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

-}

{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeFamilies #-}

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

-- | Typechecking instance declarations
module GHC.Tc.TyCl.Instance
   ( tcInstDecls1
   , tcInstDeclsDeriv
   , tcInstDecls2
   )
where

#include "GhclibHsVersions.h"

import GHC.Prelude

import GHC.Hs
import GHC.Tc.Gen.Bind
import GHC.Tc.TyCl
import GHC.Tc.TyCl.Utils ( addTyConsToGblEnv )
import GHC.Tc.TyCl.Class ( tcClassDecl2, tcATDefault,
                           HsSigFun, mkHsSigFun, badMethodErr,
                           findMethodBind, instantiateMethod )
import GHC.Tc.Solver( pushLevelAndSolveEqualitiesX, reportUnsolvedEqualities )
import GHC.Tc.Gen.Sig
import GHC.Tc.Utils.Monad
import GHC.Tc.Validity
import GHC.Tc.Utils.Zonk
import GHC.Tc.Utils.TcMType
import GHC.Tc.Utils.TcType
import GHC.Tc.Types.Constraint
import GHC.Tc.Types.Origin
import GHC.Tc.TyCl.Build
import GHC.Tc.Utils.Instantiate
import GHC.Tc.Instance.Class( AssocInstInfo(..), isNotAssociated )
import GHC.Core.Multiplicity
import GHC.Core.InstEnv
import GHC.Tc.Instance.Family
import GHC.Core.FamInstEnv
import GHC.Tc.Deriv
import GHC.Tc.Utils.Env
import GHC.Tc.Gen.HsType
import GHC.Tc.Utils.Unify
import GHC.Core        ( Expr(..), mkApps, mkVarApps, mkLams )
import GHC.Core.Make   ( nO_METHOD_BINDING_ERROR_ID )
import GHC.Core.Unfold.Make ( mkInlineUnfoldingWithArity, mkDFunUnfolding )
import GHC.Core.Type
import GHC.Core.SimpleOpt
import GHC.Core.Predicate( classMethodInstTy )
import GHC.Tc.Types.Evidence
import GHC.Core.TyCon
import GHC.Core.Coercion.Axiom
import GHC.Core.DataCon
import GHC.Core.ConLike
import GHC.Core.Class
import GHC.Types.Var as Var
import GHC.Types.Var.Env
import GHC.Types.Var.Set
import GHC.Data.Bag
import GHC.Types.Basic
import GHC.Types.Fixity
import GHC.Driver.Session
import GHC.Driver.Ppr
import GHC.Utils.Error
import GHC.Data.FastString
import GHC.Types.Id
import GHC.Types.SourceText
import GHC.Data.List.SetOps
import GHC.Types.Name
import GHC.Types.Name.Set
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Types.SrcLoc
import GHC.Utils.Misc
import GHC.Data.BooleanFormula ( isUnsatisfied, pprBooleanFormulaNice )
import qualified GHC.LanguageExtensions as LangExt

import Control.Monad
import Data.Tuple
import GHC.Data.Maybe
import Data.List( mapAccumL )


{-
Typechecking instance declarations is done in two passes. The first
pass, made by @tcInstDecls1@, collects information to be used in the
second pass.

This pre-processed info includes the as-yet-unprocessed bindings
inside the instance declaration.  These are type-checked in the second
pass, when the class-instance envs and GVE contain all the info from
all the instance and value decls.  Indeed that's the reason we need
two passes over the instance decls.


Note [How instance declarations are translated]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Here is how we translate instance declarations into Core

Running example:
        class C a where
           op1, op2 :: Ix b => a -> b -> b
           op2 = <dm-rhs>

        instance C a => C [a]
           {-# INLINE [2] op1 #-}
           op1 = <rhs>
===>
        -- Method selectors
        op1,op2 :: forall a. C a => forall b. Ix b => a -> b -> b
        op1 = ...
        op2 = ...

        -- Default methods get the 'self' dictionary as argument
        -- so they can call other methods at the same type
        -- Default methods get the same type as their method selector
        $dmop2 :: forall a. C a => forall b. Ix b => a -> b -> b
        $dmop2 = /\a. \(d:C a). /\b. \(d2: Ix b). <dm-rhs>
               -- NB: type variables 'a' and 'b' are *both* in scope in <dm-rhs>
               -- Note [Tricky type variable scoping]

        -- A top-level definition for each instance method
        -- Here op1_i, op2_i are the "instance method Ids"
        -- The INLINE pragma comes from the user pragma
        {-# INLINE [2] op1_i #-}  -- From the instance decl bindings
        op1_i, op2_i :: forall a. C a => forall b. Ix b => [a] -> b -> b
        op1_i = /\a. \(d:C a).
               let this :: C [a]
                   this = df_i a d
                     -- Note [Subtle interaction of recursion and overlap]

                   local_op1 :: forall b. Ix b => [a] -> b -> b
                   local_op1 = <rhs>
                     -- Source code; run the type checker on this
                     -- NB: Type variable 'a' (but not 'b') is in scope in <rhs>
                     -- Note [Tricky type variable scoping]

               in local_op1 a d

        op2_i = /\a \d:C a. $dmop2 [a] (df_i a d)

        -- The dictionary function itself
        {-# NOINLINE CONLIKE df_i #-}   -- Never inline dictionary functions
        df_i :: forall a. C a -> C [a]
        df_i = /\a. \d:C a. MkC (op1_i a d) (op2_i a d)
                -- But see Note [Default methods in instances]
                -- We can't apply the type checker to the default-method call

        -- Use a RULE to short-circuit applications of the class ops
        {-# RULE "op1@C[a]" forall a, d:C a.
                            op1 [a] (df_i d) = op1_i a d #-}

Note [Instances and loop breakers]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Note that df_i may be mutually recursive with both op1_i and op2_i.
  It's crucial that df_i is not chosen as the loop breaker, even
  though op1_i has a (user-specified) INLINE pragma.

* Instead the idea is to inline df_i into op1_i, which may then select
  methods from the MkC record, and thereby break the recursion with
  df_i, leaving a *self*-recursive op1_i.  (If op1_i doesn't call op at
  the same type, it won't mention df_i, so there won't be recursion in
  the first place.)

* If op1_i is marked INLINE by the user there's a danger that we won't
  inline df_i in it, and that in turn means that (since it'll be a
  loop-breaker because df_i isn't), op1_i will ironically never be
  inlined.  But this is OK: the recursion breaking happens by way of
  a RULE (the magic ClassOp rule above), and RULES work inside InlineRule
  unfoldings. See Note [RULEs enabled in InitialPhase] in GHC.Core.Opt.Simplify.Utils

Note [ClassOp/DFun selection]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
One thing we see a lot is stuff like
    op2 (df d1 d2)
where 'op2' is a ClassOp and 'df' is DFun.  Now, we could inline *both*
'op2' and 'df' to get
     case (MkD ($cop1 d1 d2) ($cop2 d1 d2) ... of
       MkD _ op2 _ _ _ -> op2
And that will reduce to ($cop2 d1 d2) which is what we wanted.

But it's tricky to make this work in practice, because it requires us to
inline both 'op2' and 'df'.  But neither is keen to inline without having
seen the other's result; and it's very easy to get code bloat (from the
big intermediate) if you inline a bit too much.

Instead we use a cunning trick.
 * We arrange that 'df' and 'op2' NEVER inline.

 * We arrange that 'df' is ALWAYS defined in the sylised form
      df d1 d2 = MkD ($cop1 d1 d2) ($cop2 d1 d2) ...

 * We give 'df' a magical unfolding (DFunUnfolding [$cop1, $cop2, ..])
   that lists its methods.

 * We make GHC.Core.Unfold.exprIsConApp_maybe spot a DFunUnfolding and return
   a suitable constructor application -- inlining df "on the fly" as it
   were.

 * ClassOp rules: We give the ClassOp 'op2' a BuiltinRule that
   extracts the right piece iff its argument satisfies
   exprIsConApp_maybe.  This is done in GHC.Types.Id.Make.mkDictSelId

 * We make 'df' CONLIKE, so that shared uses still match; eg
      let d = df d1 d2
      in ...(op2 d)...(op1 d)...

Note [Single-method classes]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If the class has just one method (or, more accurately, just one element
of {superclasses + methods}), then we use a different strategy.

   class C a where op :: a -> a
   instance C a => C [a] where op = <blah>

We translate the class decl into a newtype, which just gives a
top-level axiom. The "constructor" MkC expands to a cast, as does the
class-op selector.

   axiom Co:C a :: C a ~ (a->a)

   op :: forall a. C a -> (a -> a)
   op a d = d |> (Co:C a)

   MkC :: forall a. (a->a) -> C a
   MkC = /\a.\op. op |> (sym Co:C a)

The clever RULE stuff doesn't work now, because ($df a d) isn't
a constructor application, so exprIsConApp_maybe won't return
Just <blah>.

Instead, we simply rely on the fact that casts are cheap:

   $df :: forall a. C a => C [a]
   {-# INLINE df #-}  -- NB: INLINE this
   $df = /\a. \d. MkC [a] ($cop_list a d)
       = $cop_list |> forall a. C a -> (sym (Co:C [a]))

   $cop_list :: forall a. C a => [a] -> [a]
   $cop_list = <blah>

So if we see
   (op ($df a d))
we'll inline 'op' and '$df', since both are simply casts, and
good things happen.

Why do we use this different strategy?  Because otherwise we
end up with non-inlined dictionaries that look like
    $df = $cop |> blah
which adds an extra indirection to every use, which seems stupid.  See
#4138 for an example (although the regression reported there
wasn't due to the indirection).

There is an awkward wrinkle though: we want to be very
careful when we have
    instance C a => C [a] where
      {-# INLINE op #-}
      op = ...
then we'll get an INLINE pragma on $cop_list but it's important that
$cop_list only inlines when it's applied to *two* arguments (the
dictionary and the list argument).  So we must not eta-expand $df
above.  We ensure that this doesn't happen by putting an INLINE
pragma on the dfun itself; after all, it ends up being just a cast.

There is one more dark corner to the INLINE story, even more deeply
buried.  Consider this (#3772):

    class DeepSeq a => C a where
      gen :: Int -> a

    instance C a => C [a] where
      gen n = ...

    class DeepSeq a where
      deepSeq :: a -> b -> b

    instance DeepSeq a => DeepSeq [a] where
      {-# INLINE deepSeq #-}
      deepSeq xs b = foldr deepSeq b xs

That gives rise to these defns:

    $cdeepSeq :: DeepSeq a -> [a] -> b -> b
    -- User INLINE( 3 args )!
    $cdeepSeq a (d:DS a) b (x:[a]) (y:b) = ...

    $fDeepSeq[] :: DeepSeq a -> DeepSeq [a]
    -- DFun (with auto INLINE pragma)
    $fDeepSeq[] a d = $cdeepSeq a d |> blah

    $cp1 a d :: C a => DeepSep [a]
    -- We don't want to eta-expand this, lest
    -- $cdeepSeq gets inlined in it!
    $cp1 a d = $fDeepSep[] a (scsel a d)

    $fC[] :: C a => C [a]
    -- Ordinary DFun
    $fC[] a d = MkC ($cp1 a d) ($cgen a d)

Here $cp1 is the code that generates the superclass for C [a].  The
issue is this: we must not eta-expand $cp1 either, or else $fDeepSeq[]
and then $cdeepSeq will inline there, which is definitely wrong.  Like
on the dfun, we solve this by adding an INLINE pragma to $cp1.

Note [Subtle interaction of recursion and overlap]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this
  class C a where { op1,op2 :: a -> a }
  instance C a => C [a] where
    op1 x = op2 x ++ op2 x
    op2 x = ...
  instance C [Int] where
    ...

When type-checking the C [a] instance, we need a C [a] dictionary (for
the call of op2).  If we look up in the instance environment, we find
an overlap.  And in *general* the right thing is to complain (see Note
[Overlapping instances] in GHC.Core.InstEnv).  But in *this* case it's wrong to
complain, because we just want to delegate to the op2 of this same
instance.

Why is this justified?  Because we generate a (C [a]) constraint in
a context in which 'a' cannot be instantiated to anything that matches
other overlapping instances, or else we would not be executing this
version of op1 in the first place.

It might even be a bit disguised:

  nullFail :: C [a] => [a] -> [a]
  nullFail x = op2 x ++ op2 x

  instance C a => C [a] where
    op1 x = nullFail x

Precisely this is used in package 'regex-base', module Context.hs.
See the overlapping instances for RegexContext, and the fact that they
call 'nullFail' just like the example above.  The DoCon package also
does the same thing; it shows up in module Fraction.hs.

Conclusion: when typechecking the methods in a C [a] instance, we want to
treat the 'a' as an *existential* type variable, in the sense described
by Note [Binding when looking up instances].  That is why isOverlappableTyVar
responds True to an InstSkol, which is the kind of skolem we use in
tcInstDecl2.


Note [Tricky type variable scoping]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In our example
        class C a where
           op1, op2 :: Ix b => a -> b -> b
           op2 = <dm-rhs>

        instance C a => C [a]
           {-# INLINE [2] op1 #-}
           op1 = <rhs>

note that 'a' and 'b' are *both* in scope in <dm-rhs>, but only 'a' is
in scope in <rhs>.  In particular, we must make sure that 'b' is in
scope when typechecking <dm-rhs>.  This is achieved by subFunTys,
which brings appropriate tyvars into scope. This happens for both
<dm-rhs> and for <rhs>, but that doesn't matter: the *renamer* will have
complained if 'b' is mentioned in <rhs>.



************************************************************************
*                                                                      *
\subsection{Extracting instance decls}
*                                                                      *
************************************************************************

Gather up the instance declarations from their various sources
-}

tcInstDecls1    -- Deal with both source-code and imported instance decls
   :: [LInstDecl GhcRn]         -- Source code instance decls
   -> TcM (TcGblEnv,            -- The full inst env
           [InstInfo GhcRn],    -- Source-code instance decls to process;
                                -- contains all dfuns for this module
           [DerivInfo])         -- From data family instances

tcInstDecls1 :: [LInstDecl GhcRn] -> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
tcInstDecls1 [LInstDecl GhcRn]
inst_decls
  = do {    -- Do class and family instance declarations
       ; [([InstInfo GhcRn], [FamInst], [DerivInfo])]
stuff <- (Located (InstDecl GhcRn)
 -> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo]))
-> [Located (InstDecl GhcRn)]
-> TcRn [([InstInfo GhcRn], [FamInst], [DerivInfo])]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndRecoverM Located (InstDecl GhcRn)
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
LInstDecl GhcRn -> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
tcLocalInstDecl [Located (InstDecl GhcRn)]
[LInstDecl GhcRn]
inst_decls

       ; let ([[InstInfo GhcRn]]
local_infos_s, [[FamInst]]
fam_insts_s, [[DerivInfo]]
datafam_deriv_infos) = [([InstInfo GhcRn], [FamInst], [DerivInfo])]
-> ([[InstInfo GhcRn]], [[FamInst]], [[DerivInfo]])
forall a b c. [(a, b, c)] -> ([a], [b], [c])
unzip3 [([InstInfo GhcRn], [FamInst], [DerivInfo])]
stuff
             fam_insts :: [FamInst]
fam_insts   = [[FamInst]] -> [FamInst]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[FamInst]]
fam_insts_s
             local_infos :: [InstInfo GhcRn]
local_infos = [[InstInfo GhcRn]] -> [InstInfo GhcRn]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[InstInfo GhcRn]]
local_infos_s

       ; TcGblEnv
gbl_env <- [InstInfo GhcRn] -> TcM TcGblEnv -> TcM TcGblEnv
forall a. [InstInfo GhcRn] -> TcM a -> TcM a
addClsInsts [InstInfo GhcRn]
local_infos (TcM TcGblEnv -> TcM TcGblEnv) -> TcM TcGblEnv -> TcM TcGblEnv
forall a b. (a -> b) -> a -> b
$
                    [FamInst] -> TcM TcGblEnv -> TcM TcGblEnv
forall a. [FamInst] -> TcM a -> TcM a
addFamInsts [FamInst]
fam_insts   (TcM TcGblEnv -> TcM TcGblEnv) -> TcM TcGblEnv -> TcM TcGblEnv
forall a b. (a -> b) -> a -> b
$
                    TcM TcGblEnv
forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv

       ; (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo GhcRn], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return ( TcGblEnv
gbl_env
                , [InstInfo GhcRn]
local_infos
                , [[DerivInfo]] -> [DerivInfo]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[DerivInfo]]
datafam_deriv_infos ) }

-- | Use DerivInfo for data family instances (produced by tcInstDecls1),
--   datatype declarations (TyClDecl), and standalone deriving declarations
--   (DerivDecl) to check and process all derived class instances.
tcInstDeclsDeriv
  :: [DerivInfo]
  -> [LDerivDecl GhcRn]
  -> TcM (TcGblEnv, [InstInfo GhcRn], HsValBinds GhcRn)
tcInstDeclsDeriv :: [DerivInfo]
-> [LDerivDecl GhcRn]
-> TcM (TcGblEnv, [InstInfo GhcRn], HsValBinds GhcRn)
tcInstDeclsDeriv [DerivInfo]
deriv_infos [LDerivDecl GhcRn]
derivds
  = do ThStage
th_stage <- TcM ThStage
getStage -- See Note [Deriving inside TH brackets]
       if ThStage -> Bool
isBrackStage ThStage
th_stage
       then do { TcGblEnv
gbl_env <- TcM TcGblEnv
forall gbl lcl. TcRnIf gbl lcl gbl
getGblEnv
               ; (TcGblEnv, [InstInfo GhcRn], HsValBinds GhcRn)
-> TcM (TcGblEnv, [InstInfo GhcRn], HsValBinds GhcRn)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcGblEnv
gbl_env, Bag (InstInfo GhcRn) -> [InstInfo GhcRn]
forall a. Bag a -> [a]
bagToList Bag (InstInfo GhcRn)
forall a. Bag a
emptyBag, HsValBinds GhcRn
forall (a :: Pass) (b :: Pass).
HsValBindsLR (GhcPass a) (GhcPass b)
emptyValBindsOut) }
       else do { (TcGblEnv
tcg_env, Bag (InstInfo GhcRn)
info_bag, HsValBinds GhcRn
valbinds) <- [DerivInfo]
-> [LDerivDecl GhcRn]
-> TcM (TcGblEnv, Bag (InstInfo GhcRn), HsValBinds GhcRn)
tcDeriving [DerivInfo]
deriv_infos [LDerivDecl GhcRn]
derivds
               ; (TcGblEnv, [InstInfo GhcRn], HsValBinds GhcRn)
-> TcM (TcGblEnv, [InstInfo GhcRn], HsValBinds GhcRn)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcGblEnv
tcg_env, Bag (InstInfo GhcRn) -> [InstInfo GhcRn]
forall a. Bag a -> [a]
bagToList Bag (InstInfo GhcRn)
info_bag, HsValBinds GhcRn
valbinds) }

addClsInsts :: [InstInfo GhcRn] -> TcM a -> TcM a
addClsInsts :: [InstInfo GhcRn] -> TcM a -> TcM a
addClsInsts [InstInfo GhcRn]
infos TcM a
thing_inside
  = [ClsInst] -> TcM a -> TcM a
forall a. [ClsInst] -> TcM a -> TcM a
tcExtendLocalInstEnv ((InstInfo GhcRn -> ClsInst) -> [InstInfo GhcRn] -> [ClsInst]
forall a b. (a -> b) -> [a] -> [b]
map InstInfo GhcRn -> ClsInst
forall a. InstInfo a -> ClsInst
iSpec [InstInfo GhcRn]
infos) TcM a
thing_inside

addFamInsts :: [FamInst] -> TcM a -> TcM a
-- Extend (a) the family instance envt
--        (b) the type envt with stuff from data type decls
addFamInsts :: [FamInst] -> TcM a -> TcM a
addFamInsts [FamInst]
fam_insts TcM a
thing_inside
  = [FamInst] -> TcM a -> TcM a
forall a. [FamInst] -> TcM a -> TcM a
tcExtendLocalFamInstEnv [FamInst]
fam_insts (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    [TyThing] -> TcM a -> TcM a
forall r. [TyThing] -> TcM r -> TcM r
tcExtendGlobalEnv [TyThing]
axioms          (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"addFamInsts" ([FamInst] -> SDoc
pprFamInsts [FamInst]
fam_insts)
       ; TcGblEnv
gbl_env <- [TyCon] -> TcM TcGblEnv
addTyConsToGblEnv [TyCon]
data_rep_tycons
                    -- Does not add its axiom; that comes
                    -- from adding the 'axioms' above
       ; TcGblEnv -> TcM a -> TcM a
forall gbl lcl a. gbl -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setGblEnv TcGblEnv
gbl_env TcM a
thing_inside }
  where
    axioms :: [TyThing]
axioms = (FamInst -> TyThing) -> [FamInst] -> [TyThing]
forall a b. (a -> b) -> [a] -> [b]
map (CoAxiom Branched -> TyThing
ACoAxiom (CoAxiom Branched -> TyThing)
-> (FamInst -> CoAxiom Branched) -> FamInst -> TyThing
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CoAxiom Unbranched -> CoAxiom Branched
forall (br :: BranchFlag). CoAxiom br -> CoAxiom Branched
toBranchedAxiom (CoAxiom Unbranched -> CoAxiom Branched)
-> (FamInst -> CoAxiom Unbranched) -> FamInst -> CoAxiom Branched
forall b c a. (b -> c) -> (a -> b) -> a -> c
. FamInst -> CoAxiom Unbranched
famInstAxiom) [FamInst]
fam_insts
    data_rep_tycons :: [TyCon]
data_rep_tycons = [FamInst] -> [TyCon]
famInstsRepTyCons [FamInst]
fam_insts
      -- The representation tycons for 'data instances' declarations

{-
Note [Deriving inside TH brackets]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given a declaration bracket
  [d| data T = A | B deriving( Show ) |]

there is really no point in generating the derived code for deriving(
Show) and then type-checking it. This will happen at the call site
anyway, and the type check should never fail!  Moreover (#6005)
the scoping of the generated code inside the bracket does not seem to
work out.

The easy solution is simply not to generate the derived instances at
all.  (A less brutal solution would be to generate them with no
bindings.)  This will become moot when we shift to the new TH plan, so
the brutal solution will do.
-}

tcLocalInstDecl :: LInstDecl GhcRn
                -> TcM ([InstInfo GhcRn], [FamInst], [DerivInfo])
        -- A source-file instance declaration
        -- Type-check all the stuff before the "where"
        --
        -- We check for respectable instance type, and context
tcLocalInstDecl :: LInstDecl GhcRn -> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
tcLocalInstDecl (L loc (TyFamInstD { tfid_inst = decl }))
  = do { FamInst
fam_inst <- AssocInstInfo -> LTyFamInstDecl GhcRn -> TcM FamInst
tcTyFamInstDecl AssocInstInfo
NotAssociated (SrcSpan
-> TyFamInstDecl GhcRn -> GenLocated SrcSpan (TyFamInstDecl GhcRn)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc TyFamInstDecl GhcRn
decl)
       ; ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return ([], [FamInst
fam_inst], []) }

tcLocalInstDecl (L loc (DataFamInstD { dfid_inst = decl }))
  = do { (FamInst
fam_inst, Maybe DerivInfo
m_deriv_info) <- AssocInstInfo
-> TyVarEnv Name
-> LDataFamInstDecl GhcRn
-> TcM (FamInst, Maybe DerivInfo)
tcDataFamInstDecl AssocInstInfo
NotAssociated TyVarEnv Name
forall a. VarEnv a
emptyVarEnv (SrcSpan
-> DataFamInstDecl GhcRn
-> GenLocated SrcSpan (DataFamInstDecl GhcRn)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc DataFamInstDecl GhcRn
decl)
       ; ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return ([], [FamInst
fam_inst], Maybe DerivInfo -> [DerivInfo]
forall a. Maybe a -> [a]
maybeToList Maybe DerivInfo
m_deriv_info) }

tcLocalInstDecl (L loc (ClsInstD { cid_inst = decl }))
  = do { ([InstInfo GhcRn]
insts, [FamInst]
fam_insts, [DerivInfo]
deriv_infos) <- LClsInstDecl GhcRn
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
tcClsInstDecl (SrcSpan
-> ClsInstDecl GhcRn -> GenLocated SrcSpan (ClsInstDecl GhcRn)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc ClsInstDecl GhcRn
decl)
       ; ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return ([InstInfo GhcRn]
insts, [FamInst]
fam_insts, [DerivInfo]
deriv_infos) }

tcClsInstDecl :: LClsInstDecl GhcRn
              -> TcM ([InstInfo GhcRn], [FamInst], [DerivInfo])
-- The returned DerivInfos are for any associated data families
tcClsInstDecl :: LClsInstDecl GhcRn
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
tcClsInstDecl (L loc (ClsInstDecl { cid_poly_ty = hs_ty, cid_binds = binds
                                  , cid_sigs = uprags, cid_tyfam_insts = ats
                                  , cid_overlap_mode = overlap_mode
                                  , cid_datafam_insts = adts }))
  = SrcSpan
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc                      (TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
 -> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo]))
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall a b. (a -> b) -> a -> b
$
    SDoc
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (LHsSigType GhcRn -> SDoc
instDeclCtxt1 LHsSigType GhcRn
hs_ty)  (TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
 -> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo]))
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall a b. (a -> b) -> a -> b
$
    do  { Type
dfun_ty <- UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsClsInstType (Bool -> UserTypeCtxt
InstDeclCtxt Bool
False) LHsSigType GhcRn
hs_ty
        ; let ([TyVar]
tyvars, [Type]
theta, Class
clas, [Type]
inst_tys) = Type -> ([TyVar], [Type], Class, [Type])
tcSplitDFunTy Type
dfun_ty
             -- NB: tcHsClsInstType does checkValidInstance

        ; (TCvSubst
subst, [TyVar]
skol_tvs) <- [TyVar] -> TcM (TCvSubst, [TyVar])
tcInstSkolTyVars [TyVar]
tyvars
        ; let tv_skol_prs :: [(Name, TyVar)]
tv_skol_prs = [ (TyVar -> Name
tyVarName TyVar
tv, TyVar
skol_tv)
                            | (TyVar
tv, TyVar
skol_tv) <- [TyVar]
tyvars [TyVar] -> [TyVar] -> [(TyVar, TyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TyVar]
skol_tvs ]
              -- Map from the skolemized Names to the original Names.
              -- See Note [Associated data family instances and di_scoped_tvs].
              tv_skol_env :: TyVarEnv Name
tv_skol_env = [(TyVar, Name)] -> TyVarEnv Name
forall a. [(TyVar, a)] -> VarEnv a
mkVarEnv ([(TyVar, Name)] -> TyVarEnv Name)
-> [(TyVar, Name)] -> TyVarEnv Name
forall a b. (a -> b) -> a -> b
$ ((Name, TyVar) -> (TyVar, Name))
-> [(Name, TyVar)] -> [(TyVar, Name)]
forall a b. (a -> b) -> [a] -> [b]
map (Name, TyVar) -> (TyVar, Name)
forall a b. (a, b) -> (b, a)
swap [(Name, TyVar)]
tv_skol_prs
              n_inferred :: Int
n_inferred = (VarBndr TyVar ArgFlag -> Bool) -> [VarBndr TyVar ArgFlag] -> Int
forall a. (a -> Bool) -> [a] -> Int
countWhile ((ArgFlag -> ArgFlag -> Bool
forall a. Eq a => a -> a -> Bool
== ArgFlag
Inferred) (ArgFlag -> Bool)
-> (VarBndr TyVar ArgFlag -> ArgFlag)
-> VarBndr TyVar ArgFlag
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. VarBndr TyVar ArgFlag -> ArgFlag
forall tv argf. VarBndr tv argf -> argf
binderArgFlag) ([VarBndr TyVar ArgFlag] -> Int) -> [VarBndr TyVar ArgFlag] -> Int
forall a b. (a -> b) -> a -> b
$
                           ([VarBndr TyVar ArgFlag], Type) -> [VarBndr TyVar ArgFlag]
forall a b. (a, b) -> a
fst (([VarBndr TyVar ArgFlag], Type) -> [VarBndr TyVar ArgFlag])
-> ([VarBndr TyVar ArgFlag], Type) -> [VarBndr TyVar ArgFlag]
forall a b. (a -> b) -> a -> b
$ Type -> ([VarBndr TyVar ArgFlag], Type)
splitForAllTyCoVarBinders Type
dfun_ty
              visible_skol_tvs :: [TyVar]
visible_skol_tvs = Int -> [TyVar] -> [TyVar]
forall a. Int -> [a] -> [a]
drop Int
n_inferred [TyVar]
skol_tvs

        ; String -> SDoc -> TcRn ()
traceTc String
"tcLocalInstDecl 1" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
dfun_ty SDoc -> SDoc -> SDoc
$$ Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Type -> Int
invisibleTyBndrCount Type
dfun_ty) SDoc -> SDoc -> SDoc
$$ [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
skol_tvs)

        -- Next, process any associated types.
        ; ([(FamInst, Maybe DerivInfo)]
datafam_stuff, [FamInst]
tyfam_insts)
             <- [(Name, TyVar)]
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
tv_skol_prs (TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
 -> TcM ([(FamInst, Maybe DerivInfo)], [FamInst]))
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
forall a b. (a -> b) -> a -> b
$
                do  { let mini_env :: VarEnv Type
mini_env   = [(TyVar, Type)] -> VarEnv Type
forall a. [(TyVar, a)] -> VarEnv a
mkVarEnv (Class -> [TyVar]
classTyVars Class
clas [TyVar] -> [Type] -> [(TyVar, Type)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` HasCallStack => TCvSubst -> [Type] -> [Type]
TCvSubst -> [Type] -> [Type]
substTys TCvSubst
subst [Type]
inst_tys)
                          mini_subst :: TCvSubst
mini_subst = InScopeSet -> VarEnv Type -> TCvSubst
mkTvSubst (VarSet -> InScopeSet
mkInScopeSet ([TyVar] -> VarSet
mkVarSet [TyVar]
skol_tvs)) VarEnv Type
mini_env
                          mb_info :: AssocInstInfo
mb_info    = InClsInst :: Class -> [TyVar] -> VarEnv Type -> AssocInstInfo
InClsInst { ai_class :: Class
ai_class = Class
clas
                                                 , ai_tyvars :: [TyVar]
ai_tyvars = [TyVar]
visible_skol_tvs
                                                 , ai_inst_env :: VarEnv Type
ai_inst_env = VarEnv Type
mini_env }
                    ; [(FamInst, Maybe DerivInfo)]
df_stuff  <- (GenLocated SrcSpan (DataFamInstDecl GhcRn)
 -> TcM (FamInst, Maybe DerivInfo))
-> [GenLocated SrcSpan (DataFamInstDecl GhcRn)]
-> TcRn [(FamInst, Maybe DerivInfo)]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndRecoverM (AssocInstInfo
-> TyVarEnv Name
-> LDataFamInstDecl GhcRn
-> TcM (FamInst, Maybe DerivInfo)
tcDataFamInstDecl AssocInstInfo
mb_info TyVarEnv Name
tv_skol_env) [GenLocated SrcSpan (DataFamInstDecl GhcRn)]
[LDataFamInstDecl GhcRn]
adts
                    ; [FamInst]
tf_insts1 <- (GenLocated SrcSpan (TyFamInstDecl GhcRn) -> TcM FamInst)
-> [GenLocated SrcSpan (TyFamInstDecl GhcRn)] -> TcRn [FamInst]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndRecoverM (AssocInstInfo -> LTyFamInstDecl GhcRn -> TcM FamInst
tcTyFamInstDecl AssocInstInfo
mb_info)   [GenLocated SrcSpan (TyFamInstDecl GhcRn)]
[LTyFamInstDecl GhcRn]
ats

                      -- Check for missing associated types and build them
                      -- from their defaults (if available)
                    ; Bool
is_boot <- TcRn Bool
tcIsHsBootOrSig
                    ; let atItems :: [ClassATItem]
atItems = Class -> [ClassATItem]
classATItems Class
clas
                    ; [[FamInst]]
tf_insts2 <- (ClassATItem -> TcRn [FamInst])
-> [ClassATItem] -> IOEnv (Env TcGblEnv TcLclEnv) [[FamInst]]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (SrcSpan -> TCvSubst -> NameSet -> ClassATItem -> TcRn [FamInst]
tcATDefault SrcSpan
loc TCvSubst
mini_subst NameSet
defined_ats)
                                        (if Bool
is_boot then [] else [ClassATItem]
atItems)
                      -- Don't default type family instances, but rather omit, in hsig/hs-boot.
                      -- Since hsig/hs-boot files are essentially large binders we want omission
                      -- of the definition to result in no restriction, rather than for example
                      -- attempting to "pattern match" with the invisible defaults and generate
                      -- equalities. Without further handling, this would just result in a panic
                      -- anyway.
                      -- See https://github.com/ghc-proposals/ghc-proposals/pull/320 for
                      -- additional discussion.
                    ; ([(FamInst, Maybe DerivInfo)], [FamInst])
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
forall (m :: * -> *) a. Monad m => a -> m a
return ([(FamInst, Maybe DerivInfo)]
df_stuff, [FamInst]
tf_insts1 [FamInst] -> [FamInst] -> [FamInst]
forall a. [a] -> [a] -> [a]
++ [[FamInst]] -> [FamInst]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[FamInst]]
tf_insts2) }


        -- Finally, construct the Core representation of the instance.
        -- (This no longer includes the associated types.)
        ; Name
dfun_name <- Class -> [Type] -> SrcSpan -> TcM Name
newDFunName Class
clas [Type]
inst_tys (LHsSigType GhcRn -> SrcSpan
forall l e. GenLocated l e -> l
getLoc LHsSigType GhcRn
hs_ty)
                -- Dfun location is that of instance *header*

        ; ClsInst
ispec <- Maybe OverlapMode
-> Name -> [TyVar] -> [Type] -> Class -> [Type] -> TcM ClsInst
newClsInst ((GenLocated SrcSpan OverlapMode -> OverlapMode)
-> Maybe (GenLocated SrcSpan OverlapMode) -> Maybe OverlapMode
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap GenLocated SrcSpan OverlapMode -> OverlapMode
forall l e. GenLocated l e -> e
unLoc Maybe (GenLocated SrcSpan OverlapMode)
Maybe (XRec GhcRn OverlapMode)
overlap_mode) Name
dfun_name
                              [TyVar]
tyvars [Type]
theta Class
clas [Type]
inst_tys

        ; let inst_binds :: InstBindings GhcRn
inst_binds = InstBindings :: forall a.
[Name]
-> LHsBinds a -> [LSig a] -> [Extension] -> Bool -> InstBindings a
InstBindings
                             { ib_binds :: LHsBinds GhcRn
ib_binds = LHsBinds GhcRn
binds
                             , ib_tyvars :: [Name]
ib_tyvars = (TyVar -> Name) -> [TyVar] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Name
Var.varName [TyVar]
tyvars -- Scope over bindings
                             , ib_pragmas :: [LSig GhcRn]
ib_pragmas = [LSig GhcRn]
uprags
                             , ib_extensions :: [Extension]
ib_extensions = []
                             , ib_derived :: Bool
ib_derived = Bool
False }
              inst_info :: InstInfo GhcRn
inst_info = InstInfo :: forall a. ClsInst -> InstBindings a -> InstInfo a
InstInfo { iSpec :: ClsInst
iSpec  = ClsInst
ispec, iBinds :: InstBindings GhcRn
iBinds = InstBindings GhcRn
inst_binds }

              ([FamInst]
datafam_insts, [Maybe DerivInfo]
m_deriv_infos) = [(FamInst, Maybe DerivInfo)] -> ([FamInst], [Maybe DerivInfo])
forall a b. [(a, b)] -> ([a], [b])
unzip [(FamInst, Maybe DerivInfo)]
datafam_stuff
              deriv_infos :: [DerivInfo]
deriv_infos                    = [Maybe DerivInfo] -> [DerivInfo]
forall a. [Maybe a] -> [a]
catMaybes [Maybe DerivInfo]
m_deriv_infos
              all_insts :: [FamInst]
all_insts                      = [FamInst]
tyfam_insts [FamInst] -> [FamInst] -> [FamInst]
forall a. [a] -> [a] -> [a]
++ [FamInst]
datafam_insts

         -- In hs-boot files there should be no bindings
        ; let no_binds :: Bool
no_binds = LHsBinds GhcRn -> Bool
forall (idL :: Pass) idR. LHsBindsLR (GhcPass idL) idR -> Bool
isEmptyLHsBinds LHsBinds GhcRn
binds Bool -> Bool -> Bool
&& [Located (Sig GhcRn)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Located (Sig GhcRn)]
[LSig GhcRn]
uprags
        ; Bool
is_boot <- TcRn Bool
tcIsHsBootOrSig
        ; Bool -> SDoc -> TcRn ()
failIfTc (Bool
is_boot Bool -> Bool -> Bool
&& Bool -> Bool
not Bool
no_binds) SDoc
badBootDeclErr

        ; ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return ( [InstInfo GhcRn
inst_info], [FamInst]
all_insts, [DerivInfo]
deriv_infos ) }
  where
    defined_ats :: NameSet
defined_ats = [Name] -> NameSet
mkNameSet ((GenLocated SrcSpan (TyFamInstDecl GhcRn) -> Name)
-> [GenLocated SrcSpan (TyFamInstDecl GhcRn)] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (TyFamInstDecl GhcRn -> Name
forall (p :: Pass). TyFamInstDecl (GhcPass p) -> IdP (GhcPass p)
tyFamInstDeclName (TyFamInstDecl GhcRn -> Name)
-> (GenLocated SrcSpan (TyFamInstDecl GhcRn)
    -> TyFamInstDecl GhcRn)
-> GenLocated SrcSpan (TyFamInstDecl GhcRn)
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpan (TyFamInstDecl GhcRn) -> TyFamInstDecl GhcRn
forall l e. GenLocated l e -> e
unLoc) [GenLocated SrcSpan (TyFamInstDecl GhcRn)]
[LTyFamInstDecl GhcRn]
ats)
                  NameSet -> NameSet -> NameSet
`unionNameSet`
                  [Name] -> NameSet
mkNameSet ((GenLocated SrcSpan (DataFamInstDecl GhcRn) -> Name)
-> [GenLocated SrcSpan (DataFamInstDecl GhcRn)] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (GenLocated SrcSpan Name -> Name
forall l e. GenLocated l e -> e
unLoc (GenLocated SrcSpan Name -> Name)
-> (GenLocated SrcSpan (DataFamInstDecl GhcRn)
    -> GenLocated SrcSpan Name)
-> GenLocated SrcSpan (DataFamInstDecl GhcRn)
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. FamEqn GhcRn (HsDataDefn GhcRn) -> GenLocated SrcSpan Name
forall pass rhs. FamEqn pass rhs -> LIdP pass
feqn_tycon
                                        (FamEqn GhcRn (HsDataDefn GhcRn) -> GenLocated SrcSpan Name)
-> (GenLocated SrcSpan (DataFamInstDecl GhcRn)
    -> FamEqn GhcRn (HsDataDefn GhcRn))
-> GenLocated SrcSpan (DataFamInstDecl GhcRn)
-> GenLocated SrcSpan Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. DataFamInstDecl GhcRn -> FamEqn GhcRn (HsDataDefn GhcRn)
forall pass. DataFamInstDecl pass -> FamEqn pass (HsDataDefn pass)
dfid_eqn
                                        (DataFamInstDecl GhcRn -> FamEqn GhcRn (HsDataDefn GhcRn))
-> (GenLocated SrcSpan (DataFamInstDecl GhcRn)
    -> DataFamInstDecl GhcRn)
-> GenLocated SrcSpan (DataFamInstDecl GhcRn)
-> FamEqn GhcRn (HsDataDefn GhcRn)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpan (DataFamInstDecl GhcRn) -> DataFamInstDecl GhcRn
forall l e. GenLocated l e -> e
unLoc) [GenLocated SrcSpan (DataFamInstDecl GhcRn)]
[LDataFamInstDecl GhcRn]
adts)

{-
************************************************************************
*                                                                      *
               Type family instances
*                                                                      *
************************************************************************

Family instances are somewhat of a hybrid.  They are processed together with
class instance heads, but can contain data constructors and hence they share a
lot of kinding and type checking code with ordinary algebraic data types (and
GADTs).
-}

tcTyFamInstDecl :: AssocInstInfo
                -> LTyFamInstDecl GhcRn -> TcM FamInst
  -- "type instance"
  -- See Note [Associated type instances]
tcTyFamInstDecl :: AssocInstInfo -> LTyFamInstDecl GhcRn -> TcM FamInst
tcTyFamInstDecl AssocInstInfo
mb_clsinfo (L loc decl@(TyFamInstDecl { tfid_eqn = eqn }))
  = SrcSpan -> TcM FamInst -> TcM FamInst
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc           (TcM FamInst -> TcM FamInst) -> TcM FamInst -> TcM FamInst
forall a b. (a -> b) -> a -> b
$
    TyFamInstDecl GhcRn -> TcM FamInst -> TcM FamInst
forall a. TyFamInstDecl GhcRn -> TcM a -> TcM a
tcAddTyFamInstCtxt TyFamInstDecl GhcRn
decl  (TcM FamInst -> TcM FamInst) -> TcM FamInst -> TcM FamInst
forall a b. (a -> b) -> a -> b
$
    do { let fam_lname :: LIdP GhcRn
fam_lname = FamEqn GhcRn (Located (HsType GhcRn)) -> LIdP GhcRn
forall pass rhs. FamEqn pass rhs -> LIdP pass
feqn_tycon FamEqn GhcRn (Located (HsType GhcRn))
TyFamInstEqn GhcRn
eqn
       ; TyCon
fam_tc <- GenLocated SrcSpan Name -> TcM TyCon
tcLookupLocatedTyCon GenLocated SrcSpan Name
LIdP GhcRn
fam_lname
       ; AssocInstInfo -> TyCon -> TcRn ()
tcFamInstDeclChecks AssocInstInfo
mb_clsinfo TyCon
fam_tc

         -- (0) Check it's an open type family
       ; Bool -> SDoc -> TcRn ()
checkTc (TyCon -> Bool
isTypeFamilyTyCon TyCon
fam_tc)     (TyCon -> SDoc
wrongKindOfFamily TyCon
fam_tc)
       ; Bool -> SDoc -> TcRn ()
checkTc (TyCon -> Bool
isOpenTypeFamilyTyCon TyCon
fam_tc) (TyCon -> SDoc
notOpenFamily TyCon
fam_tc)

         -- (1) do the work of verifying the synonym group
         -- For some reason we don't have a location for the equation
         -- itself, so we make do with the location of family name
       ; KnotTied CoAxBranch
co_ax_branch <- TyCon
-> AssocInstInfo
-> LTyFamInstEqn GhcRn
-> TcM (KnotTied CoAxBranch)
tcTyFamInstEqn TyCon
fam_tc AssocInstInfo
mb_clsinfo
                                        (SrcSpan
-> FamEqn GhcRn (Located (HsType GhcRn))
-> GenLocated SrcSpan (FamEqn GhcRn (Located (HsType GhcRn)))
forall l e. l -> e -> GenLocated l e
L (GenLocated SrcSpan Name -> SrcSpan
forall l e. GenLocated l e -> l
getLoc GenLocated SrcSpan Name
LIdP GhcRn
fam_lname) FamEqn GhcRn (Located (HsType GhcRn))
TyFamInstEqn GhcRn
eqn)

         -- (2) check for validity
       ; AssocInstInfo -> TyCon -> KnotTied CoAxBranch -> TcRn ()
checkConsistentFamInst AssocInstInfo
mb_clsinfo TyCon
fam_tc KnotTied CoAxBranch
co_ax_branch
       ; TyCon -> KnotTied CoAxBranch -> TcRn ()
checkValidCoAxBranch TyCon
fam_tc KnotTied CoAxBranch
co_ax_branch

         -- (3) construct coercion axiom
       ; Name
rep_tc_name <- GenLocated SrcSpan Name -> [[Type]] -> TcM Name
newFamInstAxiomName GenLocated SrcSpan Name
LIdP GhcRn
fam_lname [KnotTied CoAxBranch -> [Type]
coAxBranchLHS KnotTied CoAxBranch
co_ax_branch]
       ; let axiom :: CoAxiom Unbranched
axiom = Name -> TyCon -> KnotTied CoAxBranch -> CoAxiom Unbranched
mkUnbranchedCoAxiom Name
rep_tc_name TyCon
fam_tc KnotTied CoAxBranch
co_ax_branch
       ; FamFlavor -> CoAxiom Unbranched -> TcM FamInst
newFamInst FamFlavor
SynFamilyInst CoAxiom Unbranched
axiom }


---------------------
tcFamInstDeclChecks :: AssocInstInfo -> TyCon -> TcM ()
-- Used for both type and data families
tcFamInstDeclChecks :: AssocInstInfo -> TyCon -> TcRn ()
tcFamInstDeclChecks AssocInstInfo
mb_clsinfo TyCon
fam_tc
  = do { -- Type family instances require -XTypeFamilies
         -- and can't (currently) be in an hs-boot file
       ; String -> SDoc -> TcRn ()
traceTc String
"tcFamInstDecl" (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc)
       ; Bool
type_families <- Extension -> TcRn Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.TypeFamilies
       ; Bool
is_boot       <- TcRn Bool
tcIsHsBootOrSig   -- Are we compiling an hs-boot file?
       ; Bool -> SDoc -> TcRn ()
checkTc Bool
type_families (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$ TyCon -> SDoc
badFamInstDecl TyCon
fam_tc
       ; Bool -> SDoc -> TcRn ()
checkTc (Bool -> Bool
not Bool
is_boot) (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$ SDoc
badBootFamInstDeclErr

       -- Check that it is a family TyCon, and that
       -- oplevel type instances are not for associated types.
       ; Bool -> SDoc -> TcRn ()
checkTc (TyCon -> Bool
isFamilyTyCon TyCon
fam_tc) (TyCon -> SDoc
notFamily TyCon
fam_tc)

       ; Bool -> TcRn () -> TcRn ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (AssocInstInfo -> Bool
isNotAssociated AssocInstInfo
mb_clsinfo Bool -> Bool -> Bool
&&   -- Not in a class decl
               TyCon -> Bool
isTyConAssoc TyCon
fam_tc)            -- but an associated type
              (SDoc -> TcRn ()
addErr (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$ TyCon -> SDoc
assocInClassErr TyCon
fam_tc)
       }

{- Note [Associated type instances]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We allow this:
  class C a where
    type T x a
  instance C Int where
    type T (S y) Int = y
    type T Z     Int = Char

Note that
  a) The variable 'x' is not bound by the class decl
  b) 'x' is instantiated to a non-type-variable in the instance
  c) There are several type instance decls for T in the instance

All this is fine.  Of course, you can't give any *more* instances
for (T ty Int) elsewhere, because it's an *associated* type.


************************************************************************
*                                                                      *
               Data family instances
*                                                                      *
************************************************************************

For some reason data family instances are a lot more complicated
than type family instances
-}

tcDataFamInstDecl ::
     AssocInstInfo
  -> TyVarEnv Name -- If this is an associated data family instance, maps the
                   -- parent class's skolemized type variables to their
                   -- original Names. If this is a non-associated instance,
                   -- this will be empty.
                   -- See Note [Associated data family instances and di_scoped_tvs].
  -> LDataFamInstDecl GhcRn -> TcM (FamInst, Maybe DerivInfo)
  -- "newtype instance" and "data instance"
tcDataFamInstDecl :: AssocInstInfo
-> TyVarEnv Name
-> LDataFamInstDecl GhcRn
-> TcM (FamInst, Maybe DerivInfo)
tcDataFamInstDecl AssocInstInfo
mb_clsinfo TyVarEnv Name
tv_skol_env
    (L loc decl@(DataFamInstDecl { dfid_eqn =
      FamEqn { feqn_bndrs  = outer_bndrs
             , feqn_pats   = hs_pats
             , feqn_tycon  = lfam_name@(L _ fam_name)
             , feqn_fixity = fixity
             , feqn_rhs    = HsDataDefn { dd_ND      = new_or_data
                                        , dd_cType   = cType
                                        , dd_ctxt    = hs_ctxt
                                        , dd_cons    = hs_cons
                                        , dd_kindSig = m_ksig
                                        , dd_derivs  = derivs } }}))
  = SrcSpan
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc             (TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo))
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a b. (a -> b) -> a -> b
$
    DataFamInstDecl GhcRn
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a. DataFamInstDecl GhcRn -> TcM a -> TcM a
tcAddDataFamInstCtxt DataFamInstDecl GhcRn
decl  (TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo))
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a b. (a -> b) -> a -> b
$
    do { TyCon
fam_tc <- GenLocated SrcSpan Name -> TcM TyCon
tcLookupLocatedTyCon GenLocated SrcSpan Name
LIdP GhcRn
lfam_name

       ; AssocInstInfo -> TyCon -> TcRn ()
tcFamInstDeclChecks AssocInstInfo
mb_clsinfo TyCon
fam_tc

       -- Check that the family declaration is for the right kind
       ; Bool -> SDoc -> TcRn ()
checkTc (TyCon -> Bool
isDataFamilyTyCon TyCon
fam_tc) (TyCon -> SDoc
wrongKindOfFamily TyCon
fam_tc)
       ; Bool
gadt_syntax <- Name
-> NewOrData -> LHsContext GhcRn -> [LConDecl GhcRn] -> TcRn Bool
dataDeclChecks Name
fam_name NewOrData
new_or_data LHsContext GhcRn
hs_ctxt [LConDecl GhcRn]
hs_cons
          -- Do /not/ check that the number of patterns = tyConArity fam_tc
          -- See [Arity of data families] in GHC.Core.FamInstEnv
       ; ([TyVar]
qtvs, [Type]
pats, Type
res_kind, [Type]
stupid_theta)
             <- AssocInstInfo
-> TyCon
-> HsOuterFamEqnTyVarBndrs GhcRn
-> LexicalFixity
-> LHsContext GhcRn
-> HsTyPats GhcRn
-> Maybe (LHsKind GhcRn)
-> [LConDecl GhcRn]
-> NewOrData
-> TcM ([TyVar], [Type], Type, [Type])
tcDataFamInstHeader AssocInstInfo
mb_clsinfo TyCon
fam_tc HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs
                                    LexicalFixity
fixity LHsContext GhcRn
hs_ctxt HsTyPats GhcRn
hs_pats Maybe (LHsKind GhcRn)
m_ksig [LConDecl GhcRn]
hs_cons
                                    NewOrData
new_or_data

       -- Eta-reduce the axiom if possible
       -- Quite tricky: see Note [Implementing eta reduction for data families]
       ; let ([Type]
eta_pats, [TyConBinder]
eta_tcbs) = TyCon -> [Type] -> ([Type], [TyConBinder])
eta_reduce TyCon
fam_tc [Type]
pats
             eta_tvs :: [TyVar]
eta_tvs       = (TyConBinder -> TyVar) -> [TyConBinder] -> [TyVar]
forall a b. (a -> b) -> [a] -> [b]
map TyConBinder -> TyVar
forall tv argf. VarBndr tv argf -> tv
binderVar [TyConBinder]
eta_tcbs
             post_eta_qtvs :: [TyVar]
post_eta_qtvs = (TyVar -> Bool) -> [TyVar] -> [TyVar]
forall a. (a -> Bool) -> [a] -> [a]
filterOut (TyVar -> [TyVar] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [TyVar]
eta_tvs) [TyVar]
qtvs

             full_tcbs :: [TyConBinder]
full_tcbs = [TyVar] -> VarSet -> [TyConBinder]
mkTyConBindersPreferAnon [TyVar]
post_eta_qtvs
                            (Type -> VarSet
tyCoVarsOfType ([TyVar] -> Type -> Type
mkSpecForAllTys [TyVar]
eta_tvs Type
res_kind))
                         [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
++ [TyConBinder]
eta_tcbs
                 -- Put the eta-removed tyvars at the end
                 -- Remember, qtvs is in arbitrary order, except kind vars are
                 -- first, so there is no reason to suppose that the eta_tvs
                 -- (obtained from the pats) are at the end (#11148)

       -- Eta-expand the representation tycon until it has result
       -- kind `TYPE r`, for some `r`. If UnliftedNewtypes is not enabled, we
       -- go one step further and ensure that it has kind `TYPE 'LiftedRep`.
       --
       -- See also Note [Arity of data families] in GHC.Core.FamInstEnv
       -- NB: we can do this after eta-reducing the axiom, because if
       --     we did it before the "extra" tvs from etaExpandAlgTyCon
       --     would always be eta-reduced
       --
       ; ([TyConBinder]
extra_tcbs, Type
final_res_kind) <- [TyConBinder] -> Type -> TcM ([TyConBinder], Type)
etaExpandAlgTyCon [TyConBinder]
full_tcbs Type
res_kind

       -- Check the result kind; it may come from a user-written signature.
       -- See Note [Datatype return kinds] in GHC.Tc.TyCl point 4(a)
       ; let extra_pats :: [Type]
extra_pats  = (TyConBinder -> Type) -> [TyConBinder] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map (TyVar -> Type
mkTyVarTy (TyVar -> Type) -> (TyConBinder -> TyVar) -> TyConBinder -> Type
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TyConBinder -> TyVar
forall tv argf. VarBndr tv argf -> tv
binderVar) [TyConBinder]
extra_tcbs
             all_pats :: [Type]
all_pats    = [Type]
pats [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
`chkAppend` [Type]
extra_pats
             orig_res_ty :: Type
orig_res_ty = TyCon -> [Type] -> Type
mkTyConApp TyCon
fam_tc [Type]
all_pats
             ty_binders :: [TyConBinder]
ty_binders  = [TyConBinder]
full_tcbs [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
`chkAppend` [TyConBinder]
extra_tcbs

       ; String -> SDoc -> TcRn ()
traceTc String
"tcDataFamInstDecl" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Fam tycon:" SDoc -> SDoc -> SDoc
<+> TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc
              , String -> SDoc
text String
"Pats:" SDoc -> SDoc -> SDoc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
pats
              , String -> SDoc
text String
"visiblities:" SDoc -> SDoc -> SDoc
<+> [TyConBndrVis] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [Type] -> [TyConBndrVis]
tcbVisibilities TyCon
fam_tc [Type]
pats)
              , String -> SDoc
text String
"all_pats:" SDoc -> SDoc -> SDoc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
all_pats
              , String -> SDoc
text String
"ty_binders" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
ty_binders
              , String -> SDoc
text String
"fam_tc_binders:" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyConBinder]
tyConBinders TyCon
fam_tc)
              , String -> SDoc
text String
"res_kind:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
res_kind
              , String -> SDoc
text String
"final_res_kind:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
final_res_kind
              , String -> SDoc
text String
"eta_pats" SDoc -> SDoc -> SDoc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
eta_pats
              , String -> SDoc
text String
"eta_tcbs" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyConBinder]
eta_tcbs ]

       ; (TyCon
rep_tc, CoAxiom Unbranched
axiom) <- ((TyCon, CoAxiom Unbranched)
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, CoAxiom Unbranched))
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, CoAxiom Unbranched)
forall a env. (a -> IOEnv env a) -> IOEnv env a
fixM (((TyCon, CoAxiom Unbranched)
  -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, CoAxiom Unbranched))
 -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, CoAxiom Unbranched))
-> ((TyCon, CoAxiom Unbranched)
    -> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, CoAxiom Unbranched))
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, CoAxiom Unbranched)
forall a b. (a -> b) -> a -> b
$ \ ~(TyCon
rec_rep_tc, CoAxiom Unbranched
_) ->
           do { [DataCon]
data_cons <- [TyVar] -> TcM [DataCon] -> TcM [DataCon]
forall r. [TyVar] -> TcM r -> TcM r
tcExtendTyVarEnv [TyVar]
qtvs (TcM [DataCon] -> TcM [DataCon]) -> TcM [DataCon] -> TcM [DataCon]
forall a b. (a -> b) -> a -> b
$
                  -- For H98 decls, the tyvars scope
                  -- over the data constructors
                  TyCon
-> NewOrData
-> [TyConBinder]
-> Type
-> Type
-> [LConDecl GhcRn]
-> TcM [DataCon]
tcConDecls TyCon
rec_rep_tc NewOrData
new_or_data [TyConBinder]
ty_binders Type
final_res_kind
                             Type
orig_res_ty [LConDecl GhcRn]
hs_cons

              ; Name
rep_tc_name <- GenLocated SrcSpan Name -> [Type] -> TcM Name
newFamInstTyConName GenLocated SrcSpan Name
LIdP GhcRn
lfam_name [Type]
pats
              ; Name
axiom_name  <- GenLocated SrcSpan Name -> [[Type]] -> TcM Name
newFamInstAxiomName GenLocated SrcSpan Name
LIdP GhcRn
lfam_name [[Type]
pats]
              ; AlgTyConRhs
tc_rhs <- case NewOrData
new_or_data of
                     NewOrData
DataType -> AlgTyConRhs -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
forall (m :: * -> *) a. Monad m => a -> m a
return ([DataCon] -> AlgTyConRhs
mkDataTyConRhs [DataCon]
data_cons)
                     NewOrData
NewType  -> ASSERT( not (null data_cons) )
                                 Name
-> TyCon -> DataCon -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
forall m n. Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
mkNewTyConRhs Name
rep_tc_name TyCon
rec_rep_tc ([DataCon] -> DataCon
forall a. [a] -> a
head [DataCon]
data_cons)

              ; let ax_rhs :: Type
ax_rhs = TyCon -> [Type] -> Type
mkTyConApp TyCon
rep_tc ([TyVar] -> [Type]
mkTyVarTys [TyVar]
post_eta_qtvs)
                    axiom :: CoAxiom Unbranched
axiom  = Role
-> Name
-> [TyVar]
-> [TyVar]
-> [TyVar]
-> TyCon
-> [Type]
-> Type
-> CoAxiom Unbranched
mkSingleCoAxiom Role
Representational Name
axiom_name
                                 [TyVar]
post_eta_qtvs [TyVar]
eta_tvs [] TyCon
fam_tc [Type]
eta_pats Type
ax_rhs
                    parent :: AlgTyConFlav
parent = CoAxiom Unbranched -> TyCon -> [Type] -> AlgTyConFlav
DataFamInstTyCon CoAxiom Unbranched
axiom TyCon
fam_tc [Type]
all_pats

                      -- NB: Use the full ty_binders from the pats. See bullet toward
                      -- the end of Note [Data type families] in GHC.Core.TyCon
                    rep_tc :: TyCon
rep_tc   = Name
-> [TyConBinder]
-> Type
-> [Role]
-> Maybe CType
-> [Type]
-> AlgTyConRhs
-> AlgTyConFlav
-> Bool
-> TyCon
mkAlgTyCon Name
rep_tc_name
                                          [TyConBinder]
ty_binders Type
final_res_kind
                                          ((TyConBinder -> Role) -> [TyConBinder] -> [Role]
forall a b. (a -> b) -> [a] -> [b]
map (Role -> TyConBinder -> Role
forall a b. a -> b -> a
const Role
Nominal) [TyConBinder]
ty_binders)
                                          ((GenLocated SrcSpan CType -> CType)
-> Maybe (GenLocated SrcSpan CType) -> Maybe CType
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap GenLocated SrcSpan CType -> CType
forall l e. GenLocated l e -> e
unLoc Maybe (GenLocated SrcSpan CType)
Maybe (XRec GhcRn CType)
cType) [Type]
stupid_theta
                                          AlgTyConRhs
tc_rhs AlgTyConFlav
parent
                                          Bool
gadt_syntax
                 -- We always assume that indexed types are recursive.  Why?
                 -- (1) Due to their open nature, we can never be sure that a
                 -- further instance might not introduce a new recursive
                 -- dependency.  (2) They are always valid loop breakers as
                 -- they involve a coercion.
              ; (TyCon, CoAxiom Unbranched)
-> IOEnv (Env TcGblEnv TcLclEnv) (TyCon, CoAxiom Unbranched)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyCon
rep_tc, CoAxiom Unbranched
axiom) }

       -- Remember to check validity; no recursion to worry about here
       -- Check that left-hand sides are ok (mono-types, no type families,
       -- consistent instantiations, etc)
       ; let ax_branch :: KnotTied CoAxBranch
ax_branch = CoAxiom Unbranched -> KnotTied CoAxBranch
coAxiomSingleBranch CoAxiom Unbranched
axiom
       ; AssocInstInfo -> TyCon -> KnotTied CoAxBranch -> TcRn ()
checkConsistentFamInst AssocInstInfo
mb_clsinfo TyCon
fam_tc KnotTied CoAxBranch
ax_branch
       ; TyCon -> KnotTied CoAxBranch -> TcRn ()
checkValidCoAxBranch TyCon
fam_tc KnotTied CoAxBranch
ax_branch
       ; TyCon -> TcRn ()
checkValidTyCon TyCon
rep_tc

       ; let scoped_tvs :: [(Name, TyVar)]
scoped_tvs = (TyVar -> (Name, TyVar)) -> [TyVar] -> [(Name, TyVar)]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> (Name, TyVar)
mk_deriv_info_scoped_tv_pr (TyCon -> [TyVar]
tyConTyVars TyCon
rep_tc)
             m_deriv_info :: Maybe DerivInfo
m_deriv_info = case HsDeriving GhcRn
derivs of
               L _ []    -> Maybe DerivInfo
forall a. Maybe a
Nothing
               L _ preds ->
                 DerivInfo -> Maybe DerivInfo
forall a. a -> Maybe a
Just (DerivInfo -> Maybe DerivInfo) -> DerivInfo -> Maybe DerivInfo
forall a b. (a -> b) -> a -> b
$ DerivInfo :: TyCon
-> [(Name, TyVar)]
-> [LHsDerivingClause GhcRn]
-> SDoc
-> DerivInfo
DerivInfo { di_rep_tc :: TyCon
di_rep_tc  = TyCon
rep_tc
                                  , di_scoped_tvs :: [(Name, TyVar)]
di_scoped_tvs = [(Name, TyVar)]
scoped_tvs
                                  , di_clauses :: [LHsDerivingClause GhcRn]
di_clauses = [Located (HsDerivingClause GhcRn)]
[LHsDerivingClause GhcRn]
preds
                                  , di_ctxt :: SDoc
di_ctxt    = DataFamInstDecl GhcRn -> SDoc
tcMkDataFamInstCtxt DataFamInstDecl GhcRn
decl }

       ; FamInst
fam_inst <- FamFlavor -> CoAxiom Unbranched -> TcM FamInst
newFamInst (TyCon -> FamFlavor
DataFamilyInst TyCon
rep_tc) CoAxiom Unbranched
axiom
       ; (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall (m :: * -> *) a. Monad m => a -> m a
return (FamInst
fam_inst, Maybe DerivInfo
m_deriv_info) }
  where
    eta_reduce :: TyCon -> [Type] -> ([Type], [TyConBinder])
    -- See Note [Eta reduction for data families] in GHC.Core.Coercion.Axiom
    -- Splits the incoming patterns into two: the [TyVar]
    -- are the patterns that can be eta-reduced away.
    -- e.g.     T [a] Int a d c   ==>  (T [a] Int a, [d,c])
    --
    -- NB: quadratic algorithm, but types are small here
    eta_reduce :: TyCon -> [Type] -> ([Type], [TyConBinder])
eta_reduce TyCon
fam_tc [Type]
pats
        = [(Type, VarSet, TyConBndrVis)]
-> [TyConBinder] -> ([Type], [TyConBinder])
forall c.
[(Type, VarSet, c)]
-> [VarBndr TyVar c] -> ([Type], [VarBndr TyVar c])
go ([(Type, VarSet, TyConBndrVis)] -> [(Type, VarSet, TyConBndrVis)]
forall a. [a] -> [a]
reverse ([Type]
-> [VarSet] -> [TyConBndrVis] -> [(Type, VarSet, TyConBndrVis)]
forall a b c. [a] -> [b] -> [c] -> [(a, b, c)]
zip3 [Type]
pats [VarSet]
fvs_s [TyConBndrVis]
vis_s)) []
        where
          vis_s :: [TyConBndrVis]
          vis_s :: [TyConBndrVis]
vis_s = TyCon -> [Type] -> [TyConBndrVis]
tcbVisibilities TyCon
fam_tc [Type]
pats

          fvs_s :: [TyCoVarSet]  -- 1-1 correspondence with pats
                                 -- Each elt is the free vars of all /earlier/ pats
          (VarSet
_, [VarSet]
fvs_s) = (VarSet -> Type -> (VarSet, VarSet))
-> VarSet -> [Type] -> (VarSet, [VarSet])
forall (t :: * -> *) a b c.
Traversable t =>
(a -> b -> (a, c)) -> a -> t b -> (a, t c)
mapAccumL VarSet -> Type -> (VarSet, VarSet)
add_fvs VarSet
emptyVarSet [Type]
pats
          add_fvs :: VarSet -> Type -> (VarSet, VarSet)
add_fvs VarSet
fvs Type
pat = (VarSet
fvs VarSet -> VarSet -> VarSet
`unionVarSet` Type -> VarSet
tyCoVarsOfType Type
pat, VarSet
fvs)

    go :: [(Type, VarSet, c)]
-> [VarBndr TyVar c] -> ([Type], [VarBndr TyVar c])
go ((Type
pat, VarSet
fvs_to_the_left, c
tcb_vis):[(Type, VarSet, c)]
pats) [VarBndr TyVar c]
etad_tvs
      | Just TyVar
tv <- Type -> Maybe TyVar
getTyVar_maybe Type
pat
      , Bool -> Bool
not (TyVar
tv TyVar -> VarSet -> Bool
`elemVarSet` VarSet
fvs_to_the_left)
      = [(Type, VarSet, c)]
-> [VarBndr TyVar c] -> ([Type], [VarBndr TyVar c])
go [(Type, VarSet, c)]
pats (TyVar -> c -> VarBndr TyVar c
forall var argf. var -> argf -> VarBndr var argf
Bndr TyVar
tv c
tcb_vis VarBndr TyVar c -> [VarBndr TyVar c] -> [VarBndr TyVar c]
forall a. a -> [a] -> [a]
: [VarBndr TyVar c]
etad_tvs)
    go [(Type, VarSet, c)]
pats [VarBndr TyVar c]
etad_tvs = ([Type] -> [Type]
forall a. [a] -> [a]
reverse (((Type, VarSet, c) -> Type) -> [(Type, VarSet, c)] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map (Type, VarSet, c) -> Type
forall a b c. (a, b, c) -> a
fstOf3 [(Type, VarSet, c)]
pats), [VarBndr TyVar c]
etad_tvs)

    -- Create a Name-TyVar mapping to bring into scope when typechecking any
    -- deriving clauses this data family instance may have.
    -- See Note [Associated data family instances and di_scoped_tvs].
    mk_deriv_info_scoped_tv_pr :: TyVar -> (Name, TyVar)
    mk_deriv_info_scoped_tv_pr :: TyVar -> (Name, TyVar)
mk_deriv_info_scoped_tv_pr TyVar
tv =
      let n :: Name
n = TyVarEnv Name -> Name -> TyVar -> Name
forall a. VarEnv a -> a -> TyVar -> a
lookupWithDefaultVarEnv TyVarEnv Name
tv_skol_env (TyVar -> Name
tyVarName TyVar
tv) TyVar
tv
      in (Name
n, TyVar
tv)

{-
Note [Associated data family instances and di_scoped_tvs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Some care is required to implement `deriving` correctly for associated data
family instances. Consider this example from #18055:

  class C a where
    data D a

  class X a b

  instance C (Maybe a) where
    data D (Maybe a) deriving (X a)

When typechecking the `X a` in `deriving (X a)`, we must ensure that the `a`
from the instance header is brought into scope. This is the role of
di_scoped_tvs, which maps from the original, renamed `a` to the skolemized,
typechecked `a`. When typechecking the `deriving` clause, this mapping will be
consulted when looking up the `a` in `X a`.

A naïve attempt at creating the di_scoped_tvs is to simply reuse the
tyConTyVars of the representation TyCon for `data D (Maybe a)`. This is only
half correct, however. We do want the typechecked `a`'s Name in the /range/
of the mapping, but we do not want it in the /domain/ of the mapping.
To ensure that the original `a`'s Name ends up in the domain, we consult a
TyVarEnv (passed as an argument to tcDataFamInstDecl) that maps from the
typechecked `a`'s Name to the original `a`'s Name. In the even that
tcDataFamInstDecl is processing a non-associated data family instance, this
TyVarEnv will simply be empty, and there is nothing to worry about.
-}

-----------------------
tcDataFamInstHeader
    :: AssocInstInfo -> TyCon -> HsOuterFamEqnTyVarBndrs GhcRn
    -> LexicalFixity -> LHsContext GhcRn
    -> HsTyPats GhcRn -> Maybe (LHsKind GhcRn) -> [LConDecl GhcRn]
    -> NewOrData
    -> TcM ([TyVar], [Type], Kind, ThetaType)
-- The "header" of a data family instance is the part other than
-- the data constructors themselves
--    e.g.  data instance D [a] :: * -> * where ...
-- Here the "header" is the bit before the "where"
tcDataFamInstHeader :: AssocInstInfo
-> TyCon
-> HsOuterFamEqnTyVarBndrs GhcRn
-> LexicalFixity
-> LHsContext GhcRn
-> HsTyPats GhcRn
-> Maybe (LHsKind GhcRn)
-> [LConDecl GhcRn]
-> NewOrData
-> TcM ([TyVar], [Type], Type, [Type])
tcDataFamInstHeader AssocInstInfo
mb_clsinfo TyCon
fam_tc HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs LexicalFixity
fixity
                    LHsContext GhcRn
hs_ctxt HsTyPats GhcRn
hs_pats Maybe (LHsKind GhcRn)
m_ksig [LConDecl GhcRn]
hs_cons NewOrData
new_or_data
  = do { String -> SDoc -> TcRn ()
traceTc String
"tcDataFamInstHeader {" (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc SDoc -> SDoc -> SDoc
<+> [HsArg (Located (HsType GhcRn)) (Located (HsType GhcRn))] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [HsArg (Located (HsType GhcRn)) (Located (HsType GhcRn))]
HsTyPats GhcRn
hs_pats)
       ; (TcLevel
tclvl, WantedConstraints
wanted, ([TyVar]
scoped_tvs, ([Type]
stupid_theta, Type
lhs_ty, Type
master_res_kind, Type
instance_res_kind)))
            <- String
-> TcM ([TyVar], ([Type], Type, Type, Type))
-> TcM
     (TcLevel, WantedConstraints, ([TyVar], ([Type], Type, Type, Type)))
forall a. String -> TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndSolveEqualitiesX String
"tcDataFamInstHeader" (TcM ([TyVar], ([Type], Type, Type, Type))
 -> TcM
      (TcLevel, WantedConstraints,
       ([TyVar], ([Type], Type, Type, Type))))
-> TcM ([TyVar], ([Type], Type, Type, Type))
-> TcM
     (TcLevel, WantedConstraints, ([TyVar], ([Type], Type, Type, Type)))
forall a b. (a -> b) -> a -> b
$
               HsOuterFamEqnTyVarBndrs GhcRn
-> TcM ([Type], Type, Type, Type)
-> TcM ([TyVar], ([Type], Type, Type, Type))
forall a.
HsOuterFamEqnTyVarBndrs GhcRn -> TcM a -> TcM ([TyVar], a)
bindOuterFamEqnTKBndrs HsOuterFamEqnTyVarBndrs GhcRn
outer_bndrs                 (TcM ([Type], Type, Type, Type)
 -> TcM ([TyVar], ([Type], Type, Type, Type)))
-> TcM ([Type], Type, Type, Type)
-> TcM ([TyVar], ([Type], Type, Type, Type))
forall a b. (a -> b) -> a -> b
$
               do { [Type]
stupid_theta <- LHsContext GhcRn -> TcM [Type]
tcHsContext LHsContext GhcRn
hs_ctxt
                  ; (Type
lhs_ty, Type
lhs_kind) <- TyCon -> HsTyPats GhcRn -> TcM (Type, Type)
tcFamTyPats TyCon
fam_tc HsTyPats GhcRn
hs_pats
                  ; (Type
lhs_applied_ty, Type
lhs_applied_kind)
                      <- Type -> Type -> TcM (Type, Type)
tcInstInvisibleTyBinders Type
lhs_ty Type
lhs_kind
                      -- See Note [Data family/instance return kinds]
                      -- in GHC.Tc.TyCl point (DF3)

                  -- Ensure that the instance is consistent
                  -- with its parent class
                  ; AssocInstInfo -> Type -> TcRn ()
addConsistencyConstraints AssocInstInfo
mb_clsinfo Type
lhs_ty

                  -- Add constraints from the result signature
                  ; Type
res_kind <- Maybe (Located (HsType GhcRn)) -> TcM Type
tc_kind_sig Maybe (Located (HsType GhcRn))
Maybe (LHsKind GhcRn)
m_ksig

                  -- Add constraints from the data constructors
                  ; NewOrData -> Type -> [LConDecl GhcRn] -> TcRn ()
kcConDecls NewOrData
new_or_data Type
res_kind [LConDecl GhcRn]
hs_cons

                  -- Check that the result kind of the TyCon applied to its args
                  -- is compatible with the explicit signature (or Type, if there
                  -- is none)
                  ; let hs_lhs :: LHsKind GhcRn
hs_lhs = LexicalFixity -> IdP GhcRn -> HsTyPats GhcRn -> LHsKind GhcRn
forall (p :: Pass).
LexicalFixity
-> IdP (GhcPass p)
-> [LHsTypeArg (GhcPass p)]
-> LHsType (GhcPass p)
nlHsTyConApp LexicalFixity
fixity (TyCon -> Name
forall a. NamedThing a => a -> Name
getName TyCon
fam_tc) HsTyPats GhcRn
hs_pats
                  ; CoercionN
_ <- Maybe SDoc -> Type -> Type -> TcM CoercionN
unifyKind (SDoc -> Maybe SDoc
forall a. a -> Maybe a
Just (Located (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr Located (HsType GhcRn)
LHsKind GhcRn
hs_lhs)) Type
lhs_applied_kind Type
res_kind

                  ; String -> SDoc -> TcRn ()
traceTc String
"tcDataFamInstHeader" (SDoc -> TcRn ()) -> SDoc -> TcRn ()
forall a b. (a -> b) -> a -> b
$
                    [SDoc] -> SDoc
vcat [ TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc, Maybe (Located (HsType GhcRn)) -> SDoc
forall a. Outputable a => a -> SDoc
ppr Maybe (Located (HsType GhcRn))
Maybe (LHsKind GhcRn)
m_ksig, Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
lhs_applied_kind, Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
res_kind ]
                  ; ([Type], Type, Type, Type) -> TcM ([Type], Type, Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ( [Type]
stupid_theta
                           , Type
lhs_applied_ty
                           , Type
lhs_applied_kind
                           , Type
res_kind ) }

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

       -- See GHC.Tc.TyCl Note [Generalising in tcFamTyPatsGuts]
       ; CandidatesQTvs
dvs  <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfTypes (Type
lhs_ty Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: [TyVar] -> [Type]
mkTyVarTys [TyVar]
scoped_tvs)
       ; [TyVar]
qtvs <- CandidatesQTvs -> TcM [TyVar]
quantifyTyVars CandidatesQTvs
dvs
       ; SkolemInfo -> [TyVar] -> TcLevel -> WantedConstraints -> TcRn ()
reportUnsolvedEqualities SkolemInfo
FamInstSkol [TyVar]
qtvs TcLevel
tclvl WantedConstraints
wanted

       -- Zonk the patterns etc into the Type world
       ; (ZonkEnv
ze, [TyVar]
qtvs)   <- [TyVar] -> TcM (ZonkEnv, [TyVar])
zonkTyBndrs [TyVar]
qtvs
       ; Type
lhs_ty       <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX   ZonkEnv
ze Type
lhs_ty
       ; [Type]
stupid_theta <- ZonkEnv -> [Type] -> TcM [Type]
zonkTcTypesToTypesX ZonkEnv
ze [Type]
stupid_theta
       ; Type
master_res_kind   <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
master_res_kind
       ; Type
instance_res_kind <- ZonkEnv -> Type -> TcM Type
zonkTcTypeToTypeX ZonkEnv
ze Type
instance_res_kind

       -- We check that res_kind is OK with checkDataKindSig in
       -- tcDataFamInstDecl, after eta-expansion.  We need to check that
       -- it's ok because res_kind can come from a user-written kind signature.
       -- See Note [Datatype return kinds], point (4a)

       ; DataSort -> Type -> TcRn ()
checkDataKindSig (NewOrData -> DataSort
DataInstanceSort NewOrData
new_or_data) Type
master_res_kind
       ; DataSort -> Type -> TcRn ()
checkDataKindSig (NewOrData -> DataSort
DataInstanceSort NewOrData
new_or_data) Type
instance_res_kind

       -- Check that type patterns match the class instance head
       -- The call to splitTyConApp_maybe here is just an inlining of
       -- the body of unravelFamInstPats.
       ; [Type]
pats <- case HasDebugCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
splitTyConApp_maybe Type
lhs_ty of
           Just (TyCon
_, [Type]
pats) -> [Type] -> TcM [Type]
forall (f :: * -> *) a. Applicative f => a -> f a
pure [Type]
pats
           Maybe (TyCon, [Type])
Nothing -> String -> SDoc -> TcM [Type]
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcDataFamInstHeader" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
lhs_ty)

       ; ([TyVar], [Type], Type, [Type])
-> TcM ([TyVar], [Type], Type, [Type])
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
qtvs, [Type]
pats, Type
master_res_kind, [Type]
stupid_theta) }
  where
    fam_name :: Name
fam_name  = TyCon -> Name
tyConName TyCon
fam_tc
    data_ctxt :: UserTypeCtxt
data_ctxt = Name -> UserTypeCtxt
DataKindCtxt Name
fam_name

    -- See Note [Implementation of UnliftedNewtypes] in GHC.Tc.TyCl, wrinkle (2).
    tc_kind_sig :: Maybe (Located (HsType GhcRn)) -> TcM Type
tc_kind_sig Maybe (Located (HsType GhcRn))
Nothing
      = do { Bool
unlifted_newtypes <- Extension -> TcRn Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.UnliftedNewtypes
           ; if Bool
unlifted_newtypes Bool -> Bool -> Bool
&& NewOrData
new_or_data NewOrData -> NewOrData -> Bool
forall a. Eq a => a -> a -> Bool
== NewOrData
NewType
               then TcM Type
newOpenTypeKind
               else Type -> TcM Type
forall (f :: * -> *) a. Applicative f => a -> f a
pure Type
liftedTypeKind
           }

    -- See Note [Result kind signature for a data family instance]
    tc_kind_sig (Just Located (HsType GhcRn)
hs_kind)
      = do { Type
sig_kind <- UserTypeCtxt -> LHsKind GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
data_ctxt Located (HsType GhcRn)
LHsKind GhcRn
hs_kind
           ; TcLevel
lvl <- TcM TcLevel
getTcLevel
           ; let ([TyVar]
tvs, Type
inner_kind) = Type -> ([TyVar], Type)
tcSplitForAllInvisTyVars Type
sig_kind
           ; (TCvSubst
subst, [TyVar]
_tvs') <- TcLevel -> Bool -> TCvSubst -> [TyVar] -> TcM (TCvSubst, [TyVar])
tcInstSkolTyVarsAt TcLevel
lvl Bool
False TCvSubst
emptyTCvSubst [TyVar]
tvs
             -- Perhaps surprisingly, we don't need the skolemised tvs themselves
           ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return (HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
inner_kind) }

{- Note [Result kind signature for a data family instance]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The expected type might have a forall at the type. Normally, we
can't skolemise in kinds because we don't have type-level lambda.
But here, we're at the top-level of an instance declaration, so
we actually have a place to put the regeneralised variables.
Thus: skolemise away. cf. GHC.Tc.Utils.Unify.tcSkolemise
Examples in indexed-types/should_compile/T12369

Note [Implementing eta reduction for data families]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   data D :: * -> * -> * -> * -> *

   data instance D [(a,b)] p q :: * -> * where
      D1 :: blah1
      D2 :: blah2

Then we'll generate a representation data type
  data Drep a b p q z where
      D1 :: blah1
      D2 :: blah2

and an axiom to connect them
  axiom AxDrep forall a b p q z. D [(a,b]] p q z = Drep a b p q z

except that we'll eta-reduce the axiom to
  axiom AxDrep forall a b. D [(a,b]] = Drep a b

This is described at some length in Note [Eta reduction for data families]
in GHC.Core.Coercion.Axiom. There are several fiddly subtleties lurking here,
however, so this Note aims to describe these subtleties:

* The representation tycon Drep is parameterised over the free
  variables of the pattern, in no particular order. So there is no
  guarantee that 'p' and 'q' will come last in Drep's parameters, and
  in the right order.  So, if the /patterns/ of the family instance
  are eta-reducible, we re-order Drep's parameters to put the
  eta-reduced type variables last.

* Although we eta-reduce the axiom, we eta-/expand/ the representation
  tycon Drep.  The kind of D says it takes four arguments, but the
  data instance header only supplies three.  But the AlgTyCon for Drep
  itself must have enough TyConBinders so that its result kind is Type.
  So, with etaExpandAlgTyCon we make up some extra TyConBinders.
  See point (3) in Note [Datatype return kinds] in GHC.Tc.TyCl.

* The result kind in the instance might be a polykind, like this:
     data family DP a :: forall k. k -> *
     data instance DP [b] :: forall k1 k2. (k1,k2) -> *

  So in type-checking the LHS (DP Int) we need to check that it is
  more polymorphic than the signature.  To do that we must skolemise
  the signature and instantiate the call of DP.  So we end up with
     data instance DP [b] @(k1,k2) (z :: (k1,k2)) where

  Note that we must parameterise the representation tycon DPrep over
  'k1' and 'k2', as well as 'b'.

  The skolemise bit is done in tc_kind_sig, while the instantiate bit
  is done by tcFamTyPats.

* Very fiddly point.  When we eta-reduce to
     axiom AxDrep forall a b. D [(a,b]] = Drep a b

  we want the kind of (D [(a,b)]) to be the same as the kind of
  (Drep a b).  This ensures that applying the axiom doesn't change the
  kind.  Why is that hard?  Because the kind of (Drep a b) depends on
  the TyConBndrVis on Drep's arguments. In particular do we have
    (forall (k::*). blah) or (* -> blah)?

  We must match whatever D does!  In #15817 we had
      data family X a :: forall k. * -> *   -- Note: a forall that is not used
      data instance X Int b = MkX

  So the data instance is really
      data istance X Int @k b = MkX

  The axiom will look like
      axiom    X Int = Xrep

  and it's important that XRep :: forall k * -> *, following X.

  To achieve this we get the TyConBndrVis flags from tcbVisibilities,
  and use those flags for any eta-reduced arguments.  Sigh.

* The final turn of the knife is that tcbVisibilities is itself
  tricky to sort out.  Consider
      data family D k :: k
  Then consider D (forall k2. k2 -> k2) Type Type
  The visibility flags on an application of D may affected by the arguments
  themselves.  Heavy sigh.  But not truly hard; that's what tcbVisibilities
  does.

-}


{- *********************************************************************
*                                                                      *
      Class instance declarations, pass 2
*                                                                      *
********************************************************************* -}

tcInstDecls2 :: [LTyClDecl GhcRn] -> [InstInfo GhcRn]
             -> TcM (LHsBinds GhcTc)
-- (a) From each class declaration,
--      generate any default-method bindings
-- (b) From each instance decl
--      generate the dfun binding

tcInstDecls2 :: [LTyClDecl GhcRn] -> [InstInfo GhcRn] -> TcM (LHsBinds GhcTc)
tcInstDecls2 [LTyClDecl GhcRn]
tycl_decls [InstInfo GhcRn]
inst_decls
  = do  { -- (a) Default methods from class decls
          let class_decls :: [GenLocated SrcSpan (TyClDecl GhcRn)]
class_decls = (GenLocated SrcSpan (TyClDecl GhcRn) -> Bool)
-> [GenLocated SrcSpan (TyClDecl GhcRn)]
-> [GenLocated SrcSpan (TyClDecl GhcRn)]
forall a. (a -> Bool) -> [a] -> [a]
filter (TyClDecl GhcRn -> Bool
forall pass. TyClDecl pass -> Bool
isClassDecl (TyClDecl GhcRn -> Bool)
-> (GenLocated SrcSpan (TyClDecl GhcRn) -> TyClDecl GhcRn)
-> GenLocated SrcSpan (TyClDecl GhcRn)
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpan (TyClDecl GhcRn) -> TyClDecl GhcRn
forall l e. GenLocated l e -> e
unLoc) [GenLocated SrcSpan (TyClDecl GhcRn)]
[LTyClDecl GhcRn]
tycl_decls
        ; [Bag (Located (HsBindLR GhcTc GhcTc))]
dm_binds_s <- (GenLocated SrcSpan (TyClDecl GhcRn)
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc))))
-> [GenLocated SrcSpan (TyClDecl GhcRn)]
-> IOEnv
     (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM GenLocated SrcSpan (TyClDecl GhcRn)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
LTyClDecl GhcRn -> TcM (LHsBinds GhcTc)
tcClassDecl2 [GenLocated SrcSpan (TyClDecl GhcRn)]
class_decls
        ; let dm_binds :: Bag (Located (HsBindLR GhcTc GhcTc))
dm_binds = [Bag (Located (HsBindLR GhcTc GhcTc))]
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. [Bag a] -> Bag a
unionManyBags [Bag (Located (HsBindLR GhcTc GhcTc))]
dm_binds_s

          -- (b) instance declarations
        ; let dm_ids :: [IdP GhcTc]
dm_ids = LHsBinds GhcTc -> [IdP GhcTc]
forall p idR. CollectPass p => LHsBindsLR p idR -> [IdP p]
collectHsBindsBinders Bag (Located (HsBindLR GhcTc GhcTc))
LHsBinds GhcTc
dm_binds
              -- Add the default method Ids (again)
              -- (they were arready added in GHC.Tc.TyCl.Utils.tcAddImplicits)
              -- See Note [Default methods in the type environment]
        ; [Bag (Located (HsBindLR GhcTc GhcTc))]
inst_binds_s <- [TyVar]
-> IOEnv
     (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))]
-> IOEnv
     (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))]
forall r. [TyVar] -> TcM r -> TcM r
tcExtendGlobalValEnv [TyVar]
[IdP GhcTc]
dm_ids (IOEnv
   (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))]
 -> IOEnv
      (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))])
-> IOEnv
     (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))]
-> IOEnv
     (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))]
forall a b. (a -> b) -> a -> b
$
                          (InstInfo GhcRn
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc))))
-> [InstInfo GhcRn]
-> IOEnv
     (Env TcGblEnv TcLclEnv) [Bag (Located (HsBindLR GhcTc GhcTc))]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM InstInfo GhcRn
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
InstInfo GhcRn -> TcM (LHsBinds GhcTc)
tcInstDecl2 [InstInfo GhcRn]
inst_decls

          -- Done
        ; Bag (Located (HsBindLR GhcTc GhcTc))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall (m :: * -> *) a. Monad m => a -> m a
return (Bag (Located (HsBindLR GhcTc GhcTc))
dm_binds Bag (Located (HsBindLR GhcTc GhcTc))
-> Bag (Located (HsBindLR GhcTc GhcTc))
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. Bag a -> Bag a -> Bag a
`unionBags` [Bag (Located (HsBindLR GhcTc GhcTc))]
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. [Bag a] -> Bag a
unionManyBags [Bag (Located (HsBindLR GhcTc GhcTc))]
inst_binds_s) }

{- Note [Default methods in the type environment]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The default method Ids are already in the type environment (see Note
[Default method Ids and Template Haskell] in TcTyDcls), BUT they
don't have their InlinePragmas yet.  Usually that would not matter,
because the simplifier propagates information from binding site to
use.  But, unusually, when compiling instance decls we *copy* the
INLINE pragma from the default method to the method for that
particular operation (see Note [INLINE and default methods] below).

So right here in tcInstDecls2 we must re-extend the type envt with
the default method Ids replete with their INLINE pragmas.  Urk.
-}

tcInstDecl2 :: InstInfo GhcRn -> TcM (LHsBinds GhcTc)
            -- Returns a binding for the dfun
tcInstDecl2 :: InstInfo GhcRn -> TcM (LHsBinds GhcTc)
tcInstDecl2 (InstInfo { iSpec :: forall a. InstInfo a -> ClsInst
iSpec = ClsInst
ispec, iBinds :: forall a. InstInfo a -> InstBindings a
iBinds = InstBindings GhcRn
ibinds })
  = IOEnv
  (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall r. TcRn r -> TcRn r -> TcRn r
recoverM (Bag (Located (HsBindLR GhcTc GhcTc))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall (m :: * -> *) a. Monad m => a -> m a
return Bag (Located (HsBindLR GhcTc GhcTc))
forall (idL :: Pass) idR. LHsBindsLR (GhcPass idL) idR
emptyLHsBinds)             (IOEnv
   (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc))))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall a b. (a -> b) -> a -> b
$
    SrcSpan
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc                              (IOEnv
   (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc))))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall a b. (a -> b) -> a -> b
$
    SDoc
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (Type -> SDoc
instDeclCtxt2 (TyVar -> Type
idType TyVar
dfun_id)) (IOEnv
   (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc))))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall a b. (a -> b) -> a -> b
$
    do {  -- Instantiate the instance decl with skolem constants
       ; ([TyVar]
inst_tyvars, [Type]
dfun_theta, Type
inst_head) <- TyVar -> TcM ([TyVar], [Type], Type)
tcSkolDFunType TyVar
dfun_id
       ; [TyVar]
dfun_ev_vars <- [Type] -> TcM [TyVar]
newEvVars [Type]
dfun_theta
                     -- We instantiate the dfun_id with superSkolems.
                     -- See Note [Subtle interaction of recursion and overlap]
                     -- and Note [Binding when looking up instances]

       ; let (Class
clas, [Type]
inst_tys) = Type -> (Class, [Type])
tcSplitDFunHead Type
inst_head
             ([TyVar]
class_tyvars, [Type]
sc_theta, [TyVar]
_, [ClassOpItem]
op_items) = Class -> ([TyVar], [Type], [TyVar], [ClassOpItem])
classBigSig Class
clas
             sc_theta' :: [Type]
sc_theta' = HasCallStack => TCvSubst -> [Type] -> [Type]
TCvSubst -> [Type] -> [Type]
substTheta ([TyVar] -> [Type] -> TCvSubst
HasDebugCallStack => [TyVar] -> [Type] -> TCvSubst
zipTvSubst [TyVar]
class_tyvars [Type]
inst_tys) [Type]
sc_theta

       ; String -> SDoc -> TcRn ()
traceTc String
"tcInstDecl2" ([SDoc] -> SDoc
vcat [[TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
inst_tyvars, [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
inst_tys, [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
dfun_theta, [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
sc_theta'])

                      -- Deal with 'SPECIALISE instance' pragmas
                      -- See Note [SPECIALISE instance pragmas]
       ; spec_inst_info :: ([Located TcSpecPrag], NameEnv [Located (Sig GhcRn)])
spec_inst_info@([Located TcSpecPrag]
spec_inst_prags,NameEnv [Located (Sig GhcRn)]
_) <- TyVar
-> InstBindings GhcRn -> TcM ([Located TcSpecPrag], TcPragEnv)
tcSpecInstPrags TyVar
dfun_id InstBindings GhcRn
ibinds

         -- Typecheck superclasses and methods
         -- See Note [Typechecking plan for instance declarations]
       ; EvBindsVar
dfun_ev_binds_var <- TcM EvBindsVar
newTcEvBinds
       ; let dfun_ev_binds :: TcEvBinds
dfun_ev_binds = EvBindsVar -> TcEvBinds
TcEvBinds EvBindsVar
dfun_ev_binds_var
       ; (TcLevel
tclvl, ([TyVar]
sc_meth_ids, Bag (Located (HsBindLR GhcTc GhcTc))
sc_meth_binds, Bag Implication
sc_meth_implics))
             <- TcM
  ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
-> TcM
     (TcLevel,
      ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication))
forall a. TcM a -> TcM (TcLevel, a)
pushTcLevelM (TcM
   ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
 -> TcM
      (TcLevel,
       ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)))
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
-> TcM
     (TcLevel,
      ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication))
forall a b. (a -> b) -> a -> b
$
                do { ([TyVar]
sc_ids, Bag (Located (HsBindLR GhcTc GhcTc))
sc_binds, Bag Implication
sc_implics)
                        <- TyVar
-> Class
-> [TyVar]
-> [TyVar]
-> [Type]
-> TcEvBinds
-> [Type]
-> TcM ([TyVar], LHsBinds GhcTc, Bag Implication)
tcSuperClasses TyVar
dfun_id Class
clas [TyVar]
inst_tyvars [TyVar]
dfun_ev_vars
                                          [Type]
inst_tys TcEvBinds
dfun_ev_binds
                                          [Type]
sc_theta'

                      -- Typecheck the methods
                   ; ([TyVar]
meth_ids, Bag (Located (HsBindLR GhcTc GhcTc))
meth_binds, Bag Implication
meth_implics)
                        <- TyVar
-> Class
-> [TyVar]
-> [TyVar]
-> [Type]
-> TcEvBinds
-> ([Located TcSpecPrag], TcPragEnv)
-> [ClassOpItem]
-> InstBindings GhcRn
-> TcM ([TyVar], LHsBinds GhcTc, Bag Implication)
tcMethods TyVar
dfun_id Class
clas [TyVar]
inst_tyvars [TyVar]
dfun_ev_vars
                                     [Type]
inst_tys TcEvBinds
dfun_ev_binds ([Located TcSpecPrag], NameEnv [Located (Sig GhcRn)])
([Located TcSpecPrag], TcPragEnv)
spec_inst_info
                                     [ClassOpItem]
op_items InstBindings GhcRn
ibinds

                   ; ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
forall (m :: * -> *) a. Monad m => a -> m a
return ( [TyVar]
sc_ids     [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++          [TyVar]
meth_ids
                            , Bag (Located (HsBindLR GhcTc GhcTc))
sc_binds   Bag (Located (HsBindLR GhcTc GhcTc))
-> Bag (Located (HsBindLR GhcTc GhcTc))
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. Bag a -> Bag a -> Bag a
`unionBags` Bag (Located (HsBindLR GhcTc GhcTc))
meth_binds
                            , Bag Implication
sc_implics Bag Implication -> Bag Implication -> Bag Implication
forall a. Bag a -> Bag a -> Bag a
`unionBags` Bag Implication
meth_implics ) }

       ; Implication
imp <- TcM Implication
newImplication
       ; Implication -> TcRn ()
emitImplication (Implication -> TcRn ()) -> Implication -> TcRn ()
forall a b. (a -> b) -> a -> b
$
         Implication
imp { ic_tclvl :: TcLevel
ic_tclvl  = TcLevel
tclvl
             , ic_skols :: [TyVar]
ic_skols  = [TyVar]
inst_tyvars
             , ic_given :: [TyVar]
ic_given  = [TyVar]
dfun_ev_vars
             , ic_wanted :: WantedConstraints
ic_wanted = Bag Implication -> WantedConstraints
mkImplicWC Bag Implication
sc_meth_implics
             , ic_binds :: EvBindsVar
ic_binds  = EvBindsVar
dfun_ev_binds_var
             , ic_info :: SkolemInfo
ic_info   = SkolemInfo
InstSkol }

       -- Create the result bindings
       ; TyVar
self_dict <- Class -> [Type] -> TcM TyVar
newDict Class
clas [Type]
inst_tys
       ; let class_tc :: TyCon
class_tc      = Class -> TyCon
classTyCon Class
clas
             [DataCon
dict_constr] = TyCon -> [DataCon]
tyConDataCons TyCon
class_tc
             dict_bind :: LHsBind GhcTc
dict_bind     = IdP GhcTc -> LHsExpr GhcTc -> LHsBind GhcTc
forall (p :: Pass).
IdP (GhcPass p) -> LHsExpr (GhcPass p) -> LHsBind (GhcPass p)
mkVarBind TyVar
IdP GhcTc
self_dict (SrcSpan -> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsExpr GhcTc
con_app_args)

                     -- We don't produce a binding for the dict_constr; instead we
                     -- rely on the simplifier to unfold this saturated application
                     -- We do this rather than generate an HsCon directly, because
                     -- it means that the special cases (e.g. dictionary with only one
                     -- member) are dealt with by the common MkId.mkDataConWrapId
                     -- code rather than needing to be repeated here.
                     --    con_app_tys  = MkD ty1 ty2
                     --    con_app_scs  = MkD ty1 ty2 sc1 sc2
                     --    con_app_args = MkD ty1 ty2 sc1 sc2 op1 op2
             con_app_tys :: HsExpr GhcTc
con_app_tys  = HsWrapper -> HsExpr GhcTc -> HsExpr GhcTc
mkHsWrap ([Type] -> HsWrapper
mkWpTyApps [Type]
inst_tys)
                                  (XConLikeOut GhcTc -> ConLike -> HsExpr GhcTc
forall p. XConLikeOut p -> ConLike -> HsExpr p
HsConLikeOut NoExtField
XConLikeOut GhcTc
noExtField (DataCon -> ConLike
RealDataCon DataCon
dict_constr))
                       -- NB: We *can* have covars in inst_tys, in the case of
                       -- promoted GADT constructors.

             con_app_args :: HsExpr GhcTc
con_app_args = (HsExpr GhcTc -> TyVar -> HsExpr GhcTc)
-> HsExpr GhcTc -> [TyVar] -> HsExpr GhcTc
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' HsExpr GhcTc -> TyVar -> HsExpr GhcTc
app_to_meth HsExpr GhcTc
con_app_tys [TyVar]
sc_meth_ids

             app_to_meth :: HsExpr GhcTc -> Id -> HsExpr GhcTc
             app_to_meth :: HsExpr GhcTc -> TyVar -> HsExpr GhcTc
app_to_meth HsExpr GhcTc
fun TyVar
meth_id = XApp GhcTc -> LHsExpr GhcTc -> LHsExpr GhcTc -> HsExpr GhcTc
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp NoExtField
XApp GhcTc
noExtField (SrcSpan -> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsExpr GhcTc
fun)
                                            (SrcSpan -> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc (HsWrapper -> TyVar -> HsExpr GhcTc
wrapId HsWrapper
arg_wrapper TyVar
meth_id))

             inst_tv_tys :: [Type]
inst_tv_tys = [TyVar] -> [Type]
mkTyVarTys [TyVar]
inst_tyvars
             arg_wrapper :: HsWrapper
arg_wrapper = [TyVar] -> HsWrapper
mkWpEvVarApps [TyVar]
dfun_ev_vars HsWrapper -> HsWrapper -> HsWrapper
<.> [Type] -> HsWrapper
mkWpTyApps [Type]
inst_tv_tys

             is_newtype :: Bool
is_newtype = TyCon -> Bool
isNewTyCon TyCon
class_tc
             dfun_id_w_prags :: TyVar
dfun_id_w_prags = TyVar -> [TyVar] -> TyVar
addDFunPrags TyVar
dfun_id [TyVar]
sc_meth_ids
             dfun_spec_prags :: TcSpecPrags
dfun_spec_prags
                | Bool
is_newtype = [Located TcSpecPrag] -> TcSpecPrags
SpecPrags []
                | Bool
otherwise  = [Located TcSpecPrag] -> TcSpecPrags
SpecPrags [Located TcSpecPrag]
spec_inst_prags
                    -- Newtype dfuns just inline unconditionally,
                    -- so don't attempt to specialise them

             export :: ABExport GhcTc
export = ABE :: forall p.
XABE p -> IdP p -> IdP p -> HsWrapper -> TcSpecPrags -> ABExport p
ABE { abe_ext :: XABE GhcTc
abe_ext  = NoExtField
XABE GhcTc
noExtField
                          , abe_wrap :: HsWrapper
abe_wrap = HsWrapper
idHsWrapper
                          , abe_poly :: IdP GhcTc
abe_poly = TyVar
IdP GhcTc
dfun_id_w_prags
                          , abe_mono :: IdP GhcTc
abe_mono = TyVar
IdP GhcTc
self_dict
                          , abe_prags :: TcSpecPrags
abe_prags = TcSpecPrags
dfun_spec_prags }
                          -- NB: see Note [SPECIALISE instance pragmas]
             main_bind :: HsBindLR GhcTc GhcTc
main_bind = AbsBinds :: forall idL idR.
XAbsBinds idL idR
-> [TyVar]
-> [TyVar]
-> [ABExport idL]
-> [TcEvBinds]
-> LHsBinds idL
-> Bool
-> HsBindLR idL idR
AbsBinds { abs_ext :: XAbsBinds GhcTc GhcTc
abs_ext = NoExtField
XAbsBinds GhcTc GhcTc
noExtField
                                  , abs_tvs :: [TyVar]
abs_tvs = [TyVar]
inst_tyvars
                                  , abs_ev_vars :: [TyVar]
abs_ev_vars = [TyVar]
dfun_ev_vars
                                  , abs_exports :: [ABExport GhcTc]
abs_exports = [ABExport GhcTc
export]
                                  , abs_ev_binds :: [TcEvBinds]
abs_ev_binds = []
                                  , abs_binds :: LHsBinds GhcTc
abs_binds = Located (HsBindLR GhcTc GhcTc)
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. a -> Bag a
unitBag Located (HsBindLR GhcTc GhcTc)
LHsBind GhcTc
dict_bind
                                  , abs_sig :: Bool
abs_sig = Bool
True }

       ; Bag (Located (HsBindLR GhcTc GhcTc))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall (m :: * -> *) a. Monad m => a -> m a
return (Located (HsBindLR GhcTc GhcTc)
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. a -> Bag a
unitBag (SrcSpan -> HsBindLR GhcTc GhcTc -> Located (HsBindLR GhcTc GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsBindLR GhcTc GhcTc
main_bind) Bag (Located (HsBindLR GhcTc GhcTc))
-> Bag (Located (HsBindLR GhcTc GhcTc))
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. Bag a -> Bag a -> Bag a
`unionBags` Bag (Located (HsBindLR GhcTc GhcTc))
sc_meth_binds)
       }
 where
   dfun_id :: TyVar
dfun_id = ClsInst -> TyVar
instanceDFunId ClsInst
ispec
   loc :: SrcSpan
loc     = TyVar -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
getSrcSpan TyVar
dfun_id

addDFunPrags :: DFunId -> [Id] -> DFunId
-- DFuns need a special Unfolding and InlinePrag
--    See Note [ClassOp/DFun selection]
--    and Note [Single-method classes]
-- It's easiest to create those unfoldings right here, where
-- have all the pieces in hand, even though we are messing with
-- Core at this point, which the typechecker doesn't usually do
-- However we take care to build the unfolding using the TyVars from
-- the DFunId rather than from the skolem pieces that the typechecker
-- is messing with.
addDFunPrags :: TyVar -> [TyVar] -> TyVar
addDFunPrags TyVar
dfun_id [TyVar]
sc_meth_ids
 | Bool
is_newtype
  = TyVar
dfun_id TyVar -> Unfolding -> TyVar
`setIdUnfolding`  Int -> SimpleOpts -> CoreExpr -> Unfolding
mkInlineUnfoldingWithArity Int
0 SimpleOpts
defaultSimpleOpts CoreExpr
con_app
            TyVar -> InlinePragma -> TyVar
`setInlinePragma` InlinePragma
alwaysInlinePragma { inl_sat :: Maybe Int
inl_sat = Int -> Maybe Int
forall a. a -> Maybe a
Just Int
0 }
 | Bool
otherwise
 = TyVar
dfun_id TyVar -> Unfolding -> TyVar
`setIdUnfolding`  [TyVar] -> DataCon -> [CoreExpr] -> Unfolding
mkDFunUnfolding [TyVar]
dfun_bndrs DataCon
dict_con [CoreExpr]
dict_args
           TyVar -> InlinePragma -> TyVar
`setInlinePragma` InlinePragma
dfunInlinePragma
 where
   con_app :: CoreExpr
con_app    = [TyVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [TyVar]
dfun_bndrs (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (TyVar -> CoreExpr
forall b. TyVar -> Expr b
Var (DataCon -> TyVar
dataConWrapId DataCon
dict_con)) [CoreExpr]
dict_args
                 -- mkApps is OK because of the checkForLevPoly call in checkValidClass
                 -- See Note [Levity polymorphism checking] in GHC.HsToCore.Monad
   dict_args :: [CoreExpr]
dict_args  = (Type -> CoreExpr) -> [Type] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map Type -> CoreExpr
forall b. Type -> Expr b
Type [Type]
inst_tys [CoreExpr] -> [CoreExpr] -> [CoreExpr]
forall a. [a] -> [a] -> [a]
++
                [CoreExpr -> [TyVar] -> CoreExpr
forall b. Expr b -> [TyVar] -> Expr b
mkVarApps (TyVar -> CoreExpr
forall b. TyVar -> Expr b
Var TyVar
id) [TyVar]
dfun_bndrs | TyVar
id <- [TyVar]
sc_meth_ids]

   ([TyVar]
dfun_tvs, [Type]
dfun_theta, Class
clas, [Type]
inst_tys) = Type -> ([TyVar], [Type], Class, [Type])
tcSplitDFunTy (TyVar -> Type
idType TyVar
dfun_id)
   ev_ids :: [TyVar]
ev_ids      = Int -> [Type] -> [TyVar]
mkTemplateLocalsNum Int
1                    [Type]
dfun_theta
   dfun_bndrs :: [TyVar]
dfun_bndrs  = [TyVar]
dfun_tvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
ev_ids
   clas_tc :: TyCon
clas_tc     = Class -> TyCon
classTyCon Class
clas
   [DataCon
dict_con]  = TyCon -> [DataCon]
tyConDataCons TyCon
clas_tc
   is_newtype :: Bool
is_newtype  = TyCon -> Bool
isNewTyCon TyCon
clas_tc

wrapId :: HsWrapper -> Id -> HsExpr GhcTc
wrapId :: HsWrapper -> TyVar -> HsExpr GhcTc
wrapId HsWrapper
wrapper TyVar
id = HsWrapper -> HsExpr GhcTc -> HsExpr GhcTc
mkHsWrap HsWrapper
wrapper (XVar GhcTc -> LIdP GhcTc -> HsExpr GhcTc
forall p. XVar p -> LIdP p -> HsExpr p
HsVar NoExtField
XVar GhcTc
noExtField (TyVar -> Located TyVar
forall e. e -> Located e
noLoc TyVar
id))

{- Note [Typechecking plan for instance declarations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For instance declarations we generate the following bindings and implication
constraints.  Example:

   instance Ord a => Ord [a] where compare = <compare-rhs>

generates this:

   Bindings:
      -- Method bindings
      $ccompare :: forall a. Ord a => a -> a -> Ordering
      $ccompare = /\a \(d:Ord a). let <meth-ev-binds> in ...

      -- Superclass bindings
      $cp1Ord :: forall a. Ord a => Eq [a]
      $cp1Ord = /\a \(d:Ord a). let <sc-ev-binds>
               in dfEqList (dw :: Eq a)

   Constraints:
      forall a. Ord a =>
                -- Method constraint
             (forall. (empty) => <constraints from compare-rhs>)
                -- Superclass constraint
          /\ (forall. (empty) => dw :: Eq a)

Notice that

 * Per-meth/sc implication.  There is one inner implication per
   superclass or method, with no skolem variables or givens.  The only
   reason for this one is to gather the evidence bindings privately
   for this superclass or method.  This implication is generated
   by checkInstConstraints.

 * Overall instance implication. There is an overall enclosing
   implication for the whole instance declaration, with the expected
   skolems and givens.  We need this to get the correct "redundant
   constraint" warnings, gathering all the uses from all the methods
   and superclasses.  See GHC.Tc.Solver Note [Tracking redundant
   constraints]

 * The given constraints in the outer implication may generate
   evidence, notably by superclass selection.  Since the method and
   superclass bindings are top-level, we want that evidence copied
   into *every* method or superclass definition.  (Some of it will
   be usused in some, but dead-code elimination will drop it.)

   We achieve this by putting the evidence variable for the overall
   instance implication into the AbsBinds for each method/superclass.
   Hence the 'dfun_ev_binds' passed into tcMethods and tcSuperClasses.
   (And that in turn is why the abs_ev_binds field of AbBinds is a
   [TcEvBinds] rather than simply TcEvBinds.

   This is a bit of a hack, but works very nicely in practice.

 * Note that if a method has a locally-polymorphic binding, there will
   be yet another implication for that, generated by tcPolyCheck
   in tcMethodBody. E.g.
          class C a where
            foo :: forall b. Ord b => blah


************************************************************************
*                                                                      *
      Type-checking superclasses
*                                                                      *
************************************************************************
-}

tcSuperClasses :: DFunId -> Class -> [TcTyVar] -> [EvVar] -> [TcType]
               -> TcEvBinds
               -> TcThetaType
               -> TcM ([EvVar], LHsBinds GhcTc, Bag Implication)
-- Make a new top-level function binding for each superclass,
-- something like
--    $Ordp1 :: forall a. Ord a => Eq [a]
--    $Ordp1 = /\a \(d:Ord a). dfunEqList a (sc_sel d)
--
-- See Note [Recursive superclasses] for why this is so hard!
-- In effect, we build a special-purpose solver for the first step
-- of solving each superclass constraint
tcSuperClasses :: TyVar
-> Class
-> [TyVar]
-> [TyVar]
-> [Type]
-> TcEvBinds
-> [Type]
-> TcM ([TyVar], LHsBinds GhcTc, Bag Implication)
tcSuperClasses TyVar
dfun_id Class
cls [TyVar]
tyvars [TyVar]
dfun_evs [Type]
inst_tys TcEvBinds
dfun_ev_binds [Type]
sc_theta
  = do { ([TyVar]
ids, [Located (HsBindLR GhcTc GhcTc)]
binds, [Implication]
implics) <- ((Type, Int)
 -> IOEnv
      (Env TcGblEnv TcLclEnv)
      (TyVar, Located (HsBindLR GhcTc GhcTc), Implication))
-> [(Type, Int)]
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Implication])
forall (m :: * -> *) a b c d.
Monad m =>
(a -> m (b, c, d)) -> [a] -> m ([b], [c], [d])
mapAndUnzip3M (Type, Int)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Implication)
tc_super ([Type] -> [Int] -> [(Type, Int)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Type]
sc_theta [Int
fIRST_TAG..])
       ; ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
ids, [Located (HsBindLR GhcTc GhcTc)]
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. [a] -> Bag a
listToBag [Located (HsBindLR GhcTc GhcTc)]
binds, [Implication] -> Bag Implication
forall a. [a] -> Bag a
listToBag [Implication]
implics) }
  where
    loc :: SrcSpan
loc = TyVar -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
getSrcSpan TyVar
dfun_id
    size :: TypeSize
size = [Type] -> TypeSize
sizeTypes [Type]
inst_tys
    tc_super :: (Type, Int)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Implication)
tc_super (Type
sc_pred, Int
n)
      = do { (Implication
sc_implic, EvBindsVar
ev_binds_var, EvTerm
sc_ev_tm)
                <- TcM EvTerm -> TcM (Implication, EvBindsVar, EvTerm)
forall result. TcM result -> TcM (Implication, EvBindsVar, result)
checkInstConstraints (TcM EvTerm -> TcM (Implication, EvBindsVar, EvTerm))
-> TcM EvTerm -> TcM (Implication, EvBindsVar, EvTerm)
forall a b. (a -> b) -> a -> b
$ CtOrigin -> Type -> TcM EvTerm
emitWanted (TypeSize -> CtOrigin
ScOrigin TypeSize
size) Type
sc_pred

           ; Name
sc_top_name  <- OccName -> TcM Name
newName (Int -> OccName -> OccName
mkSuperDictAuxOcc Int
n (Class -> OccName
forall a. NamedThing a => a -> OccName
getOccName Class
cls))
           ; TyVar
sc_ev_id     <- Type -> TcM TyVar
forall gbl lcl. Type -> TcRnIf gbl lcl TyVar
newEvVar Type
sc_pred
           ; EvBindsVar -> EvBind -> TcRn ()
addTcEvBind EvBindsVar
ev_binds_var (EvBind -> TcRn ()) -> EvBind -> TcRn ()
forall a b. (a -> b) -> a -> b
$ TyVar -> EvTerm -> EvBind
mkWantedEvBind TyVar
sc_ev_id EvTerm
sc_ev_tm
           ; let sc_top_ty :: Type
sc_top_ty = [TyVar] -> Type -> Type
mkInfForAllTys [TyVar]
tyvars (Type -> Type) -> Type -> Type
forall a b. (a -> b) -> a -> b
$
                             [Type] -> Type -> Type
mkPhiTy ((TyVar -> Type) -> [TyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Type
idType [TyVar]
dfun_evs) Type
sc_pred
                 sc_top_id :: TyVar
sc_top_id = HasDebugCallStack => Name -> Type -> Type -> TyVar
Name -> Type -> Type -> TyVar
mkLocalId Name
sc_top_name Type
Many Type
sc_top_ty
                 export :: ABExport GhcTc
export = ABE :: forall p.
XABE p -> IdP p -> IdP p -> HsWrapper -> TcSpecPrags -> ABExport p
ABE { abe_ext :: XABE GhcTc
abe_ext  = NoExtField
XABE GhcTc
noExtField
                              , abe_wrap :: HsWrapper
abe_wrap = HsWrapper
idHsWrapper
                              , abe_poly :: IdP GhcTc
abe_poly = TyVar
IdP GhcTc
sc_top_id
                              , abe_mono :: IdP GhcTc
abe_mono = TyVar
IdP GhcTc
sc_ev_id
                              , abe_prags :: TcSpecPrags
abe_prags = TcSpecPrags
noSpecPrags }
                 local_ev_binds :: TcEvBinds
local_ev_binds = EvBindsVar -> TcEvBinds
TcEvBinds EvBindsVar
ev_binds_var
                 bind :: HsBindLR GhcTc GhcTc
bind = AbsBinds :: forall idL idR.
XAbsBinds idL idR
-> [TyVar]
-> [TyVar]
-> [ABExport idL]
-> [TcEvBinds]
-> LHsBinds idL
-> Bool
-> HsBindLR idL idR
AbsBinds { abs_ext :: XAbsBinds GhcTc GhcTc
abs_ext      = NoExtField
XAbsBinds GhcTc GhcTc
noExtField
                                 , abs_tvs :: [TyVar]
abs_tvs      = [TyVar]
tyvars
                                 , abs_ev_vars :: [TyVar]
abs_ev_vars  = [TyVar]
dfun_evs
                                 , abs_exports :: [ABExport GhcTc]
abs_exports  = [ABExport GhcTc
export]
                                 , abs_ev_binds :: [TcEvBinds]
abs_ev_binds = [TcEvBinds
dfun_ev_binds, TcEvBinds
local_ev_binds]
                                 , abs_binds :: LHsBinds GhcTc
abs_binds    = LHsBinds GhcTc
forall a. Bag a
emptyBag
                                 , abs_sig :: Bool
abs_sig      = Bool
False }
           ; (TyVar, Located (HsBindLR GhcTc GhcTc), Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Implication)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar
sc_top_id, SrcSpan -> HsBindLR GhcTc GhcTc -> Located (HsBindLR GhcTc GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsBindLR GhcTc GhcTc
bind, Implication
sc_implic) }

-------------------
checkInstConstraints :: TcM result
                     -> TcM (Implication, EvBindsVar, result)
-- See Note [Typechecking plan for instance declarations]
checkInstConstraints :: TcM result -> TcM (Implication, EvBindsVar, result)
checkInstConstraints TcM result
thing_inside
  = do { (TcLevel
tclvl, WantedConstraints
wanted, result
result) <- TcM result -> TcM (TcLevel, WantedConstraints, result)
forall a. TcM a -> TcM (TcLevel, WantedConstraints, a)
pushLevelAndCaptureConstraints  (TcM result -> TcM (TcLevel, WantedConstraints, result))
-> TcM result -> TcM (TcLevel, WantedConstraints, result)
forall a b. (a -> b) -> a -> b
$
                                    TcM result
thing_inside

       ; EvBindsVar
ev_binds_var <- TcM EvBindsVar
newTcEvBinds
       ; Implication
implic <- TcM Implication
newImplication
       ; let implic' :: Implication
implic' = Implication
implic { ic_tclvl :: TcLevel
ic_tclvl  = TcLevel
tclvl
                              , ic_wanted :: WantedConstraints
ic_wanted = WantedConstraints
wanted
                              , ic_binds :: EvBindsVar
ic_binds  = EvBindsVar
ev_binds_var
                              , ic_info :: SkolemInfo
ic_info   = SkolemInfo
InstSkol }

       ; (Implication, EvBindsVar, result)
-> TcM (Implication, EvBindsVar, result)
forall (m :: * -> *) a. Monad m => a -> m a
return (Implication
implic', EvBindsVar
ev_binds_var, result
result) }

{-
Note [Recursive superclasses]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See #3731, #4809, #5751, #5913, #6117, #6161, which all
describe somewhat more complicated situations, but ones
encountered in practice.

See also tests tcrun020, tcrun021, tcrun033, and #11427.

----- THE PROBLEM --------
The problem is that it is all too easy to create a class whose
superclass is bottom when it should not be.

Consider the following (extreme) situation:
        class C a => D a where ...
        instance D [a] => D [a] where ...   (dfunD)
        instance C [a] => C [a] where ...   (dfunC)
Although this looks wrong (assume D [a] to prove D [a]), it is only a
more extreme case of what happens with recursive dictionaries, and it
can, just about, make sense because the methods do some work before
recursing.

To implement the dfunD we must generate code for the superclass C [a],
which we had better not get by superclass selection from the supplied
argument:
       dfunD :: forall a. D [a] -> D [a]
       dfunD = \d::D [a] -> MkD (scsel d) ..

Otherwise if we later encounter a situation where
we have a [Wanted] dw::D [a] we might solve it thus:
     dw := dfunD dw
Which is all fine except that now ** the superclass C is bottom **!

The instance we want is:
       dfunD :: forall a. D [a] -> D [a]
       dfunD = \d::D [a] -> MkD (dfunC (scsel d)) ...

----- THE SOLUTION --------
The basic solution is simple: be very careful about using superclass
selection to generate a superclass witness in a dictionary function
definition.  More precisely:

  Superclass Invariant: in every class dictionary,
                        every superclass dictionary field
                        is non-bottom

To achieve the Superclass Invariant, in a dfun definition we can
generate a guaranteed-non-bottom superclass witness from:
  (sc1) one of the dictionary arguments itself (all non-bottom)
  (sc2) an immediate superclass of a smaller dictionary
  (sc3) a call of a dfun (always returns a dictionary constructor)

The tricky case is (sc2).  We proceed by induction on the size of
the (type of) the dictionary, defined by GHC.Tc.Validity.sizeTypes.
Let's suppose we are building a dictionary of size 3, and
suppose the Superclass Invariant holds of smaller dictionaries.
Then if we have a smaller dictionary, its immediate superclasses
will be non-bottom by induction.

What does "we have a smaller dictionary" mean?  It might be
one of the arguments of the instance, or one of its superclasses.
Here is an example, taken from CmmExpr:
       class Ord r => UserOfRegs r a where ...
(i1)   instance UserOfRegs r a => UserOfRegs r (Maybe a) where
(i2)   instance (Ord r, UserOfRegs r CmmReg) => UserOfRegs r CmmExpr where

For (i1) we can get the (Ord r) superclass by selection from (UserOfRegs r a),
since it is smaller than the thing we are building (UserOfRegs r (Maybe a).

But for (i2) that isn't the case, so we must add an explicit, and
perhaps surprising, (Ord r) argument to the instance declaration.

Here's another example from #6161:

       class       Super a => Duper a  where ...
       class Duper (Fam a) => Foo a    where ...
(i3)   instance Foo a => Duper (Fam a) where ...
(i4)   instance              Foo Float where ...

It would be horribly wrong to define
   dfDuperFam :: Foo a -> Duper (Fam a)  -- from (i3)
   dfDuperFam d = MkDuper (sc_sel1 (sc_sel2 d)) ...

   dfFooFloat :: Foo Float               -- from (i4)
   dfFooFloat = MkFoo (dfDuperFam dfFooFloat) ...

Now the Super superclass of Duper is definitely bottom!

This won't happen because when processing (i3) we can use the
superclasses of (Foo a), which is smaller, namely Duper (Fam a).  But
that is *not* smaller than the target so we can't take *its*
superclasses.  As a result the program is rightly rejected, unless you
add (Super (Fam a)) to the context of (i3).

Note [Solving superclass constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
How do we ensure that every superclass witness is generated by
one of (sc1) (sc2) or (sc3) in Note [Recursive superclasses].
Answer:

  * Superclass "wanted" constraints have CtOrigin of (ScOrigin size)
    where 'size' is the size of the instance declaration. e.g.
          class C a => D a where...
          instance blah => D [a] where ...
    The wanted superclass constraint for C [a] has origin
    ScOrigin size, where size = size( D [a] ).

  * (sc1) When we rewrite such a wanted constraint, it retains its
    origin.  But if we apply an instance declaration, we can set the
    origin to (ScOrigin infinity), thus lifting any restrictions by
    making prohibitedSuperClassSolve return False.

  * (sc2) ScOrigin wanted constraints can't be solved from a
    superclass selection, except at a smaller type.  This test is
    implemented by GHC.Tc.Solver.Interact.prohibitedSuperClassSolve

  * The "given" constraints of an instance decl have CtOrigin
    GivenOrigin InstSkol.

  * When we make a superclass selection from InstSkol we use
    a SkolemInfo of (InstSC size), where 'size' is the size of
    the constraint whose superclass we are taking.  A similarly
    when taking the superclass of an InstSC.  This is implemented
    in GHC.Tc.Solver.Canonical.newSCWorkFromFlavored

Note [Silent superclass arguments] (historical interest only)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NB1: this note describes our *old* solution to the
     recursive-superclass problem. I'm keeping the Note
     for now, just as institutional memory.
     However, the code for silent superclass arguments
     was removed in late Dec 2014

NB2: the silent-superclass solution introduced new problems
     of its own, in the form of instance overlap.  Tests
     SilentParametersOverlapping, T5051, and T7862 are examples

NB3: the silent-superclass solution also generated tons of
     extra dictionaries.  For example, in monad-transformer
     code, when constructing a Monad dictionary you had to pass
     an Applicative dictionary; and to construct that you need
     a Functor dictionary. Yet these extra dictionaries were
     often never used.  Test T3064 compiled *far* faster after
     silent superclasses were eliminated.

Our solution to this problem "silent superclass arguments".  We pass
to each dfun some ``silent superclass arguments’’, which are the
immediate superclasses of the dictionary we are trying to
construct. In our example:
       dfun :: forall a. C [a] -> D [a] -> D [a]
       dfun = \(dc::C [a]) (dd::D [a]) -> DOrd dc ...
Notice the extra (dc :: C [a]) argument compared to the previous version.

This gives us:

     -----------------------------------------------------------
     DFun Superclass Invariant
     ~~~~~~~~~~~~~~~~~~~~~~~~
     In the body of a DFun, every superclass argument to the
     returned dictionary is
       either   * one of the arguments of the DFun,
       or       * constant, bound at top level
     -----------------------------------------------------------

This net effect is that it is safe to treat a dfun application as
wrapping a dictionary constructor around its arguments (in particular,
a dfun never picks superclasses from the arguments under the
dictionary constructor). No superclass is hidden inside a dfun
application.

The extra arguments required to satisfy the DFun Superclass Invariant
always come first, and are called the "silent" arguments.  You can
find out how many silent arguments there are using Id.dfunNSilent;
and then you can just drop that number of arguments to see the ones
that were in the original instance declaration.

DFun types are built (only) by MkId.mkDictFunId, so that is where we
decide what silent arguments are to be added.
-}

{-
************************************************************************
*                                                                      *
      Type-checking an instance method
*                                                                      *
************************************************************************

tcMethod
- Make the method bindings, as a [(NonRec, HsBinds)], one per method
- Remembering to use fresh Name (the instance method Name) as the binder
- Bring the instance method Ids into scope, for the benefit of tcInstSig
- Use sig_fn mapping instance method Name -> instance tyvars
- Ditto prag_fn
- Use tcValBinds to do the checking
-}

tcMethods :: DFunId -> Class
          -> [TcTyVar] -> [EvVar]
          -> [TcType]
          -> TcEvBinds
          -> ([Located TcSpecPrag], TcPragEnv)
          -> [ClassOpItem]
          -> InstBindings GhcRn
          -> TcM ([Id], LHsBinds GhcTc, Bag Implication)
        -- The returned inst_meth_ids all have types starting
        --      forall tvs. theta => ...
tcMethods :: TyVar
-> Class
-> [TyVar]
-> [TyVar]
-> [Type]
-> TcEvBinds
-> ([Located TcSpecPrag], TcPragEnv)
-> [ClassOpItem]
-> InstBindings GhcRn
-> TcM ([TyVar], LHsBinds GhcTc, Bag Implication)
tcMethods TyVar
dfun_id Class
clas [TyVar]
tyvars [TyVar]
dfun_ev_vars [Type]
inst_tys
                  TcEvBinds
dfun_ev_binds ([Located TcSpecPrag]
spec_inst_prags, TcPragEnv
prag_fn) [ClassOpItem]
op_items
                  (InstBindings { ib_binds :: forall a. InstBindings a -> LHsBinds a
ib_binds      = LHsBinds GhcRn
binds
                                , ib_tyvars :: forall a. InstBindings a -> [Name]
ib_tyvars     = [Name]
lexical_tvs
                                , ib_pragmas :: forall a. InstBindings a -> [LSig a]
ib_pragmas    = [LSig GhcRn]
sigs
                                , ib_extensions :: forall a. InstBindings a -> [Extension]
ib_extensions = [Extension]
exts
                                , ib_derived :: forall a. InstBindings a -> Bool
ib_derived    = Bool
is_derived })
  = [(Name, TyVar)]
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv ([Name]
lexical_tvs [Name] -> [TyVar] -> [(Name, TyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TyVar]
tyvars) (TcM
   ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
 -> TcM
      ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication))
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
forall a b. (a -> b) -> a -> b
$
       -- The lexical_tvs scope over the 'where' part
    do { String -> SDoc -> TcRn ()
traceTc String
"tcInstMeth" ([Located (Sig GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Located (Sig GhcRn)]
[LSig GhcRn]
sigs SDoc -> SDoc -> SDoc
$$ Bag (Located (HsBindLR GhcRn GhcRn)) -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bag (Located (HsBindLR GhcRn GhcRn))
LHsBinds GhcRn
binds)
       ; TcRn ()
checkMinimalDefinition
       ; TcRn ()
checkMethBindMembership
       ; ([TyVar]
ids, [Located (HsBindLR GhcTc GhcTc)]
binds, [Maybe Implication]
mb_implics) <- [Extension]
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
forall a. [Extension] -> TcM a -> TcM a
set_exts [Extension]
exts (TcM
   ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
 -> TcM
      ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication]))
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
forall a b. (a -> b) -> a -> b
$
                                     TcM
  ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
forall a. TcM a -> TcM a
unset_warnings_deriving (TcM
   ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
 -> TcM
      ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication]))
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
forall a b. (a -> b) -> a -> b
$
                                     (ClassOpItem
 -> IOEnv
      (Env TcGblEnv TcLclEnv)
      (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication))
-> [ClassOpItem]
-> TcM
     ([TyVar], [Located (HsBindLR GhcTc GhcTc)], [Maybe Implication])
forall (m :: * -> *) a b c d.
Monad m =>
(a -> m (b, c, d)) -> [a] -> m ([b], [c], [d])
mapAndUnzip3M ClassOpItem
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
ClassOpItem -> TcM (TyVar, LHsBind GhcTc, Maybe Implication)
tc_item [ClassOpItem]
op_items
       ; ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
-> TcM
     ([TyVar], Bag (Located (HsBindLR GhcTc GhcTc)), Bag Implication)
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
ids, [Located (HsBindLR GhcTc GhcTc)]
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. [a] -> Bag a
listToBag [Located (HsBindLR GhcTc GhcTc)]
binds, [Implication] -> Bag Implication
forall a. [a] -> Bag a
listToBag ([Maybe Implication] -> [Implication]
forall a. [Maybe a] -> [a]
catMaybes [Maybe Implication]
mb_implics)) }
  where
    set_exts :: [LangExt.Extension] -> TcM a -> TcM a
    set_exts :: [Extension] -> TcM a -> TcM a
set_exts [Extension]
es TcM a
thing = (Extension -> TcM a -> TcM a) -> TcM a -> [Extension] -> TcM a
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Extension -> TcM a -> TcM a
forall gbl lcl a. Extension -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
setXOptM TcM a
thing [Extension]
es

    -- See Note [Avoid -Winaccessible-code when deriving]
    unset_warnings_deriving :: TcM a -> TcM a
    unset_warnings_deriving :: TcM a -> TcM a
unset_warnings_deriving
      | Bool
is_derived = WarningFlag -> TcM a -> TcM a
forall gbl lcl a.
WarningFlag -> TcRnIf gbl lcl a -> TcRnIf gbl lcl a
unsetWOptM WarningFlag
Opt_WarnInaccessibleCode
      | Bool
otherwise  = TcM a -> TcM a
forall a. a -> a
id

    hs_sig_fn :: HsSigFun
hs_sig_fn = [LSig GhcRn] -> HsSigFun
mkHsSigFun [LSig GhcRn]
sigs
    inst_loc :: SrcSpan
inst_loc  = TyVar -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
getSrcSpan TyVar
dfun_id

    ----------------------
    tc_item :: ClassOpItem -> TcM (Id, LHsBind GhcTc, Maybe Implication)
    tc_item :: ClassOpItem -> TcM (TyVar, LHsBind GhcTc, Maybe Implication)
tc_item (TyVar
sel_id, DefMethInfo
dm_info)
      | Just (LHsBind GhcRn
user_bind, SrcSpan
bndr_loc, [LSig GhcRn]
prags) <- Name
-> LHsBinds GhcRn
-> TcPragEnv
-> Maybe (LHsBind GhcRn, SrcSpan, [LSig GhcRn])
findMethodBind (TyVar -> Name
idName TyVar
sel_id) LHsBinds GhcRn
binds TcPragEnv
prag_fn
      = Class
-> [TyVar]
-> [TyVar]
-> [Type]
-> TcEvBinds
-> Bool
-> HsSigFun
-> [Located TcSpecPrag]
-> [LSig GhcRn]
-> TyVar
-> LHsBind GhcRn
-> SrcSpan
-> TcM (TyVar, LHsBind GhcTc, Maybe Implication)
tcMethodBody Class
clas [TyVar]
tyvars [TyVar]
dfun_ev_vars [Type]
inst_tys
                              TcEvBinds
dfun_ev_binds Bool
is_derived HsSigFun
hs_sig_fn
                              [Located TcSpecPrag]
spec_inst_prags [LSig GhcRn]
prags
                              TyVar
sel_id LHsBind GhcRn
user_bind SrcSpan
bndr_loc
      | Bool
otherwise
      = do { String -> SDoc -> TcRn ()
traceTc String
"tc_def" (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id)
           ; TyVar
-> DefMethInfo -> TcM (TyVar, LHsBind GhcTc, Maybe Implication)
tc_default TyVar
sel_id DefMethInfo
dm_info }

    ----------------------
    tc_default :: Id -> DefMethInfo
               -> TcM (TcId, LHsBind GhcTc, Maybe Implication)

    tc_default :: TyVar
-> DefMethInfo -> TcM (TyVar, LHsBind GhcTc, Maybe Implication)
tc_default TyVar
sel_id (Just (Name
dm_name, DefMethSpec Type
_))
      = do { (Located (HsBindLR GhcRn GhcRn)
meth_bind, [Located (Sig GhcRn)]
inline_prags) <- TyVar
-> Class -> TyVar -> Name -> TcM (LHsBind GhcRn, [LSig GhcRn])
mkDefMethBind TyVar
dfun_id Class
clas TyVar
sel_id Name
dm_name
           ; Class
-> [TyVar]
-> [TyVar]
-> [Type]
-> TcEvBinds
-> Bool
-> HsSigFun
-> [Located TcSpecPrag]
-> [LSig GhcRn]
-> TyVar
-> LHsBind GhcRn
-> SrcSpan
-> TcM (TyVar, LHsBind GhcTc, Maybe Implication)
tcMethodBody Class
clas [TyVar]
tyvars [TyVar]
dfun_ev_vars [Type]
inst_tys
                          TcEvBinds
dfun_ev_binds Bool
is_derived HsSigFun
hs_sig_fn
                          [Located TcSpecPrag]
spec_inst_prags [Located (Sig GhcRn)]
[LSig GhcRn]
inline_prags
                          TyVar
sel_id Located (HsBindLR GhcRn GhcRn)
LHsBind GhcRn
meth_bind SrcSpan
inst_loc }

    tc_default TyVar
sel_id DefMethInfo
Nothing     -- No default method at all
      = do { String -> SDoc -> TcRn ()
traceTc String
"tc_def: warn" (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id)
           ; (TyVar
meth_id, TyVar
_) <- Class
-> [TyVar] -> [TyVar] -> [Type] -> TyVar -> TcM (TyVar, TyVar)
mkMethIds Class
clas [TyVar]
tyvars [TyVar]
dfun_ev_vars
                                       [Type]
inst_tys TyVar
sel_id
           ; DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
           ; let meth_bind :: LHsBind GhcTc
meth_bind = IdP GhcTc -> LHsExpr GhcTc -> LHsBind GhcTc
forall (p :: Pass).
IdP (GhcPass p) -> LHsExpr (GhcPass p) -> LHsBind (GhcPass p)
mkVarBind TyVar
IdP GhcTc
meth_id (LHsExpr GhcTc -> LHsBind GhcTc) -> LHsExpr GhcTc -> LHsBind GhcTc
forall a b. (a -> b) -> a -> b
$
                             HsWrapper -> LHsExpr GhcTc -> LHsExpr GhcTc
mkLHsWrap HsWrapper
lam_wrapper (DynFlags -> GenLocated SrcSpan (HsExpr GhcTc)
error_rhs DynFlags
dflags)
           ; (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar
meth_id, Located (HsBindLR GhcTc GhcTc)
LHsBind GhcTc
meth_bind, Maybe Implication
forall a. Maybe a
Nothing) }
      where
        error_rhs :: DynFlags -> GenLocated SrcSpan (HsExpr GhcTc)
error_rhs DynFlags
dflags = SrcSpan -> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc))
-> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall a b. (a -> b) -> a -> b
$ XApp GhcTc -> LHsExpr GhcTc -> LHsExpr GhcTc -> HsExpr GhcTc
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp NoExtField
XApp GhcTc
noExtField GenLocated SrcSpan (HsExpr GhcTc)
LHsExpr GhcTc
error_fun (DynFlags -> GenLocated SrcSpan (HsExpr GhcTc)
error_msg DynFlags
dflags)
        error_fun :: GenLocated SrcSpan (HsExpr GhcTc)
error_fun    = SrcSpan -> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc))
-> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall a b. (a -> b) -> a -> b
$
                       HsWrapper -> TyVar -> HsExpr GhcTc
wrapId ([Type] -> HsWrapper
mkWpTyApps
                                [ HasDebugCallStack => Type -> Type
Type -> Type
getRuntimeRep Type
meth_tau, Type
meth_tau])
                              TyVar
nO_METHOD_BINDING_ERROR_ID
        error_msg :: DynFlags -> GenLocated SrcSpan (HsExpr GhcTc)
error_msg DynFlags
dflags = SrcSpan -> HsExpr GhcTc -> GenLocated SrcSpan (HsExpr GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (XLitE GhcTc -> HsLit GhcTc -> HsExpr GhcTc
forall p. XLitE p -> HsLit p -> HsExpr p
HsLit NoExtField
XLitE GhcTc
noExtField (XHsStringPrim GhcTc -> ByteString -> HsLit GhcTc
forall x. XHsStringPrim x -> ByteString -> HsLit x
HsStringPrim SourceText
XHsStringPrim GhcTc
NoSourceText
                                              (String -> ByteString
unsafeMkByteString (DynFlags -> String
error_string DynFlags
dflags))))
        meth_tau :: Type
meth_tau     = TyVar -> [Type] -> Type
classMethodInstTy TyVar
sel_id [Type]
inst_tys
        error_string :: DynFlags -> String
error_string DynFlags
dflags = DynFlags -> SDoc -> String
showSDoc DynFlags
dflags
                              ([SDoc] -> SDoc
hcat [SrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
ppr SrcSpan
inst_loc, SDoc
vbar, TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id ])
        lam_wrapper :: HsWrapper
lam_wrapper  = [TyVar] -> HsWrapper
mkWpTyLams [TyVar]
tyvars HsWrapper -> HsWrapper -> HsWrapper
<.> [TyVar] -> HsWrapper
mkWpLams [TyVar]
dfun_ev_vars

    ----------------------
    -- Check if one of the minimal complete definitions is satisfied
    checkMinimalDefinition :: TcRn ()
checkMinimalDefinition
      = Maybe (BooleanFormula Name)
-> (BooleanFormula Name -> TcRn ()) -> TcRn ()
forall (m :: * -> *) a. Monad m => Maybe a -> (a -> m ()) -> m ()
whenIsJust ((Name -> Bool)
-> BooleanFormula Name -> Maybe (BooleanFormula Name)
forall a.
Eq a =>
(a -> Bool) -> BooleanFormula a -> Maybe (BooleanFormula a)
isUnsatisfied Name -> Bool
methodExists (Class -> BooleanFormula Name
classMinimalDef Class
clas)) ((BooleanFormula Name -> TcRn ()) -> TcRn ())
-> (BooleanFormula Name -> TcRn ()) -> TcRn ()
forall a b. (a -> b) -> a -> b
$
        BooleanFormula Name -> TcRn ()
warnUnsatisfiedMinimalDefinition

    methodExists :: Name -> Bool
methodExists Name
meth = Maybe
  (Located (HsBindLR GhcRn GhcRn), SrcSpan, [Located (Sig GhcRn)])
-> Bool
forall a. Maybe a -> Bool
isJust (Name
-> LHsBinds GhcRn
-> TcPragEnv
-> Maybe (LHsBind GhcRn, SrcSpan, [LSig GhcRn])
findMethodBind Name
meth LHsBinds GhcRn
binds TcPragEnv
prag_fn)

    ----------------------
    -- Check if any method bindings do not correspond to the class.
    -- See Note [Mismatched class methods and associated type families].
    checkMethBindMembership :: TcRn ()
checkMethBindMembership
      = (Name -> TcRn ()) -> [Name] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (SDoc -> TcRn ()
addErrTc (SDoc -> TcRn ()) -> (Name -> SDoc) -> Name -> TcRn ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Class -> Name -> SDoc
forall a. Outputable a => a -> Name -> SDoc
badMethodErr Class
clas) [Name]
mismatched_meths
      where
        bind_nms :: [Name]
bind_nms         = (GenLocated SrcSpan Name -> Name)
-> [GenLocated SrcSpan Name] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map GenLocated SrcSpan Name -> Name
forall l e. GenLocated l e -> e
unLoc ([GenLocated SrcSpan Name] -> [Name])
-> [GenLocated SrcSpan Name] -> [Name]
forall a b. (a -> b) -> a -> b
$ LHsBinds GhcRn -> [LIdP GhcRn]
forall idL idR. UnXRec idL => LHsBindsLR idL idR -> [LIdP idL]
collectMethodBinders LHsBinds GhcRn
binds
        cls_meth_nms :: [Name]
cls_meth_nms     = (ClassOpItem -> Name) -> [ClassOpItem] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (TyVar -> Name
idName (TyVar -> Name) -> (ClassOpItem -> TyVar) -> ClassOpItem -> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ClassOpItem -> TyVar
forall a b. (a, b) -> a
fst) [ClassOpItem]
op_items
        mismatched_meths :: [Name]
mismatched_meths = [Name]
bind_nms [Name] -> [Name] -> [Name]
forall a. Ord a => [a] -> [a] -> [a]
`minusList` [Name]
cls_meth_nms

{-
Note [Mismatched class methods and associated type families]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It's entirely possible for someone to put methods or associated type family
instances inside of a class in which it doesn't belong. For instance, we'd
want to fail if someone wrote this:

  instance Eq () where
    type Rep () = Maybe
    compare = undefined

Since neither the type family `Rep` nor the method `compare` belong to the
class `Eq`. Normally, this is caught in the renamer when resolving RdrNames,
since that would discover that the parent class `Eq` is incorrect.

However, there is a scenario in which the renamer could fail to catch this:
if the instance was generated through Template Haskell, as in #12387. In that
case, Template Haskell will provide fully resolved names (e.g.,
`GHC.Classes.compare`), so the renamer won't notice the sleight-of-hand going
on. For this reason, we also put an extra validity check for this in the
typechecker as a last resort.

Note [Avoid -Winaccessible-code when deriving]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Winaccessible-code can be particularly noisy when deriving instances for
GADTs. Consider the following example (adapted from #8128):

  data T a where
    MkT1 :: Int -> T Int
    MkT2 :: T Bool
    MkT3 :: T Bool
  deriving instance Eq (T a)
  deriving instance Ord (T a)

In the derived Ord instance, GHC will generate the following code:

  instance Ord (T a) where
    compare x y
      = case x of
          MkT2
            -> case y of
                 MkT1 {} -> GT
                 MkT2    -> EQ
                 _       -> LT
          ...

However, that MkT1 is unreachable, since the type indices for MkT1 and MkT2
differ, so if -Winaccessible-code is enabled, then deriving this instance will
result in unwelcome warnings.

One conceivable approach to fixing this issue would be to change `deriving Ord`
such that it becomes smarter about not generating unreachable cases. This,
however, would be a highly nontrivial refactor, as we'd have to propagate
through typing information everywhere in the algorithm that generates Ord
instances in order to determine which cases were unreachable. This seems like
a lot of work for minimal gain, so we have opted not to go for this approach.

Instead, we take the much simpler approach of always disabling
-Winaccessible-code for derived code. To accomplish this, we do the following:

1. In tcMethods (which typechecks method bindings), disable
   -Winaccessible-code.
2. When creating Implications during typechecking, record this flag
   (in ic_warn_inaccessible) at the time of creation.
3. After typechecking comes error reporting, where GHC must decide how to
   report inaccessible code to the user, on an Implication-by-Implication
   basis. If an Implication's DynFlags indicate that -Winaccessible-code was
   disabled, then don't bother reporting it. That's it!
-}

------------------------
tcMethodBody :: Class -> [TcTyVar] -> [EvVar] -> [TcType]
             -> TcEvBinds -> Bool
             -> HsSigFun
             -> [LTcSpecPrag] -> [LSig GhcRn]
             -> Id -> LHsBind GhcRn -> SrcSpan
             -> TcM (TcId, LHsBind GhcTc, Maybe Implication)
tcMethodBody :: Class
-> [TyVar]
-> [TyVar]
-> [Type]
-> TcEvBinds
-> Bool
-> HsSigFun
-> [Located TcSpecPrag]
-> [LSig GhcRn]
-> TyVar
-> LHsBind GhcRn
-> SrcSpan
-> TcM (TyVar, LHsBind GhcTc, Maybe Implication)
tcMethodBody Class
clas [TyVar]
tyvars [TyVar]
dfun_ev_vars [Type]
inst_tys
                     TcEvBinds
dfun_ev_binds Bool
is_derived
                     HsSigFun
sig_fn [Located TcSpecPrag]
spec_inst_prags [LSig GhcRn]
prags
                     TyVar
sel_id (L bind_loc meth_bind) SrcSpan
bndr_loc
  = IOEnv
  (Env TcGblEnv TcLclEnv)
  (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
add_meth_ctxt (IOEnv
   (Env TcGblEnv TcLclEnv)
   (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
 -> IOEnv
      (Env TcGblEnv TcLclEnv)
      (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication))
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcMethodBody" (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyVar -> Type
idType TyVar
sel_id) SDoc -> SDoc -> SDoc
$$ SrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
ppr SrcSpan
bndr_loc)
       ; (TyVar
global_meth_id, TyVar
local_meth_id) <- SrcSpan -> TcM (TyVar, TyVar) -> TcM (TyVar, TyVar)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
bndr_loc (TcM (TyVar, TyVar) -> TcM (TyVar, TyVar))
-> TcM (TyVar, TyVar) -> TcM (TyVar, TyVar)
forall a b. (a -> b) -> a -> b
$
                                            Class
-> [TyVar] -> [TyVar] -> [Type] -> TyVar -> TcM (TyVar, TyVar)
mkMethIds Class
clas [TyVar]
tyvars [TyVar]
dfun_ev_vars
                                                      [Type]
inst_tys TyVar
sel_id

       ; let lm_bind :: HsBindLR GhcRn GhcRn
lm_bind = HsBindLR GhcRn GhcRn
meth_bind { fun_id :: LIdP GhcRn
fun_id = SrcSpan -> Name -> GenLocated SrcSpan Name
forall l e. l -> e -> GenLocated l e
L SrcSpan
bndr_loc (TyVar -> Name
idName TyVar
local_meth_id) }
                       -- Substitute the local_meth_name for the binder
                       -- NB: the binding is always a FunBind

            -- taking instance signature into account might change the type of
            -- the local_meth_id
       ; (Implication
meth_implic, EvBindsVar
ev_binds_var, Bag (Located (HsBindLR GhcTc GhcTc))
tc_bind)
             <- IOEnv
  (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> TcM
     (Implication, EvBindsVar, Bag (Located (HsBindLR GhcTc GhcTc)))
forall result. TcM result -> TcM (Implication, EvBindsVar, result)
checkInstConstraints (IOEnv
   (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
 -> TcM
      (Implication, EvBindsVar, Bag (Located (HsBindLR GhcTc GhcTc))))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
-> TcM
     (Implication, EvBindsVar, Bag (Located (HsBindLR GhcTc GhcTc)))
forall a b. (a -> b) -> a -> b
$
                HsSigFun -> TyVar -> TyVar -> LHsBind GhcRn -> TcM (LHsBinds GhcTc)
tcMethodBodyHelp HsSigFun
sig_fn TyVar
sel_id TyVar
local_meth_id (SrcSpan -> HsBindLR GhcRn GhcRn -> Located (HsBindLR GhcRn GhcRn)
forall l e. l -> e -> GenLocated l e
L SrcSpan
bind_loc HsBindLR GhcRn GhcRn
lm_bind)

       ; TyVar
global_meth_id <- TyVar -> [LSig GhcRn] -> TcM TyVar
addInlinePrags TyVar
global_meth_id [LSig GhcRn]
prags
       ; [Located TcSpecPrag]
spec_prags     <- TyVar -> [LSig GhcRn] -> TcM [Located TcSpecPrag]
tcSpecPrags TyVar
global_meth_id [LSig GhcRn]
prags

        ; let specs :: TcSpecPrags
specs  = TyVar
-> [Located TcSpecPrag] -> [Located TcSpecPrag] -> TcSpecPrags
mk_meth_spec_prags TyVar
global_meth_id [Located TcSpecPrag]
spec_inst_prags [Located TcSpecPrag]
spec_prags
              export :: ABExport GhcTc
export = ABE :: forall p.
XABE p -> IdP p -> IdP p -> HsWrapper -> TcSpecPrags -> ABExport p
ABE { abe_ext :: XABE GhcTc
abe_ext   = NoExtField
XABE GhcTc
noExtField
                           , abe_poly :: IdP GhcTc
abe_poly  = TyVar
IdP GhcTc
global_meth_id
                           , abe_mono :: IdP GhcTc
abe_mono  = TyVar
IdP GhcTc
local_meth_id
                           , abe_wrap :: HsWrapper
abe_wrap  = HsWrapper
idHsWrapper
                           , abe_prags :: TcSpecPrags
abe_prags = TcSpecPrags
specs }

              local_ev_binds :: TcEvBinds
local_ev_binds = EvBindsVar -> TcEvBinds
TcEvBinds EvBindsVar
ev_binds_var
              full_bind :: HsBindLR GhcTc GhcTc
full_bind = AbsBinds :: forall idL idR.
XAbsBinds idL idR
-> [TyVar]
-> [TyVar]
-> [ABExport idL]
-> [TcEvBinds]
-> LHsBinds idL
-> Bool
-> HsBindLR idL idR
AbsBinds { abs_ext :: XAbsBinds GhcTc GhcTc
abs_ext      = NoExtField
XAbsBinds GhcTc GhcTc
noExtField
                                   , abs_tvs :: [TyVar]
abs_tvs      = [TyVar]
tyvars
                                   , abs_ev_vars :: [TyVar]
abs_ev_vars  = [TyVar]
dfun_ev_vars
                                   , abs_exports :: [ABExport GhcTc]
abs_exports  = [ABExport GhcTc
export]
                                   , abs_ev_binds :: [TcEvBinds]
abs_ev_binds = [TcEvBinds
dfun_ev_binds, TcEvBinds
local_ev_binds]
                                   , abs_binds :: LHsBinds GhcTc
abs_binds    = Bag (Located (HsBindLR GhcTc GhcTc))
LHsBinds GhcTc
tc_bind
                                   , abs_sig :: Bool
abs_sig      = Bool
True }

        ; (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar
global_meth_id, SrcSpan -> HsBindLR GhcTc GhcTc -> Located (HsBindLR GhcTc GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
bind_loc HsBindLR GhcTc GhcTc
full_bind, Implication -> Maybe Implication
forall a. a -> Maybe a
Just Implication
meth_implic) }
  where
        -- For instance decls that come from deriving clauses
        -- we want to print out the full source code if there's an error
        -- because otherwise the user won't see the code at all
    add_meth_ctxt :: IOEnv
  (Env TcGblEnv TcLclEnv)
  (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
add_meth_ctxt IOEnv
  (Env TcGblEnv TcLclEnv)
  (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
thing
      | Bool
is_derived = SDoc
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
forall a. SDoc -> TcM a -> TcM a
addLandmarkErrCtxt (TyVar -> Class -> [Type] -> SDoc
derivBindCtxt TyVar
sel_id Class
clas [Type]
inst_tys) IOEnv
  (Env TcGblEnv TcLclEnv)
  (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
thing
      | Bool
otherwise  = IOEnv
  (Env TcGblEnv TcLclEnv)
  (TyVar, Located (HsBindLR GhcTc GhcTc), Maybe Implication)
thing

tcMethodBodyHelp :: HsSigFun -> Id -> TcId
                 -> LHsBind GhcRn -> TcM (LHsBinds GhcTc)
tcMethodBodyHelp :: HsSigFun -> TyVar -> TyVar -> LHsBind GhcRn -> TcM (LHsBinds GhcTc)
tcMethodBodyHelp HsSigFun
hs_sig_fn TyVar
sel_id TyVar
local_meth_id LHsBind GhcRn
meth_bind
  | Just LHsSigType GhcRn
hs_sig_ty <- HsSigFun
hs_sig_fn Name
sel_name
              -- There is a signature in the instance
              -- See Note [Instance method signatures]
  = do { (Type
sig_ty, HsWrapper
hs_wrap)
             <- SrcSpan -> TcRn (Type, HsWrapper) -> TcRn (Type, HsWrapper)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (LHsSigType GhcRn -> SrcSpan
forall l e. GenLocated l e -> l
getLoc LHsSigType GhcRn
hs_sig_ty) (TcRn (Type, HsWrapper) -> TcRn (Type, HsWrapper))
-> TcRn (Type, HsWrapper) -> TcRn (Type, HsWrapper)
forall a b. (a -> b) -> a -> b
$
                do { Bool
inst_sigs <- Extension -> TcRn Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.InstanceSigs
                   ; Bool -> SDoc -> TcRn ()
checkTc Bool
inst_sigs (Name -> LHsSigType GhcRn -> SDoc
misplacedInstSig Name
sel_name LHsSigType GhcRn
hs_sig_ty)
                   ; Type
sig_ty  <- UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsSigType (Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
sel_name Bool
False) LHsSigType GhcRn
hs_sig_ty
                   ; let local_meth_ty :: Type
local_meth_ty = TyVar -> Type
idType TyVar
local_meth_id
                         ctxt :: UserTypeCtxt
ctxt = Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
sel_name Bool
False
                                -- False <=> do not report redundant constraints when
                                --           checking instance-sig <= class-meth-sig
                                -- The instance-sig is the focus here; the class-meth-sig
                                -- is fixed (#18036)
                   ; HsWrapper
hs_wrap <- (TidyEnv -> TcM (TidyEnv, SDoc)) -> TcM HsWrapper -> TcM HsWrapper
forall a. (TidyEnv -> TcM (TidyEnv, SDoc)) -> TcM a -> TcM a
addErrCtxtM (Name -> Type -> Type -> TidyEnv -> TcM (TidyEnv, SDoc)
methSigCtxt Name
sel_name Type
sig_ty Type
local_meth_ty) (TcM HsWrapper -> TcM HsWrapper) -> TcM HsWrapper -> TcM HsWrapper
forall a b. (a -> b) -> a -> b
$
                                UserTypeCtxt -> Type -> Type -> TcM HsWrapper
tcSubTypeSigma UserTypeCtxt
ctxt Type
sig_ty Type
local_meth_ty
                   ; (Type, HsWrapper) -> TcRn (Type, HsWrapper)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
sig_ty, HsWrapper
hs_wrap) }

       ; Name
inner_meth_name <- OccName -> TcM Name
newName (Name -> OccName
nameOccName Name
sel_name)
       ; let ctxt :: UserTypeCtxt
ctxt = Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
sel_name Bool
True
                    -- True <=> check for redundant constraints in the
                    --          user-specified instance signature
             inner_meth_id :: TyVar
inner_meth_id  = HasDebugCallStack => Name -> Type -> Type -> TyVar
Name -> Type -> Type -> TyVar
mkLocalId Name
inner_meth_name Type
Many Type
sig_ty
             inner_meth_sig :: TcIdSigInfo
inner_meth_sig = CompleteSig :: TyVar -> UserTypeCtxt -> SrcSpan -> TcIdSigInfo
CompleteSig { sig_bndr :: TyVar
sig_bndr = TyVar
inner_meth_id
                                          , sig_ctxt :: UserTypeCtxt
sig_ctxt = UserTypeCtxt
ctxt
                                          , sig_loc :: SrcSpan
sig_loc  = LHsSigType GhcRn -> SrcSpan
forall l e. GenLocated l e -> l
getLoc LHsSigType GhcRn
hs_sig_ty }


       ; (Bag (Located (HsBindLR GhcTc GhcTc))
tc_bind, [TyVar
inner_id]) <- TcPragEnv
-> TcIdSigInfo -> LHsBind GhcRn -> TcM (LHsBinds GhcTc, [TyVar])
tcPolyCheck NameEnv [Located (Sig GhcRn)]
TcPragEnv
no_prag_fn TcIdSigInfo
inner_meth_sig LHsBind GhcRn
meth_bind

       ; let export :: ABExport GhcTc
export = ABE :: forall p.
XABE p -> IdP p -> IdP p -> HsWrapper -> TcSpecPrags -> ABExport p
ABE { abe_ext :: XABE GhcTc
abe_ext   = NoExtField
XABE GhcTc
noExtField
                          , abe_poly :: IdP GhcTc
abe_poly  = TyVar
IdP GhcTc
local_meth_id
                          , abe_mono :: IdP GhcTc
abe_mono  = TyVar
IdP GhcTc
inner_id
                          , abe_wrap :: HsWrapper
abe_wrap  = HsWrapper
hs_wrap
                          , abe_prags :: TcSpecPrags
abe_prags = TcSpecPrags
noSpecPrags }

       ; Bag (Located (HsBindLR GhcTc GhcTc))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall (m :: * -> *) a. Monad m => a -> m a
return (Located (HsBindLR GhcTc GhcTc)
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a. a -> Bag a
unitBag (Located (HsBindLR GhcTc GhcTc)
 -> Bag (Located (HsBindLR GhcTc GhcTc)))
-> Located (HsBindLR GhcTc GhcTc)
-> Bag (Located (HsBindLR GhcTc GhcTc))
forall a b. (a -> b) -> a -> b
$ SrcSpan -> HsBindLR GhcTc GhcTc -> Located (HsBindLR GhcTc GhcTc)
forall l e. l -> e -> GenLocated l e
L (Located (HsBindLR GhcRn GhcRn) -> SrcSpan
forall l e. GenLocated l e -> l
getLoc Located (HsBindLR GhcRn GhcRn)
LHsBind GhcRn
meth_bind) (HsBindLR GhcTc GhcTc -> Located (HsBindLR GhcTc GhcTc))
-> HsBindLR GhcTc GhcTc -> Located (HsBindLR GhcTc GhcTc)
forall a b. (a -> b) -> a -> b
$
                 AbsBinds :: forall idL idR.
XAbsBinds idL idR
-> [TyVar]
-> [TyVar]
-> [ABExport idL]
-> [TcEvBinds]
-> LHsBinds idL
-> Bool
-> HsBindLR idL idR
AbsBinds { abs_ext :: XAbsBinds GhcTc GhcTc
abs_ext = NoExtField
XAbsBinds GhcTc GhcTc
noExtField, abs_tvs :: [TyVar]
abs_tvs = [], abs_ev_vars :: [TyVar]
abs_ev_vars = []
                          , abs_exports :: [ABExport GhcTc]
abs_exports = [ABExport GhcTc
export]
                          , abs_binds :: LHsBinds GhcTc
abs_binds = Bag (Located (HsBindLR GhcTc GhcTc))
LHsBinds GhcTc
tc_bind, abs_ev_binds :: [TcEvBinds]
abs_ev_binds = []
                          , abs_sig :: Bool
abs_sig = Bool
True }) }

  | Bool
otherwise  -- No instance signature
  = do { let ctxt :: UserTypeCtxt
ctxt = Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
sel_name Bool
False
                    -- False <=> don't report redundant constraints
                    -- The signature is not under the users control!
             tc_sig :: TcIdSigInfo
tc_sig = UserTypeCtxt -> TyVar -> TcIdSigInfo
completeSigFromId UserTypeCtxt
ctxt TyVar
local_meth_id
              -- Absent a type sig, there are no new scoped type variables here
              -- Only the ones from the instance decl itself, which are already
              -- in scope.  Example:
              --      class C a where { op :: forall b. Eq b => ... }
              --      instance C [c] where { op = <rhs> }
              -- In <rhs>, 'c' is scope but 'b' is not!

       ; (Bag (Located (HsBindLR GhcTc GhcTc))
tc_bind, [TyVar]
_) <- TcPragEnv
-> TcIdSigInfo -> LHsBind GhcRn -> TcM (LHsBinds GhcTc, [TyVar])
tcPolyCheck NameEnv [Located (Sig GhcRn)]
TcPragEnv
no_prag_fn TcIdSigInfo
tc_sig LHsBind GhcRn
meth_bind
       ; Bag (Located (HsBindLR GhcTc GhcTc))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Bag (Located (HsBindLR GhcTc GhcTc)))
forall (m :: * -> *) a. Monad m => a -> m a
return Bag (Located (HsBindLR GhcTc GhcTc))
tc_bind }

  where
    sel_name :: Name
sel_name   = TyVar -> Name
idName TyVar
sel_id
    no_prag_fn :: TcPragEnv
no_prag_fn = TcPragEnv
emptyPragEnv   -- No pragmas for local_meth_id;
                                -- they are all for meth_id


------------------------
mkMethIds :: Class -> [TcTyVar] -> [EvVar]
          -> [TcType] -> Id -> TcM (TcId, TcId)
             -- returns (poly_id, local_id), but ignoring any instance signature
             -- See Note [Instance method signatures]
mkMethIds :: Class
-> [TyVar] -> [TyVar] -> [Type] -> TyVar -> TcM (TyVar, TyVar)
mkMethIds Class
clas [TyVar]
tyvars [TyVar]
dfun_ev_vars [Type]
inst_tys TyVar
sel_id
  = do  { Name
poly_meth_name  <- OccName -> TcM Name
newName (OccName -> OccName
mkClassOpAuxOcc OccName
sel_occ)
        ; Name
local_meth_name <- OccName -> TcM Name
newName OccName
sel_occ
                  -- Base the local_meth_name on the selector name, because
                  -- type errors from tcMethodBody come from here
        ; let poly_meth_id :: TyVar
poly_meth_id  = HasDebugCallStack => Name -> Type -> Type -> TyVar
Name -> Type -> Type -> TyVar
mkLocalId Name
poly_meth_name  Type
Many Type
poly_meth_ty
              local_meth_id :: TyVar
local_meth_id = HasDebugCallStack => Name -> Type -> Type -> TyVar
Name -> Type -> Type -> TyVar
mkLocalId Name
local_meth_name Type
Many Type
local_meth_ty

        ; (TyVar, TyVar) -> TcM (TyVar, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar
poly_meth_id, TyVar
local_meth_id) }
  where
    sel_name :: Name
sel_name      = TyVar -> Name
idName TyVar
sel_id
    sel_occ :: OccName
sel_occ       = Name -> OccName
nameOccName Name
sel_name
    local_meth_ty :: Type
local_meth_ty = Class -> TyVar -> [Type] -> Type
instantiateMethod Class
clas TyVar
sel_id [Type]
inst_tys
    poly_meth_ty :: Type
poly_meth_ty  = [TyVar] -> [Type] -> Type -> Type
mkSpecSigmaTy [TyVar]
tyvars [Type]
theta Type
local_meth_ty
    theta :: [Type]
theta         = (TyVar -> Type) -> [TyVar] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map TyVar -> Type
idType [TyVar]
dfun_ev_vars

methSigCtxt :: Name -> TcType -> TcType -> TidyEnv -> TcM (TidyEnv, MsgDoc)
methSigCtxt :: Name -> Type -> Type -> TidyEnv -> TcM (TidyEnv, SDoc)
methSigCtxt Name
sel_name Type
sig_ty Type
meth_ty TidyEnv
env0
  = do { (TidyEnv
env1, Type
sig_ty)  <- TidyEnv -> Type -> TcM (TidyEnv, Type)
zonkTidyTcType TidyEnv
env0 Type
sig_ty
       ; (TidyEnv
env2, Type
meth_ty) <- TidyEnv -> Type -> TcM (TidyEnv, Type)
zonkTidyTcType TidyEnv
env1 Type
meth_ty
       ; let msg :: SDoc
msg = SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"When checking that instance signature for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
sel_name))
                      Int
2 ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"is more general than its signature in the class"
                              , String -> SDoc
text String
"Instance sig:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
sig_ty
                              , String -> SDoc
text String
"   Class sig:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
meth_ty ])
       ; (TidyEnv, SDoc) -> TcM (TidyEnv, SDoc)
forall (m :: * -> *) a. Monad m => a -> m a
return (TidyEnv
env2, SDoc
msg) }

misplacedInstSig :: Name -> LHsSigType GhcRn -> SDoc
misplacedInstSig :: Name -> LHsSigType GhcRn -> SDoc
misplacedInstSig Name
name LHsSigType GhcRn
hs_ty
  = [SDoc] -> SDoc
vcat [ SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"Illegal type signature in instance declaration:")
              Int
2 (SDoc -> Int -> SDoc -> SDoc
hang (Name -> SDoc
forall a. NamedThing a => a -> SDoc
pprPrefixName Name
name)
                    Int
2 (SDoc
dcolon SDoc -> SDoc -> SDoc
<+> LHsSigType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsSigType GhcRn
hs_ty))
         , String -> SDoc
text String
"(Use InstanceSigs to allow this)" ]

{- Note [Instance method signatures]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
With -XInstanceSigs we allow the user to supply a signature for the
method in an instance declaration.  Here is an artificial example:

       data T a = MkT a
       instance Ord a => Ord (T a) where
         (>) :: forall b. b -> b -> Bool
         (>) = error "You can't compare Ts"

The instance signature can be *more* polymorphic than the instantiated
class method (in this case: Age -> Age -> Bool), but it cannot be less
polymorphic.  Moreover, if a signature is given, the implementation
code should match the signature, and type variables bound in the
singature should scope over the method body.

We achieve this by building a TcSigInfo for the method, whether or not
there is an instance method signature, and using that to typecheck
the declaration (in tcMethodBody).  That means, conveniently,
that the type variables bound in the signature will scope over the body.

What about the check that the instance method signature is more
polymorphic than the instantiated class method type?  We just do a
tcSubType call in tcMethodBodyHelp, and generate a nested AbsBind, like
this (for the example above

 AbsBind { abs_tvs = [a], abs_ev_vars = [d:Ord a]
         , abs_exports
             = ABExport { (>) :: forall a. Ord a => T a -> T a -> Bool
                        , gr_lcl :: T a -> T a -> Bool }
         , abs_binds
             = AbsBind { abs_tvs = [], abs_ev_vars = []
                       , abs_exports = ABExport { gr_lcl :: T a -> T a -> Bool
                                                , gr_inner :: forall b. b -> b -> Bool }
                       , abs_binds = AbsBind { abs_tvs = [b], abs_ev_vars = []
                                             , ..etc.. }
               } }

Wow!  Three nested AbsBinds!
 * The outer one abstracts over the tyvars and dicts for the instance
 * The middle one is only present if there is an instance signature,
   and does the impedance matching for that signature
 * The inner one is for the method binding itself against either the
   signature from the class, or the instance signature.
-}

----------------------
mk_meth_spec_prags :: Id -> [LTcSpecPrag] -> [LTcSpecPrag] -> TcSpecPrags
        -- Adapt the 'SPECIALISE instance' pragmas to work for this method Id
        -- There are two sources:
        --   * spec_prags_for_me: {-# SPECIALISE op :: <blah> #-}
        --   * spec_prags_from_inst: derived from {-# SPECIALISE instance :: <blah> #-}
        --     These ones have the dfun inside, but [perhaps surprisingly]
        --     the correct wrapper.
        -- See Note [Handling SPECIALISE pragmas] in GHC.Tc.Gen.Bind
mk_meth_spec_prags :: TyVar
-> [Located TcSpecPrag] -> [Located TcSpecPrag] -> TcSpecPrags
mk_meth_spec_prags TyVar
meth_id [Located TcSpecPrag]
spec_inst_prags [Located TcSpecPrag]
spec_prags_for_me
  = [Located TcSpecPrag] -> TcSpecPrags
SpecPrags ([Located TcSpecPrag]
spec_prags_for_me [Located TcSpecPrag]
-> [Located TcSpecPrag] -> [Located TcSpecPrag]
forall a. [a] -> [a] -> [a]
++ [Located TcSpecPrag]
spec_prags_from_inst)
  where
    spec_prags_from_inst :: [Located TcSpecPrag]
spec_prags_from_inst
       | InlinePragma -> Bool
isInlinePragma (TyVar -> InlinePragma
idInlinePragma TyVar
meth_id)
       = []  -- Do not inherit SPECIALISE from the instance if the
             -- method is marked INLINE, because then it'll be inlined
             -- and the specialisation would do nothing. (Indeed it'll provoke
             -- a warning from the desugarer
       | Bool
otherwise
       = [ SrcSpan -> TcSpecPrag -> Located TcSpecPrag
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (TyVar -> HsWrapper -> InlinePragma -> TcSpecPrag
SpecPrag TyVar
meth_id HsWrapper
wrap InlinePragma
inl)
         | L SrcSpan
inst_loc (SpecPrag TyVar
_       HsWrapper
wrap InlinePragma
inl) <- [Located TcSpecPrag]
spec_inst_prags]


mkDefMethBind :: DFunId -> Class -> Id -> Name
              -> TcM (LHsBind GhcRn, [LSig GhcRn])
-- The is a default method (vanailla or generic) defined in the class
-- So make a binding   op = $dmop @t1 @t2
-- where $dmop is the name of the default method in the class,
-- and t1,t2 are the instance types.
-- See Note [Default methods in instances] for why we use
-- visible type application here
mkDefMethBind :: TyVar
-> Class -> TyVar -> Name -> TcM (LHsBind GhcRn, [LSig GhcRn])
mkDefMethBind TyVar
dfun_id Class
clas TyVar
sel_id Name
dm_name
  = do  { DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
        ; TyVar
dm_id <- Name -> TcM TyVar
tcLookupId Name
dm_name
        ; let inline_prag :: InlinePragma
inline_prag = TyVar -> InlinePragma
idInlinePragma TyVar
dm_id
              inline_prags :: [Located (Sig GhcRn)]
inline_prags | InlinePragma -> Bool
isAnyInlinePragma InlinePragma
inline_prag
                           = [Sig GhcRn -> Located (Sig GhcRn)
forall e. e -> Located e
noLoc (XInlineSig GhcRn -> LIdP GhcRn -> InlinePragma -> Sig GhcRn
forall pass.
XInlineSig pass -> LIdP pass -> InlinePragma -> Sig pass
InlineSig NoExtField
XInlineSig GhcRn
noExtField GenLocated SrcSpan Name
LIdP GhcRn
fn InlinePragma
inline_prag)]
                           | Bool
otherwise
                           = []
                 -- Copy the inline pragma (if any) from the default method
                 -- to this version. Note [INLINE and default methods]

              fn :: GenLocated SrcSpan Name
fn   = Name -> GenLocated SrcSpan Name
forall e. e -> Located e
noLoc (TyVar -> Name
idName TyVar
sel_id)
              visible_inst_tys :: [Type]
visible_inst_tys = [ Type
ty | (TyConBinder
tcb, Type
ty) <- TyCon -> [TyConBinder]
tyConBinders (Class -> TyCon
classTyCon Class
clas) [TyConBinder] -> [Type] -> [(TyConBinder, Type)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Type]
inst_tys
                                      , TyConBinder -> ArgFlag
tyConBinderArgFlag TyConBinder
tcb ArgFlag -> ArgFlag -> Bool
forall a. Eq a => a -> a -> Bool
/= ArgFlag
Inferred ]
              rhs :: Located (HsExpr GhcRn)
rhs  = (Located (HsExpr GhcRn) -> Type -> Located (HsExpr GhcRn))
-> Located (HsExpr GhcRn) -> [Type] -> Located (HsExpr GhcRn)
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' Located (HsExpr GhcRn) -> Type -> Located (HsExpr GhcRn)
LHsExpr GhcRn -> Type -> LHsExpr GhcRn
mk_vta (IdP GhcRn -> LHsExpr GhcRn
forall (id :: Pass). IdP (GhcPass id) -> LHsExpr (GhcPass id)
nlHsVar Name
IdP GhcRn
dm_name) [Type]
visible_inst_tys
              bind :: Located (HsBindLR GhcRn GhcRn)
bind = HsBindLR GhcRn GhcRn -> Located (HsBindLR GhcRn GhcRn)
forall e. e -> Located e
noLoc (HsBindLR GhcRn GhcRn -> Located (HsBindLR GhcRn GhcRn))
-> HsBindLR GhcRn GhcRn -> Located (HsBindLR GhcRn GhcRn)
forall a b. (a -> b) -> a -> b
$ Origin
-> GenLocated SrcSpan Name
-> [LMatch GhcRn (LHsExpr GhcRn)]
-> HsBindLR GhcRn GhcRn
mkTopFunBind Origin
Generated GenLocated SrcSpan Name
fn ([LMatch GhcRn (LHsExpr GhcRn)] -> HsBindLR GhcRn GhcRn)
-> [LMatch GhcRn (LHsExpr GhcRn)] -> HsBindLR GhcRn GhcRn
forall a b. (a -> b) -> a -> b
$
                             [HsMatchContext (NoGhcTc GhcRn)
-> [LPat GhcRn]
-> Located (HsExpr GhcRn)
-> LMatch GhcRn (Located (HsExpr GhcRn))
forall (p :: Pass) (body :: * -> *).
HsMatchContext (NoGhcTc (GhcPass p))
-> [LPat (GhcPass p)]
-> Located (body (GhcPass p))
-> LMatch (GhcPass p) (Located (body (GhcPass p)))
mkSimpleMatch (LIdP GhcRn -> HsMatchContext GhcRn
forall p. LIdP p -> HsMatchContext p
mkPrefixFunRhs GenLocated SrcSpan Name
LIdP GhcRn
fn) [] Located (HsExpr GhcRn)
rhs]

        ; IO () -> TcRn ()
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO (DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
dumpIfSet_dyn DynFlags
dflags DumpFlag
Opt_D_dump_deriv String
"Filling in method body"
                   DumpFormat
FormatHaskell
                   ([SDoc] -> SDoc
vcat [Class -> SDoc
forall a. Outputable a => a -> SDoc
ppr Class
clas SDoc -> SDoc -> SDoc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
inst_tys,
                          Int -> SDoc -> SDoc
nest Int
2 (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id SDoc -> SDoc -> SDoc
<+> SDoc
equals SDoc -> SDoc -> SDoc
<+> Located (HsExpr GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr Located (HsExpr GhcRn)
rhs)]))

       ; (Located (HsBindLR GhcRn GhcRn), [Located (Sig GhcRn)])
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (Located (HsBindLR GhcRn GhcRn), [Located (Sig GhcRn)])
forall (m :: * -> *) a. Monad m => a -> m a
return (Located (HsBindLR GhcRn GhcRn)
bind, [Located (Sig GhcRn)]
inline_prags) }
  where
    ([TyVar]
_, [Type]
_, Class
_, [Type]
inst_tys) = Type -> ([TyVar], [Type], Class, [Type])
tcSplitDFunTy (TyVar -> Type
idType TyVar
dfun_id)

    mk_vta :: LHsExpr GhcRn -> Type -> LHsExpr GhcRn
    mk_vta :: LHsExpr GhcRn -> Type -> LHsExpr GhcRn
mk_vta LHsExpr GhcRn
fun Type
ty = HsExpr GhcRn -> Located (HsExpr GhcRn)
forall e. e -> Located e
noLoc (XAppTypeE GhcRn
-> LHsExpr GhcRn -> LHsWcType (NoGhcTc GhcRn) -> HsExpr GhcRn
forall p.
XAppTypeE p -> LHsExpr p -> LHsWcType (NoGhcTc p) -> HsExpr p
HsAppType NoExtField
XAppTypeE GhcRn
noExtField LHsExpr GhcRn
fun (Located (HsType GhcRn)
-> HsWildCardBndrs GhcRn (Located (HsType GhcRn))
forall thing. thing -> HsWildCardBndrs GhcRn thing
mkEmptyWildCardBndrs (Located (HsType GhcRn)
 -> HsWildCardBndrs GhcRn (Located (HsType GhcRn)))
-> Located (HsType GhcRn)
-> HsWildCardBndrs GhcRn (Located (HsType GhcRn))
forall a b. (a -> b) -> a -> b
$ LHsKind GhcRn -> LHsKind GhcRn
forall (p :: Pass). LHsType (GhcPass p) -> LHsType (GhcPass p)
nlHsParTy
                                                (LHsKind GhcRn -> LHsKind GhcRn) -> LHsKind GhcRn -> LHsKind GhcRn
forall a b. (a -> b) -> a -> b
$ HsType GhcRn -> Located (HsType GhcRn)
forall e. e -> Located e
noLoc (HsType GhcRn -> Located (HsType GhcRn))
-> HsType GhcRn -> Located (HsType GhcRn)
forall a b. (a -> b) -> a -> b
$ XXType GhcRn -> HsType GhcRn
forall pass. XXType pass -> HsType pass
XHsType (XXType GhcRn -> HsType GhcRn) -> XXType GhcRn -> HsType GhcRn
forall a b. (a -> b) -> a -> b
$ Type -> NewHsTypeX
NHsCoreTy Type
ty))
       -- NB: use visible type application
       -- See Note [Default methods in instances]

----------------------
derivBindCtxt :: Id -> Class -> [Type ] -> SDoc
derivBindCtxt :: TyVar -> Class -> [Type] -> SDoc
derivBindCtxt TyVar
sel_id Class
clas [Type]
tys
   = [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"When typechecking the code for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
sel_id)
          , Int -> SDoc -> SDoc
nest Int
2 (String -> SDoc
text String
"in a derived instance for"
                    SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Class -> [Type] -> SDoc
pprClassPred Class
clas [Type]
tys) SDoc -> SDoc -> SDoc
<> SDoc
colon)
          , Int -> SDoc -> SDoc
nest Int
2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"To see the code I am typechecking, use -ddump-deriv" ]

warnUnsatisfiedMinimalDefinition :: ClassMinimalDef -> TcM ()
warnUnsatisfiedMinimalDefinition :: BooleanFormula Name -> TcRn ()
warnUnsatisfiedMinimalDefinition BooleanFormula Name
mindef
  = do { Bool
warn <- WarningFlag -> TcRn Bool
forall gbl lcl. WarningFlag -> TcRnIf gbl lcl Bool
woptM WarningFlag
Opt_WarnMissingMethods
       ; WarnReason -> Bool -> SDoc -> TcRn ()
warnTc (WarningFlag -> WarnReason
Reason WarningFlag
Opt_WarnMissingMethods) Bool
warn SDoc
message
       }
  where
    message :: SDoc
message = [SDoc] -> SDoc
vcat [String -> SDoc
text String
"No explicit implementation for"
                   ,Int -> SDoc -> SDoc
nest Int
2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ BooleanFormula Name -> SDoc
forall a. Outputable a => BooleanFormula a -> SDoc
pprBooleanFormulaNice BooleanFormula Name
mindef
                   ]

{-
Note [Export helper functions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We arrange to export the "helper functions" of an instance declaration,
so that they are not subject to preInlineUnconditionally, even if their
RHS is trivial.  Reason: they are mentioned in the DFunUnfolding of
the dict fun as Ids, not as CoreExprs, so we can't substitute a
non-variable for them.

We could change this by making DFunUnfoldings have CoreExprs, but it
seems a bit simpler this way.

Note [Default methods in instances]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this

   class Baz v x where
      foo :: x -> x
      foo y = <blah>

   instance Baz Int Int

From the class decl we get

   $dmfoo :: forall v x. Baz v x => x -> x
   $dmfoo y = <blah>

Notice that the type is ambiguous.  So we use Visible Type Application
to disambiguate:

   $dBazIntInt = MkBaz fooIntInt
   fooIntInt = $dmfoo @Int @Int

Lacking VTA we'd get ambiguity errors involving the default method.  This applies
equally to vanilla default methods (#1061) and generic default methods
(#12220).

Historical note: before we had VTA we had to generate
post-type-checked code, which took a lot more code, and didn't work for
generic default methods.

Note [INLINE and default methods]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Default methods need special case.  They are supposed to behave rather like
macros.  For example

  class Foo a where
    op1, op2 :: Bool -> a -> a

    {-# INLINE op1 #-}
    op1 b x = op2 (not b) x

  instance Foo Int where
    -- op1 via default method
    op2 b x = <blah>

The instance declaration should behave

   just as if 'op1' had been defined with the
   code, and INLINE pragma, from its original
   definition.

That is, just as if you'd written

  instance Foo Int where
    op2 b x = <blah>

    {-# INLINE op1 #-}
    op1 b x = op2 (not b) x

So for the above example we generate:

  {-# INLINE $dmop1 #-}
  -- $dmop1 has an InlineCompulsory unfolding
  $dmop1 d b x = op2 d (not b) x

  $fFooInt = MkD $cop1 $cop2

  {-# INLINE $cop1 #-}
  $cop1 = $dmop1 $fFooInt

  $cop2 = <blah>

Note carefully:

* We *copy* any INLINE pragma from the default method $dmop1 to the
  instance $cop1.  Otherwise we'll just inline the former in the
  latter and stop, which isn't what the user expected

* Regardless of its pragma, we give the default method an
  unfolding with an InlineCompulsory source. That means
  that it'll be inlined at every use site, notably in
  each instance declaration, such as $cop1.  This inlining
  must happen even though
    a) $dmop1 is not saturated in $cop1
    b) $cop1 itself has an INLINE pragma

  It's vital that $dmop1 *is* inlined in this way, to allow the mutual
  recursion between $fooInt and $cop1 to be broken

* To communicate the need for an InlineCompulsory to the desugarer
  (which makes the Unfoldings), we use the IsDefaultMethod constructor
  in TcSpecPrags.


************************************************************************
*                                                                      *
        Specialise instance pragmas
*                                                                      *
************************************************************************

Note [SPECIALISE instance pragmas]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

   instance (Ix a, Ix b) => Ix (a,b) where
     {-# SPECIALISE instance Ix (Int,Int) #-}
     range (x,y) = ...

We make a specialised version of the dictionary function, AND
specialised versions of each *method*.  Thus we should generate
something like this:

  $dfIxPair :: (Ix a, Ix b) => Ix (a,b)
  {-# DFUN [$crangePair, ...] #-}
  {-# SPECIALISE $dfIxPair :: Ix (Int,Int) #-}
  $dfIxPair da db = Ix ($crangePair da db) (...other methods...)

  $crange :: (Ix a, Ix b) -> ((a,b),(a,b)) -> [(a,b)]
  {-# SPECIALISE $crange :: ((Int,Int),(Int,Int)) -> [(Int,Int)] #-}
  $crange da db = <blah>

The SPECIALISE pragmas are acted upon by the desugarer, which generate

  dii :: Ix Int
  dii = ...

  $s$dfIxPair :: Ix ((Int,Int),(Int,Int))
  {-# DFUN [$crangePair di di, ...] #-}
  $s$dfIxPair = Ix ($crangePair di di) (...)

  {-# RULE forall (d1,d2:Ix Int). $dfIxPair Int Int d1 d2 = $s$dfIxPair #-}

  $s$crangePair :: ((Int,Int),(Int,Int)) -> [(Int,Int)]
  $c$crangePair = ...specialised RHS of $crangePair...

  {-# RULE forall (d1,d2:Ix Int). $crangePair Int Int d1 d2 = $s$crangePair #-}

Note that

  * The specialised dictionary $s$dfIxPair is very much needed, in case we
    call a function that takes a dictionary, but in a context where the
    specialised dictionary can be used.  See #7797.

  * The ClassOp rule for 'range' works equally well on $s$dfIxPair, because
    it still has a DFunUnfolding.  See Note [ClassOp/DFun selection]

  * A call (range ($dfIxPair Int Int d1 d2)) might simplify two ways:
       --> {ClassOp rule for range}     $crangePair Int Int d1 d2
       --> {SPEC rule for $crangePair}  $s$crangePair
    or thus:
       --> {SPEC rule for $dfIxPair}    range $s$dfIxPair
       --> {ClassOpRule for range}      $s$crangePair
    It doesn't matter which way.

  * We want to specialise the RHS of both $dfIxPair and $crangePair,
    but the SAME HsWrapper will do for both!  We can call tcSpecPrag
    just once, and pass the result (in spec_inst_info) to tcMethods.
-}

tcSpecInstPrags :: DFunId -> InstBindings GhcRn
                -> TcM ([Located TcSpecPrag], TcPragEnv)
tcSpecInstPrags :: TyVar
-> InstBindings GhcRn -> TcM ([Located TcSpecPrag], TcPragEnv)
tcSpecInstPrags TyVar
dfun_id (InstBindings { ib_binds :: forall a. InstBindings a -> LHsBinds a
ib_binds = LHsBinds GhcRn
binds, ib_pragmas :: forall a. InstBindings a -> [LSig a]
ib_pragmas = [LSig GhcRn]
uprags })
  = do { [Located TcSpecPrag]
spec_inst_prags <- (Located (Sig GhcRn)
 -> IOEnv (Env TcGblEnv TcLclEnv) (Located TcSpecPrag))
-> [Located (Sig GhcRn)] -> TcM [Located TcSpecPrag]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ((Sig GhcRn -> TcM TcSpecPrag)
-> Located (Sig GhcRn)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located TcSpecPrag)
forall a b. (a -> TcM b) -> Located a -> TcM (Located b)
wrapLocM (TyVar -> Sig GhcRn -> TcM TcSpecPrag
tcSpecInst TyVar
dfun_id)) ([Located (Sig GhcRn)] -> TcM [Located TcSpecPrag])
-> [Located (Sig GhcRn)] -> TcM [Located TcSpecPrag]
forall a b. (a -> b) -> a -> b
$
                            (Located (Sig GhcRn) -> Bool)
-> [Located (Sig GhcRn)] -> [Located (Sig GhcRn)]
forall a. (a -> Bool) -> [a] -> [a]
filter Located (Sig GhcRn) -> Bool
forall p. UnXRec p => LSig p -> Bool
isSpecInstLSig [Located (Sig GhcRn)]
[LSig GhcRn]
uprags
             -- The filter removes the pragmas for methods
       ; ([Located TcSpecPrag], NameEnv [Located (Sig GhcRn)])
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     ([Located TcSpecPrag], NameEnv [Located (Sig GhcRn)])
forall (m :: * -> *) a. Monad m => a -> m a
return ([Located TcSpecPrag]
spec_inst_prags, [LSig GhcRn] -> LHsBinds GhcRn -> TcPragEnv
mkPragEnv [LSig GhcRn]
uprags LHsBinds GhcRn
binds) }

------------------------------
tcSpecInst :: Id -> Sig GhcRn -> TcM TcSpecPrag
tcSpecInst :: TyVar -> Sig GhcRn -> TcM TcSpecPrag
tcSpecInst TyVar
dfun_id prag :: Sig GhcRn
prag@(SpecInstSig XSpecInstSig GhcRn
_ SourceText
_ LHsSigType GhcRn
hs_ty)
  = SDoc -> TcM TcSpecPrag -> TcM TcSpecPrag
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (Sig GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
spec_ctxt Sig GhcRn
prag) (TcM TcSpecPrag -> TcM TcSpecPrag)
-> TcM TcSpecPrag -> TcM TcSpecPrag
forall a b. (a -> b) -> a -> b
$
    do  { Type
spec_dfun_ty <- UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsClsInstType UserTypeCtxt
SpecInstCtxt LHsSigType GhcRn
hs_ty
        ; HsWrapper
co_fn <- UserTypeCtxt -> Type -> Type -> TcM HsWrapper
tcSpecWrapper UserTypeCtxt
SpecInstCtxt (TyVar -> Type
idType TyVar
dfun_id) Type
spec_dfun_ty
        ; TcSpecPrag -> TcM TcSpecPrag
forall (m :: * -> *) a. Monad m => a -> m a
return (TyVar -> HsWrapper -> InlinePragma -> TcSpecPrag
SpecPrag TyVar
dfun_id HsWrapper
co_fn InlinePragma
defaultInlinePragma) }
  where
    spec_ctxt :: a -> SDoc
spec_ctxt a
prag = SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"In the pragma:") Int
2 (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
prag)

tcSpecInst TyVar
_  Sig GhcRn
_ = String -> TcM TcSpecPrag
forall a. String -> a
panic String
"tcSpecInst"

{-
************************************************************************
*                                                                      *
\subsection{Error messages}
*                                                                      *
************************************************************************
-}

instDeclCtxt1 :: LHsSigType GhcRn -> SDoc
instDeclCtxt1 :: LHsSigType GhcRn -> SDoc
instDeclCtxt1 LHsSigType GhcRn
hs_inst_ty
  = SDoc -> SDoc
inst_decl_ctxt (Located (HsType GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr (LHsSigType GhcRn -> LHsKind GhcRn
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
getLHsInstDeclHead LHsSigType GhcRn
hs_inst_ty))

instDeclCtxt2 :: Type -> SDoc
instDeclCtxt2 :: Type -> SDoc
instDeclCtxt2 Type
dfun_ty
  = SDoc -> SDoc
inst_decl_ctxt (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Class -> [Type] -> Type
mkClassPred Class
cls [Type]
tys))
  where
    ([TyVar]
_,[Type]
_,Class
cls,[Type]
tys) = Type -> ([TyVar], [Type], Class, [Type])
tcSplitDFunTy Type
dfun_ty

inst_decl_ctxt :: SDoc -> SDoc
inst_decl_ctxt :: SDoc -> SDoc
inst_decl_ctxt SDoc
doc = SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"In the instance declaration for")
                        Int
2 (SDoc -> SDoc
quotes SDoc
doc)

badBootFamInstDeclErr :: SDoc
badBootFamInstDeclErr :: SDoc
badBootFamInstDeclErr
  = String -> SDoc
text String
"Illegal family instance in hs-boot file"

notFamily :: TyCon -> SDoc
notFamily :: TyCon -> SDoc
notFamily TyCon
tycon
  = [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Illegal family instance for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tycon)
         , Int -> SDoc -> SDoc
nest Int
2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ SDoc -> SDoc
parens (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tycon SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"is not an indexed type family")]

assocInClassErr :: TyCon -> SDoc
assocInClassErr :: TyCon -> SDoc
assocInClassErr TyCon
name
 = String -> SDoc
text String
"Associated type" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
name) SDoc -> SDoc -> SDoc
<+>
   String -> SDoc
text String
"must be inside a class instance"

badFamInstDecl :: TyCon -> SDoc
badFamInstDecl :: TyCon -> SDoc
badFamInstDecl TyCon
tc_name
  = [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Illegal family instance for" SDoc -> SDoc -> SDoc
<+>
           SDoc -> SDoc
quotes (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc_name)
         , Int -> SDoc -> SDoc
nest Int
2 (SDoc -> SDoc
parens (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ String -> SDoc
text String
"Use TypeFamilies to allow indexed type families") ]

notOpenFamily :: TyCon -> SDoc
notOpenFamily :: TyCon -> SDoc
notOpenFamily TyCon
tc
  = String -> SDoc
text String
"Illegal instance for closed family" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc)