs = [(Name, TcTyVar)]
implicit_tv_prs [(Name, TcTyVar)] -> [(Name, TcTyVar)] -> [(Name, TcTyVar)]
forall a. [a] -> [a] -> [a]
++ [(Name, TcTyVar)]
explicit_tv_prs
            tc :: TyCon
tc = Name
-> [TyConBinder]
-> Type
-> [(Name, TcTyVar)]
-> Bool
-> TyConFlavour
-> TyCon
mkTcTyCon Name
name [TyConBinder]
tcbs Type
r_ki [(Name, TcTyVar)]
all_tv_prs Bool
True TyConFlavour
flav

        String -> MsgDoc -> TcM ()
traceTc String
"kcCheckDeclHeader_sig done:" (MsgDoc -> TcM ()) -> MsgDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$ [MsgDoc] -> MsgDoc
vcat
          [ String -> MsgDoc
text String
"tyConName = " MsgDoc -> MsgDoc -> MsgDoc
<+> Name -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr (TyCon -> Name
tyConName TyCon
tc)
          , String -> MsgDoc
text String
"kisig =" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
debugPprType Type
kisig
          , String -> MsgDoc
text String
"tyConKind =" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
debugPprType (TyCon -> Type
tyConKind TyCon
tc)
          , String -> MsgDoc
text String
"tyConBinders = " MsgDoc -> MsgDoc -> MsgDoc
<+> [TyConBinder] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr (TyCon -> [TyConBinder]
tyConBinders TyCon
tc)
          , String -> MsgDoc
text String
"tcTyConScopedTyVars" MsgDoc -> MsgDoc -> MsgDoc
<+> [(Name, TcTyVar)] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr (TyCon -> [(Name, TcTyVar)]
tcTyConScopedTyVars TyCon
tc)
          , String -> MsgDoc
text String
"tyConResKind" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
debugPprType (TyCon -> Type
tyConResKind TyCon
tc)
          ]
        TyCon -> TcM TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tc
  where
    -- Consider this declaration:
    --
    --    type T :: forall a. forall b -> (a~b) => Proxy a -> Type
    --    data T x p = MkT
    --
    -- Here, we have every possible variant of ZippedBinder:
    --
    --                   TyBinder           LHsTyVarBndr
    --    ----------------------------------------------
    --    ZippedBinder   forall {k}.
    --    ZippedBinder   forall (a::k).
    --    ZippedBinder   forall (b::k) ->   x
    --    ZippedBinder   (a~b) =>
    --    ZippedBinder   Proxy a ->         p
    --
    -- Given a ZippedBinder zipped_to_tcb produces:
    --
    --  * TyConBinder      for  tyConBinders
    --  * (Name, TcTyVar)  for  tcTyConScopedTyVars, if there's a user-written LHsTyVarBndr
    --
    zipped_to_tcb :: ZippedBinder -> TcM (TyConBinder, [(Name, TcTyVar)])
    zipped_to_tcb :: ZippedBinder
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
zipped_to_tcb ZippedBinder
zb = case ZippedBinder
zb of

      -- Inferred variable, no user-written binder.
      -- Example:   forall {k}.
      ZippedBinder (Named (Bndr TcTyVar
v ArgFlag
Specified)) Maybe (LHsTyVarBndr GhcRn)
Nothing ->
        (TyConBinder, [(Name, TcTyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return (ArgFlag -> TcTyVar -> TyConBinder
mkNamedTyConBinder ArgFlag
Specified TcTyVar
v, [])

      -- Specified variable, no user-written binder.
      -- Example:   forall (a::k).
      ZippedBinder (Named (Bndr TcTyVar
v ArgFlag
Inferred)) Maybe (LHsTyVarBndr GhcRn)
Nothing ->
        (TyConBinder, [(Name, TcTyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return (ArgFlag -> TcTyVar -> TyConBinder
mkNamedTyConBinder ArgFlag
Inferred TcTyVar
v, [])

      -- Constraint, no user-written binder.
      -- Example:   (a~b) =>
      ZippedBinder (Anon AnonArgFlag
InvisArg Type
bndr_ki) Maybe (LHsTyVarBndr GhcRn)
Nothing -> do
        Name
name <- OccName -> TcRnIf TcGblEnv TcLclEnv Name
forall gbl lcl. OccName -> TcRnIf gbl lcl Name
newSysName (FastString -> OccName
mkTyVarOccFS (String -> FastString
fsLit String
"ev"))
        let tv :: TcTyVar
tv = Name -> Type -> TcTyVar
mkTyVar Name
name Type
bndr_ki
        (TyConBinder, [(Name, TcTyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return (AnonArgFlag -> TcTyVar -> TyConBinder
mkAnonTyConBinder AnonArgFlag
InvisArg TcTyVar
tv, [])

      -- Non-dependent visible argument with a user-written binder.
      -- Example:   Proxy a ->
      ZippedBinder (Anon AnonArgFlag
VisArg Type
bndr_ki) (Just LHsTyVarBndr GhcRn
b) ->
        (TyConBinder, [(Name, TcTyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return ((TyConBinder, [(Name, TcTyVar)])
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)]))
-> (TyConBinder, [(Name, TcTyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall a b. (a -> b) -> a -> b
$
          let v_name :: Name
v_name = LHsTyVarBndr GhcRn -> Name
forall a. NamedThing a => a -> Name
getName LHsTyVarBndr GhcRn
b
              tv :: TcTyVar
tv = Name -> Type -> TcTyVar
mkTyVar Name
v_name Type
bndr_ki
              tcb :: TyConBinder
tcb = AnonArgFlag -> TcTyVar -> TyConBinder
mkAnonTyConBinder AnonArgFlag
VisArg TcTyVar
tv
          in (TyConBinder
tcb, [(Name
v_name, TcTyVar
tv)])

      -- Dependent visible argument with a user-written binder.
      -- Example:   forall (b::k) ->
      ZippedBinder (Named (Bndr TcTyVar
v ArgFlag
Required)) (Just LHsTyVarBndr GhcRn
b) ->
        (TyConBinder, [(Name, TcTyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall (m :: * -> *) a. Monad m => a -> m a
return ((TyConBinder, [(Name, TcTyVar)])
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)]))
-> (TyConBinder, [(Name, TcTyVar)])
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall a b. (a -> b) -> a -> b
$
          let v_name :: Name
v_name = LHsTyVarBndr GhcRn -> Name
forall a. NamedThing a => a -> Name
getName LHsTyVarBndr GhcRn
b
              tcb :: TyConBinder
tcb = ArgFlag -> TcTyVar -> TyConBinder
mkNamedTyConBinder ArgFlag
Required TcTyVar
v
          in (TyConBinder
tcb, [(Name
v_name, TcTyVar
v)])

      -- 'zipBinders' does not produce any other variants of ZippedBinder.
      ZippedBinder
_ -> String
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
forall a. String -> a
panic String
"goVis: invalid ZippedBinder"

    -- Given an invisible binder that comes from 'split_invis',
    -- convert it to TyConBinder.
    invis_to_tcb :: TyCoBinder -> TcM TyConBinder
    invis_to_tcb :: TyBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder
invis_to_tcb TyBinder
tb = do
      (TyConBinder
tcb, [(Name, TcTyVar)]
stv) <- ZippedBinder
-> IOEnv (Env TcGblEnv TcLclEnv) (TyConBinder, [(Name, TcTyVar)])
zipped_to_tcb (TyBinder -> Maybe (LHsTyVarBndr GhcRn) -> ZippedBinder
ZippedBinder TyBinder
tb Maybe (LHsTyVarBndr GhcRn)
forall a. Maybe a
Nothing)
      MASSERT(null stv)
      TyConBinder -> IOEnv (Env TcGblEnv TcLclEnv) TyConBinder
forall (m :: * -> *) a. Monad m => a -> m a
return TyConBinder
tcb

    -- similar to:  bindImplicitTKBndrs_Tv
    bind_implicit :: [Name] -> ([(Name,TcTyVar)] -> TcM a) -> TcM a
    bind_implicit :: [Name] -> ([(Name, TcTyVar)] -> TcM a) -> TcM a
bind_implicit [Name]
tv_names [(Name, TcTyVar)] -> TcM a
thing_inside =
      do { let new_tv :: Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar)
new_tv Name
name = do { TcTyVar
tcv <- Name -> TcM TcTyVar
newFlexiKindedTyVarTyVar Name
name
                                ; (Name, TcTyVar) -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (Name
name, TcTyVar
tcv) }
         ; [(Name, TcTyVar)]
tcvs <- (Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar))
-> [Name] -> IOEnv (Env TcGblEnv TcLclEnv) [(Name, TcTyVar)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar)
new_tv [Name]
tv_names
         ; [(Name, TcTyVar)] -> TcM a -> TcM a
forall r. [(Name, TcTyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TcTyVar)]
tcvs ([(Name, TcTyVar)] -> TcM a
thing_inside [(Name, TcTyVar)]
tcvs) }

    -- Check that the inline kind annotation on a binder is valid
    -- by unifying it with the kind of the quantifier.
    check_zipped_binder :: ZippedBinder -> TcM ()
    check_zipped_binder :: ZippedBinder -> TcM ()
check_zipped_binder (ZippedBinder TyBinder
_ Maybe (LHsTyVarBndr GhcRn)
Nothing) = () -> TcM ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()
    check_zipped_binder (ZippedBinder TyBinder
tb (Just LHsTyVarBndr GhcRn
b)) =
      case LHsTyVarBndr GhcRn -> SrcSpanLess (LHsTyVarBndr GhcRn)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc LHsTyVarBndr GhcRn
b of
        UserTyVar _ _ -> () -> TcM ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()
        KindedTyVar _ v v_hs_ki -> do
          Type
v_ki <- UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig (Name -> UserTypeCtxt
TyVarBndrKindCtxt (Located Name -> SrcSpanLess (Located Name)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc Located Name
GenLocated SrcSpan (IdP GhcRn)
v)) LHsType GhcRn
v_hs_ki
          TcM Coercion -> TcM ()
forall a. TcM a -> TcM ()
discardResult (TcM Coercion -> TcM ()) -> TcM Coercion -> TcM ()
forall a b. (a -> b) -> a -> b
$ -- See Note [discardResult in kcCheckDeclHeader_sig]
            Maybe (HsType GhcRn) -> Type -> Type -> TcM Coercion
unifyKind (HsType GhcRn -> Maybe (HsType GhcRn)
forall a. a -> Maybe a
Just (XTyVar GhcRn
-> PromotionFlag -> GenLocated SrcSpan (IdP GhcRn) -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> Located (IdP pass) -> HsType pass
HsTyVar XTyVar GhcRn
NoExtField
noExtField PromotionFlag
NotPromoted GenLocated SrcSpan (IdP GhcRn)
v))
                      (TyBinder -> Type
tyBinderType TyBinder
tb)
                      Type
v_ki
        XTyVarBndr nec -> NoExtCon -> TcM ()
forall a. NoExtCon -> a
noExtCon XXTyVarBndr GhcRn
NoExtCon
nec

    -- Split the invisible binders that should become a part of 'tyConBinders'
    -- rather than 'tyConResKind'.
    -- See Note [Arity inference in kcCheckDeclHeader_sig]
    split_invis :: Kind -> Maybe Kind -> ([TyCoBinder], Kind)
    split_invis :: Type -> Maybe Type -> ([TyBinder], Type)
split_invis Type
sig_ki Maybe Type
Nothing =
      -- instantiate all invisible binders
      Type -> ([TyBinder], Type)
splitPiTysInvisible Type
sig_ki
    split_invis Type
sig_ki (Just Type
res_ki) =
      -- subtraction a la checkExpectedKind
      let n_res_invis_bndrs :: Int
n_res_invis_bndrs = Type -> Int
invisibleTyBndrCount Type
res_ki
          n_sig_invis_bndrs :: Int
n_sig_invis_bndrs = Type -> Int
invisibleTyBndrCount Type
sig_ki
          n_inst :: Int
n_inst = Int
n_sig_invis_bndrs Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
n_res_invis_bndrs
      in Int -> Type -> ([TyBinder], Type)
splitPiTysInvisibleN Int
n_inst Type
sig_ki

-- A quantifier from a kind signature zipped with a user-written binder for it.
data ZippedBinder =
  ZippedBinder TyBinder (Maybe (LHsTyVarBndr GhcRn))

-- See Note [Arity inference in kcCheckDeclHeader_sig]
zipBinders
  :: Kind                      -- kind signature
  -> [LHsTyVarBndr GhcRn]      -- user-written binders
  -> ([ZippedBinder],          -- zipped binders
      [LHsTyVarBndr GhcRn],    -- remaining user-written binders
      Kind)                    -- remainder of the kind signature
zipBinders :: Type
-> [LHsTyVarBndr GhcRn]
-> ([ZippedBinder], [LHsTyVarBndr GhcRn], Type)
zipBinders = [ZippedBinder]
-> Type
-> [LHsTyVarBndr GhcRn]
-> ([ZippedBinder], [LHsTyVarBndr GhcRn], Type)
zip_binders []
  where
    zip_binders :: [ZippedBinder]
-> Type
-> [LHsTyVarBndr GhcRn]
-> ([ZippedBinder], [LHsTyVarBndr GhcRn], Type)
zip_binders [ZippedBinder]
acc Type
ki [] = ([ZippedBinder] -> [ZippedBinder]
forall a. [a] -> [a]
reverse [ZippedBinder]
acc, [], Type
ki)
    zip_binders [ZippedBinder]
acc Type
ki (LHsTyVarBndr GhcRn
b:[LHsTyVarBndr GhcRn]
bs) =
      case Type -> Maybe (TyBinder, Type)
tcSplitPiTy_maybe Type
ki of
        Maybe (TyBinder, Type)
Nothing -> ([ZippedBinder] -> [ZippedBinder]
forall a. [a] -> [a]
reverse [ZippedBinder]
acc, LHsTyVarBndr GhcRn
bLHsTyVarBndr GhcRn -> [LHsTyVarBndr GhcRn] -> [LHsTyVarBndr GhcRn]
forall a. a -> [a] -> [a]
:[LHsTyVarBndr GhcRn]
bs, Type
ki)
        Just (TyBinder
tb, Type
ki') ->
          let
            (ZippedBinder
zb, [LHsTyVarBndr GhcRn]
bs') | Bool
zippable  = (TyBinder -> Maybe (LHsTyVarBndr GhcRn) -> ZippedBinder
ZippedBinder TyBinder
tb (LHsTyVarBndr GhcRn -> Maybe (LHsTyVarBndr GhcRn)
forall a. a -> Maybe a
Just LHsTyVarBndr GhcRn
b),  [LHsTyVarBndr GhcRn]
bs)
                      | Bool
otherwise = (TyBinder -> Maybe (LHsTyVarBndr GhcRn) -> ZippedBinder
ZippedBinder TyBinder
tb Maybe (LHsTyVarBndr GhcRn)
forall a. Maybe a
Nothing, LHsTyVarBndr GhcRn
bLHsTyVarBndr GhcRn -> [LHsTyVarBndr GhcRn] -> [LHsTyVarBndr GhcRn]
forall a. a -> [a] -> [a]
:[LHsTyVarBndr GhcRn]
bs)
            zippable :: Bool
zippable =
              case TyBinder
tb of
                Named (Bndr TcTyVar
_ ArgFlag
Specified) -> Bool
False
                Named (Bndr TcTyVar
_ ArgFlag
Inferred)  -> Bool
False
                Named (Bndr TcTyVar
_ ArgFlag
Required)  -> Bool
True
                Anon AnonArgFlag
InvisArg Type
_ -> Bool
False
                Anon AnonArgFlag
VisArg   Type
_ -> Bool
True
          in
            [ZippedBinder]
-> Type
-> [LHsTyVarBndr GhcRn]
-> ([ZippedBinder], [LHsTyVarBndr GhcRn], Type)
zip_binders (ZippedBinder
zbZippedBinder -> [ZippedBinder] -> [ZippedBinder]
forall a. a -> [a] -> [a]
:[ZippedBinder]
acc) Type
ki' [LHsTyVarBndr GhcRn]
bs'

tooManyBindersErr :: Kind -> [LHsTyVarBndr GhcRn] -> SDoc
tooManyBindersErr :: Type -> [LHsTyVarBndr GhcRn] -> MsgDoc
tooManyBindersErr Type
ki [LHsTyVarBndr GhcRn]
bndrs =
   MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"Not a function kind:")
      Int
4 (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
ki) MsgDoc -> MsgDoc -> MsgDoc
$$
   MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"but extra binders found:")
      Int
4 ([MsgDoc] -> MsgDoc
fsep ((LHsTyVarBndr GhcRn -> MsgDoc) -> [LHsTyVarBndr GhcRn] -> [MsgDoc]
forall a b. (a -> b) -> [a] -> [b]
map LHsTyVarBndr GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsTyVarBndr GhcRn]
bndrs))

{- Note [Arity inference in kcCheckDeclHeader_sig]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given a kind signature 'kisig' and a declaration header, kcCheckDeclHeader_sig
verifies that the declaration conforms to the signature. The end result is a
TcTyCon 'tc' such that:

  tyConKind tc == kisig

This TcTyCon would be rather easy to produce if we didn't have to worry about
arity. Consider these declarations:

  type family S1 :: forall k. k -> Type
  type family S2 (a :: k) :: Type

Both S1 and S2 can be given the same standalone kind signature:

  type S2 :: forall k. k -> Type

And, indeed, tyConKind S1 == tyConKind S2. However, tyConKind is built from
tyConBinders and tyConResKind, such that

  tyConKind tc == mkTyConKind (tyConBinders tc) (tyConResKind tc)

For S1 and S2, tyConBinders and tyConResKind are different:

  tyConBinders S1  ==  []
  tyConResKind S1  ==  forall k. k -> Type
  tyConKind    S1  ==  forall k. k -> Type

  tyConBinders S2  ==  [spec k, anon-vis (a :: k)]
  tyConResKind S2  ==  Type
  tyConKind    S1  ==  forall k. k -> Type

This difference determines the arity:

  tyConArity tc == length (tyConBinders tc)

That is, the arity of S1 is 0, while the arity of S2 is 2.

'kcCheckDeclHeader_sig' needs to infer the desired arity to split the standalone
kind signature into binders and the result kind. It does so in two rounds:

1. zip user-written binders (vis_tcbs)
2. split off invisible binders (invis_tcbs)

Consider the following declarations:

    type F :: Type -> forall j. j -> forall k1 k2. (k1, k2) -> Type
    type family F a b

    type G :: Type -> forall j. j -> forall k1 k2. (k1, k2) -> Type
    type family G a b :: forall r2. (r1, r2) -> Type

In step 1 (zip user-written binders), we zip the quantifiers in the signature
with the binders in the header using 'zipBinders'. In both F and G, this results in
the following zipped binders:

                   TyBinder     LHsTyVarBndr
    ---------------------------------------
    ZippedBinder   Type ->      a
    ZippedBinder   forall j.
    ZippedBinder   j ->         b


At this point, we have accumulated three zipped binders which correspond to a
prefix of the standalone kind signature:

  Type -> forall j. j -> ...

In step 2 (split off invisible binders), we have to decide how much remaining
invisible binders of the standalone kind signature to split off:

    forall k1 k2. (k1, k2) -> Type
    ^^^^^^^^^^^^^
    split off or not?

This decision is made in 'split_invis':

* If a user-written result kind signature is not provided, as in F,
  then split off all invisible binders. This is why we need special treatment
  for AnyKind.
* If a user-written result kind signature is provided, as in G,
  then do as checkExpectedKind does and split off (n_sig - n_res) binders.
  That is, split off such an amount of binders that the remainder of the
  standalone kind signature and the user-written result kind signature have the
  same amount of invisible quantifiers.

For F, split_invis splits away all invisible binders, and we have 2:

    forall k1 k2. (k1, k2) -> Type
    ^^^^^^^^^^^^^
    split away both binders

The resulting arity of F is 3+2=5.  (length vis_tcbs = 3,
                                     length invis_tcbs = 2,
                                     length tcbs = 5)

For G, split_invis decides to split off 1 invisible binder, so that we have the
same amount of invisible quantifiers left:

    res_ki  =  forall    r2. (r1, r2) -> Type
    kisig   =  forall k1 k2. (k1, k2) -> Type
                     ^^^
                     split off this one.

The resulting arity of G is 3+1=4. (length vis_tcbs = 3,
                                    length invis_tcbs = 1,
                                    length tcbs = 4)

-}

{- Note [discardResult in kcCheckDeclHeader_sig]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We use 'unifyKind' to check inline kind annotations in declaration headers
against the signature.

  type T :: [i] -> Maybe j -> Type
  data T (a :: [k1]) (b :: Maybe k2) :: Type where ...

Here, we will unify:

       [k1] ~ [i]
  Maybe k2  ~ Maybe j
      Type  ~ Type

The end result is that we fill in unification variables k1, k2:

    k1  :=  i
    k2  :=  j

We also validate that the user isn't confused:

  type T :: Type -> Type
  data T (a :: Bool) = ...

This will report that (Type ~ Bool) failed to unify.

Now, consider the following example:

  type family Id a where Id x = x
  type T :: Bool -> Type
  type T (a :: Id Bool) = ...

We will unify (Bool ~ Id Bool), and this will produce a non-reflexive coercion.
However, we are free to discard it, as the kind of 'T' is determined by the
signature, not by the inline kind annotation:

      we have   T ::    Bool -> Type
  rather than   T :: Id Bool -> Type

This (Id Bool) will not show up anywhere after we're done validating it, so we
have no use for the produced coercion.
-}

{- Note [No polymorphic recursion]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Should this kind-check?
  data T ka (a::ka) b  = MkT (T Type           Int   Bool)
                             (T (Type -> Type) Maybe Bool)

Notice that T is used at two different kinds in its RHS.  No!
This should not kind-check.  Polymorphic recursion is known to
be a tough nut.

Previously, we laboriously (with help from the renamer)
tried to give T the polymoprhic kind
   T :: forall ka -> ka -> kappa -> Type
where kappa is a unification variable, even in the inferInitialKinds
phase (which is what kcInferDeclHeader is all about).  But
that is dangerously fragile (see the ticket).

Solution: make kcInferDeclHeader give T a straightforward
monomorphic kind, with no quantification whatsoever. That's why
we use mkAnonTyConBinder for all arguments when figuring out
tc_binders.

But notice that (#16322 comment:3)

* The algorithm successfully kind-checks this declaration:
    data T2 ka (a::ka) = MkT2 (T2 Type a)

  Starting with (inferInitialKinds)
    T2 :: (kappa1 :: kappa2 :: *) -> (kappa3 :: kappa4 :: *) -> *
  we get
    kappa4 := kappa1   -- from the (a:ka) kind signature
    kappa1 := Type     -- From application T2 Type

  These constraints are soluble so generaliseTcTyCon gives
    T2 :: forall (k::Type) -> k -> *

  But now the /typechecking/ (aka desugaring, tcTyClDecl) phase
  fails, because the call (T2 Type a) in the RHS is ill-kinded.

  We'd really prefer all errors to show up in the kind checking
  phase.

* This algorithm still accepts (in all phases)
     data T3 ka (a::ka) = forall b. MkT3 (T3 Type b)
  although T3 is really polymorphic-recursive too.
  Perhaps we should somehow reject that.

Note [Kind-checking tyvar binders for associated types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When kind-checking the type-variable binders for associated
   data/newtype decls
   family decls
we behave specially for type variables that are already in scope;
that is, bound by the enclosing class decl.  This is done in
kcLHsQTyVarBndrs:
  * The use of tcImplicitQTKBndrs
  * The tcLookupLocal_maybe code in kc_hs_tv

See Note [Associated type tyvar names] in Class and
    Note [TyVar binders for associated decls] in GHC.Hs.Decls

We must do the same for family instance decls, where the in-scope
variables may be bound by the enclosing class instance decl.
Hence the use of tcImplicitQTKBndrs in tcFamTyPatsAndGen.

Note [Kind variable ordering for associated types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
What should be the kind of `T` in the following example? (#15591)

  class C (a :: Type) where
    type T (x :: f a)

As per Note [Ordering of implicit variables] in RnTypes, we want to quantify
the kind variables in left-to-right order of first occurrence in order to
support visible kind application. But we cannot perform this analysis on just
T alone, since its variable `a` actually occurs /before/ `f` if you consider
the fact that `a` was previously bound by the parent class `C`. That is to say,
the kind of `T` should end up being:

  T :: forall a f. f a -> Type

(It wouldn't necessarily be /wrong/ if the kind ended up being, say,
forall f a. f a -> Type, but that would not be as predictable for users of
visible kind application.)

In contrast, if `T` were redefined to be a top-level type family, like `T2`
below:

  type family T2 (x :: f (a :: Type))

Then `a` first appears /after/ `f`, so the kind of `T2` should be:

  T2 :: forall f a. f a -> Type

In order to make this distinction, we need to know (in kcCheckDeclHeader) which
type variables have been bound by the parent class (if there is one). With
the class-bound variables in hand, we can ensure that we always quantify
these first.
-}


{- *********************************************************************
*                                                                      *
             Expected kinds
*                                                                      *
********************************************************************* -}

-- | Describes the kind expected in a certain context.
data ContextKind = TheKind Kind   -- ^ a specific kind
                 | AnyKind        -- ^ any kind will do
                 | OpenKind       -- ^ something of the form @TYPE _@

-----------------------
newExpectedKind :: ContextKind -> TcM Kind
newExpectedKind :: ContextKind -> TcM Type
newExpectedKind (TheKind Type
k) = Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
k
newExpectedKind ContextKind
AnyKind     = TcM Type
newMetaKindVar
newExpectedKind ContextKind
OpenKind    = TcM Type
newOpenTypeKind

-----------------------
expectedKindInCtxt :: UserTypeCtxt -> ContextKind
-- Depending on the context, we might accept any kind (for instance, in a TH
-- splice), or only certain kinds (like in type signatures).
expectedKindInCtxt :: UserTypeCtxt -> ContextKind
expectedKindInCtxt (TySynCtxt Name
_)   = ContextKind
AnyKind
expectedKindInCtxt UserTypeCtxt
ThBrackCtxt     = ContextKind
AnyKind
expectedKindInCtxt (GhciCtxt {})   = ContextKind
AnyKind
-- The types in a 'default' decl can have varying kinds
-- See Note [Extended defaults]" in TcEnv
expectedKindInCtxt UserTypeCtxt
DefaultDeclCtxt     = ContextKind
AnyKind
expectedKindInCtxt UserTypeCtxt
TypeAppCtxt         = ContextKind
AnyKind
expectedKindInCtxt (ForSigCtxt Name
_)      = Type -> ContextKind
TheKind Type
liftedTypeKind
expectedKindInCtxt (InstDeclCtxt {})   = Type -> ContextKind
TheKind Type
constraintKind
expectedKindInCtxt UserTypeCtxt
SpecInstCtxt        = Type -> ContextKind
TheKind Type
constraintKind
expectedKindInCtxt UserTypeCtxt
_                   = ContextKind
OpenKind


{- *********************************************************************
*                                                                      *
             Bringing type variables into scope
*                                                                      *
********************************************************************* -}

--------------------------------------
-- Implicit binders
--------------------------------------

bindImplicitTKBndrs_Skol, bindImplicitTKBndrs_Tv,
  bindImplicitTKBndrs_Q_Skol, bindImplicitTKBndrs_Q_Tv
  :: [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Skol :: [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Skol   = (Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrsX Name -> TcM TcTyVar
newFlexiKindedSkolemTyVar
bindImplicitTKBndrs_Tv :: [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Tv     = (Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrsX Name -> TcM TcTyVar
newFlexiKindedTyVarTyVar
bindImplicitTKBndrs_Q_Skol :: [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Q_Skol = (Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrsX ((Name -> TcM TcTyVar) -> Name -> TcM TcTyVar
newImplicitTyVarQ Name -> TcM TcTyVar
newFlexiKindedSkolemTyVar)
bindImplicitTKBndrs_Q_Tv :: [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Q_Tv   = (Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrsX ((Name -> TcM TcTyVar) -> Name -> TcM TcTyVar
newImplicitTyVarQ Name -> TcM TcTyVar
newFlexiKindedTyVarTyVar)

bindImplicitTKBndrsX
   :: (Name -> TcM TcTyVar) -- new_tv function
   -> [Name]
   -> TcM a
   -> TcM ([TcTyVar], a)   -- Returned [TcTyVar] are in 1-1 correspondence
                           -- with the passed in [Name]
bindImplicitTKBndrsX :: (Name -> TcM TcTyVar) -> [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrsX Name -> TcM TcTyVar
new_tv [Name]
tv_names TcM a
thing_inside
  = do { [TcTyVar]
tkvs <- (Name -> TcM TcTyVar) -> [Name] -> TcM [TcTyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> TcM TcTyVar
new_tv [Name]
tv_names
       ; String -> MsgDoc -> TcM ()
traceTc String
"bindImplicitTKBndrs" ([Name] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [Name]
tv_names MsgDoc -> MsgDoc -> MsgDoc
$$ [TcTyVar] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TcTyVar]
tkvs)
       ; a
res <- [(Name, TcTyVar)] -> TcM a -> TcM a
forall r. [(Name, TcTyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv ([Name]
tv_names [Name] -> [TcTyVar] -> [(Name, TcTyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcTyVar]
tkvs)
                TcM a
thing_inside
       ; ([TcTyVar], a) -> TcM ([TcTyVar], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TcTyVar]
tkvs, a
res) }

newImplicitTyVarQ :: (Name -> TcM TcTyVar) ->  Name -> TcM TcTyVar
-- Behave like new_tv, except that if the tyvar is in scope, use it
newImplicitTyVarQ :: (Name -> TcM TcTyVar) -> Name -> TcM TcTyVar
newImplicitTyVarQ Name -> TcM TcTyVar
new_tv Name
name
  = do { Maybe TcTyThing
mb_tv <- Name -> TcM (Maybe TcTyThing)
tcLookupLcl_maybe Name
name
       ; case Maybe TcTyThing
mb_tv of
           Just (ATyVar Name
_ TcTyVar
tv) -> TcTyVar -> TcM TcTyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TcTyVar
tv
           Maybe TcTyThing
_ -> Name -> TcM TcTyVar
new_tv Name
name }

newFlexiKindedTyVar :: (Name -> Kind -> TcM TyVar) -> Name -> TcM TyVar
newFlexiKindedTyVar :: (Name -> Type -> TcM TcTyVar) -> Name -> TcM TcTyVar
newFlexiKindedTyVar Name -> Type -> TcM TcTyVar
new_tv Name
name
  = do { Type
kind <- TcM Type
newMetaKindVar
       ; Name -> Type -> TcM TcTyVar
new_tv Name
name Type
kind }

newFlexiKindedSkolemTyVar :: Name -> TcM TyVar
newFlexiKindedSkolemTyVar :: Name -> TcM TcTyVar
newFlexiKindedSkolemTyVar = (Name -> Type -> TcM TcTyVar) -> Name -> TcM TcTyVar
newFlexiKindedTyVar Name -> Type -> TcM TcTyVar
newSkolemTyVar

newFlexiKindedTyVarTyVar :: Name -> TcM TyVar
newFlexiKindedTyVarTyVar :: Name -> TcM TcTyVar
newFlexiKindedTyVarTyVar = (Name -> Type -> TcM TcTyVar) -> Name -> TcM TcTyVar
newFlexiKindedTyVar Name -> Type -> TcM TcTyVar
newTyVarTyVar
   -- See Note [Unification variables need fresh Names] in TcMType

--------------------------------------
-- Explicit binders
--------------------------------------

bindExplicitTKBndrs_Skol, bindExplicitTKBndrs_Tv
    :: [LHsTyVarBndr GhcRn]
    -> TcM a
    -> TcM ([TcTyVar], a)

bindExplicitTKBndrs_Skol :: [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Skol = (HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrsX ((Name -> Type -> TcM TcTyVar) -> HsTyVarBndr GhcRn -> TcM TcTyVar
tcHsTyVarBndr Name -> Type -> TcM TcTyVar
newSkolemTyVar)
bindExplicitTKBndrs_Tv :: [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Tv   = (HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrsX ((Name -> Type -> TcM TcTyVar) -> HsTyVarBndr GhcRn -> TcM TcTyVar
tcHsTyVarBndr Name -> Type -> TcM TcTyVar
newTyVarTyVar)

bindExplicitTKBndrs_Q_Skol, bindExplicitTKBndrs_Q_Tv
    :: ContextKind
    -> [LHsTyVarBndr GhcRn]
    -> TcM a
    -> TcM ([TcTyVar], a)

bindExplicitTKBndrs_Q_Skol :: ContextKind -> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Q_Skol ContextKind
ctxt_kind = (HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrsX (ContextKind
-> (Name -> Type -> TcM TcTyVar)
-> HsTyVarBndr GhcRn
-> TcM TcTyVar
tcHsQTyVarBndr ContextKind
ctxt_kind Name -> Type -> TcM TcTyVar
newSkolemTyVar)
bindExplicitTKBndrs_Q_Tv :: ContextKind -> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Q_Tv   ContextKind
ctxt_kind = (HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
forall a.
(HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrsX (ContextKind
-> (Name -> Type -> TcM TcTyVar)
-> HsTyVarBndr GhcRn
-> TcM TcTyVar
tcHsQTyVarBndr ContextKind
ctxt_kind Name -> Type -> TcM TcTyVar
newTyVarTyVar)

bindExplicitTKBndrsX
    :: (HsTyVarBndr GhcRn -> TcM TcTyVar)
    -> [LHsTyVarBndr GhcRn]
    -> TcM a
    -> TcM ([TcTyVar], a)  -- Returned [TcTyVar] are in 1-1 correspondence
                           -- with the passed-in [LHsTyVarBndr]
bindExplicitTKBndrsX :: (HsTyVarBndr GhcRn -> TcM TcTyVar)
-> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrsX HsTyVarBndr GhcRn -> TcM TcTyVar
tc_tv [LHsTyVarBndr GhcRn]
hs_tvs TcM a
thing_inside
  = do { String -> MsgDoc -> TcM ()
traceTc String
"bindExplicTKBndrs" ([LHsTyVarBndr GhcRn] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [LHsTyVarBndr GhcRn]
hs_tvs)
       ; [LHsTyVarBndr GhcRn] -> TcM ([TcTyVar], a)
go [LHsTyVarBndr GhcRn]
hs_tvs }
  where
    go :: [LHsTyVarBndr GhcRn] -> TcM ([TcTyVar], a)
go [] = do { a
res <- TcM a
thing_inside
               ; ([TcTyVar], a) -> TcM ([TcTyVar], a)
forall (m :: * -> *) a. Monad m => a -> m a
return ([], a
res) }
    go (L SrcSpan
_ HsTyVarBndr GhcRn
hs_tv : [LHsTyVarBndr GhcRn]
hs_tvs)
       = do { TcTyVar
tv <- HsTyVarBndr GhcRn -> TcM TcTyVar
tc_tv HsTyVarBndr GhcRn
hs_tv
            -- Extend the environment as we go, in case a binder
            -- is mentioned in the kind of a later binder
            --   e.g. forall k (a::k). blah
            -- NB: tv's Name may differ from hs_tv's
            -- See TcMType Note [Unification variables need fresh Names]
            ; ([TcTyVar]
tvs,a
res) <- [(Name, TcTyVar)] -> TcM ([TcTyVar], a) -> TcM ([TcTyVar], a)
forall r. [(Name, TcTyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(HsTyVarBndr GhcRn -> IdP GhcRn
forall (p :: Pass). HsTyVarBndr (GhcPass p) -> IdP (GhcPass p)
hsTyVarName HsTyVarBndr GhcRn
hs_tv, TcTyVar
tv)] (TcM ([TcTyVar], a) -> TcM ([TcTyVar], a))
-> TcM ([TcTyVar], a) -> TcM ([TcTyVar], a)
forall a b. (a -> b) -> a -> b
$
                           [LHsTyVarBndr GhcRn] -> TcM ([TcTyVar], a)
go [LHsTyVarBndr GhcRn]
hs_tvs
            ; ([TcTyVar], a) -> TcM ([TcTyVar], a)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcTyVar
tvTcTyVar -> [TcTyVar] -> [TcTyVar]
forall a. a -> [a] -> [a]
:[TcTyVar]
tvs, a
res) }

-----------------
tcHsTyVarBndr :: (Name -> Kind -> TcM TyVar)
              -> HsTyVarBndr GhcRn -> TcM TcTyVar
-- Returned TcTyVar has the same name; no cloning
tcHsTyVarBndr :: (Name -> Type -> TcM TcTyVar) -> HsTyVarBndr GhcRn -> TcM TcTyVar
tcHsTyVarBndr Name -> Type -> TcM TcTyVar
new_tv (UserTyVar XUserTyVar GhcRn
_ (L SrcSpan
_ IdP GhcRn
tv_nm))
  = do { Type
kind <- TcM Type
newMetaKindVar
       ; Name -> Type -> TcM TcTyVar
new_tv Name
IdP GhcRn
tv_nm Type
kind }
tcHsTyVarBndr Name -> Type -> TcM TcTyVar
new_tv (KindedTyVar XKindedTyVar GhcRn
_ (L SrcSpan
_ IdP GhcRn
tv_nm) LHsType GhcRn
lhs_kind)
  = do { Type
kind <- UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig (Name -> UserTypeCtxt
TyVarBndrKindCtxt Name
IdP GhcRn
tv_nm) LHsType GhcRn
lhs_kind
       ; Name -> Type -> TcM TcTyVar
new_tv Name
IdP GhcRn
tv_nm Type
kind }
tcHsTyVarBndr Name -> Type -> TcM TcTyVar
_ (XTyVarBndr XXTyVarBndr GhcRn
nec) = NoExtCon -> TcM TcTyVar
forall a. NoExtCon -> a
noExtCon XXTyVarBndr GhcRn
NoExtCon
nec

-----------------
tcHsQTyVarBndr :: ContextKind
               -> (Name -> Kind -> TcM TyVar)
               -> HsTyVarBndr GhcRn -> TcM TcTyVar
-- Just like tcHsTyVarBndr, but also
--   - uses the in-scope TyVar from class, if it exists
--   - takes a ContextKind to use for the no-sig case
tcHsQTyVarBndr :: ContextKind
-> (Name -> Type -> TcM TcTyVar)
-> HsTyVarBndr GhcRn
-> TcM TcTyVar
tcHsQTyVarBndr ContextKind
ctxt_kind Name -> Type -> TcM TcTyVar
new_tv (UserTyVar XUserTyVar GhcRn
_ (L SrcSpan
_ IdP GhcRn
tv_nm))
  = do { Maybe TcTyThing
mb_tv <- Name -> TcM (Maybe TcTyThing)
tcLookupLcl_maybe Name
IdP GhcRn
tv_nm
       ; case Maybe TcTyThing
mb_tv of
           Just (ATyVar Name
_ TcTyVar
tv) -> TcTyVar -> TcM TcTyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TcTyVar
tv
           Maybe TcTyThing
_ -> do { Type
kind <- ContextKind -> TcM Type
newExpectedKind ContextKind
ctxt_kind
                   ; Name -> Type -> TcM TcTyVar
new_tv Name
IdP GhcRn
tv_nm Type
kind } }

tcHsQTyVarBndr ContextKind
_ Name -> Type -> TcM TcTyVar
new_tv (KindedTyVar XKindedTyVar GhcRn
_ (L SrcSpan
_ IdP GhcRn
tv_nm) LHsType GhcRn
lhs_kind)
  = do { Type
kind <- UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig (Name -> UserTypeCtxt
TyVarBndrKindCtxt Name
IdP GhcRn
tv_nm) LHsType GhcRn
lhs_kind
       ; Maybe TcTyThing
mb_tv <- Name -> TcM (Maybe TcTyThing)
tcLookupLcl_maybe Name
IdP GhcRn
tv_nm
       ; case Maybe TcTyThing
mb_tv of
           Just (ATyVar Name
_ TcTyVar
tv)
             -> do { TcM Coercion -> TcM ()
forall a. TcM a -> TcM ()
discardResult (TcM Coercion -> TcM ()) -> TcM Coercion -> TcM ()
forall a b. (a -> b) -> a -> b
$ Maybe (HsType GhcRn) -> Type -> Type -> TcM Coercion
unifyKind (HsType GhcRn -> Maybe (HsType GhcRn)
forall a. a -> Maybe a
Just HsType GhcRn
hs_tv)
                                        Type
kind (TcTyVar -> Type
tyVarKind TcTyVar
tv)
                       -- This unify rejects:
                       --    class C (m :: * -> *) where
                       --      type F (m :: *) = ...
                   ; TcTyVar -> TcM TcTyVar
forall (m :: * -> *) a. Monad m => a -> m a
return TcTyVar
tv }

           Maybe TcTyThing
_ -> Name -> Type -> TcM TcTyVar
new_tv Name
IdP GhcRn
tv_nm Type
kind }
  where
    hs_tv :: HsType GhcRn
hs_tv = XTyVar GhcRn
-> PromotionFlag -> GenLocated SrcSpan (IdP GhcRn) -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> Located (IdP pass) -> HsType pass
HsTyVar XTyVar GhcRn
NoExtField
noExtField PromotionFlag
NotPromoted (SrcSpanLess (Located Name) -> Located Name
forall a. HasSrcSpan a => SrcSpanLess a -> a
noLoc SrcSpanLess (Located Name)
IdP GhcRn
tv_nm)
            -- Used for error messages only

tcHsQTyVarBndr ContextKind
_ Name -> Type -> TcM TcTyVar
_ (XTyVarBndr XXTyVarBndr GhcRn
nec) = NoExtCon -> TcM TcTyVar
forall a. NoExtCon -> a
noExtCon XXTyVarBndr GhcRn
NoExtCon
nec

--------------------------------------
-- Binding type/class variables in the
-- kind-checking and typechecking phases
--------------------------------------

bindTyClTyVars :: Name
               -> ([TyConBinder] -> Kind -> TcM a) -> TcM a
-- ^ Used for the type variables of a type or class decl
-- in the "kind checking" and "type checking" pass,
-- but not in the initial-kind run.
bindTyClTyVars :: Name -> ([TyConBinder] -> Type -> TcM a) -> TcM a
bindTyClTyVars Name
tycon_name [TyConBinder] -> Type -> TcM a
thing_inside
  = do { TyCon
tycon <- Name -> TcM TyCon
kcLookupTcTyCon Name
tycon_name
       ; let scoped_prs :: [(Name, TcTyVar)]
scoped_prs = TyCon -> [(Name, TcTyVar)]
tcTyConScopedTyVars TyCon
tycon
             res_kind :: Type
res_kind   = TyCon -> Type
tyConResKind TyCon
tycon
             binders :: [TyConBinder]
binders    = TyCon -> [TyConBinder]
tyConBinders TyCon
tycon
       ; String -> MsgDoc -> TcM ()
traceTc String
"bindTyClTyVars" (Name -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Name
tycon_name MsgDoc -> MsgDoc -> MsgDoc
<+> [TyConBinder] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [TyConBinder]
binders MsgDoc -> MsgDoc -> MsgDoc
$$ [(Name, TcTyVar)] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [(Name, TcTyVar)]
scoped_prs)
       ; [(Name, TcTyVar)] -> TcM a -> TcM a
forall r. [(Name, TcTyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TcTyVar)]
scoped_prs (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
         [TyConBinder] -> Type -> TcM a
thing_inside [TyConBinder]
binders Type
res_kind }

-- inferInitialKind has made a suitably-shaped kind for the type or class
-- Look it up in the local environment. This is used only for tycons
-- that we're currently type-checking, so we're sure to find a TcTyCon.
kcLookupTcTyCon :: Name -> TcM TcTyCon
kcLookupTcTyCon :: Name -> TcM TyCon
kcLookupTcTyCon Name
nm
  = do { TcTyThing
tc_ty_thing <- Name -> TcM TcTyThing
tcLookup Name
nm
       ; TyCon -> TcM TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon -> TcM TyCon) -> TyCon -> TcM TyCon
forall a b. (a -> b) -> a -> b
$ case TcTyThing
tc_ty_thing of
           ATcTyCon TyCon
tc -> TyCon
tc
           TcTyThing
_           -> String -> MsgDoc -> TyCon
forall a. HasCallStack => String -> MsgDoc -> a
pprPanic String
"kcLookupTcTyCon" (TcTyThing -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TcTyThing
tc_ty_thing) }


{- *********************************************************************
*                                                                      *
             Kind generalisation
*                                                                      *
********************************************************************* -}

zonkAndScopedSort :: [TcTyVar] -> TcM [TcTyVar]
zonkAndScopedSort :: [TcTyVar] -> TcM [TcTyVar]
zonkAndScopedSort [TcTyVar]
spec_tkvs
  = do { [TcTyVar]
spec_tkvs <- (TcTyVar -> TcM TcTyVar) -> [TcTyVar] -> TcM [TcTyVar]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM TcTyVar -> TcM TcTyVar
zonkAndSkolemise [TcTyVar]
spec_tkvs
          -- Use zonkAndSkolemise because a skol_tv might be a TyVarTv

       -- Do a stable topological sort, following
       -- Note [Ordering of implicit variables] in RnTypes
       ; [TcTyVar] -> TcM [TcTyVar]
forall (m :: * -> *) a. Monad m => a -> m a
return ([TcTyVar] -> [TcTyVar]
scopedSort [TcTyVar]
spec_tkvs) }

-- | Generalize some of the free variables in the given type.
-- All such variables should be *kind* variables; any type variables
-- should be explicitly quantified (with a `forall`) before now.
-- The supplied predicate says which free variables to quantify.
-- But in all cases,
-- generalize only those variables whose TcLevel is strictly greater
-- than the ambient level. This "strictly greater than" means that
-- you likely need to push the level before creating whatever type
-- gets passed here. Any variable whose level is greater than the
-- ambient level but is not selected to be generalized will be
-- promoted. (See [Promoting unification variables] in TcSimplify
-- and Note [Recipe for checking a signature].)
-- The resulting KindVar are the variables to
-- quantify over, in the correct, well-scoped order. They should
-- generally be Inferred, not Specified, but that's really up to
-- the caller of this function.
kindGeneralizeSome :: (TcTyVar -> Bool)
                   -> TcType    -- ^ needn't be zonked
                   -> TcM [KindVar]
kindGeneralizeSome :: (TcTyVar -> Bool) -> Type -> TcM [TcTyVar]
kindGeneralizeSome TcTyVar -> Bool
should_gen Type
kind_or_type
  = do { String -> MsgDoc -> TcM ()
traceTc String
"kindGeneralizeSome {" (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
kind_or_type)

         -- use the "Kind" variant here, as any types we see
         -- here will already have all type variables quantified;
         -- thus, every free variable is really a kv, never a tv.
       ; CandidatesQTvs
dvs <- Type -> TcM CandidatesQTvs
candidateQTyVarsOfKind Type
kind_or_type

       -- So 'dvs' are the variables free in kind_or_type, with a level greater
       -- than the ambient level, hence candidates for quantification
       -- Next: filter out the ones we don't want to generalize (specified by should_gen)
       -- and promote them instead

       ; let (DTyVarSet
to_promote, CandidatesQTvs
dvs') = CandidatesQTvs -> (TcTyVar -> Bool) -> (DTyVarSet, CandidatesQTvs)
partitionCandidates CandidatesQTvs
dvs (Bool -> Bool
not (Bool -> Bool) -> (TcTyVar -> Bool) -> TcTyVar -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcTyVar -> Bool
should_gen)

       ; (Bool
_, TyCoVarSet
promoted) <- TyCoVarSet -> TcM (Bool, TyCoVarSet)
promoteTyVarSet (DTyVarSet -> TyCoVarSet
dVarSetToVarSet DTyVarSet
to_promote)
       ; [TcTyVar]
qkvs <- CandidatesQTvs -> TcM [TcTyVar]
quantifyTyVars CandidatesQTvs
dvs'

       ; String -> MsgDoc -> TcM ()
traceTc String
"kindGeneralizeSome }" (MsgDoc -> TcM ()) -> MsgDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [MsgDoc] -> MsgDoc
vcat [ String -> MsgDoc
text String
"Kind or type:" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
kind_or_type
              , String -> MsgDoc
text String
"dvs:" MsgDoc -> MsgDoc -> MsgDoc
<+> CandidatesQTvs -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr CandidatesQTvs
dvs
              , String -> MsgDoc
text String
"dvs':" MsgDoc -> MsgDoc -> MsgDoc
<+> CandidatesQTvs -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr CandidatesQTvs
dvs'
              , String -> MsgDoc
text String
"to_promote:" MsgDoc -> MsgDoc -> MsgDoc
<+> [TcTyVar] -> MsgDoc
pprTyVars (DTyVarSet -> [TcTyVar]
dVarSetElems DTyVarSet
to_promote)
              , String -> MsgDoc
text String
"promoted:" MsgDoc -> MsgDoc -> MsgDoc
<+> [TcTyVar] -> MsgDoc
pprTyVars (TyCoVarSet -> [TcTyVar]
forall elt. UniqSet elt -> [elt]
nonDetEltsUniqSet TyCoVarSet
promoted)
              , String -> MsgDoc
text String
"qkvs:" MsgDoc -> MsgDoc -> MsgDoc
<+> [TcTyVar] -> MsgDoc
pprTyVars [TcTyVar]
qkvs ]

       ; [TcTyVar] -> TcM [TcTyVar]
forall (m :: * -> *) a. Monad m => a -> m a
return [TcTyVar]
qkvs }

-- | Specialized version of 'kindGeneralizeSome', but where all variables
-- can be generalized. Use this variant when you can be sure that no more
-- constraints on the type's metavariables will arise or be solved.
kindGeneralizeAll :: TcType  -- needn't be zonked
                  -> TcM [KindVar]
kindGeneralizeAll :: Type -> TcM [TcTyVar]
kindGeneralizeAll Type
ty = do { String -> MsgDoc -> TcM ()
traceTc String
"kindGeneralizeAll" MsgDoc
empty
                          ; (TcTyVar -> Bool) -> Type -> TcM [TcTyVar]
kindGeneralizeSome (Bool -> TcTyVar -> Bool
forall a b. a -> b -> a
const Bool
True) Type
ty }

-- | Specialized version of 'kindGeneralizeSome', but where no variables
-- can be generalized. Use this variant when it is unknowable whether metavariables
-- might later be constrained.
-- See Note [Recipe for checking a signature] for why and where this
-- function is needed.
kindGeneralizeNone :: TcType  -- needn't be zonked
                   -> TcM ()
kindGeneralizeNone :: Type -> TcM ()
kindGeneralizeNone Type
ty
  = do { String -> MsgDoc -> TcM ()
traceTc String
"kindGeneralizeNone" MsgDoc
empty
       ; [TcTyVar]
kvs <- (TcTyVar -> Bool) -> Type -> TcM [TcTyVar]
kindGeneralizeSome (Bool -> TcTyVar -> Bool
forall a b. a -> b -> a
const Bool
False) Type
ty
       ; MASSERT( null kvs )
       }

{- Note [Levels and generalisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
  f x = e
with no type signature. We are currently at level i.
We must
  * Push the level to level (i+1)
  * Allocate a fresh alpha[i+1] for the result type
  * Check that e :: alpha[i+1], gathering constraint WC
  * Solve WC as far as possible
  * Zonking the result type alpha[i+1], say to beta[i-1] -> gamma[i]
  * Find the free variables with level > i, in this case gamma[i]
  * Skolemise those free variables and quantify over them, giving
       f :: forall g. beta[i-1] -> g
  * Emit the residiual constraint wrapped in an implication for g,
    thus   forall g. WC

All of this happens for types too.  Consider
  f :: Int -> (forall a. Proxy a -> Int)

Note [Kind generalisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~
We do kind generalisation only at the outer level of a type signature.
For example, consider
  T :: forall k. k -> *
  f :: (forall a. T a -> Int) -> Int
When kind-checking f's type signature we generalise the kind at
the outermost level, thus:
  f1 :: forall k. (forall (a:k). T k a -> Int) -> Int  -- YES!
and *not* at the inner forall:
  f2 :: (forall k. forall (a:k). T k a -> Int) -> Int  -- NO!
Reason: same as for HM inference on value level declarations,
we want to infer the most general type.  The f2 type signature
would be *less applicable* than f1, because it requires a more
polymorphic argument.

NB: There are no explicit kind variables written in f's signature.
When there are, the renamer adds these kind variables to the list of
variables bound by the forall, so you can indeed have a type that's
higher-rank in its kind. But only by explicit request.

Note [Kinds of quantified type variables]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tcTyVarBndrsGen quantifies over a specified list of type variables,
*and* over the kind variables mentioned in the kinds of those tyvars.

Note that we must zonk those kinds (obviously) but less obviously, we
must return type variables whose kinds are zonked too. Example
    (a :: k7)  where  k7 := k9 -> k9
We must return
    [k9, a:k9->k9]
and NOT
    [k9, a:k7]
Reason: we're going to turn this into a for-all type,
   forall k9. forall (a:k7). blah
which the type checker will then instantiate, and instantiate does not
look through unification variables!

Hence using zonked_kinds when forming tvs'.

-}

-----------------------------------
etaExpandAlgTyCon :: [TyConBinder]
                  -> Kind
                  -> TcM ([TyConBinder], Kind)
-- GADT decls can have a (perhaps partial) kind signature
--      e.g.  data T a :: * -> * -> * where ...
-- This function makes up suitable (kinded) TyConBinders for the
-- argument kinds.  E.g. in this case it might return
--   ([b::*, c::*], *)
-- Never emits constraints.
-- It's a little trickier than you might think: see
-- Note [TyConBinders for the result kind signature of a data type]
etaExpandAlgTyCon :: [TyConBinder] -> Type -> TcM ([TyConBinder], Type)
etaExpandAlgTyCon [TyConBinder]
tc_bndrs Type
kind
  = do  { SrcSpan
loc     <- TcRn SrcSpan
getSrcSpanM
        ; UniqSupply
uniqs   <- TcRnIf TcGblEnv TcLclEnv UniqSupply
forall gbl lcl. TcRnIf gbl lcl UniqSupply
newUniqueSupply
        ; LocalRdrEnv
rdr_env <- RnM LocalRdrEnv
getLocalRdrEnv
        ; let new_occs :: [OccName]
new_occs = [ OccName
occ
                         | String
str <- [String]
allNameStrings
                         , let occ :: OccName
occ = NameSpace -> String -> OccName
mkOccName NameSpace
tvName String
str
                         , Maybe Name -> Bool
forall a. Maybe a -> Bool
isNothing (LocalRdrEnv -> OccName -> Maybe Name
lookupLocalRdrOcc LocalRdrEnv
rdr_env OccName
occ)
                         -- Note [Avoid name clashes for associated data types]
                         , Bool -> Bool
not (OccName
occ OccName -> [OccName] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [OccName]
lhs_occs) ]
              new_uniqs :: [Unique]
new_uniqs = UniqSupply -> [Unique]
uniqsFromSupply UniqSupply
uniqs
              subst :: TCvSubst
subst = InScopeSet -> TCvSubst
mkEmptyTCvSubst (TyCoVarSet -> InScopeSet
mkInScopeSet ([TcTyVar] -> TyCoVarSet
mkVarSet [TcTyVar]
lhs_tvs))
        ; ([TyConBinder], Type) -> TcM ([TyConBinder], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return (SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
new_occs [Unique]
new_uniqs TCvSubst
subst [] Type
kind) }
  where
    lhs_tvs :: [TcTyVar]
lhs_tvs  = (TyConBinder -> TcTyVar) -> [TyConBinder] -> [TcTyVar]
forall a b. (a -> b) -> [a] -> [b]
map TyConBinder -> TcTyVar
forall tv argf. VarBndr tv argf -> tv
binderVar [TyConBinder]
tc_bndrs
    lhs_occs :: [OccName]
lhs_occs = (TcTyVar -> OccName) -> [TcTyVar] -> [OccName]
forall a b. (a -> b) -> [a] -> [b]
map TcTyVar -> OccName
forall a. NamedThing a => a -> OccName
getOccName [TcTyVar]
lhs_tvs

    go :: SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
occs [Unique]
uniqs TCvSubst
subst [TyConBinder]
acc Type
kind
      = case Type -> Maybe (TyBinder, Type)
splitPiTy_maybe Type
kind of
          Maybe (TyBinder, Type)
Nothing -> ([TyConBinder] -> [TyConBinder]
forall a. [a] -> [a]
reverse [TyConBinder]
acc, HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
kind)

          Just (Anon AnonArgFlag
af Type
arg, Type
kind')
            -> SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
occs' [Unique]
uniqs' TCvSubst
subst' (TyConBinder
tcb TyConBinder -> [TyConBinder] -> [TyConBinder]
forall a. a -> [a] -> [a]
: [TyConBinder]
acc) Type
kind'
            where
              arg' :: Type
arg'   = HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
arg
              tv :: TcTyVar
tv     = Name -> Type -> TcTyVar
mkTyVar (Unique -> OccName -> SrcSpan -> Name
mkInternalName Unique
uniq OccName
occ SrcSpan
loc) Type
arg'
              subst' :: TCvSubst
subst' = TCvSubst -> TcTyVar -> TCvSubst
extendTCvInScope TCvSubst
subst TcTyVar
tv
              tcb :: TyConBinder
tcb    = TcTyVar -> TyConBndrVis -> TyConBinder
forall var argf. var -> argf -> VarBndr var argf
Bndr TcTyVar
tv (AnonArgFlag -> TyConBndrVis
AnonTCB AnonArgFlag
af)
              (Unique
uniq:[Unique]
uniqs') = [Unique]
uniqs
              (OccName
occ:[OccName]
occs')   = [OccName]
occs

          Just (Named (Bndr TcTyVar
tv ArgFlag
vis), Type
kind')
            -> SrcSpan
-> [OccName]
-> [Unique]
-> TCvSubst
-> [TyConBinder]
-> Type
-> ([TyConBinder], Type)
go SrcSpan
loc [OccName]
occs [Unique]
uniqs TCvSubst
subst' (TyConBinder
tcb TyConBinder -> [TyConBinder] -> [TyConBinder]
forall a. a -> [a] -> [a]
: [TyConBinder]
acc) Type
kind'
            where
              (TCvSubst
subst', TcTyVar
tv') = HasCallStack => TCvSubst -> TcTyVar -> (TCvSubst, TcTyVar)
TCvSubst -> TcTyVar -> (TCvSubst, TcTyVar)
substTyVarBndr TCvSubst
subst TcTyVar
tv
              tcb :: TyConBinder
tcb = TcTyVar -> TyConBndrVis -> TyConBinder
forall var argf. var -> argf -> VarBndr var argf
Bndr TcTyVar
tv' (ArgFlag -> TyConBndrVis
NamedTCB ArgFlag
vis)

-- | A description of whether something is a
--
-- * @data@ or @newtype@ ('DataDeclSort')
--
-- * @data instance@ or @newtype instance@ ('DataInstanceSort')
--
-- * @data family@ ('DataFamilySort')
--
-- At present, this data type is only consumed by 'checkDataKindSig'.
data DataSort
  = DataDeclSort     NewOrData
  | DataInstanceSort NewOrData
  | DataFamilySort

-- | Checks that the return kind in a data declaration's kind signature is
-- permissible. There are three cases:
--
-- If dealing with a @data@, @newtype@, @data instance@, or @newtype instance@
-- declaration, check that the return kind is @Type@.
--
-- If the declaration is a @newtype@ or @newtype instance@ and the
-- @UnliftedNewtypes@ extension is enabled, this check is slightly relaxed so
-- that a return kind of the form @TYPE r@ (for some @r@) is permitted.
-- See @Note [Implementation of UnliftedNewtypes]@ in "TcTyClsDecls".
--
-- If dealing with a @data family@ declaration, check that the return kind is
-- either of the form:
--
-- 1. @TYPE r@ (for some @r@), or
--
-- 2. @k@ (where @k@ is a bare kind variable; see #12369)
checkDataKindSig :: DataSort -> Kind -> TcM ()
checkDataKindSig :: DataSort -> Type -> TcM ()
checkDataKindSig DataSort
data_sort Type
kind = do
  DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
  Bool -> MsgDoc -> TcM ()
checkTc (DynFlags -> Bool
is_TYPE_or_Type DynFlags
dflags Bool -> Bool -> Bool
|| Bool
is_kind_var) (DynFlags -> MsgDoc
err_msg DynFlags
dflags)
  where
    pp_dec :: SDoc
    pp_dec :: MsgDoc
pp_dec = String -> MsgDoc
text (String -> MsgDoc) -> String -> MsgDoc
forall a b. (a -> b) -> a -> b
$
      case DataSort
data_sort of
        DataDeclSort     NewOrData
DataType -> String
"data type"
        DataDeclSort     NewOrData
NewType  -> String
"newtype"
        DataInstanceSort NewOrData
DataType -> String
"data instance"
        DataInstanceSort NewOrData
NewType  -> String
"newtype instance"
        DataSort
DataFamilySort            -> String
"data family"

    is_newtype :: Bool
    is_newtype :: Bool
is_newtype =
      case DataSort
data_sort of
        DataDeclSort     NewOrData
new_or_data -> NewOrData
new_or_data NewOrData -> NewOrData -> Bool
forall a. Eq a => a -> a -> Bool
== NewOrData
NewType
        DataInstanceSort NewOrData
new_or_data -> NewOrData
new_or_data NewOrData -> NewOrData -> Bool
forall a. Eq a => a -> a -> Bool
== NewOrData
NewType
        DataSort
DataFamilySort               -> Bool
False

    is_data_family :: Bool
    is_data_family :: Bool
is_data_family =
      case DataSort
data_sort of
        DataDeclSort{}     -> Bool
False
        DataInstanceSort{} -> Bool
False
        DataSort
DataFamilySort     -> Bool
True

    tYPE_ok :: DynFlags -> Bool
    tYPE_ok :: DynFlags -> Bool
tYPE_ok DynFlags
dflags =
         (Bool
is_newtype Bool -> Bool -> Bool
&& Extension -> DynFlags -> Bool
xopt Extension
LangExt.UnliftedNewtypes DynFlags
dflags)
           -- With UnliftedNewtypes, we allow kinds other than Type, but they
           -- must still be of the form `TYPE r` since we don't want to accept
           -- Constraint or Nat.
           -- See Note [Implementation of UnliftedNewtypes] in TcTyClsDecls.
      Bool -> Bool -> Bool
|| Bool
is_data_family
           -- If this is a `data family` declaration, we don't need to check if
           -- UnliftedNewtypes is enabled, since data family declarations can
           -- have return kind `TYPE r` unconditionally (#16827).

    is_TYPE :: Bool
    is_TYPE :: Bool
is_TYPE = Type -> Bool
tcIsRuntimeTypeKind Type
kind

    is_TYPE_or_Type :: DynFlags -> Bool
    is_TYPE_or_Type :: DynFlags -> Bool
is_TYPE_or_Type DynFlags
dflags | DynFlags -> Bool
tYPE_ok DynFlags
dflags = Bool
is_TYPE
                           | Bool
otherwise      = Type -> Bool
tcIsLiftedTypeKind Type
kind

    -- In the particular case of a data family, permit a return kind of the
    -- form `:: k` (where `k` is a bare kind variable).
    is_kind_var :: Bool
    is_kind_var :: Bool
is_kind_var | Bool
is_data_family = Maybe (TcTyVar, Coercion) -> Bool
forall a. Maybe a -> Bool
isJust (Type -> Maybe (TcTyVar, Coercion)
tcGetCastedTyVar_maybe Type
kind)
                | Bool
otherwise      = Bool
False

    err_msg :: DynFlags -> SDoc
    err_msg :: DynFlags -> MsgDoc
err_msg DynFlags
dflags =
      [MsgDoc] -> MsgDoc
sep [ ([MsgDoc] -> MsgDoc
sep [ String -> MsgDoc
text String
"Kind signature on" MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc
pp_dec MsgDoc -> MsgDoc -> MsgDoc
<+>
                   String -> MsgDoc
text String
"declaration has non-" MsgDoc -> MsgDoc -> MsgDoc
<>
                   (if DynFlags -> Bool
tYPE_ok DynFlags
dflags then String -> MsgDoc
text String
"TYPE" else Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
liftedTypeKind)
                 , (if Bool
is_data_family then String -> MsgDoc
text String
"and non-variable" else MsgDoc
empty) MsgDoc -> MsgDoc -> MsgDoc
<+>
                   String -> MsgDoc
text String
"return kind" MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
kind) ])
          , if Bool -> Bool
not (DynFlags -> Bool
tYPE_ok DynFlags
dflags) Bool -> Bool -> Bool
&& Bool
is_TYPE Bool -> Bool -> Bool
&& Bool
is_newtype Bool -> Bool -> Bool
&&
               Bool -> Bool
not (Extension -> DynFlags -> Bool
xopt Extension
LangExt.UnliftedNewtypes DynFlags
dflags)
            then String -> MsgDoc
text String
"Perhaps you intended to use UnliftedNewtypes"
            else MsgDoc
empty ]

-- | Checks that the result kind of a class is exactly `Constraint`, rejecting
-- type synonyms and type families that reduce to `Constraint`. See #16826.
checkClassKindSig :: Kind -> TcM ()
checkClassKindSig :: Type -> TcM ()
checkClassKindSig Type
kind = Bool -> MsgDoc -> TcM ()
checkTc (Type -> Bool
tcIsConstraintKind Type
kind) MsgDoc
err_msg
  where
    err_msg :: SDoc
    err_msg :: MsgDoc
err_msg =
      String -> MsgDoc
text String
"Kind signature on a class must end with" MsgDoc -> MsgDoc -> MsgDoc
<+> Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
constraintKind MsgDoc -> MsgDoc -> MsgDoc
$$
      String -> MsgDoc
text String
"unobscured by type families"

tcbVisibilities :: TyCon -> [Type] -> [TyConBndrVis]
-- Result is in 1-1 correpondence with orig_args
tcbVisibilities :: TyCon -> [Type] -> [TyConBndrVis]
tcbVisibilities TyCon
tc [Type]
orig_args
  = Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go (TyCon -> Type
tyConKind TyCon
tc) TCvSubst
init_subst [Type]
orig_args
  where
    init_subst :: TCvSubst
init_subst = InScopeSet -> TCvSubst
mkEmptyTCvSubst (TyCoVarSet -> InScopeSet
mkInScopeSet ([Type] -> TyCoVarSet
tyCoVarsOfTypes [Type]
orig_args))
    go :: Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go Type
_ TCvSubst
_ []
      = []

    go Type
fun_kind TCvSubst
subst all_args :: [Type]
all_args@(Type
arg : [Type]
args)
      | Just (TyBinder
tcb, Type
inner_kind) <- Type -> Maybe (TyBinder, Type)
splitPiTy_maybe Type
fun_kind
      = case TyBinder
tcb of
          Anon AnonArgFlag
af Type
_           -> AnonArgFlag -> TyConBndrVis
AnonTCB AnonArgFlag
af   TyConBndrVis -> [TyConBndrVis] -> [TyConBndrVis]
forall a. a -> [a] -> [a]
: Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go Type
inner_kind TCvSubst
subst  [Type]
args
          Named (Bndr TcTyVar
tv ArgFlag
vis) -> ArgFlag -> TyConBndrVis
NamedTCB ArgFlag
vis TyConBndrVis -> [TyConBndrVis] -> [TyConBndrVis]
forall a. a -> [a] -> [a]
: Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go Type
inner_kind TCvSubst
subst' [Type]
args
                 where
                    subst' :: TCvSubst
subst' = TCvSubst -> TcTyVar -> Type -> TCvSubst
extendTCvSubst TCvSubst
subst TcTyVar
tv Type
arg

      | Bool -> Bool
not (TCvSubst -> Bool
isEmptyTCvSubst TCvSubst
subst)
      = Type -> TCvSubst -> [Type] -> [TyConBndrVis]
go (HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
fun_kind) TCvSubst
init_subst [Type]
all_args

      | Bool
otherwise
      = String -> MsgDoc -> [TyConBndrVis]
forall a. HasCallStack => String -> MsgDoc -> a
pprPanic String
"addTcbVisibilities" (TyCon -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TyCon
tc MsgDoc -> MsgDoc -> MsgDoc
<+> [Type] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [Type]
orig_args)


{- Note [TyConBinders for the result kind signature of a data type]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given
  data T (a::*) :: * -> forall k. k -> *
we want to generate the extra TyConBinders for T, so we finally get
  (a::*) (b::*) (k::*) (c::k)
The function etaExpandAlgTyCon generates these extra TyConBinders from
the result kind signature.

We need to take care to give the TyConBinders
  (a) OccNames that are fresh (because the TyConBinders of a TyCon
      must have distinct OccNames

  (b) Uniques that are fresh (obviously)

For (a) we need to avoid clashes with the tyvars declared by
the user before the "::"; in the above example that is 'a'.
And also see Note [Avoid name clashes for associated data types].

For (b) suppose we have
   data T :: forall k. k -> forall k. k -> *
where the two k's are identical even up to their uniques.  Surprisingly,
this can happen: see #14515.

It's reasonably easy to solve all this; just run down the list with a
substitution; hence the recursive 'go' function.  But it has to be
done.

Note [Avoid name clashes for associated data types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider    class C a b where
               data D b :: * -> *
When typechecking the decl for D, we'll invent an extra type variable
for D, to fill out its kind.  Ideally we don't want this type variable
to be 'a', because when pretty printing we'll get
            class C a b where
               data D b a0
(NB: the tidying happens in the conversion to IfaceSyn, which happens
as part of pretty-printing a TyThing.)

That's why we look in the LocalRdrEnv to see what's in scope. This is
important only to get nice-looking output when doing ":info C" in GHCi.
It isn't essential for correctness.


************************************************************************
*                                                                      *
             Partial signatures
*                                                                      *
************************************************************************

-}

tcHsPartialSigType
  :: UserTypeCtxt
  -> LHsSigWcType GhcRn       -- The type signature
  -> TcM ( [(Name, TcTyVar)]  -- Wildcards
         , Maybe TcType       -- Extra-constraints wildcard
         , [(Name,TcTyVar)]   -- Original tyvar names, in correspondence with
                              --   the implicitly and explicitly bound type variables
         , TcThetaType        -- Theta part
         , TcType )           -- Tau part
-- See Note [Checking partial type signatures]
tcHsPartialSigType :: UserTypeCtxt
-> LHsSigWcType GhcRn
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
tcHsPartialSigType UserTypeCtxt
ctxt LHsSigWcType GhcRn
sig_ty
  | HsWC { hswc_ext :: forall pass thing. HsWildCardBndrs pass thing -> XHsWC pass thing
hswc_ext  = XHsWC GhcRn (LHsSigType GhcRn)
sig_wcs, hswc_body :: forall pass thing. HsWildCardBndrs pass thing -> thing
hswc_body = LHsSigType GhcRn
ib_ty } <- LHsSigWcType GhcRn
sig_ty
  , HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext = XHsIB GhcRn (LHsType GhcRn)
implicit_hs_tvs
         , hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body = LHsType GhcRn
hs_ty } <- LHsSigType GhcRn
ib_ty
  , ([LHsTyVarBndr GhcRn]
explicit_hs_tvs, L SrcSpan
_ [LHsType GhcRn]
hs_ctxt, LHsType GhcRn
hs_tau) <- LHsType GhcRn
-> ([LHsTyVarBndr GhcRn], LHsContext GhcRn, LHsType GhcRn)
forall pass.
LHsType pass
-> ([LHsTyVarBndr pass], LHsContext pass, LHsType pass)
splitLHsSigmaTyInvis LHsType GhcRn
hs_ty
  = UserTypeCtxt
-> LHsType GhcRn
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
forall a. UserTypeCtxt -> LHsType GhcRn -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt LHsType GhcRn
hs_ty (TcM
   ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
 -> TcM
      ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type))
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
forall a b. (a -> b) -> a -> b
$
    do { ([TcTyVar]
implicit_tvs, ([TcTyVar]
explicit_tvs, ([(Name, TcTyVar)]
wcs, Maybe Type
wcx, [Type]
theta, Type
tau)))
            <- String
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
forall a. String -> TcM a -> TcM a
solveLocalEqualities String
"tcHsPartialSigType"    (TcM
   ([TcTyVar],
    ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
 -> TcM
      ([TcTyVar],
       ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))))
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
forall a b. (a -> b) -> a -> b
$
                 -- This solveLocalEqualiltes fails fast if there are
                 -- insoluble equalities. See TcSimplify
                 -- Note [Fail fast if there are insoluble kind equalities]
               [Name]
-> ([(Name, TcTyVar)]
    -> TcM
         ([TcTyVar],
          ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))))
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
forall a. [Name] -> ([(Name, TcTyVar)] -> TcM a) -> TcM a
tcNamedWildCardBinders [Name]
XHsWC GhcRn (LHsSigType GhcRn)
sig_wcs (([(Name, TcTyVar)]
  -> TcM
       ([TcTyVar],
        ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))))
 -> TcM
      ([TcTyVar],
       ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))))
-> ([(Name, TcTyVar)]
    -> TcM
         ([TcTyVar],
          ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))))
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
forall a b. (a -> b) -> a -> b
$ \ [(Name, TcTyVar)]
wcs ->
               [Name]
-> TcM ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
forall a. [Name] -> TcM a -> TcM ([TcTyVar], a)
bindImplicitTKBndrs_Tv [Name]
XHsIB GhcRn (LHsType GhcRn)
implicit_hs_tvs       (TcM ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))
 -> TcM
      ([TcTyVar],
       ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))))
-> TcM ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))
-> TcM
     ([TcTyVar],
      ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
forall a b. (a -> b) -> a -> b
$
               [LHsTyVarBndr GhcRn]
-> TcM ([(Name, TcTyVar)], Maybe Type, [Type], Type)
-> TcM ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))
forall a. [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TcTyVar], a)
bindExplicitTKBndrs_Tv [LHsTyVarBndr GhcRn]
explicit_hs_tvs       (TcM ([(Name, TcTyVar)], Maybe Type, [Type], Type)
 -> TcM ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type)))
-> TcM ([(Name, TcTyVar)], Maybe Type, [Type], Type)
-> TcM ([TcTyVar], ([(Name, TcTyVar)], Maybe Type, [Type], Type))
forall a b. (a -> b) -> a -> b
$
               do {   -- Instantiate the type-class context; but if there
                      -- is an extra-constraints wildcard, just discard it here
                    ([Type]
theta, Maybe Type
wcx) <- [LHsType GhcRn] -> TcM ([Type], Maybe Type)
tcPartialContext [LHsType GhcRn]
hs_ctxt

                  ; Type
tau <- LHsType GhcRn -> TcM Type
tcHsOpenType LHsType GhcRn
hs_tau

                  ; ([(Name, TcTyVar)], Maybe Type, [Type], Type)
-> TcM ([(Name, TcTyVar)], Maybe Type, [Type], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TcTyVar)]
wcs, Maybe Type
wcx, [Type]
theta, Type
tau) }

         -- No kind-generalization here:
       ; Type -> TcM ()
kindGeneralizeNone ([TcTyVar] -> Type -> Type
mkSpecForAllTys [TcTyVar]
implicit_tvs (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                             [TcTyVar] -> Type -> Type
mkSpecForAllTys [TcTyVar]
explicit_tvs (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                             [Type] -> Type -> Type
mkPhiTy [Type]
theta (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                             Type
tau)

       -- Spit out the wildcards (including the extra-constraints one)
       -- as "hole" constraints, so that they'll be reported if necessary
       -- See Note [Extra-constraint holes in partial type signatures]
       ; [(Name, TcTyVar)] -> TcM ()
emitNamedWildCardHoleConstraints [(Name, TcTyVar)]
wcs

         -- We return a proper (Name,TyVar) environment, to be sure that
         -- we bring the right name into scope in the function body.
         -- Test case: partial-sigs/should_compile/LocalDefinitionBug
       ; let tv_prs :: [(Name, TcTyVar)]
tv_prs = ([Name]
XHsIB GhcRn (LHsType GhcRn)
implicit_hs_tvs                  [Name] -> [TcTyVar] -> [(Name, TcTyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcTyVar]
implicit_tvs)
                      [(Name, TcTyVar)] -> [(Name, TcTyVar)] -> [(Name, TcTyVar)]
forall a. [a] -> [a] -> [a]
++ ([LHsTyVarBndr GhcRn] -> [IdP GhcRn]
forall (p :: Pass). [LHsTyVarBndr (GhcPass p)] -> [IdP (GhcPass p)]
hsLTyVarNames [LHsTyVarBndr GhcRn]
explicit_hs_tvs [Name] -> [TcTyVar] -> [(Name, TcTyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TcTyVar]
explicit_tvs)

      -- NB: checkValidType on the final inferred type will be
      --     done later by checkInferredPolyId.  We can't do it
      --     here because we don't have a complete tuype to check

       ; String -> MsgDoc -> TcM ()
traceTc String
"tcHsPartialSigType" ([(Name, TcTyVar)] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [(Name, TcTyVar)]
tv_prs)
       ; ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TcTyVar)]
wcs, Maybe Type
wcx, [(Name, TcTyVar)]
tv_prs, [Type]
theta, Type
tau) }

tcHsPartialSigType UserTypeCtxt
_ (HsWC XHsWC GhcRn (LHsSigType GhcRn)
_ (XHsImplicitBndrs XXHsImplicitBndrs GhcRn (LHsType GhcRn)
nec)) = NoExtCon
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
forall a. NoExtCon -> a
noExtCon XXHsImplicitBndrs GhcRn (LHsType GhcRn)
NoExtCon
nec
tcHsPartialSigType UserTypeCtxt
_ (XHsWildCardBndrs XXHsWildCardBndrs GhcRn (LHsSigType GhcRn)
nec) = NoExtCon
-> TcM
     ([(Name, TcTyVar)], Maybe Type, [(Name, TcTyVar)], [Type], Type)
forall a. NoExtCon -> a
noExtCon XXHsWildCardBndrs GhcRn (LHsSigType GhcRn)
NoExtCon
nec

tcPartialContext :: HsContext GhcRn -> TcM (TcThetaType, Maybe TcType)
tcPartialContext :: [LHsType GhcRn] -> TcM ([Type], Maybe Type)
tcPartialContext [LHsType GhcRn]
hs_theta
  | Just ([LHsType GhcRn]
hs_theta1, LHsType GhcRn
hs_ctxt_last) <- [LHsType GhcRn] -> Maybe ([LHsType GhcRn], LHsType GhcRn)
forall a. [a] -> Maybe ([a], a)
snocView [LHsType GhcRn]
hs_theta
  , L SrcSpan
wc_loc wc :: HsType GhcRn
wc@(HsWildCardTy XWildCardTy GhcRn
_) <- LHsType GhcRn -> LHsType GhcRn
forall pass. LHsType pass -> LHsType pass
ignoreParens LHsType GhcRn
hs_ctxt_last
  = do { Type
wc_tv_ty <- SrcSpan -> TcM Type -> TcM Type
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
wc_loc (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                     HsType GhcRn -> Type -> TcM Type
tcAnonWildCardOcc HsType GhcRn
wc Type
constraintKind
       ; [Type]
theta <- (LHsType GhcRn -> TcM Type) -> [LHsType GhcRn] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM LHsType GhcRn -> TcM Type
tcLHsPredType [LHsType GhcRn]
hs_theta1
       ; ([Type], Maybe Type) -> TcM ([Type], Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
theta, Type -> Maybe Type
forall a. a -> Maybe a
Just Type
wc_tv_ty) }
  | Bool
otherwise
  = do { [Type]
theta <- (LHsType GhcRn -> TcM Type) -> [LHsType GhcRn] -> TcM [Type]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM LHsType GhcRn -> TcM Type
tcLHsPredType [LHsType GhcRn]
hs_theta
       ; ([Type], Maybe Type) -> TcM ([Type], Maybe Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
theta, Maybe Type
forall a. Maybe a
Nothing) }

{- Note [Checking partial type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See also Note [Recipe for checking a signature]

When we have a parital signature like
   f,g :: forall a. a -> _
we do the following

* In TcSigs.tcUserSigType we return a PartialSig, which (unlike
  the companion CompleteSig) contains the original, as-yet-unchecked
  source-code LHsSigWcType

* Then, for f and g /separately/, we call tcInstSig, which in turn
  call tchsPartialSig (defined near this Note).  It kind-checks the
  LHsSigWcType, creating fresh unification variables for each "_"
  wildcard.  It's important that the wildcards for f and g are distinct
  becase they migh get instantiated completely differently.  E.g.
     f,g :: forall a. a -> _
     f x = a
     g x = True
  It's really as if we'd written two distinct signatures.

* Note that we don't make quantified type (forall a. blah) and then
  instantiate it -- it makes no sense to instantiate a type with
  wildcards in it.  Rather, tcHsPartialSigType just returns the
  'a' and the 'blah' separately.

  Nor, for the same reason, do we push a level in tcHsPartialSigType.

Note [Extra-constraint holes in partial type signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
  f :: (_) => a -> a
  f x = ...

* The renamer leaves '_' untouched.

* Then, in tcHsPartialSigType, we make a new hole TcTyVar, in
  tcWildCardBinders.

* TcBinds.chooseInferredQuantifiers fills in that hole TcTyVar
  with the inferred constraints, e.g. (Eq a, Show a)

* TcErrors.mkHoleError finally reports the error.

An annoying difficulty happens if there are more than 62 inferred
constraints. Then we need to fill in the TcTyVar with (say) a 70-tuple.
Where do we find the TyCon?  For good reasons we only have constraint
tuples up to 62 (see Note [How tuples work] in TysWiredIn).  So how
can we make a 70-tuple?  This was the root cause of #14217.

It's incredibly tiresome, because we only need this type to fill
in the hole, to communicate to the error reporting machinery.  Nothing
more.  So I use a HACK:

* I make an /ordinary/ tuple of the constraints, in
  TcBinds.chooseInferredQuantifiers. This is ill-kinded because
  ordinary tuples can't contain constraints, but it works fine. And for
  ordinary tuples we don't have the same limit as for constraint
  tuples (which need selectors and an assocated class).

* Because it is ill-kinded, it trips an assert in writeMetaTyVar,
  so now I disable the assertion if we are writing a type of
  kind Constraint.  (That seldom/never normally happens so we aren't
  losing much.)

Result works fine, but it may eventually bite us.


************************************************************************
*                                                                      *
      Pattern signatures (i.e signatures that occur in patterns)
*                                                                      *
********************************************************************* -}

tcHsPatSigType :: UserTypeCtxt
               -> LHsSigWcType GhcRn          -- The type signature
               -> TcM ( [(Name, TcTyVar)]     -- Wildcards
                      , [(Name, TcTyVar)]     -- The new bit of type environment, binding
                                              -- the scoped type variables
                      , TcType)       -- The type
-- Used for type-checking type signatures in
-- (a) patterns           e.g  f (x::Int) = e
-- (b) RULE forall bndrs  e.g. forall (x::Int). f x = x
--
-- This may emit constraints
-- See Note [Recipe for checking a signature]
tcHsPatSigType :: UserTypeCtxt
-> LHsSigWcType GhcRn
-> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
tcHsPatSigType UserTypeCtxt
ctxt LHsSigWcType GhcRn
sig_ty
  | HsWC { hswc_ext :: forall pass thing. HsWildCardBndrs pass thing -> XHsWC pass thing
hswc_ext = XHsWC GhcRn (LHsSigType GhcRn)
sig_wcs,   hswc_body :: forall pass thing. HsWildCardBndrs pass thing -> thing
hswc_body = LHsSigType GhcRn
ib_ty } <- LHsSigWcType GhcRn
sig_ty
  , HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext = XHsIB GhcRn (LHsType GhcRn)
sig_ns
         , hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body = LHsType GhcRn
hs_ty } <- LHsSigType GhcRn
ib_ty
  = UserTypeCtxt
-> LHsType GhcRn
-> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
-> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
forall a. UserTypeCtxt -> LHsType GhcRn -> TcM a -> TcM a
addSigCtxt UserTypeCtxt
ctxt LHsType GhcRn
hs_ty (TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
 -> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type))
-> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
-> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
forall a b. (a -> b) -> a -> b
$
    do { [(Name, TcTyVar)]
sig_tkv_prs <- (Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar))
-> [Name] -> IOEnv (Env TcGblEnv TcLclEnv) [(Name, TcTyVar)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar)
new_implicit_tv [Name]
XHsIB GhcRn (LHsType GhcRn)
sig_ns
       ; ([(Name, TcTyVar)]
wcs, Type
sig_ty)
            <- String
-> TcM ([(Name, TcTyVar)], Type) -> TcM ([(Name, TcTyVar)], Type)
forall a. String -> TcM a -> TcM a
solveLocalEqualities String
"tcHsPatSigType" (TcM ([(Name, TcTyVar)], Type) -> TcM ([(Name, TcTyVar)], Type))
-> TcM ([(Name, TcTyVar)], Type) -> TcM ([(Name, TcTyVar)], Type)
forall a b. (a -> b) -> a -> b
$
                 -- Always solve local equalities if possible,
                 -- else casts get in the way of deep skolemisation
                 -- (#16033)
               [Name]
-> ([(Name, TcTyVar)] -> TcM ([(Name, TcTyVar)], Type))
-> TcM ([(Name, TcTyVar)], Type)
forall a. [Name] -> ([(Name, TcTyVar)] -> TcM a) -> TcM a
tcNamedWildCardBinders [Name]
XHsWC GhcRn (LHsSigType GhcRn)
sig_wcs        (([(Name, TcTyVar)] -> TcM ([(Name, TcTyVar)], Type))
 -> TcM ([(Name, TcTyVar)], Type))
-> ([(Name, TcTyVar)] -> TcM ([(Name, TcTyVar)], Type))
-> TcM ([(Name, TcTyVar)], Type)
forall a b. (a -> b) -> a -> b
$ \ [(Name, TcTyVar)]
wcs ->
               [(Name, TcTyVar)]
-> TcM ([(Name, TcTyVar)], Type) -> TcM ([(Name, TcTyVar)], Type)
forall r. [(Name, TcTyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TcTyVar)]
sig_tkv_prs (TcM ([(Name, TcTyVar)], Type) -> TcM ([(Name, TcTyVar)], Type))
-> TcM ([(Name, TcTyVar)], Type) -> TcM ([(Name, TcTyVar)], Type)
forall a b. (a -> b) -> a -> b
$
               do { Type
sig_ty <- LHsType GhcRn -> TcM Type
tcHsOpenType LHsType GhcRn
hs_ty
                  ; ([(Name, TcTyVar)], Type) -> TcM ([(Name, TcTyVar)], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TcTyVar)]
wcs, Type
sig_ty) }

        ; [(Name, TcTyVar)] -> TcM ()
emitNamedWildCardHoleConstraints [(Name, TcTyVar)]
wcs

          -- sig_ty might have tyvars that are at a higher TcLevel (if hs_ty
          -- contains a forall). Promote these.
          -- Ex: f (x :: forall a. Proxy a -> ()) = ... x ...
          -- When we instantiate x, we have to compare the kind of the argument
          -- to a's kind, which will be a metavariable.
          -- kindGeneralizeNone does this:
        ; Type -> TcM ()
kindGeneralizeNone Type
sig_ty
        ; Type
sig_ty <- Type -> TcM Type
zonkTcType Type
sig_ty
        ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
sig_ty

        ; String -> MsgDoc -> TcM ()
traceTc String
"tcHsPatSigType" ([(Name, TcTyVar)] -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr [(Name, TcTyVar)]
sig_tkv_prs)
        ; ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
-> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, TcTyVar)]
wcs, [(Name, TcTyVar)]
sig_tkv_prs, Type
sig_ty) }
  where
    new_implicit_tv :: Name -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar)
new_implicit_tv Name
name
      = do { Type
kind <- TcM Type
newMetaKindVar
           ; TcTyVar
tv   <- case UserTypeCtxt
ctxt of
                       RuleSigCtxt {} -> Name -> Type -> TcM TcTyVar
newSkolemTyVar Name
name Type
kind
                       UserTypeCtxt
_              -> Name -> Type -> TcM TcTyVar
newPatSigTyVar Name
name Type
kind
                       -- See Note [Pattern signature binders]
             -- NB: tv's Name may be fresh (in the case of newPatSigTyVar)
           ; (Name, TcTyVar) -> IOEnv (Env TcGblEnv TcLclEnv) (Name, TcTyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (Name
name, TcTyVar
tv) }

tcHsPatSigType UserTypeCtxt
_ (HsWC XHsWC GhcRn (LHsSigType GhcRn)
_ (XHsImplicitBndrs XXHsImplicitBndrs GhcRn (LHsType GhcRn)
nec)) = NoExtCon -> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
forall a. NoExtCon -> a
noExtCon XXHsImplicitBndrs GhcRn (LHsType GhcRn)
NoExtCon
nec
tcHsPatSigType UserTypeCtxt
_ (XHsWildCardBndrs XXHsWildCardBndrs GhcRn (LHsSigType GhcRn)
nec)          = NoExtCon -> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
forall a. NoExtCon -> a
noExtCon XXHsWildCardBndrs GhcRn (LHsSigType GhcRn)
NoExtCon
nec

tcPatSig :: Bool                    -- True <=> pattern binding
         -> LHsSigWcType GhcRn
         -> ExpSigmaType
         -> TcM (TcType,            -- The type to use for "inside" the signature
                 [(Name,TcTyVar)],  -- The new bit of type environment, binding
                                    -- the scoped type variables
                 [(Name,TcTyVar)],  -- The wildcards
                 HsWrapper)         -- Coercion due to unification with actual ty
                                    -- Of shape:  res_ty ~ sig_ty
tcPatSig :: Bool
-> LHsSigWcType GhcRn
-> ExpSigmaType
-> TcM (Type, [(Name, TcTyVar)], [(Name, TcTyVar)], HsWrapper)
tcPatSig Bool
in_pat_bind LHsSigWcType GhcRn
sig ExpSigmaType
res_ty
 = do  { ([(Name, TcTyVar)]
sig_wcs, [(Name, TcTyVar)]
sig_tvs, Type
sig_ty) <- UserTypeCtxt
-> LHsSigWcType GhcRn
-> TcM ([(Name, TcTyVar)], [(Name, TcTyVar)], Type)
tcHsPatSigType UserTypeCtxt
PatSigCtxt LHsSigWcType GhcRn
sig
        -- sig_tvs are the type variables free in 'sig',
        -- and not already in scope. These are the ones
        -- that should be brought into scope

        ; if [(Name, TcTyVar)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [(Name, TcTyVar)]
sig_tvs then do {
                -- Just do the subsumption check and return
                  HsWrapper
wrap <- (TidyEnv -> TcM (TidyEnv, MsgDoc))
-> TcM HsWrapper -> TcM HsWrapper
forall a. (TidyEnv -> TcM (TidyEnv, MsgDoc)) -> TcM a -> TcM a
addErrCtxtM (Type -> TidyEnv -> TcM (TidyEnv, MsgDoc)
mk_msg Type
sig_ty) (TcM HsWrapper -> TcM HsWrapper) -> TcM HsWrapper -> TcM HsWrapper
forall a b. (a -> b) -> a -> b
$
                          CtOrigin -> UserTypeCtxt -> ExpSigmaType -> Type -> TcM HsWrapper
tcSubTypeET CtOrigin
PatSigOrigin UserTypeCtxt
PatSigCtxt ExpSigmaType
res_ty Type
sig_ty
                ; (Type, [(Name, TcTyVar)], [(Name, TcTyVar)], HsWrapper)
-> TcM (Type, [(Name, TcTyVar)], [(Name, TcTyVar)], HsWrapper)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
sig_ty, [], [(Name, TcTyVar)]
sig_wcs, HsWrapper
wrap)
        } else do
                -- Type signature binds at least one scoped type variable

                -- A pattern binding cannot bind scoped type variables
                -- It is more convenient to make the test here
                -- than in the renamer
        { Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
in_pat_bind (MsgDoc -> TcM ()
addErr ([(Name, TcTyVar)] -> MsgDoc
patBindSigErr [(Name, TcTyVar)]
sig_tvs))

        -- Now do a subsumption check of the pattern signature against res_ty
        ; HsWrapper
wrap <- (TidyEnv -> TcM (TidyEnv, MsgDoc))
-> TcM HsWrapper -> TcM HsWrapper
forall a. (TidyEnv -> TcM (TidyEnv, MsgDoc)) -> TcM a -> TcM a
addErrCtxtM (Type -> TidyEnv -> TcM (TidyEnv, MsgDoc)
mk_msg Type
sig_ty) (TcM HsWrapper -> TcM HsWrapper) -> TcM HsWrapper -> TcM HsWrapper
forall a b. (a -> b) -> a -> b
$
                  CtOrigin -> UserTypeCtxt -> ExpSigmaType -> Type -> TcM HsWrapper
tcSubTypeET CtOrigin
PatSigOrigin UserTypeCtxt
PatSigCtxt ExpSigmaType
res_ty Type
sig_ty

        -- Phew!
        ; (Type, [(Name, TcTyVar)], [(Name, TcTyVar)], HsWrapper)
-> TcM (Type, [(Name, TcTyVar)], [(Name, TcTyVar)], HsWrapper)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
sig_ty, [(Name, TcTyVar)]
sig_tvs, [(Name, TcTyVar)]
sig_wcs, HsWrapper
wrap)
        } }
  where
    mk_msg :: Type -> TidyEnv -> TcM (TidyEnv, MsgDoc)
mk_msg Type
sig_ty TidyEnv
tidy_env
       = do { (TidyEnv
tidy_env, Type
sig_ty) <- TidyEnv -> Type -> TcM (TidyEnv, Type)
zonkTidyTcType TidyEnv
tidy_env Type
sig_ty
            ; Type
res_ty <- ExpSigmaType -> TcM Type
readExpType ExpSigmaType
res_ty   -- should be filled in by now
            ; (TidyEnv
tidy_env, Type
res_ty) <- TidyEnv -> Type -> TcM (TidyEnv, Type)
zonkTidyTcType TidyEnv
tidy_env Type
res_ty
            ; let msg :: MsgDoc
msg = [MsgDoc] -> MsgDoc
vcat [ MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"When checking that the pattern signature:")
                                  Int
4 (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
sig_ty)
                             , Int -> MsgDoc -> MsgDoc
nest Int
2 (MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"fits the type of its context:")
                                          Int
2 (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
res_ty)) ]
            ; (TidyEnv, MsgDoc) -> TcM (TidyEnv, MsgDoc)
forall (m :: * -> *) a. Monad m => a -> m a
return (TidyEnv
tidy_env, MsgDoc
msg) }

patBindSigErr :: [(Name,TcTyVar)] -> SDoc
patBindSigErr :: [(Name, TcTyVar)] -> MsgDoc
patBindSigErr [(Name, TcTyVar)]
sig_tvs
  = MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (String -> MsgDoc
text String
"You cannot bind scoped type variable" MsgDoc -> MsgDoc -> MsgDoc
<> [(Name, TcTyVar)] -> MsgDoc
forall a. [a] -> MsgDoc
plural [(Name, TcTyVar)]
sig_tvs
          MsgDoc -> MsgDoc -> MsgDoc
<+> [Name] -> MsgDoc
forall a. Outputable a => [a] -> MsgDoc
pprQuotedList (((Name, TcTyVar) -> Name) -> [(Name, TcTyVar)] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (Name, TcTyVar) -> Name
forall a b. (a, b) -> a
fst [(Name, TcTyVar)]
sig_tvs))
       Int
2 (String -> MsgDoc
text String
"in a pattern binding signature")

{- Note [Pattern signature binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See also Note [Type variables in the type environment] in TcRnTypes.
Consider

  data T where
    MkT :: forall a. a -> (a -> Int) -> T

  f :: T -> ...
  f (MkT x (f :: b -> c)) = <blah>

Here
 * The pattern (MkT p1 p2) creates a *skolem* type variable 'a_sk',
   It must be a skolem so that that it retains its identity, and
   TcErrors.getSkolemInfo can thereby find the binding site for the skolem.

 * The type signature pattern (f :: b -> c) makes freshs meta-tyvars
   beta and gamma (TauTvs), and binds "b" :-> beta, "c" :-> gamma in the
   environment

 * Then unification makes beta := a_sk, gamma := Int
   That's why we must make beta and gamma a MetaTv,
   not a SkolemTv, so that it can unify to a_sk (or Int, respectively).

 * Finally, in '<blah>' we have the envt "b" :-> beta, "c" :-> gamma,
   so we return the pairs ("b" :-> beta, "c" :-> gamma) from tcHsPatSigType,

Another example (#13881):
   fl :: forall (l :: [a]). Sing l -> Sing l
   fl (SNil :: Sing (l :: [y])) = SNil
When we reach the pattern signature, 'l' is in scope from the
outer 'forall':
   "a" :-> a_sk :: *
   "l" :-> l_sk :: [a_sk]
We make up a fresh meta-TauTv, y_sig, for 'y', and kind-check
the pattern signature
   Sing (l :: [y])
That unifies y_sig := a_sk.  We return from tcHsPatSigType with
the pair ("y" :-> y_sig).

For RULE binders, though, things are a bit different (yuk).
  RULE "foo" forall (x::a) (y::[a]).  f x y = ...
Here this really is the binding site of the type variable so we'd like
to use a skolem, so that we get a complaint if we unify two of them
together.  Hence the new_tv function in tcHsPatSigType.


************************************************************************
*                                                                      *
        Checking kinds
*                                                                      *
************************************************************************

-}

unifyKinds :: [LHsType GhcRn] -> [(TcType, TcKind)] -> TcM ([TcType], TcKind)
unifyKinds :: [LHsType GhcRn] -> [(Type, Type)] -> TcM ([Type], Type)
unifyKinds [LHsType GhcRn]
rn_tys [(Type, Type)]
act_kinds
  = do { Type
kind <- TcM Type
newMetaKindVar
       ; let check :: LHsType GhcRn -> (Type, Type) -> TcM Type
check LHsType GhcRn
rn_ty (Type
ty, Type
act_kind)
               = HasDebugCallStack =>
HsType GhcRn -> Type -> Type -> Type -> TcM Type
HsType GhcRn -> Type -> Type -> Type -> TcM Type
checkExpectedKind (LHsType GhcRn -> SrcSpanLess (LHsType GhcRn)
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc LHsType GhcRn
rn_ty) Type
ty Type
act_kind Type
kind
       ; [Type]
tys' <- (LHsType GhcRn -> (Type, Type) -> TcM Type)
-> [LHsType GhcRn] -> [(Type, Type)] -> TcM [Type]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM LHsType GhcRn -> (Type, Type) -> TcM Type
check [LHsType GhcRn]
rn_tys [(Type, Type)]
act_kinds
       ; ([Type], Type) -> TcM ([Type], Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
tys', Type
kind) }

{-
************************************************************************
*                                                                      *
        Sort checking kinds
*                                                                      *
************************************************************************

tcLHsKindSig converts a user-written kind to an internal, sort-checked kind.
It does sort checking and desugaring at the same time, in one single pass.
-}

tcLHsKindSig :: UserTypeCtxt -> LHsKind GhcRn -> TcM Kind
tcLHsKindSig :: UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
ctxt LHsType GhcRn
hs_kind
-- See  Note [Recipe for checking a signature] in TcHsType
-- Result is zonked
  = do { Type
kind <- String -> TcM Type -> TcM Type
forall a. String -> TcM a -> TcM a
solveLocalEqualities String
"tcLHsKindSig" (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
                 TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_kind TcTyMode
kindLevelMode LHsType GhcRn
hs_kind
       ; String -> MsgDoc -> TcM ()
traceTc String
"tcLHsKindSig" (LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
hs_kind MsgDoc -> MsgDoc -> MsgDoc
$$ Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
kind)
       -- No generalization:
       ; Type -> TcM ()
kindGeneralizeNone Type
kind
       ; Type
kind <- Type -> TcM Type
zonkTcType Type
kind
         -- This zonk is very important in the case of higher rank kinds
         -- E.g. #13879    f :: forall (p :: forall z (y::z). <blah>).
         --                          <more blah>
         --      When instantiating p's kind at occurrences of p in <more blah>
         --      it's crucial that the kind we instantiate is fully zonked,
         --      else we may fail to substitute properly

       ; UserTypeCtxt -> Type -> TcM ()
checkValidType UserTypeCtxt
ctxt Type
kind
       ; String -> MsgDoc -> TcM ()
traceTc String
"tcLHsKindSig2" (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
kind)
       ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
kind }

tc_lhs_kind :: TcTyMode -> LHsKind GhcRn -> TcM Kind
tc_lhs_kind :: TcTyMode -> LHsType GhcRn -> TcM Type
tc_lhs_kind TcTyMode
mode LHsType GhcRn
k
  = MsgDoc -> TcM Type -> TcM Type
forall a. MsgDoc -> TcM a -> TcM a
addErrCtxt (String -> MsgDoc
text String
"In the kind" MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (LHsType GhcRn -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr LHsType GhcRn
k)) (TcM Type -> TcM Type) -> TcM Type -> TcM Type
forall a b. (a -> b) -> a -> b
$
    TcTyMode -> LHsType GhcRn -> Type -> TcM Type
tc_lhs_type (TcTyMode -> TcTyMode
kindLevel TcTyMode
mode) LHsType GhcRn
k Type
liftedTypeKind

promotionErr :: Name -> PromotionErr -> TcM a
promotionErr :: Name -> PromotionErr -> TcM a
promotionErr Name
name PromotionErr
err
  = MsgDoc -> TcM a
forall a. MsgDoc -> TcM a
failWithTc (MsgDoc -> Int -> MsgDoc -> MsgDoc
hang (PromotionErr -> MsgDoc
pprPECategory PromotionErr
err MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (Name -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Name
name) MsgDoc -> MsgDoc -> MsgDoc
<+> String -> MsgDoc
text String
"cannot be used here")
                   Int
2 (MsgDoc -> MsgDoc
parens MsgDoc
reason))
  where
    reason :: MsgDoc
reason = case PromotionErr
err of
               ConstrainedDataConPE Type
pred
                              -> String -> MsgDoc
text String
"it has an unpromotable context"
                                 MsgDoc -> MsgDoc -> MsgDoc
<+> MsgDoc -> MsgDoc
quotes (Type -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Type
pred)
               PromotionErr
FamDataConPE   -> String -> MsgDoc
text String
"it comes from a data family instance"
               PromotionErr
NoDataKindsTC  -> String -> MsgDoc
text String
"perhaps you intended to use DataKinds"
               PromotionErr
NoDataKindsDC  -> String -> MsgDoc
text String
"perhaps you intended to use DataKinds"
               PromotionErr
PatSynPE       -> String -> MsgDoc
text String
"pattern synonyms cannot be promoted"
               PromotionErr
_ -> String -> MsgDoc
text String
"it is defined and used in the same recursive group"

{-
************************************************************************
*                                                                      *
          Error messages and such
*                                                                      *
************************************************************************
-}


-- | If the inner action emits constraints, report them as errors and fail;
-- otherwise, propagates the return value. Useful as a wrapper around
-- 'tcImplicitTKBndrs', which uses solveLocalEqualities, when there won't be
-- another chance to solve constraints
failIfEmitsConstraints :: TcM a -> TcM a
failIfEmitsConstraints :: TcM a -> TcM a
failIfEmitsConstraints TcM a
thing_inside
  = TcM a -> TcM a
forall a. TcM a -> TcM a
checkNoErrs (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$  -- We say that we fail if there are constraints!
                   -- c.f same checkNoErrs in solveEqualities
    do { (a
res, WantedConstraints
lie) <- TcM a -> TcM (a, WantedConstraints)
forall a. TcM a -> TcM (a, WantedConstraints)
captureConstraints TcM a
thing_inside
       ; WantedConstraints -> TcM ()
reportAllUnsolved WantedConstraints
lie
       ; a -> TcM a
forall (m :: * -> *) a. Monad m => a -> m a
return a
res
       }

-- | Make an appropriate message for an error in a function argument.
-- Used for both expressions and types.
funAppCtxt :: (Outputable fun, Outputable arg) => fun -> arg -> Int -> SDoc
funAppCtxt :: fun -> arg -> Int -> MsgDoc
funAppCtxt fun
fun arg
arg Int
arg_no
  = MsgDoc -> Int -> MsgDoc -> MsgDoc
hang ([MsgDoc] -> MsgDoc
hsep [ String -> MsgDoc
text String
"In the", Int -> MsgDoc
speakNth Int
arg_no, PtrString -> MsgDoc
ptext (String -> PtrString
sLit String
"argument of"),
                    MsgDoc -> MsgDoc
quotes (fun -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr fun
fun) MsgDoc -> MsgDoc -> MsgDoc
<> String -> MsgDoc
text String
", namely"])
       Int
2 (MsgDoc -> MsgDoc
quotes (arg -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr arg
arg))

-- | Add a "In the data declaration for T" or some such.
addTyConFlavCtxt :: Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt :: Name -> TyConFlavour -> TcM a -> TcM a
addTyConFlavCtxt Name
name TyConFlavour
flav
  = MsgDoc -> TcM a -> TcM a
forall a. MsgDoc -> TcM a -> TcM a
addErrCtxt (MsgDoc -> TcM a -> TcM a) -> MsgDoc -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$ [MsgDoc] -> MsgDoc
hsep [ String -> MsgDoc
text String
"In the", TyConFlavour -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr TyConFlavour
flav
                      , String -> MsgDoc
text String
"declaration for", MsgDoc -> MsgDoc
quotes (Name -> MsgDoc
forall a. Outputable a => a -> MsgDoc
ppr Name
name) ]