{-
(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 "HsVersions.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.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.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 ( mkInlineUnfoldingWithArity, mkDFunUnfolding )
import GHC.Core.Type
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.Driver.Session
import GHC.Utils.Error
import GHC.Data.FastString
import GHC.Types.Id
import GHC.Data.List.SetOps
import GHC.Types.Name
import GHC.Types.Name.Set
import GHC.Utils.Outputable
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 (GhcPass 'Renamed)]
-> TcM (TcGblEnv, [InstInfo (GhcPass 'Renamed)], [DerivInfo])
tcInstDecls1 [LInstDecl (GhcPass 'Renamed)]
inst_decls
  = do {    -- Do class and family instance declarations
       ; [([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])]
stuff <- (LInstDecl (GhcPass 'Renamed)
 -> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo]))
-> [LInstDecl (GhcPass 'Renamed)]
-> TcRn [([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndRecoverM LInstDecl (GhcPass 'Renamed)
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
tcLocalInstDecl [LInstDecl (GhcPass 'Renamed)]
inst_decls

       ; let ([[InstInfo (GhcPass 'Renamed)]]
local_infos_s, [[FamInst]]
fam_insts_s, [[DerivInfo]]
datafam_deriv_infos) = [([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])]
-> ([[InstInfo (GhcPass 'Renamed)]], [[FamInst]], [[DerivInfo]])
forall a b c. [(a, b, c)] -> ([a], [b], [c])
unzip3 [([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])]
stuff
             fam_insts :: [FamInst]
fam_insts   = [[FamInst]] -> [FamInst]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
External instance of the constraint type Foldable []
concat [[FamInst]]
fam_insts_s
             local_infos :: [InstInfo (GhcPass 'Renamed)]
local_infos = [[InstInfo (GhcPass 'Renamed)]] -> [InstInfo (GhcPass 'Renamed)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
External instance of the constraint type Foldable []
concat [[InstInfo (GhcPass 'Renamed)]]
local_infos_s

       ; TcGblEnv
gbl_env <- [InstInfo (GhcPass 'Renamed)] -> TcM TcGblEnv -> TcM TcGblEnv
forall a. [InstInfo (GhcPass 'Renamed)] -> TcM a -> TcM a
addClsInsts [InstInfo (GhcPass 'Renamed)]
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 (GhcPass 'Renamed)], [DerivInfo])
-> TcM (TcGblEnv, [InstInfo (GhcPass 'Renamed)], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ( TcGblEnv
gbl_env
                , [InstInfo (GhcPass 'Renamed)]
local_infos
                , [[DerivInfo]] -> [DerivInfo]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
External instance of the constraint type Foldable []
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 (GhcPass 'Renamed)]
-> TcM
     (TcGblEnv, [InstInfo (GhcPass 'Renamed)],
      HsValBinds (GhcPass 'Renamed))
tcInstDeclsDeriv [DerivInfo]
deriv_infos [LDerivDecl (GhcPass 'Renamed)]
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 (GhcPass 'Renamed)],
 HsValBinds (GhcPass 'Renamed))
-> TcM
     (TcGblEnv, [InstInfo (GhcPass 'Renamed)],
      HsValBinds (GhcPass 'Renamed))
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (TcGblEnv
gbl_env, Bag (InstInfo (GhcPass 'Renamed)) -> [InstInfo (GhcPass 'Renamed)]
forall a. Bag a -> [a]
bagToList Bag (InstInfo (GhcPass 'Renamed))
forall a. Bag a
emptyBag, HsValBinds (GhcPass 'Renamed)
forall (a :: Pass) (b :: Pass).
HsValBindsLR (GhcPass a) (GhcPass b)
emptyValBindsOut) }
       else do { (TcGblEnv
tcg_env, Bag (InstInfo (GhcPass 'Renamed))
info_bag, HsValBinds (GhcPass 'Renamed)
valbinds) <- [DerivInfo]
-> [LDerivDecl (GhcPass 'Renamed)]
-> TcM
     (TcGblEnv, Bag (InstInfo (GhcPass 'Renamed)),
      HsValBinds (GhcPass 'Renamed))
tcDeriving [DerivInfo]
deriv_infos [LDerivDecl (GhcPass 'Renamed)]
derivds
               ; (TcGblEnv, [InstInfo (GhcPass 'Renamed)],
 HsValBinds (GhcPass 'Renamed))
-> TcM
     (TcGblEnv, [InstInfo (GhcPass 'Renamed)],
      HsValBinds (GhcPass 'Renamed))
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (TcGblEnv
tcg_env, Bag (InstInfo (GhcPass 'Renamed)) -> [InstInfo (GhcPass 'Renamed)]
forall a. Bag a -> [a]
bagToList Bag (InstInfo (GhcPass 'Renamed))
info_bag, HsValBinds (GhcPass 'Renamed)
valbinds) }

addClsInsts :: [InstInfo GhcRn] -> TcM a -> TcM a
addClsInsts :: [InstInfo (GhcPass 'Renamed)] -> TcM a -> TcM a
addClsInsts [InstInfo (GhcPass 'Renamed)]
infos TcM a
thing_inside
  = [ClsInst] -> TcM a -> TcM a
forall a. [ClsInst] -> TcM a -> TcM a
tcExtendLocalInstEnv ((InstInfo (GhcPass 'Renamed) -> ClsInst)
-> [InstInfo (GhcPass 'Renamed)] -> [ClsInst]
forall a b. (a -> b) -> [a] -> [b]
map InstInfo (GhcPass 'Renamed) -> ClsInst
forall a. InstInfo a -> ClsInst
iSpec [InstInfo (GhcPass 'Renamed)]
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 (GhcPass 'Renamed)
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
tcLocalInstDecl (L SrcSpan
loc (TyFamInstD { tfid_inst :: forall pass. InstDecl pass -> TyFamInstDecl pass
tfid_inst = TyFamInstDecl (GhcPass 'Renamed)
decl }))
  = do { FamInst
fam_inst <- AssocInstInfo -> LTyFamInstDecl (GhcPass 'Renamed) -> TcM FamInst
tcTyFamInstDecl AssocInstInfo
NotAssociated (SrcSpan
-> TyFamInstDecl (GhcPass 'Renamed)
-> LTyFamInstDecl (GhcPass 'Renamed)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc TyFamInstDecl (GhcPass 'Renamed)
decl)
       ; ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([], [FamInst
fam_inst], []) }

tcLocalInstDecl (L SrcSpan
loc (DataFamInstD { dfid_inst :: forall pass. InstDecl pass -> DataFamInstDecl pass
dfid_inst = DataFamInstDecl (GhcPass 'Renamed)
decl }))
  = do { (FamInst
fam_inst, Maybe DerivInfo
m_deriv_info) <- AssocInstInfo
-> TyVarEnv Name
-> LDataFamInstDecl (GhcPass 'Renamed)
-> TcM (FamInst, Maybe DerivInfo)
tcDataFamInstDecl AssocInstInfo
NotAssociated TyVarEnv Name
forall a. VarEnv a
emptyVarEnv (SrcSpan
-> DataFamInstDecl (GhcPass 'Renamed)
-> LDataFamInstDecl (GhcPass 'Renamed)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc DataFamInstDecl (GhcPass 'Renamed)
decl)
       ; ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([], [FamInst
fam_inst], Maybe DerivInfo -> [DerivInfo]
forall a. Maybe a -> [a]
maybeToList Maybe DerivInfo
m_deriv_info) }

tcLocalInstDecl (L SrcSpan
loc (ClsInstD { cid_inst :: forall pass. InstDecl pass -> ClsInstDecl pass
cid_inst = ClsInstDecl (GhcPass 'Renamed)
decl }))
  = do { ([InstInfo (GhcPass 'Renamed)]
insts, [FamInst]
fam_insts, [DerivInfo]
deriv_infos) <- LClsInstDecl (GhcPass 'Renamed)
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
tcClsInstDecl (SrcSpan
-> ClsInstDecl (GhcPass 'Renamed)
-> LClsInstDecl (GhcPass 'Renamed)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc ClsInstDecl (GhcPass 'Renamed)
decl)
       ; ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([InstInfo (GhcPass 'Renamed)]
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 (GhcPass 'Renamed)
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
tcClsInstDecl (L SrcSpan
loc (ClsInstDecl { cid_poly_ty :: forall pass. ClsInstDecl pass -> LHsSigType pass
cid_poly_ty = LHsSigType (GhcPass 'Renamed)
hs_ty, cid_binds :: forall pass. ClsInstDecl pass -> LHsBinds pass
cid_binds = LHsBinds (GhcPass 'Renamed)
binds
                                  , cid_sigs :: forall pass. ClsInstDecl pass -> [LSig pass]
cid_sigs = [LSig (GhcPass 'Renamed)]
uprags, cid_tyfam_insts :: forall pass. ClsInstDecl pass -> [LTyFamInstDecl pass]
cid_tyfam_insts = [LTyFamInstDecl (GhcPass 'Renamed)]
ats
                                  , cid_overlap_mode :: forall pass. ClsInstDecl pass -> Maybe (Located OverlapMode)
cid_overlap_mode = Maybe (Located OverlapMode)
overlap_mode
                                  , cid_datafam_insts :: forall pass. ClsInstDecl pass -> [LDataFamInstDecl pass]
cid_datafam_insts = [LDataFamInstDecl (GhcPass 'Renamed)]
adts }))
  = SrcSpan
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc                      (TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
 -> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo]))
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall a b. (a -> b) -> a -> b
$
    SDoc
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (LHsSigType (GhcPass 'Renamed) -> SDoc
instDeclCtxt1 LHsSigType (GhcPass 'Renamed)
hs_ty)  (TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
 -> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo]))
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall a b. (a -> b) -> a -> b
$
    do  { PredType
dfun_ty <- UserTypeCtxt -> LHsSigType (GhcPass 'Renamed) -> TcM PredType
tcHsClsInstType (Bool -> UserTypeCtxt
InstDeclCtxt Bool
False) LHsSigType (GhcPass 'Renamed)
hs_ty
        ; let ([Id]
tyvars, [PredType]
theta, Class
clas, [PredType]
inst_tys) = PredType -> ([Id], [PredType], Class, [PredType])
tcSplitDFunTy PredType
dfun_ty
             -- NB: tcHsClsInstType does checkValidInstance

        ; (TCvSubst
subst, [Id]
skol_tvs) <- [Id] -> TcM (TCvSubst, [Id])
tcInstSkolTyVars [Id]
tyvars
        ; let tv_skol_prs :: [(Name, Id)]
tv_skol_prs = [ (Id -> Name
tyVarName Id
tv, Id
skol_tv)
                            | (Id
tv, Id
skol_tv) <- [Id]
tyvars [Id] -> [Id] -> [(Id, Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Id]
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 = [(Id, Name)] -> TyVarEnv Name
forall a. [(Id, a)] -> VarEnv a
mkVarEnv ([(Id, Name)] -> TyVarEnv Name) -> [(Id, Name)] -> TyVarEnv Name
forall a b. (a -> b) -> a -> b
$ ((Name, Id) -> (Id, Name)) -> [(Name, Id)] -> [(Id, Name)]
forall a b. (a -> b) -> [a] -> [b]
map (Name, Id) -> (Id, Name)
forall a b. (a, b) -> (b, a)
swap [(Name, Id)]
tv_skol_prs
              n_inferred :: ConTag
n_inferred = (VarBndr Id ArgFlag -> Bool) -> [VarBndr Id ArgFlag] -> ConTag
forall a. (a -> Bool) -> [a] -> ConTag
countWhile ((ArgFlag -> ArgFlag -> Bool
forall a. Eq a => a -> a -> Bool
External instance of the constraint type Eq ArgFlag
== ArgFlag
Inferred) (ArgFlag -> Bool)
-> (VarBndr Id ArgFlag -> ArgFlag) -> VarBndr Id ArgFlag -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. VarBndr Id ArgFlag -> ArgFlag
forall tv argf. VarBndr tv argf -> argf
binderArgFlag) ([VarBndr Id ArgFlag] -> ConTag) -> [VarBndr Id ArgFlag] -> ConTag
forall a b. (a -> b) -> a -> b
$
                           ([VarBndr Id ArgFlag], PredType) -> [VarBndr Id ArgFlag]
forall a b. (a, b) -> a
fst (([VarBndr Id ArgFlag], PredType) -> [VarBndr Id ArgFlag])
-> ([VarBndr Id ArgFlag], PredType) -> [VarBndr Id ArgFlag]
forall a b. (a -> b) -> a -> b
$ PredType -> ([VarBndr Id ArgFlag], PredType)
splitForAllVarBndrs PredType
dfun_ty
              visible_skol_tvs :: [Id]
visible_skol_tvs = ConTag -> [Id] -> [Id]
forall a. ConTag -> [a] -> [a]
drop ConTag
n_inferred [Id]
skol_tvs

        ; String -> SDoc -> TcRn ()
traceTc String
"tcLocalInstDecl 1" (PredType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable PredType
ppr PredType
dfun_ty SDoc -> SDoc -> SDoc
$$ ConTag -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable ConTag
ppr (PredType -> ConTag
invisibleTyBndrCount PredType
dfun_ty) SDoc -> SDoc -> SDoc
$$ [Id] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable Id
ppr [Id]
skol_tvs)

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

                      -- Check for missing associated types and build them
                      -- from their defaults (if available)
                    ; [[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)
External instance of the constraint type forall m. Monad (IOEnv m)
External instance of the constraint type Traversable []
mapM (SrcSpan -> TCvSubst -> NameSet -> ClassATItem -> TcRn [FamInst]
tcATDefault SrcSpan
loc TCvSubst
mini_subst NameSet
defined_ats)
                                        (Class -> [ClassATItem]
classATItems Class
clas)

                    ; ([(FamInst, Maybe DerivInfo)], [FamInst])
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
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]
External instance of the constraint type Foldable []
concat [[FamInst]]
tf_insts2) }


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

        ; ClsInst
ispec <- Maybe OverlapMode
-> Name -> [Id] -> [PredType] -> Class -> [PredType] -> TcM ClsInst
newClsInst ((Located OverlapMode -> OverlapMode)
-> Maybe (Located OverlapMode) -> Maybe OverlapMode
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
External instance of the constraint type Functor Maybe
fmap Located OverlapMode -> OverlapMode
forall l e. GenLocated l e -> e
unLoc Maybe (Located OverlapMode)
overlap_mode) Name
dfun_name
                              [Id]
tyvars [PredType]
theta Class
clas [PredType]
inst_tys

        ; let inst_binds :: InstBindings (GhcPass 'Renamed)
inst_binds = InstBindings :: forall a.
[Name]
-> LHsBinds a -> [LSig a] -> [Extension] -> Bool -> InstBindings a
InstBindings
                             { ib_binds :: LHsBinds (GhcPass 'Renamed)
ib_binds = LHsBinds (GhcPass 'Renamed)
binds
                             , ib_tyvars :: [Name]
ib_tyvars = (Id -> Name) -> [Id] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map Id -> Name
Var.varName [Id]
tyvars -- Scope over bindings
                             , ib_pragmas :: [LSig (GhcPass 'Renamed)]
ib_pragmas = [LSig (GhcPass 'Renamed)]
uprags
                             , ib_extensions :: [Extension]
ib_extensions = []
                             , ib_derived :: Bool
ib_derived = Bool
False }
              inst_info :: InstInfo (GhcPass 'Renamed)
inst_info = InstInfo :: forall a. ClsInst -> InstBindings a -> InstInfo a
InstInfo { iSpec :: ClsInst
iSpec  = ClsInst
ispec, iBinds :: InstBindings (GhcPass 'Renamed)
iBinds = InstBindings (GhcPass 'Renamed)
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
        ; Bool
is_boot <- TcRn Bool
tcIsHsBootOrSig
        ; let no_binds :: Bool
no_binds = LHsBinds (GhcPass 'Renamed) -> Bool
forall idL idR. LHsBindsLR idL idR -> Bool
isEmptyLHsBinds LHsBinds (GhcPass 'Renamed)
binds Bool -> Bool -> Bool
&& [LSig (GhcPass 'Renamed)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
External instance of the constraint type Foldable []
null [LSig (GhcPass 'Renamed)]
uprags
        ; Bool -> SDoc -> TcRn ()
failIfTc (Bool
is_boot Bool -> Bool -> Bool
&& Bool -> Bool
not Bool
no_binds) SDoc
badBootDeclErr

        ; ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
-> TcRn ([InstInfo (GhcPass 'Renamed)], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ( [InstInfo (GhcPass 'Renamed)
inst_info], [FamInst]
all_insts, [DerivInfo]
deriv_infos ) }
  where
    defined_ats :: NameSet
defined_ats = [Name] -> NameSet
mkNameSet ((LTyFamInstDecl (GhcPass 'Renamed) -> Name)
-> [LTyFamInstDecl (GhcPass 'Renamed)] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (TyFamInstDecl (GhcPass 'Renamed) -> Name
forall (p :: Pass). TyFamInstDecl (GhcPass p) -> IdP (GhcPass p)
tyFamInstDeclName (TyFamInstDecl (GhcPass 'Renamed) -> Name)
-> (LTyFamInstDecl (GhcPass 'Renamed)
    -> TyFamInstDecl (GhcPass 'Renamed))
-> LTyFamInstDecl (GhcPass 'Renamed)
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyFamInstDecl (GhcPass 'Renamed)
-> TyFamInstDecl (GhcPass 'Renamed)
forall l e. GenLocated l e -> e
unLoc) [LTyFamInstDecl (GhcPass 'Renamed)]
ats)
                  NameSet -> NameSet -> NameSet
`unionNameSet`
                  [Name] -> NameSet
mkNameSet ((LDataFamInstDecl (GhcPass 'Renamed) -> Name)
-> [LDataFamInstDecl (GhcPass 'Renamed)] -> [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)
-> (LDataFamInstDecl (GhcPass 'Renamed) -> GenLocated SrcSpan Name)
-> LDataFamInstDecl (GhcPass 'Renamed)
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed))
-> GenLocated SrcSpan Name
forall pass rhs. FamEqn pass rhs -> Located (IdP pass)
feqn_tycon
                                        (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed))
 -> GenLocated SrcSpan Name)
-> (LDataFamInstDecl (GhcPass 'Renamed)
    -> FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
-> LDataFamInstDecl (GhcPass 'Renamed)
-> GenLocated SrcSpan Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. HsImplicitBndrs
  (GhcPass 'Renamed)
  (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
-> FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed))
forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body
                                        (HsImplicitBndrs
   (GhcPass 'Renamed)
   (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
 -> FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
-> (LDataFamInstDecl (GhcPass 'Renamed)
    -> HsImplicitBndrs
         (GhcPass 'Renamed)
         (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed))))
-> LDataFamInstDecl (GhcPass 'Renamed)
-> FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed))
forall b c a. (b -> c) -> (a -> b) -> a -> c
. DataFamInstDecl (GhcPass 'Renamed)
-> HsImplicitBndrs
     (GhcPass 'Renamed)
     (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
forall pass.
DataFamInstDecl pass -> FamInstEqn pass (HsDataDefn pass)
dfid_eqn
                                        (DataFamInstDecl (GhcPass 'Renamed)
 -> HsImplicitBndrs
      (GhcPass 'Renamed)
      (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed))))
-> (LDataFamInstDecl (GhcPass 'Renamed)
    -> DataFamInstDecl (GhcPass 'Renamed))
-> LDataFamInstDecl (GhcPass 'Renamed)
-> HsImplicitBndrs
     (GhcPass 'Renamed)
     (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LDataFamInstDecl (GhcPass 'Renamed)
-> DataFamInstDecl (GhcPass 'Renamed)
forall l e. GenLocated l e -> e
unLoc) [LDataFamInstDecl (GhcPass 'Renamed)]
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 (GhcPass 'Renamed) -> TcM FamInst
tcTyFamInstDecl AssocInstInfo
mb_clsinfo (L SrcSpan
loc decl :: TyFamInstDecl (GhcPass 'Renamed)
decl@(TyFamInstDecl { tfid_eqn :: forall pass. TyFamInstDecl pass -> TyFamInstEqn pass
tfid_eqn = TyFamInstEqn (GhcPass 'Renamed)
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 (GhcPass 'Renamed) -> TcM FamInst -> TcM FamInst
forall a. TyFamInstDecl (GhcPass 'Renamed) -> TcM a -> TcM a
tcAddTyFamInstCtxt TyFamInstDecl (GhcPass 'Renamed)
decl  (TcM FamInst -> TcM FamInst) -> TcM FamInst -> TcM FamInst
forall a b. (a -> b) -> a -> b
$
    do { let fam_lname :: Located (IdP (GhcPass 'Renamed))
fam_lname = FamEqn (GhcPass 'Renamed) (LHsType (GhcPass 'Renamed))
-> Located (IdP (GhcPass 'Renamed))
forall pass rhs. FamEqn pass rhs -> Located (IdP pass)
feqn_tycon (TyFamInstEqn (GhcPass 'Renamed)
-> FamEqn (GhcPass 'Renamed) (LHsType (GhcPass 'Renamed))
forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body TyFamInstEqn (GhcPass 'Renamed)
eqn)
       ; TyCon
fam_tc <- GenLocated SrcSpan Name -> TcM TyCon
tcLookupLocatedTyCon GenLocated SrcSpan Name
Located (IdP (GhcPass 'Renamed))
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
       ; KnotTied CoAxBranch
co_ax_branch <- TyCon
-> AssocInstInfo
-> LTyFamInstEqn (GhcPass 'Renamed)
-> TcM (KnotTied CoAxBranch)
tcTyFamInstEqn TyCon
fam_tc AssocInstInfo
mb_clsinfo
                                        (SrcSpan
-> TyFamInstEqn (GhcPass 'Renamed)
-> LTyFamInstEqn (GhcPass 'Renamed)
forall l e. l -> e -> GenLocated l e
L (GenLocated SrcSpan Name -> SrcSpan
forall l e. GenLocated l e -> l
getLoc GenLocated SrcSpan Name
Located (IdP (GhcPass 'Renamed))
fam_lname) TyFamInstEqn (GhcPass 'Renamed)
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 -> [[PredType]] -> TcM Name
newFamInstAxiomName GenLocated SrcSpan Name
Located (IdP (GhcPass 'Renamed))
fam_lname [KnotTied CoAxBranch -> [PredType]
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
External instance of the constraint type Outputable TyCon
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 ()
External instance of the constraint type forall m. Applicative (IOEnv m)
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 (GhcPass 'Renamed)
-> TcM (FamInst, Maybe DerivInfo)
tcDataFamInstDecl AssocInstInfo
mb_clsinfo TyVarEnv Name
tv_skol_env
    (L SrcSpan
loc decl :: DataFamInstDecl (GhcPass 'Renamed)
decl@(DataFamInstDecl { dfid_eqn :: forall pass.
DataFamInstDecl pass -> FamInstEqn pass (HsDataDefn pass)
dfid_eqn = HsIB { hsib_ext :: forall pass thing. HsImplicitBndrs pass thing -> XHsIB pass thing
hsib_ext = XHsIB
  (GhcPass 'Renamed)
  (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
imp_vars
                                                   , hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body =
      FamEqn { feqn_bndrs :: forall pass rhs. FamEqn pass rhs -> Maybe [LHsTyVarBndr () pass]
feqn_bndrs  = Maybe [LHsTyVarBndr () (GhcPass 'Renamed)]
mb_bndrs
             , feqn_pats :: forall pass rhs. FamEqn pass rhs -> HsTyPats pass
feqn_pats   = HsTyPats (GhcPass 'Renamed)
hs_pats
             , feqn_tycon :: forall pass rhs. FamEqn pass rhs -> Located (IdP pass)
feqn_tycon  = lfam_name :: Located (IdP (GhcPass 'Renamed))
lfam_name@(L SrcSpan
_ IdP (GhcPass 'Renamed)
fam_name)
             , feqn_fixity :: forall pass rhs. FamEqn pass rhs -> LexicalFixity
feqn_fixity = LexicalFixity
fixity
             , feqn_rhs :: forall pass rhs. FamEqn pass rhs -> rhs
feqn_rhs    = HsDataDefn { dd_ND :: forall pass. HsDataDefn pass -> NewOrData
dd_ND      = NewOrData
new_or_data
                                        , dd_cType :: forall pass. HsDataDefn pass -> Maybe (Located CType)
dd_cType   = Maybe (Located CType)
cType
                                        , dd_ctxt :: forall pass. HsDataDefn pass -> LHsContext pass
dd_ctxt    = LHsContext (GhcPass 'Renamed)
hs_ctxt
                                        , dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons    = [LConDecl (GhcPass 'Renamed)]
hs_cons
                                        , dd_kindSig :: forall pass. HsDataDefn pass -> Maybe (LHsKind pass)
dd_kindSig = Maybe (LHsType (GhcPass 'Renamed))
m_ksig
                                        , dd_derivs :: forall pass. HsDataDefn pass -> HsDeriving pass
dd_derivs  = HsDeriving (GhcPass 'Renamed)
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 (GhcPass 'Renamed)
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a. DataFamInstDecl (GhcPass 'Renamed) -> TcM a -> TcM a
tcAddDataFamInstCtxt DataFamInstDecl (GhcPass 'Renamed)
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
Located (IdP (GhcPass 'Renamed))
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 (GhcPass 'Renamed)
-> [LConDecl (GhcPass 'Renamed)]
-> TcRn Bool
dataDeclChecks Name
IdP (GhcPass 'Renamed)
fam_name NewOrData
new_or_data LHsContext (GhcPass 'Renamed)
hs_ctxt [LConDecl (GhcPass 'Renamed)]
hs_cons
          -- Do /not/ check that the number of patterns = tyConArity fam_tc
          -- See [Arity of data families] in GHC.Core.FamInstEnv
       ; ([Id]
qtvs, [PredType]
pats, PredType
res_kind, [PredType]
stupid_theta)
             <- AssocInstInfo
-> TyCon
-> [Name]
-> Maybe [LHsTyVarBndr () (GhcPass 'Renamed)]
-> LexicalFixity
-> LHsContext (GhcPass 'Renamed)
-> HsTyPats (GhcPass 'Renamed)
-> Maybe (LHsType (GhcPass 'Renamed))
-> [LConDecl (GhcPass 'Renamed)]
-> NewOrData
-> TcM ([Id], [PredType], PredType, [PredType])
tcDataFamInstHeader AssocInstInfo
mb_clsinfo TyCon
fam_tc [Name]
XHsIB
  (GhcPass 'Renamed)
  (FamEqn (GhcPass 'Renamed) (HsDataDefn (GhcPass 'Renamed)))
imp_vars Maybe [LHsTyVarBndr () (GhcPass 'Renamed)]
mb_bndrs
                                    LexicalFixity
fixity LHsContext (GhcPass 'Renamed)
hs_ctxt HsTyPats (GhcPass 'Renamed)
hs_pats Maybe (LHsType (GhcPass 'Renamed))
m_ksig [LConDecl (GhcPass 'Renamed)]
hs_cons
                                    NewOrData
new_or_data

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

             full_tcbs :: [TyConBinder]
full_tcbs = [Id] -> VarSet -> [TyConBinder]
mkTyConBindersPreferAnon [Id]
post_eta_qtvs
                            (PredType -> VarSet
tyCoVarsOfType ([Id] -> PredType -> PredType
mkSpecForAllTys [Id]
eta_tvs PredType
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
       --
       -- See also Note [Datatype return kinds] in GHC.Tc.TyCl
       ; ([TyConBinder]
extra_tcbs, PredType
final_res_kind) <- [TyConBinder] -> PredType -> TcM ([TyConBinder], PredType)
etaExpandAlgTyCon [TyConBinder]
full_tcbs PredType
res_kind
       ; DataSort -> PredType -> TcRn ()
checkDataKindSig (NewOrData -> DataSort
DataInstanceSort NewOrData
new_or_data) PredType
final_res_kind
       ; let extra_pats :: [PredType]
extra_pats  = (TyConBinder -> PredType) -> [TyConBinder] -> [PredType]
forall a b. (a -> b) -> [a] -> [b]
map (Id -> PredType
mkTyVarTy (Id -> PredType) -> (TyConBinder -> Id) -> TyConBinder -> PredType
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TyConBinder -> Id
forall tv argf. VarBndr tv argf -> tv
binderVar) [TyConBinder]
extra_tcbs
             all_pats :: [PredType]
all_pats    = [PredType]
pats [PredType] -> [PredType] -> [PredType]
forall a. [a] -> [a] -> [a]
`chkAppend` [PredType]
extra_pats
             orig_res_ty :: PredType
orig_res_ty = TyCon -> [PredType] -> PredType
mkTyConApp TyCon
fam_tc [PredType]
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
External instance of the constraint type Outputable TyCon
ppr TyCon
fam_tc
              , String -> SDoc
text String
"Pats:" SDoc -> SDoc -> SDoc
<+> [PredType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable PredType
ppr [PredType]
pats
              , String -> SDoc
text String
"visibliities:" SDoc -> SDoc -> SDoc
<+> [TyConBndrVis] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TyConBndrVis
ppr (TyCon -> [PredType] -> [TyConBndrVis]
tcbVisibilities TyCon
fam_tc [PredType]
pats)
              , String -> SDoc
text String
"all_pats:" SDoc -> SDoc -> SDoc
<+> [PredType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable PredType
ppr [PredType]
all_pats
              , String -> SDoc
text String
"ty_binders" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type forall tv.
OutputableBndr tv =>
Outputable (VarBndr tv TyConBndrVis)
External instance of the constraint type OutputableBndr Id
ppr [TyConBinder]
ty_binders
              , String -> SDoc
text String
"fam_tc_binders:" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type forall tv.
OutputableBndr tv =>
Outputable (VarBndr tv TyConBndrVis)
External instance of the constraint type OutputableBndr Id
ppr (TyCon -> [TyConBinder]
tyConBinders TyCon
fam_tc)
              , String -> SDoc
text String
"eta_pats" SDoc -> SDoc -> SDoc
<+> [PredType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable PredType
ppr [PredType]
eta_pats
              , String -> SDoc
text String
"eta_tcbs" SDoc -> SDoc -> SDoc
<+> [TyConBinder] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type forall tv.
OutputableBndr tv =>
Outputable (VarBndr tv TyConBndrVis)
External instance of the constraint type OutputableBndr Id
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 <- [Id] -> TcM [DataCon] -> TcM [DataCon]
forall r. [Id] -> TcM r -> TcM r
tcExtendTyVarEnv [Id]
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]
-> PredType
-> PredType
-> [LConDecl (GhcPass 'Renamed)]
-> TcM [DataCon]
tcConDecls TyCon
rec_rep_tc NewOrData
new_or_data [TyConBinder]
ty_binders PredType
final_res_kind
                             PredType
orig_res_ty [LConDecl (GhcPass 'Renamed)]
hs_cons

              ; Name
rep_tc_name <- GenLocated SrcSpan Name -> [PredType] -> TcM Name
newFamInstTyConName GenLocated SrcSpan Name
Located (IdP (GhcPass 'Renamed))
lfam_name [PredType]
pats
              ; Name
axiom_name  <- GenLocated SrcSpan Name -> [[PredType]] -> TcM Name
newFamInstAxiomName GenLocated SrcSpan Name
Located (IdP (GhcPass 'Renamed))
lfam_name [[PredType]
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
External instance of the constraint type forall m. Monad (IOEnv m)
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 axiom :: CoAxiom Unbranched
axiom  = Role
-> Name
-> [Id]
-> [Id]
-> [Id]
-> TyCon
-> [PredType]
-> PredType
-> CoAxiom Unbranched
mkSingleCoAxiom Role
Representational Name
axiom_name
                                 [Id]
post_eta_qtvs [Id]
eta_tvs [] TyCon
fam_tc [PredType]
eta_pats
                                 (TyCon -> [PredType] -> PredType
mkTyConApp TyCon
rep_tc ([Id] -> [PredType]
mkTyVarTys [Id]
post_eta_qtvs))
                    parent :: AlgTyConFlav
parent = CoAxiom Unbranched -> TyCon -> [PredType] -> AlgTyConFlav
DataFamInstTyCon CoAxiom Unbranched
axiom TyCon
fam_tc [PredType]
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]
-> PredType
-> [Role]
-> Maybe CType
-> [PredType]
-> AlgTyConRhs
-> AlgTyConFlav
-> Bool
-> TyCon
mkAlgTyCon Name
rep_tc_name
                                          [TyConBinder]
ty_binders PredType
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)
                                          ((Located CType -> CType) -> Maybe (Located CType) -> Maybe CType
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
External instance of the constraint type Functor Maybe
fmap Located CType -> CType
forall l e. GenLocated l e -> e
unLoc Maybe (Located CType)
cType) [PredType]
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
External instance of the constraint type forall m. Monad (IOEnv m)
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, Id)]
scoped_tvs = (Id -> (Name, Id)) -> [Id] -> [(Name, Id)]
forall a b. (a -> b) -> [a] -> [b]
map Id -> (Name, Id)
mk_deriv_info_scoped_tv_pr (TyCon -> [Id]
tyConTyVars TyCon
rep_tc)
             m_deriv_info :: Maybe DerivInfo
m_deriv_info = case HsDeriving (GhcPass 'Renamed)
derivs of
               L SrcSpan
_ []    -> Maybe DerivInfo
forall a. Maybe a
Nothing
               L SrcSpan
_ [LHsDerivingClause (GhcPass 'Renamed)]
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, Id)]
-> [LHsDerivingClause (GhcPass 'Renamed)]
-> SDoc
-> DerivInfo
DerivInfo { di_rep_tc :: TyCon
di_rep_tc  = TyCon
rep_tc
                                  , di_scoped_tvs :: [(Name, Id)]
di_scoped_tvs = [(Name, Id)]
scoped_tvs
                                  , di_clauses :: [LHsDerivingClause (GhcPass 'Renamed)]
di_clauses = [LHsDerivingClause (GhcPass 'Renamed)]
preds
                                  , di_ctxt :: SDoc
di_ctxt    = DataFamInstDecl (GhcPass 'Renamed) -> SDoc
tcMkDataFamInstCtxt DataFamInstDecl (GhcPass 'Renamed)
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
External instance of the constraint type forall m. Monad (IOEnv m)
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 -> [PredType] -> ([PredType], [TyConBinder])
eta_reduce TyCon
fam_tc [PredType]
pats
        = [(PredType, VarSet, TyConBndrVis)]
-> [TyConBinder] -> ([PredType], [TyConBinder])
forall {c}.
[(PredType, VarSet, c)]
-> [VarBndr Id c] -> ([PredType], [VarBndr Id c])
go ([(PredType, VarSet, TyConBndrVis)]
-> [(PredType, VarSet, TyConBndrVis)]
forall a. [a] -> [a]
reverse ([PredType]
-> [VarSet] -> [TyConBndrVis] -> [(PredType, VarSet, TyConBndrVis)]
forall a b c. [a] -> [b] -> [c] -> [(a, b, c)]
zip3 [PredType]
pats [VarSet]
fvs_s [TyConBndrVis]
vis_s)) []
        where
          vis_s :: [TyConBndrVis]
          vis_s :: [TyConBndrVis]
vis_s = TyCon -> [PredType] -> [TyConBndrVis]
tcbVisibilities TyCon
fam_tc [PredType]
pats

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

    go :: [(PredType, VarSet, c)]
-> [VarBndr Id c] -> ([PredType], [VarBndr Id c])
go ((PredType
pat, VarSet
fvs_to_the_left, c
tcb_vis):[(PredType, VarSet, c)]
pats) [VarBndr Id c]
etad_tvs
      | Just Id
tv <- PredType -> Maybe Id
getTyVar_maybe PredType
pat
      , Bool -> Bool
not (Id
tv Id -> VarSet -> Bool
`elemVarSet` VarSet
fvs_to_the_left)
      = [(PredType, VarSet, c)]
-> [VarBndr Id c] -> ([PredType], [VarBndr Id c])
go [(PredType, VarSet, c)]
pats (Id -> c -> VarBndr Id c
forall var argf. var -> argf -> VarBndr var argf
Bndr Id
tv c
tcb_vis VarBndr Id c -> [VarBndr Id c] -> [VarBndr Id c]
forall a. a -> [a] -> [a]
: [VarBndr Id c]
etad_tvs)
    go [(PredType, VarSet, c)]
pats [VarBndr Id c]
etad_tvs = ([PredType] -> [PredType]
forall a. [a] -> [a]
reverse (((PredType, VarSet, c) -> PredType)
-> [(PredType, VarSet, c)] -> [PredType]
forall a b. (a -> b) -> [a] -> [b]
map (PredType, VarSet, c) -> PredType
forall a b c. (a, b, c) -> a
fstOf3 [(PredType, VarSet, c)]
pats), [VarBndr Id 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 :: Id -> (Name, Id)
mk_deriv_info_scoped_tv_pr Id
tv =
      let n :: Name
n = TyVarEnv Name -> Name -> Id -> Name
forall a. VarEnv a -> a -> Id -> a
lookupWithDefaultVarEnv TyVarEnv Name
tv_skol_env (Id -> Name
tyVarName Id
tv) Id
tv
      in (Name
n, Id
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 -> [Name] -> Maybe [LHsTyVarBndr () 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
-> [Name]
-> Maybe [LHsTyVarBndr () (GhcPass 'Renamed)]
-> LexicalFixity
-> LHsContext (GhcPass 'Renamed)
-> HsTyPats (GhcPass 'Renamed)
-> Maybe (LHsType (GhcPass 'Renamed))
-> [LConDecl (GhcPass 'Renamed)]
-> NewOrData
-> TcM ([Id], [PredType], PredType, [PredType])
tcDataFamInstHeader AssocInstInfo
mb_clsinfo TyCon
fam_tc [Name]
imp_vars Maybe [LHsTyVarBndr () (GhcPass 'Renamed)]
mb_bndrs LexicalFixity
fixity
                    LHsContext (GhcPass 'Renamed)
hs_ctxt HsTyPats (GhcPass 'Renamed)
hs_pats Maybe (LHsType (GhcPass 'Renamed))
m_ksig [LConDecl (GhcPass 'Renamed)]
hs_cons NewOrData
new_or_data
  = do { ([Id]
imp_tvs, ([Id]
exp_tvs, ([PredType]
stupid_theta, PredType
lhs_ty, PredType
lhs_applied_kind)))
            <- TcM ([Id], ([Id], ([PredType], PredType, PredType)))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
forall a. TcM a -> TcM a
pushTcLevelM_                                (TcM ([Id], ([Id], ([PredType], PredType, PredType)))
 -> TcM ([Id], ([Id], ([PredType], PredType, PredType))))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
forall a b. (a -> b) -> a -> b
$
               TcM ([Id], ([Id], ([PredType], PredType, PredType)))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
forall a. TcM a -> TcM a
solveEqualities                              (TcM ([Id], ([Id], ([PredType], PredType, PredType)))
 -> TcM ([Id], ([Id], ([PredType], PredType, PredType))))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
forall a b. (a -> b) -> a -> b
$
               [Name]
-> TcM ([Id], ([PredType], PredType, PredType))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
forall a. [Name] -> TcM a -> TcM ([Id], a)
bindImplicitTKBndrs_Q_Skol [Name]
imp_vars          (TcM ([Id], ([PredType], PredType, PredType))
 -> TcM ([Id], ([Id], ([PredType], PredType, PredType))))
-> TcM ([Id], ([PredType], PredType, PredType))
-> TcM ([Id], ([Id], ([PredType], PredType, PredType)))
forall a b. (a -> b) -> a -> b
$
               ContextKind
-> [LHsTyVarBndr () (GhcPass 'Renamed)]
-> TcM ([PredType], PredType, PredType)
-> TcM ([Id], ([PredType], PredType, PredType))
forall a.
ContextKind
-> [LHsTyVarBndr () (GhcPass 'Renamed)] -> TcM a -> TcM ([Id], a)
bindExplicitTKBndrs_Q_Skol ContextKind
AnyKind [LHsTyVarBndr () (GhcPass 'Renamed)]
exp_bndrs (TcM ([PredType], PredType, PredType)
 -> TcM ([Id], ([PredType], PredType, PredType)))
-> TcM ([PredType], PredType, PredType)
-> TcM ([Id], ([PredType], PredType, PredType))
forall a b. (a -> b) -> a -> b
$
               do { [PredType]
stupid_theta <- LHsContext (GhcPass 'Renamed) -> TcM [PredType]
tcHsContext LHsContext (GhcPass 'Renamed)
hs_ctxt
                  ; (PredType
lhs_ty, PredType
lhs_kind) <- TyCon -> HsTyPats (GhcPass 'Renamed) -> TcM (PredType, PredType)
tcFamTyPats TyCon
fam_tc HsTyPats (GhcPass 'Renamed)
hs_pats

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

                  -- Add constraints from the result signature
                  ; PredType
res_kind <- Maybe (LHsType (GhcPass 'Renamed)) -> TcM PredType
tc_kind_sig Maybe (LHsType (GhcPass 'Renamed))
m_ksig

                  -- Add constraints from the data constructors
                  ; NewOrData -> PredType -> [LConDecl (GhcPass 'Renamed)] -> TcRn ()
kcConDecls NewOrData
new_or_data PredType
res_kind [LConDecl (GhcPass 'Renamed)]
hs_cons

                  -- See Note [Datatype return kinds] in GHC.Tc.TyCl, point (7).
                  ; ([PredType]
lhs_extra_args, PredType
lhs_applied_kind)
                      <- ConTag -> PredType -> TcM ([PredType], PredType)
tcInstInvisibleTyBinders (PredType -> ConTag
invisibleTyBndrCount PredType
lhs_kind)
                                                  PredType
lhs_kind
                  ; let lhs_applied_ty :: PredType
lhs_applied_ty = PredType
lhs_ty PredType -> [PredType] -> PredType
`mkTcAppTys` [PredType]
lhs_extra_args
                        hs_lhs :: LHsType (GhcPass 'Renamed)
hs_lhs         = LexicalFixity
-> IdP (GhcPass 'Renamed)
-> HsTyPats (GhcPass 'Renamed)
-> LHsType (GhcPass 'Renamed)
forall (p :: Pass).
LexicalFixity
-> IdP (GhcPass p)
-> [LHsTypeArg (GhcPass p)]
-> LHsType (GhcPass p)
nlHsTyConApp LexicalFixity
fixity (TyCon -> Name
forall a. NamedThing a => a -> Name
External instance of the constraint type NamedThing TyCon
getName TyCon
fam_tc) HsTyPats (GhcPass 'Renamed)
hs_pats
                  ; CoercionN
_ <- Maybe (HsType (GhcPass 'Renamed))
-> PredType -> PredType -> TcM CoercionN
unifyKind (HsType (GhcPass 'Renamed) -> Maybe (HsType (GhcPass 'Renamed))
forall a. a -> Maybe a
Just (LHsType (GhcPass 'Renamed) -> HsType (GhcPass 'Renamed)
forall l e. GenLocated l e -> e
unLoc LHsType (GhcPass 'Renamed)
hs_lhs)) PredType
lhs_applied_kind PredType
res_kind

                  ; ([PredType], PredType, PredType)
-> TcM ([PredType], PredType, PredType)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ( [PredType]
stupid_theta
                           , PredType
lhs_applied_ty
                           , PredType
lhs_applied_kind ) }

       -- See GHC.Tc.TyCl Note [Generalising in tcFamTyPatsGuts]
       -- 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!
       ; let scoped_tvs :: [Id]
scoped_tvs = [Id]
imp_tvs [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id]
exp_tvs
       ; CandidatesQTvs
dvs  <- [PredType] -> TcM CandidatesQTvs
candidateQTyVarsOfTypes (PredType
lhs_ty PredType -> [PredType] -> [PredType]
forall a. a -> [a] -> [a]
: [Id] -> [PredType]
mkTyVarTys [Id]
scoped_tvs)
       ; [Id]
qtvs <- CandidatesQTvs -> TcM [Id]
quantifyTyVars CandidatesQTvs
dvs

       -- Zonk the patterns etc into the Type world
       ; (ZonkEnv
ze, [Id]
qtvs)       <- [Id] -> TcM (ZonkEnv, [Id])
zonkTyBndrs [Id]
qtvs
       ; PredType
lhs_ty           <- ZonkEnv -> PredType -> TcM PredType
zonkTcTypeToTypeX ZonkEnv
ze PredType
lhs_ty
       ; [PredType]
stupid_theta     <- ZonkEnv -> [PredType] -> TcM [PredType]
zonkTcTypesToTypesX ZonkEnv
ze [PredType]
stupid_theta
       ; PredType
lhs_applied_kind <- ZonkEnv -> PredType -> TcM PredType
zonkTcTypeToTypeX ZonkEnv
ze PredType
lhs_applied_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.
       ; [PredType]
pats <- case HasDebugCallStack => PredType -> Maybe (TyCon, [PredType])
PredType -> Maybe (TyCon, [PredType])
External instance of the constraint type HasDebugCallStack
splitTyConApp_maybe PredType
lhs_ty of
           Just (TyCon
_, [PredType]
pats) -> [PredType] -> TcM [PredType]
forall (f :: * -> *) a. Applicative f => a -> f a
External instance of the constraint type forall m. Applicative (IOEnv m)
pure [PredType]
pats
           Maybe (TyCon, [PredType])
Nothing -> String -> SDoc -> TcM [PredType]
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcDataFamInstHeader" (PredType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable PredType
ppr PredType
lhs_ty)
       ; ([Id], [PredType], PredType, [PredType])
-> TcM ([Id], [PredType], PredType, [PredType])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([Id]
qtvs, [PredType]
pats, PredType
lhs_applied_kind, [PredType]
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
    exp_bndrs :: [LHsTyVarBndr () (GhcPass 'Renamed)]
exp_bndrs = Maybe [LHsTyVarBndr () (GhcPass 'Renamed)]
mb_bndrs Maybe [LHsTyVarBndr () (GhcPass 'Renamed)]
-> [LHsTyVarBndr () (GhcPass 'Renamed)]
-> [LHsTyVarBndr () (GhcPass 'Renamed)]
forall a. Maybe a -> a -> a
`orElse` []

    -- See Note [Implementation of UnliftedNewtypes] in GHC.Tc.TyCl, wrinkle (2).
    tc_kind_sig :: Maybe (LHsType (GhcPass 'Renamed)) -> TcM PredType
tc_kind_sig Maybe (LHsType (GhcPass 'Renamed))
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
External instance of the constraint type Eq NewOrData
== NewOrData
NewType
               then TcM PredType
newOpenTypeKind
               else PredType -> TcM PredType
forall (f :: * -> *) a. Applicative f => a -> f a
External instance of the constraint type forall m. Applicative (IOEnv m)
pure PredType
liftedTypeKind
           }

    -- See Note [Result kind signature for a data family instance]
    tc_kind_sig (Just LHsType (GhcPass 'Renamed)
hs_kind)
      = do { PredType
sig_kind <- UserTypeCtxt -> LHsType (GhcPass 'Renamed) -> TcM PredType
tcLHsKindSig UserTypeCtxt
data_ctxt LHsType (GhcPass 'Renamed)
hs_kind
           ; let ([Id]
tvs, PredType
inner_kind) = PredType -> ([Id], PredType)
tcSplitForAllTys PredType
sig_kind
           ; TcLevel
lvl <- TcM TcLevel
getTcLevel
           ; (TCvSubst
subst, [Id]
_tvs') <- TcLevel -> Bool -> TCvSubst -> [Id] -> TcM (TCvSubst, [Id])
tcInstSkolTyVarsAt TcLevel
lvl Bool
False TCvSubst
emptyTCvSubst [Id]
tvs
             -- Perhaps surprisingly, we don't need the skolemised tvs themselves
           ; let final_kind :: PredType
final_kind = HasCallStack => TCvSubst -> PredType -> PredType
TCvSubst -> PredType -> PredType
substTy TCvSubst
subst PredType
inner_kind
           ; DataSort -> PredType -> TcRn ()
checkDataKindSig (NewOrData -> DataSort
DataInstanceSort NewOrData
new_or_data) (PredType -> TcRn ()) -> PredType -> TcRn ()
forall a b. (a -> b) -> a -> b
$
               ([TyBinder], PredType) -> PredType
forall a b. (a, b) -> b
snd (([TyBinder], PredType) -> PredType)
-> ([TyBinder], PredType) -> PredType
forall a b. (a -> b) -> a -> b
$ PredType -> ([TyBinder], PredType)
tcSplitPiTys PredType
final_kind
             -- See Note [Datatype return kinds], end of point (4)
           ; PredType -> TcM PredType
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return PredType
final_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. Inst.deeplySkolemise and 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 insatance
  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 (GhcPass 'Renamed)]
-> [InstInfo (GhcPass 'Renamed)] -> TcM (LHsBinds GhcTcId)
tcInstDecls2 [LTyClDecl (GhcPass 'Renamed)]
tycl_decls [InstInfo (GhcPass 'Renamed)]
inst_decls
  = do  { -- (a) Default methods from class decls
          let class_decls :: [LTyClDecl (GhcPass 'Renamed)]
class_decls = (LTyClDecl (GhcPass 'Renamed) -> Bool)
-> [LTyClDecl (GhcPass 'Renamed)] -> [LTyClDecl (GhcPass 'Renamed)]
forall a. (a -> Bool) -> [a] -> [a]
filter (TyClDecl (GhcPass 'Renamed) -> Bool
forall pass. TyClDecl pass -> Bool
isClassDecl (TyClDecl (GhcPass 'Renamed) -> Bool)
-> (LTyClDecl (GhcPass 'Renamed) -> TyClDecl (GhcPass 'Renamed))
-> LTyClDecl (GhcPass 'Renamed)
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyClDecl (GhcPass 'Renamed) -> TyClDecl (GhcPass 'Renamed)
forall l e. GenLocated l e -> e
unLoc) [LTyClDecl (GhcPass 'Renamed)]
tycl_decls
        ; [LHsBinds GhcTcId]
dm_binds_s <- (LTyClDecl (GhcPass 'Renamed) -> TcM (LHsBinds GhcTcId))
-> [LTyClDecl (GhcPass 'Renamed)]
-> IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
External instance of the constraint type forall m. Monad (IOEnv m)
External instance of the constraint type Traversable []
mapM LTyClDecl (GhcPass 'Renamed) -> TcM (LHsBinds GhcTcId)
tcClassDecl2 [LTyClDecl (GhcPass 'Renamed)]
class_decls
        ; let dm_binds :: LHsBinds GhcTcId
dm_binds = [LHsBinds GhcTcId] -> LHsBinds GhcTcId
forall a. [Bag a] -> Bag a
unionManyBags [LHsBinds GhcTcId]
dm_binds_s

          -- (b) instance declarations
        ; let dm_ids :: [IdP GhcTcId]
dm_ids = LHsBinds GhcTcId -> [IdP GhcTcId]
forall p idR. CollectPass p => LHsBindsLR p idR -> [IdP p]
External instance of the constraint type CollectPass GhcTcId
collectHsBindsBinders LHsBinds GhcTcId
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]
        ; [LHsBinds GhcTcId]
inst_binds_s <- [Id]
-> IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId]
-> IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId]
forall r. [Id] -> TcM r -> TcM r
tcExtendGlobalValEnv [Id]
[IdP GhcTcId]
dm_ids (IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId]
 -> IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId])
-> IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId]
-> IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId]
forall a b. (a -> b) -> a -> b
$
                          (InstInfo (GhcPass 'Renamed) -> TcM (LHsBinds GhcTcId))
-> [InstInfo (GhcPass 'Renamed)]
-> IOEnv (Env TcGblEnv TcLclEnv) [LHsBinds GhcTcId]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
External instance of the constraint type forall m. Monad (IOEnv m)
External instance of the constraint type Traversable []
mapM InstInfo (GhcPass 'Renamed) -> TcM (LHsBinds GhcTcId)
tcInstDecl2 [InstInfo (GhcPass 'Renamed)]
inst_decls

          -- Done
        ; LHsBinds GhcTcId -> TcM (LHsBinds GhcTcId)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (LHsBinds GhcTcId
dm_binds LHsBinds GhcTcId -> LHsBinds GhcTcId -> LHsBinds GhcTcId
forall a. Bag a -> Bag a -> Bag a
`unionBags` [LHsBinds GhcTcId] -> LHsBinds GhcTcId
forall a. [Bag a] -> Bag a
unionManyBags [LHsBinds GhcTcId]
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 (GhcPass 'Renamed) -> TcM (LHsBinds GhcTcId)
tcInstDecl2 (InstInfo { iSpec :: forall a. InstInfo a -> ClsInst
iSpec = ClsInst
ispec, iBinds :: forall a. InstInfo a -> InstBindings a
iBinds = InstBindings (GhcPass 'Renamed)
ibinds })
  = TcM (LHsBinds GhcTcId)
-> TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId)
forall r. TcRn r -> TcRn r -> TcRn r
recoverM (LHsBinds GhcTcId -> TcM (LHsBinds GhcTcId)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return LHsBinds GhcTcId
forall idL idR. LHsBindsLR idL idR
emptyLHsBinds)             (TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId))
-> TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId)
forall a b. (a -> b) -> a -> b
$
    SrcSpan -> TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc                              (TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId))
-> TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId)
forall a b. (a -> b) -> a -> b
$
    SDoc -> TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId)
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (PredType -> SDoc
instDeclCtxt2 (Id -> PredType
idType Id
dfun_id)) (TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId))
-> TcM (LHsBinds GhcTcId) -> TcM (LHsBinds GhcTcId)
forall a b. (a -> b) -> a -> b
$
    do {  -- Instantiate the instance decl with skolem constants
       ; ([Id]
inst_tyvars, [PredType]
dfun_theta, PredType
inst_head) <- Id -> TcM ([Id], [PredType], PredType)
tcSkolDFunType Id
dfun_id
       ; [Id]
dfun_ev_vars <- [PredType] -> TcM [Id]
newEvVars [PredType]
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, [PredType]
inst_tys) = PredType -> (Class, [PredType])
tcSplitDFunHead PredType
inst_head
             ([Id]
class_tyvars, [PredType]
sc_theta, [Id]
_, [ClassOpItem]
op_items) = Class -> ([Id], [PredType], [Id], [ClassOpItem])
classBigSig Class
clas
             sc_theta' :: [PredType]
sc_theta' = HasCallStack => TCvSubst -> [PredType] -> [PredType]
TCvSubst -> [PredType] -> [PredType]
substTheta ([Id] -> [PredType] -> TCvSubst
HasDebugCallStack => [Id] -> [PredType] -> TCvSubst
External instance of the constraint type HasDebugCallStack
zipTvSubst [Id]
class_tyvars [PredType]
inst_tys) [PredType]
sc_theta

       ; String -> SDoc -> TcRn ()
traceTc String
"tcInstDecl2" ([SDoc] -> SDoc
vcat [[Id] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable Id
ppr [Id]
inst_tyvars, [PredType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable PredType
ppr [PredType]
inst_tys, [PredType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable PredType
ppr [PredType]
dfun_theta, [PredType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable PredType
ppr [PredType]
sc_theta'])

                      -- Deal with 'SPECIALISE instance' pragmas
                      -- See Note [SPECIALISE instance pragmas]
       ; spec_inst_info :: ([Located TcSpecPrag], TcPragEnv)
spec_inst_info@([Located TcSpecPrag]
spec_inst_prags,TcPragEnv
_) <- Id
-> InstBindings (GhcPass 'Renamed)
-> TcM ([Located TcSpecPrag], TcPragEnv)
tcSpecInstPrags Id
dfun_id InstBindings (GhcPass 'Renamed)
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, ([Id]
sc_meth_ids, LHsBinds GhcTcId
sc_meth_binds, Bag Implication
sc_meth_implics))
             <- TcM ([Id], LHsBinds GhcTcId, Bag Implication)
-> TcM (TcLevel, ([Id], LHsBinds GhcTcId, Bag Implication))
forall a. TcM a -> TcM (TcLevel, a)
pushTcLevelM (TcM ([Id], LHsBinds GhcTcId, Bag Implication)
 -> TcM (TcLevel, ([Id], LHsBinds GhcTcId, Bag Implication)))
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
-> TcM (TcLevel, ([Id], LHsBinds GhcTcId, Bag Implication))
forall a b. (a -> b) -> a -> b
$
                do { ([Id]
sc_ids, LHsBinds GhcTcId
sc_binds, Bag Implication
sc_implics)
                        <- Id
-> Class
-> [Id]
-> [Id]
-> [PredType]
-> TcEvBinds
-> [PredType]
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
tcSuperClasses Id
dfun_id Class
clas [Id]
inst_tyvars [Id]
dfun_ev_vars
                                          [PredType]
inst_tys TcEvBinds
dfun_ev_binds
                                          [PredType]
sc_theta'

                      -- Typecheck the methods
                   ; ([Id]
meth_ids, LHsBinds GhcTcId
meth_binds, Bag Implication
meth_implics)
                        <- Id
-> Class
-> [Id]
-> [Id]
-> [PredType]
-> TcEvBinds
-> ([Located TcSpecPrag], TcPragEnv)
-> [ClassOpItem]
-> InstBindings (GhcPass 'Renamed)
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
tcMethods Id
dfun_id Class
clas [Id]
inst_tyvars [Id]
dfun_ev_vars
                                     [PredType]
inst_tys TcEvBinds
dfun_ev_binds ([Located TcSpecPrag], TcPragEnv)
spec_inst_info
                                     [ClassOpItem]
op_items InstBindings (GhcPass 'Renamed)
ibinds

                   ; ([Id], LHsBinds GhcTcId, Bag Implication)
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ( [Id]
sc_ids     [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++          [Id]
meth_ids
                            , LHsBinds GhcTcId
sc_binds   LHsBinds GhcTcId -> LHsBinds GhcTcId -> LHsBinds GhcTcId
forall a. Bag a -> Bag a -> Bag a
`unionBags` LHsBinds GhcTcId
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 :: [Id]
ic_skols  = [Id]
inst_tyvars
             , ic_given :: [Id]
ic_given  = [Id]
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
       ; Id
self_dict <- Class -> [PredType] -> TcM Id
newDict Class
clas [PredType]
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 GhcTcId
dict_bind     = IdP GhcTcId -> LHsExpr GhcTcId -> LHsBind GhcTcId
forall (p :: Pass).
IdP (GhcPass p) -> LHsExpr (GhcPass p) -> LHsBind (GhcPass p)
mkVarBind Id
IdP GhcTcId
self_dict (SrcSpan -> HsExpr GhcTcId -> LHsExpr GhcTcId
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsExpr GhcTcId
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 GhcTcId
con_app_tys  = HsWrapper -> HsExpr GhcTcId -> HsExpr GhcTcId
mkHsWrap ([PredType] -> HsWrapper
mkWpTyApps [PredType]
inst_tys)
                                  (XConLikeOut GhcTcId -> ConLike -> HsExpr GhcTcId
forall p. XConLikeOut p -> ConLike -> HsExpr p
HsConLikeOut XConLikeOut GhcTcId
NoExtField
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 GhcTcId
con_app_args = (HsExpr GhcTcId -> Id -> HsExpr GhcTcId)
-> HsExpr GhcTcId -> [Id] -> HsExpr GhcTcId
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
External instance of the constraint type Foldable []
foldl' HsExpr GhcTcId -> Id -> HsExpr GhcTcId
app_to_meth HsExpr GhcTcId
con_app_tys [Id]
sc_meth_ids

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

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

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

       ; LHsBinds GhcTcId -> TcM (LHsBinds GhcTcId)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (LHsBind GhcTcId -> LHsBinds GhcTcId
forall a. a -> Bag a
unitBag (SrcSpan -> HsBindLR GhcTcId GhcTcId -> LHsBind GhcTcId
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsBindLR GhcTcId GhcTcId
main_bind) LHsBinds GhcTcId -> LHsBinds GhcTcId -> LHsBinds GhcTcId
forall a. Bag a -> Bag a -> Bag a
`unionBags` LHsBinds GhcTcId
sc_meth_binds)
       }
 where
   dfun_id :: Id
dfun_id = ClsInst -> Id
instanceDFunId ClsInst
ispec
   loc :: SrcSpan
loc     = Id -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
External instance of the constraint type NamedThing Id
getSrcSpan Id
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 :: Id -> [Id] -> Id
addDFunPrags Id
dfun_id [Id]
sc_meth_ids
 | Bool
is_newtype
  = Id
dfun_id Id -> Unfolding -> Id
`setIdUnfolding`  ConTag -> CoreExpr -> Unfolding
mkInlineUnfoldingWithArity ConTag
0 CoreExpr
con_app
            Id -> InlinePragma -> Id
`setInlinePragma` InlinePragma
alwaysInlinePragma { inl_sat :: Maybe ConTag
inl_sat = ConTag -> Maybe ConTag
forall a. a -> Maybe a
Just ConTag
0 }
 | Bool
otherwise
 = Id
dfun_id Id -> Unfolding -> Id
`setIdUnfolding`  [Id] -> DataCon -> [CoreExpr] -> Unfolding
mkDFunUnfolding [Id]
dfun_bndrs DataCon
dict_con [CoreExpr]
dict_args
           Id -> InlinePragma -> Id
`setInlinePragma` InlinePragma
dfunInlinePragma
 where
   con_app :: CoreExpr
con_app    = [Id] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
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 (Id -> CoreExpr
forall b. Id -> Expr b
Var (DataCon -> Id
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  = (PredType -> CoreExpr) -> [PredType] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map PredType -> CoreExpr
forall b. PredType -> Expr b
Type [PredType]
inst_tys [CoreExpr] -> [CoreExpr] -> [CoreExpr]
forall a. [a] -> [a] -> [a]
++
                [CoreExpr -> [Id] -> CoreExpr
forall b. Expr b -> [Id] -> Expr b
mkVarApps (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
id) [Id]
dfun_bndrs | Id
id <- [Id]
sc_meth_ids]

   ([Id]
dfun_tvs, [PredType]
dfun_theta, Class
clas, [PredType]
inst_tys) = PredType -> ([Id], [PredType], Class, [PredType])
tcSplitDFunTy (Id -> PredType
idType Id
dfun_id)
   ev_ids :: [Id]
ev_ids      = ConTag -> [PredType] -> [Id]
mkTemplateLocalsNum ConTag
1                    [PredType]
dfun_theta
   dfun_bndrs :: [Id]
dfun_bndrs  = [Id]
dfun_tvs [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id]
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 -> Id -> HsExpr GhcTcId
wrapId HsWrapper
wrapper Id
id = HsWrapper -> HsExpr GhcTcId -> HsExpr GhcTcId
mkHsWrap HsWrapper
wrapper (XVar GhcTcId -> Located (IdP GhcTcId) -> HsExpr GhcTcId
forall p. XVar p -> Located (IdP p) -> HsExpr p
HsVar XVar GhcTcId
NoExtField
noExtField (Id -> Located Id
forall e. e -> Located e
noLoc Id
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 :: Id
-> Class
-> [Id]
-> [Id]
-> [PredType]
-> TcEvBinds
-> [PredType]
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
tcSuperClasses Id
dfun_id Class
cls [Id]
tyvars [Id]
dfun_evs [PredType]
inst_tys TcEvBinds
dfun_ev_binds [PredType]
sc_theta
  = do { ([Id]
ids, [LHsBind GhcTcId]
binds, [Implication]
implics) <- ((PredType, ConTag)
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Implication))
-> [(PredType, ConTag)]
-> IOEnv
     (Env TcGblEnv TcLclEnv) ([Id], [LHsBind GhcTcId], [Implication])
forall (m :: * -> *) a b c d.
Monad m =>
(a -> m (b, c, d)) -> [a] -> m ([b], [c], [d])
External instance of the constraint type forall m. Monad (IOEnv m)
mapAndUnzip3M (PredType, ConTag)
-> IOEnv (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Implication)
tc_super ([PredType] -> [ConTag] -> [(PredType, ConTag)]
forall a b. [a] -> [b] -> [(a, b)]
zip [PredType]
sc_theta [ConTag
fIRST_TAG..])
       ; ([Id], LHsBinds GhcTcId, Bag Implication)
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([Id]
ids, [LHsBind GhcTcId] -> LHsBinds GhcTcId
forall a. [a] -> Bag a
listToBag [LHsBind GhcTcId]
binds, [Implication] -> Bag Implication
forall a. [a] -> Bag a
listToBag [Implication]
implics) }
  where
    loc :: SrcSpan
loc = Id -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
External instance of the constraint type NamedThing Id
getSrcSpan Id
dfun_id
    size :: TypeSize
size = [PredType] -> TypeSize
sizeTypes [PredType]
inst_tys
    tc_super :: (PredType, ConTag)
-> IOEnv (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Implication)
tc_super (PredType
sc_pred, ConTag
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 -> PredType -> TcM EvTerm
emitWanted (TypeSize -> CtOrigin
ScOrigin TypeSize
size) PredType
sc_pred

           ; Name
sc_top_name  <- OccName -> TcM Name
newName (ConTag -> OccName -> OccName
mkSuperDictAuxOcc ConTag
n (Class -> OccName
forall a. NamedThing a => a -> OccName
External instance of the constraint type NamedThing Class
getOccName Class
cls))
           ; Id
sc_ev_id     <- PredType -> TcM Id
forall gbl lcl. PredType -> TcRnIf gbl lcl Id
newEvVar PredType
sc_pred
           ; EvBindsVar -> EvBind -> TcRn ()
addTcEvBind EvBindsVar
ev_binds_var (EvBind -> TcRn ()) -> EvBind -> TcRn ()
forall a b. (a -> b) -> a -> b
$ Id -> EvTerm -> EvBind
mkWantedEvBind Id
sc_ev_id EvTerm
sc_ev_tm
           ; let sc_top_ty :: PredType
sc_top_ty = [Id] -> PredType -> PredType
mkInfForAllTys [Id]
tyvars (PredType -> PredType) -> PredType -> PredType
forall a b. (a -> b) -> a -> b
$
                             [PredType] -> PredType -> PredType
mkPhiTy ((Id -> PredType) -> [Id] -> [PredType]
forall a b. (a -> b) -> [a] -> [b]
map Id -> PredType
idType [Id]
dfun_evs) PredType
sc_pred
                 sc_top_id :: Id
sc_top_id = HasDebugCallStack => Name -> PredType -> Id
Name -> PredType -> Id
External instance of the constraint type HasDebugCallStack
mkLocalId Name
sc_top_name PredType
sc_top_ty
                 export :: ABExport GhcTcId
export = ABE :: forall p.
XABE p -> IdP p -> IdP p -> HsWrapper -> TcSpecPrags -> ABExport p
ABE { abe_ext :: XABE GhcTcId
abe_ext  = XABE GhcTcId
NoExtField
noExtField
                              , abe_wrap :: HsWrapper
abe_wrap = HsWrapper
idHsWrapper
                              , abe_poly :: IdP GhcTcId
abe_poly = Id
IdP GhcTcId
sc_top_id
                              , abe_mono :: IdP GhcTcId
abe_mono = Id
IdP GhcTcId
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 GhcTcId GhcTcId
bind = AbsBinds :: forall idL idR.
XAbsBinds idL idR
-> [Id]
-> [Id]
-> [ABExport idL]
-> [TcEvBinds]
-> LHsBinds idL
-> Bool
-> HsBindLR idL idR
AbsBinds { abs_ext :: XAbsBinds GhcTcId GhcTcId
abs_ext      = XAbsBinds GhcTcId GhcTcId
NoExtField
noExtField
                                 , abs_tvs :: [Id]
abs_tvs      = [Id]
tyvars
                                 , abs_ev_vars :: [Id]
abs_ev_vars  = [Id]
dfun_evs
                                 , abs_exports :: [ABExport GhcTcId]
abs_exports  = [ABExport GhcTcId
export]
                                 , abs_ev_binds :: [TcEvBinds]
abs_ev_binds = [TcEvBinds
dfun_ev_binds, TcEvBinds
local_ev_binds]
                                 , abs_binds :: LHsBinds GhcTcId
abs_binds    = LHsBinds GhcTcId
forall a. Bag a
emptyBag
                                 , abs_sig :: Bool
abs_sig      = Bool
False }
           ; (Id, LHsBind GhcTcId, Implication)
-> IOEnv (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Implication)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (Id
sc_top_id, SrcSpan -> HsBindLR GhcTcId GhcTcId -> LHsBind GhcTcId
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsBindLR GhcTcId GhcTcId
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
External instance of the constraint type forall m. Monad (IOEnv m)
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 :: Id
-> Class
-> [Id]
-> [Id]
-> [PredType]
-> TcEvBinds
-> ([Located TcSpecPrag], TcPragEnv)
-> [ClassOpItem]
-> InstBindings (GhcPass 'Renamed)
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
tcMethods Id
dfun_id Class
clas [Id]
tyvars [Id]
dfun_ev_vars [PredType]
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 (GhcPass 'Renamed)
binds
                                , ib_tyvars :: forall a. InstBindings a -> [Name]
ib_tyvars     = [Name]
lexical_tvs
                                , ib_pragmas :: forall a. InstBindings a -> [LSig a]
ib_pragmas    = [LSig (GhcPass 'Renamed)]
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, Id)]
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
forall r. [(Name, Id)] -> TcM r -> TcM r
tcExtendNameTyVarEnv ([Name]
lexical_tvs [Name] -> [Id] -> [(Name, Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Id]
tyvars) (TcM ([Id], LHsBinds GhcTcId, Bag Implication)
 -> TcM ([Id], LHsBinds GhcTcId, Bag Implication))
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
forall a b. (a -> b) -> a -> b
$
       -- The lexical_tvs scope over the 'where' part
    do { String -> SDoc -> TcRn ()
traceTc String
"tcInstMeth" ([LSig (GhcPass 'Renamed)] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (Sig (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr [LSig (GhcPass 'Renamed)]
sigs SDoc -> SDoc -> SDoc
$$ LHsBinds (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable (Bag a)
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (pl :: Pass) (pr :: Pass).
(OutputableBndrId pl, OutputableBndrId pr) =>
Outputable (HsBindLR (GhcPass pl) (GhcPass pr))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr LHsBinds (GhcPass 'Renamed)
binds)
       ; TcRn ()
checkMinimalDefinition
       ; TcRn ()
checkMethBindMembership
       ; ([Id]
ids, [LHsBind GhcTcId]
binds, [Maybe Implication]
mb_implics) <- [Extension]
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
forall a. [Extension] -> TcM a -> TcM a
set_exts [Extension]
exts (TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
 -> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication]))
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
forall a b. (a -> b) -> a -> b
$
                                     TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
forall a. TcM a -> TcM a
unset_warnings_deriving (TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
 -> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication]))
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
forall a b. (a -> b) -> a -> b
$
                                     (ClassOpItem
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication))
-> [ClassOpItem]
-> TcM ([Id], [LHsBind GhcTcId], [Maybe Implication])
forall (m :: * -> *) a b c d.
Monad m =>
(a -> m (b, c, d)) -> [a] -> m ([b], [c], [d])
External instance of the constraint type forall m. Monad (IOEnv m)
mapAndUnzip3M ClassOpItem
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
tc_item [ClassOpItem]
op_items
       ; ([Id], LHsBinds GhcTcId, Bag Implication)
-> TcM ([Id], LHsBinds GhcTcId, Bag Implication)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([Id]
ids, [LHsBind GhcTcId] -> LHsBinds GhcTcId
forall a. [a] -> Bag a
listToBag [LHsBind GhcTcId]
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
External instance of the constraint type Foldable []
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 (GhcPass 'Renamed)] -> HsSigFun
mkHsSigFun [LSig (GhcPass 'Renamed)]
sigs
    inst_loc :: SrcSpan
inst_loc  = Id -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
External instance of the constraint type NamedThing Id
getSrcSpan Id
dfun_id

    ----------------------
    tc_item :: ClassOpItem -> TcM (Id, LHsBind GhcTc, Maybe Implication)
    tc_item :: ClassOpItem
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
tc_item (Id
sel_id, DefMethInfo
dm_info)
      | Just (GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
user_bind, SrcSpan
bndr_loc, [LSig (GhcPass 'Renamed)]
prags) <- Name
-> LHsBinds (GhcPass 'Renamed)
-> TcPragEnv
-> Maybe
     (GenLocated
        SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)),
      SrcSpan, [LSig (GhcPass 'Renamed)])
findMethodBind (Id -> Name
idName Id
sel_id) LHsBinds (GhcPass 'Renamed)
binds TcPragEnv
prag_fn
      = Class
-> [Id]
-> [Id]
-> [PredType]
-> TcEvBinds
-> Bool
-> HsSigFun
-> [Located TcSpecPrag]
-> [LSig (GhcPass 'Renamed)]
-> Id
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> SrcSpan
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
tcMethodBody Class
clas [Id]
tyvars [Id]
dfun_ev_vars [PredType]
inst_tys
                              TcEvBinds
dfun_ev_binds Bool
is_derived HsSigFun
hs_sig_fn
                              [Located TcSpecPrag]
spec_inst_prags [LSig (GhcPass 'Renamed)]
prags
                              Id
sel_id GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
user_bind SrcSpan
bndr_loc
      | Bool
otherwise
      = do { String -> SDoc -> TcRn ()
traceTc String
"tc_def" (Id -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Id
ppr Id
sel_id)
           ; Id
-> DefMethInfo
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
tc_default Id
sel_id DefMethInfo
dm_info }

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

    tc_default :: Id
-> DefMethInfo
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
tc_default Id
sel_id (Just (Name
dm_name, DefMethSpec PredType
_))
      = do { (GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
meth_bind, [LSig (GhcPass 'Renamed)]
inline_prags) <- Class
-> [PredType]
-> Id
-> Name
-> TcM
     (GenLocated
        SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)),
      [LSig (GhcPass 'Renamed)])
mkDefMethBind Class
clas [PredType]
inst_tys Id
sel_id Name
dm_name
           ; Class
-> [Id]
-> [Id]
-> [PredType]
-> TcEvBinds
-> Bool
-> HsSigFun
-> [Located TcSpecPrag]
-> [LSig (GhcPass 'Renamed)]
-> Id
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> SrcSpan
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
tcMethodBody Class
clas [Id]
tyvars [Id]
dfun_ev_vars [PredType]
inst_tys
                          TcEvBinds
dfun_ev_binds Bool
is_derived HsSigFun
hs_sig_fn
                          [Located TcSpecPrag]
spec_inst_prags [LSig (GhcPass 'Renamed)]
inline_prags
                          Id
sel_id GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
meth_bind SrcSpan
inst_loc }

    tc_default Id
sel_id DefMethInfo
Nothing     -- No default method at all
      = do { String -> SDoc -> TcRn ()
traceTc String
"tc_def: warn" (Id -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Id
ppr Id
sel_id)
           ; (Id
meth_id, Id
_) <- Class -> [Id] -> [Id] -> [PredType] -> Id -> TcM (Id, Id)
mkMethIds Class
clas [Id]
tyvars [Id]
dfun_ev_vars
                                       [PredType]
inst_tys Id
sel_id
           ; DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
External instance of the constraint type forall env. ContainsDynFlags env => HasDynFlags (IOEnv env)
External instance of the constraint type forall gbl lcl. ContainsDynFlags (Env gbl lcl)
getDynFlags
           ; let meth_bind :: LHsBind GhcTcId
meth_bind = IdP GhcTcId -> LHsExpr GhcTcId -> LHsBind GhcTcId
forall (p :: Pass).
IdP (GhcPass p) -> LHsExpr (GhcPass p) -> LHsBind (GhcPass p)
mkVarBind Id
IdP GhcTcId
meth_id (LHsExpr GhcTcId -> LHsBind GhcTcId)
-> LHsExpr GhcTcId -> LHsBind GhcTcId
forall a b. (a -> b) -> a -> b
$
                             HsWrapper -> LHsExpr GhcTcId -> LHsExpr GhcTcId
mkLHsWrap HsWrapper
lam_wrapper (DynFlags -> LHsExpr GhcTcId
error_rhs DynFlags
dflags)
           ; (Id, LHsBind GhcTcId, Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (Id
meth_id, LHsBind GhcTcId
meth_bind, Maybe Implication
forall a. Maybe a
Nothing) }
      where
        error_rhs :: DynFlags -> LHsExpr GhcTcId
error_rhs DynFlags
dflags = SrcSpan -> HsExpr GhcTcId -> LHsExpr GhcTcId
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (HsExpr GhcTcId -> LHsExpr GhcTcId)
-> HsExpr GhcTcId -> LHsExpr GhcTcId
forall a b. (a -> b) -> a -> b
$ XApp GhcTcId
-> LHsExpr GhcTcId -> LHsExpr GhcTcId -> HsExpr GhcTcId
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp XApp GhcTcId
NoExtField
noExtField LHsExpr GhcTcId
error_fun (DynFlags -> LHsExpr GhcTcId
error_msg DynFlags
dflags)
        error_fun :: LHsExpr GhcTcId
error_fun    = SrcSpan -> HsExpr GhcTcId -> LHsExpr GhcTcId
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (HsExpr GhcTcId -> LHsExpr GhcTcId)
-> HsExpr GhcTcId -> LHsExpr GhcTcId
forall a b. (a -> b) -> a -> b
$
                       HsWrapper -> Id -> HsExpr GhcTcId
wrapId ([PredType] -> HsWrapper
mkWpTyApps
                                [ HasDebugCallStack => PredType -> PredType
PredType -> PredType
External instance of the constraint type HasDebugCallStack
getRuntimeRep PredType
meth_tau, PredType
meth_tau])
                              Id
nO_METHOD_BINDING_ERROR_ID
        error_msg :: DynFlags -> LHsExpr GhcTcId
error_msg DynFlags
dflags = SrcSpan -> HsExpr GhcTcId -> LHsExpr GhcTcId
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (XLitE GhcTcId -> HsLit GhcTcId -> HsExpr GhcTcId
forall p. XLitE p -> HsLit p -> HsExpr p
HsLit XLitE GhcTcId
NoExtField
noExtField (XHsStringPrim GhcTcId -> ByteString -> HsLit GhcTcId
forall x. XHsStringPrim x -> ByteString -> HsLit x
HsStringPrim SourceText
XHsStringPrim GhcTcId
NoSourceText
                                              (String -> ByteString
unsafeMkByteString (DynFlags -> String
error_string DynFlags
dflags))))
        meth_tau :: PredType
meth_tau     = PredType -> PredType
funResultTy (HasDebugCallStack => PredType -> [PredType] -> PredType
PredType -> [PredType] -> PredType
External instance of the constraint type HasDebugCallStack
piResultTys (Id -> PredType
idType Id
sel_id) [PredType]
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
External instance of the constraint type Outputable SrcSpan
ppr SrcSpan
inst_loc, SDoc
vbar, Id -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Id
ppr Id
sel_id ])
        lam_wrapper :: HsWrapper
lam_wrapper  = [Id] -> HsWrapper
mkWpTyLams [Id]
tyvars HsWrapper -> HsWrapper -> HsWrapper
<.> [Id] -> HsWrapper
mkWpLams [Id]
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 ()
External instance of the constraint type forall m. Monad (IOEnv m)
whenIsJust ((Name -> Bool)
-> BooleanFormula Name -> Maybe (BooleanFormula Name)
forall a.
Eq a =>
(a -> Bool) -> BooleanFormula a -> Maybe (BooleanFormula a)
External instance of the constraint type Eq Name
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
  (GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)),
   SrcSpan, [LSig (GhcPass 'Renamed)])
-> Bool
forall a. Maybe a -> Bool
isJust (Name
-> LHsBinds (GhcPass 'Renamed)
-> TcPragEnv
-> Maybe
     (GenLocated
        SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)),
      SrcSpan, [LSig (GhcPass 'Renamed)])
findMethodBind Name
meth LHsBinds (GhcPass 'Renamed)
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 ()
External instance of the constraint type forall m. Monad (IOEnv m)
External instance of the constraint type Foldable []
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
External instance of the constraint type Outputable Class
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 (GhcPass 'Renamed) -> [Located (IdP (GhcPass 'Renamed))]
forall idL idR. LHsBindsLR idL idR -> [Located (IdP idL)]
collectMethodBinders LHsBinds (GhcPass 'Renamed)
binds
        cls_meth_nms :: [Name]
cls_meth_nms     = (ClassOpItem -> Name) -> [ClassOpItem] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (Id -> Name
idName (Id -> Name) -> (ClassOpItem -> Id) -> ClassOpItem -> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ClassOpItem -> Id
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]
External instance of the constraint type Ord Name
`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
-> [Id]
-> [Id]
-> [PredType]
-> TcEvBinds
-> Bool
-> HsSigFun
-> [Located TcSpecPrag]
-> [LSig (GhcPass 'Renamed)]
-> Id
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> SrcSpan
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
tcMethodBody Class
clas [Id]
tyvars [Id]
dfun_ev_vars [PredType]
inst_tys
                     TcEvBinds
dfun_ev_binds Bool
is_derived
                     HsSigFun
sig_fn [Located TcSpecPrag]
spec_inst_prags [LSig (GhcPass 'Renamed)]
prags
                     Id
sel_id (L SrcSpan
bind_loc HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
meth_bind) SrcSpan
bndr_loc
  = IOEnv
  (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
add_meth_ctxt (IOEnv
   (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcRn ()
traceTc String
"tcMethodBody" (Id -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Id
ppr Id
sel_id SDoc -> SDoc -> SDoc
<+> PredType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable PredType
ppr (Id -> PredType
idType Id
sel_id) SDoc -> SDoc -> SDoc
$$ SrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable SrcSpan
ppr SrcSpan
bndr_loc)
       ; (Id
global_meth_id, Id
local_meth_id) <- SrcSpan -> TcM (Id, Id) -> TcM (Id, Id)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
bndr_loc (TcM (Id, Id) -> TcM (Id, Id)) -> TcM (Id, Id) -> TcM (Id, Id)
forall a b. (a -> b) -> a -> b
$
                                            Class -> [Id] -> [Id] -> [PredType] -> Id -> TcM (Id, Id)
mkMethIds Class
clas [Id]
tyvars [Id]
dfun_ev_vars
                                                      [PredType]
inst_tys Id
sel_id

       ; let lm_bind :: HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
lm_bind = HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
meth_bind { fun_id :: Located (IdP (GhcPass 'Renamed))
fun_id = SrcSpan -> Name -> GenLocated SrcSpan Name
forall l e. l -> e -> GenLocated l e
L SrcSpan
bndr_loc (Id -> Name
idName Id
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, LHsBinds GhcTcId
tc_bind)
             <- TcM (LHsBinds GhcTcId)
-> TcM (Implication, EvBindsVar, LHsBinds GhcTcId)
forall result. TcM result -> TcM (Implication, EvBindsVar, result)
checkInstConstraints (TcM (LHsBinds GhcTcId)
 -> TcM (Implication, EvBindsVar, LHsBinds GhcTcId))
-> TcM (LHsBinds GhcTcId)
-> TcM (Implication, EvBindsVar, LHsBinds GhcTcId)
forall a b. (a -> b) -> a -> b
$
                HsSigFun
-> Id
-> Id
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> TcM (LHsBinds GhcTcId)
tcMethodBodyHelp HsSigFun
sig_fn Id
sel_id Id
local_meth_id (SrcSpan
-> HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
forall l e. l -> e -> GenLocated l e
L SrcSpan
bind_loc HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
lm_bind)

       ; Id
global_meth_id <- Id -> [LSig (GhcPass 'Renamed)] -> TcM Id
addInlinePrags Id
global_meth_id [LSig (GhcPass 'Renamed)]
prags
       ; [Located TcSpecPrag]
spec_prags     <- Id -> [LSig (GhcPass 'Renamed)] -> TcM [Located TcSpecPrag]
tcSpecPrags Id
global_meth_id [LSig (GhcPass 'Renamed)]
prags

        ; let specs :: TcSpecPrags
specs  = Id -> [Located TcSpecPrag] -> [Located TcSpecPrag] -> TcSpecPrags
mk_meth_spec_prags Id
global_meth_id [Located TcSpecPrag]
spec_inst_prags [Located TcSpecPrag]
spec_prags
              export :: ABExport GhcTcId
export = ABE :: forall p.
XABE p -> IdP p -> IdP p -> HsWrapper -> TcSpecPrags -> ABExport p
ABE { abe_ext :: XABE GhcTcId
abe_ext   = XABE GhcTcId
NoExtField
noExtField
                           , abe_poly :: IdP GhcTcId
abe_poly  = Id
IdP GhcTcId
global_meth_id
                           , abe_mono :: IdP GhcTcId
abe_mono  = Id
IdP GhcTcId
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 GhcTcId GhcTcId
full_bind = AbsBinds :: forall idL idR.
XAbsBinds idL idR
-> [Id]
-> [Id]
-> [ABExport idL]
-> [TcEvBinds]
-> LHsBinds idL
-> Bool
-> HsBindLR idL idR
AbsBinds { abs_ext :: XAbsBinds GhcTcId GhcTcId
abs_ext      = XAbsBinds GhcTcId GhcTcId
NoExtField
noExtField
                                   , abs_tvs :: [Id]
abs_tvs      = [Id]
tyvars
                                   , abs_ev_vars :: [Id]
abs_ev_vars  = [Id]
dfun_ev_vars
                                   , abs_exports :: [ABExport GhcTcId]
abs_exports  = [ABExport GhcTcId
export]
                                   , abs_ev_binds :: [TcEvBinds]
abs_ev_binds = [TcEvBinds
dfun_ev_binds, TcEvBinds
local_ev_binds]
                                   , abs_binds :: LHsBinds GhcTcId
abs_binds    = LHsBinds GhcTcId
tc_bind
                                   , abs_sig :: Bool
abs_sig      = Bool
True }

        ; (Id, LHsBind GhcTcId, Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (Id
global_meth_id, SrcSpan -> HsBindLR GhcTcId GhcTcId -> LHsBind GhcTcId
forall l e. l -> e -> GenLocated l e
L SrcSpan
bind_loc HsBindLR GhcTcId GhcTcId
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) (Id, LHsBind GhcTcId, Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
add_meth_ctxt IOEnv
  (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
thing
      | Bool
is_derived = SDoc
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
forall a. SDoc -> TcM a -> TcM a
addLandmarkErrCtxt (Id -> Class -> [PredType] -> SDoc
derivBindCtxt Id
sel_id Class
clas [PredType]
inst_tys) IOEnv
  (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
thing
      | Bool
otherwise  = IOEnv
  (Env TcGblEnv TcLclEnv) (Id, LHsBind GhcTcId, Maybe Implication)
thing

tcMethodBodyHelp :: HsSigFun -> Id -> TcId
                 -> LHsBind GhcRn -> TcM (LHsBinds GhcTcId)
tcMethodBodyHelp :: HsSigFun
-> Id
-> Id
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> TcM (LHsBinds GhcTcId)
tcMethodBodyHelp HsSigFun
hs_sig_fn Id
sel_id Id
local_meth_id GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
meth_bind
  | Just LHsSigType (GhcPass 'Renamed)
hs_sig_ty <- HsSigFun
hs_sig_fn Name
sel_name
              -- There is a signature in the instance
              -- See Note [Instance method signatures]
  = do { (PredType
sig_ty, HsWrapper
hs_wrap)
             <- SrcSpan -> TcRn (PredType, HsWrapper) -> TcRn (PredType, HsWrapper)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (LHsType (GhcPass 'Renamed) -> SrcSpan
forall l e. GenLocated l e -> l
getLoc (LHsSigType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed)
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
hsSigType LHsSigType (GhcPass 'Renamed)
hs_sig_ty)) (TcRn (PredType, HsWrapper) -> TcRn (PredType, HsWrapper))
-> TcRn (PredType, HsWrapper) -> TcRn (PredType, 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 (GhcPass 'Renamed) -> SDoc
misplacedInstSig Name
sel_name LHsSigType (GhcPass 'Renamed)
hs_sig_ty)
                   ; PredType
sig_ty  <- UserTypeCtxt -> LHsSigType (GhcPass 'Renamed) -> TcM PredType
tcHsSigType (Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
sel_name Bool
False) LHsSigType (GhcPass 'Renamed)
hs_sig_ty
                   ; let local_meth_ty :: PredType
local_meth_ty = Id -> PredType
idType Id
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 -> PredType -> PredType -> TidyEnv -> TcM (TidyEnv, SDoc)
methSigCtxt Name
sel_name PredType
sig_ty PredType
local_meth_ty) (TcM HsWrapper -> TcM HsWrapper) -> TcM HsWrapper -> TcM HsWrapper
forall a b. (a -> b) -> a -> b
$
                                UserTypeCtxt -> PredType -> PredType -> TcM HsWrapper
tcSubType_NC UserTypeCtxt
ctxt PredType
sig_ty PredType
local_meth_ty
                   ; (PredType, HsWrapper) -> TcRn (PredType, HsWrapper)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (PredType
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 :: Id
inner_meth_id  = HasDebugCallStack => Name -> PredType -> Id
Name -> PredType -> Id
External instance of the constraint type HasDebugCallStack
mkLocalId Name
inner_meth_name PredType
sig_ty
             inner_meth_sig :: TcIdSigInfo
inner_meth_sig = CompleteSig :: Id -> UserTypeCtxt -> SrcSpan -> TcIdSigInfo
CompleteSig { sig_bndr :: Id
sig_bndr = Id
inner_meth_id
                                          , sig_ctxt :: UserTypeCtxt
sig_ctxt = UserTypeCtxt
ctxt
                                          , sig_loc :: SrcSpan
sig_loc  = LHsType (GhcPass 'Renamed) -> SrcSpan
forall l e. GenLocated l e -> l
getLoc (LHsSigType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed)
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
hsSigType LHsSigType (GhcPass 'Renamed)
hs_sig_ty) }


       ; (LHsBinds GhcTcId
tc_bind, [Id
inner_id]) <- TcPragEnv
-> TcIdSigInfo
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> TcM (LHsBinds GhcTcId, [Id])
tcPolyCheck TcPragEnv
no_prag_fn TcIdSigInfo
inner_meth_sig GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
meth_bind

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

       ; LHsBinds GhcTcId -> TcM (LHsBinds GhcTcId)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (LHsBind GhcTcId -> LHsBinds GhcTcId
forall a. a -> Bag a
unitBag (LHsBind GhcTcId -> LHsBinds GhcTcId)
-> LHsBind GhcTcId -> LHsBinds GhcTcId
forall a b. (a -> b) -> a -> b
$ SrcSpan -> HsBindLR GhcTcId GhcTcId -> LHsBind GhcTcId
forall l e. l -> e -> GenLocated l e
L (GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> SrcSpan
forall l e. GenLocated l e -> l
getLoc GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
meth_bind) (HsBindLR GhcTcId GhcTcId -> LHsBind GhcTcId)
-> HsBindLR GhcTcId GhcTcId -> LHsBind GhcTcId
forall a b. (a -> b) -> a -> b
$
                 AbsBinds :: forall idL idR.
XAbsBinds idL idR
-> [Id]
-> [Id]
-> [ABExport idL]
-> [TcEvBinds]
-> LHsBinds idL
-> Bool
-> HsBindLR idL idR
AbsBinds { abs_ext :: XAbsBinds GhcTcId GhcTcId
abs_ext = XAbsBinds GhcTcId GhcTcId
NoExtField
noExtField, abs_tvs :: [Id]
abs_tvs = [], abs_ev_vars :: [Id]
abs_ev_vars = []
                          , abs_exports :: [ABExport GhcTcId]
abs_exports = [ABExport GhcTcId
export]
                          , abs_binds :: LHsBinds GhcTcId
abs_binds = LHsBinds GhcTcId
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 -> Id -> TcIdSigInfo
completeSigFromId UserTypeCtxt
ctxt Id
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!

       ; (LHsBinds GhcTcId
tc_bind, [Id]
_) <- TcPragEnv
-> TcIdSigInfo
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> TcM (LHsBinds GhcTcId, [Id])
tcPolyCheck TcPragEnv
no_prag_fn TcIdSigInfo
tc_sig GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
meth_bind
       ; LHsBinds GhcTcId -> TcM (LHsBinds GhcTcId)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return LHsBinds GhcTcId
tc_bind }

  where
    sel_name :: Name
sel_name   = Id -> Name
idName Id
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 -> [Id] -> [Id] -> [PredType] -> Id -> TcM (Id, Id)
mkMethIds Class
clas [Id]
tyvars [Id]
dfun_ev_vars [PredType]
inst_tys Id
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 :: Id
poly_meth_id  = HasDebugCallStack => Name -> PredType -> Id
Name -> PredType -> Id
External instance of the constraint type HasDebugCallStack
mkLocalId Name
poly_meth_name  PredType
poly_meth_ty
              local_meth_id :: Id
local_meth_id = HasDebugCallStack => Name -> PredType -> Id
Name -> PredType -> Id
External instance of the constraint type HasDebugCallStack
mkLocalId Name
local_meth_name PredType
local_meth_ty

        ; (Id, Id) -> TcM (Id, Id)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (Id
poly_meth_id, Id
local_meth_id) }
  where
    sel_name :: Name
sel_name      = Id -> Name
idName Id
sel_id
    sel_occ :: OccName
sel_occ       = Name -> OccName
nameOccName Name
sel_name
    local_meth_ty :: PredType
local_meth_ty = Class -> Id -> [PredType] -> PredType
instantiateMethod Class
clas Id
sel_id [PredType]
inst_tys
    poly_meth_ty :: PredType
poly_meth_ty  = [Id] -> [PredType] -> PredType -> PredType
mkSpecSigmaTy [Id]
tyvars [PredType]
theta PredType
local_meth_ty
    theta :: [PredType]
theta         = (Id -> PredType) -> [Id] -> [PredType]
forall a b. (a -> b) -> [a] -> [b]
map Id -> PredType
idType [Id]
dfun_ev_vars

methSigCtxt :: Name -> TcType -> TcType -> TidyEnv -> TcM (TidyEnv, MsgDoc)
methSigCtxt :: Name -> PredType -> PredType -> TidyEnv -> TcM (TidyEnv, SDoc)
methSigCtxt Name
sel_name PredType
sig_ty PredType
meth_ty TidyEnv
env0
  = do { (TidyEnv
env1, PredType
sig_ty)  <- TidyEnv -> PredType -> TcM (TidyEnv, PredType)
zonkTidyTcType TidyEnv
env0 PredType
sig_ty
       ; (TidyEnv
env2, PredType
meth_ty) <- TidyEnv -> PredType -> TcM (TidyEnv, PredType)
zonkTidyTcType TidyEnv
env1 PredType
meth_ty
       ; let msg :: SDoc
msg = SDoc -> ConTag -> 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
External instance of the constraint type Outputable Name
ppr Name
sel_name))
                      ConTag
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
<+> PredType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable PredType
ppr PredType
sig_ty
                              , String -> SDoc
text String
"   Class sig:" SDoc -> SDoc -> SDoc
<+> PredType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable PredType
ppr PredType
meth_ty ])
       ; (TidyEnv, SDoc) -> TcM (TidyEnv, SDoc)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (TidyEnv
env2, SDoc
msg) }

misplacedInstSig :: Name -> LHsSigType GhcRn -> SDoc
misplacedInstSig :: Name -> LHsSigType (GhcPass 'Renamed) -> SDoc
misplacedInstSig Name
name LHsSigType (GhcPass 'Renamed)
hs_ty
  = [SDoc] -> SDoc
vcat [ SDoc -> ConTag -> SDoc -> SDoc
hang (String -> SDoc
text String
"Illegal type signature in instance declaration:")
              ConTag
2 (SDoc -> ConTag -> SDoc -> SDoc
hang (Name -> SDoc
forall a. NamedThing a => a -> SDoc
External instance of the constraint type NamedThing Name
pprPrefixName Name
name)
                    ConTag
2 (SDoc
dcolon SDoc -> SDoc -> SDoc
<+> LHsSigType (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall thing (p :: Pass).
Outputable thing =>
Outputable (HsImplicitBndrs (GhcPass p) thing)
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (HsType (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr LHsSigType (GhcPass 'Renamed)
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 :: Id -> [Located TcSpecPrag] -> [Located TcSpecPrag] -> TcSpecPrags
mk_meth_spec_prags Id
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 (Id -> InlinePragma
idInlinePragma Id
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 (Id -> HsWrapper -> InlinePragma -> TcSpecPrag
SpecPrag Id
meth_id HsWrapper
wrap InlinePragma
inl)
         | L SrcSpan
inst_loc (SpecPrag Id
_       HsWrapper
wrap InlinePragma
inl) <- [Located TcSpecPrag]
spec_inst_prags]


mkDefMethBind :: Class -> [Type] -> 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 :: Class
-> [PredType]
-> Id
-> Name
-> TcM
     (GenLocated
        SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)),
      [LSig (GhcPass 'Renamed)])
mkDefMethBind Class
clas [PredType]
inst_tys Id
sel_id Name
dm_name
  = do  { DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
External instance of the constraint type forall env. ContainsDynFlags env => HasDynFlags (IOEnv env)
External instance of the constraint type forall gbl lcl. ContainsDynFlags (Env gbl lcl)
getDynFlags
        ; Id
dm_id <- Name -> TcM Id
tcLookupId Name
dm_name
        ; let inline_prag :: InlinePragma
inline_prag = Id -> InlinePragma
idInlinePragma Id
dm_id
              inline_prags :: [LSig (GhcPass 'Renamed)]
inline_prags | InlinePragma -> Bool
isAnyInlinePragma InlinePragma
inline_prag
                           = [Sig (GhcPass 'Renamed) -> LSig (GhcPass 'Renamed)
forall e. e -> Located e
noLoc (XInlineSig (GhcPass 'Renamed)
-> Located (IdP (GhcPass 'Renamed))
-> InlinePragma
-> Sig (GhcPass 'Renamed)
forall pass.
XInlineSig pass -> Located (IdP pass) -> InlinePragma -> Sig pass
InlineSig XInlineSig (GhcPass 'Renamed)
NoExtField
noExtField GenLocated SrcSpan Name
Located (IdP (GhcPass 'Renamed))
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 (Id -> Name
idName Id
sel_id)
              visible_inst_tys :: [PredType]
visible_inst_tys = [ PredType
ty | (TyConBinder
tcb, PredType
ty) <- TyCon -> [TyConBinder]
tyConBinders (Class -> TyCon
classTyCon Class
clas) [TyConBinder] -> [PredType] -> [(TyConBinder, PredType)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [PredType]
inst_tys
                                      , TyConBinder -> ArgFlag
tyConBinderArgFlag TyConBinder
tcb ArgFlag -> ArgFlag -> Bool
forall a. Eq a => a -> a -> Bool
External instance of the constraint type Eq ArgFlag
/= ArgFlag
Inferred ]
              rhs :: LHsExpr (GhcPass 'Renamed)
rhs  = (LHsExpr (GhcPass 'Renamed)
 -> PredType -> LHsExpr (GhcPass 'Renamed))
-> LHsExpr (GhcPass 'Renamed)
-> [PredType]
-> LHsExpr (GhcPass 'Renamed)
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
External instance of the constraint type Foldable []
foldl' LHsExpr (GhcPass 'Renamed)
-> PredType -> LHsExpr (GhcPass 'Renamed)
mk_vta (IdP (GhcPass 'Renamed) -> LHsExpr (GhcPass 'Renamed)
forall (id :: Pass). IdP (GhcPass id) -> LHsExpr (GhcPass id)
nlHsVar Name
IdP (GhcPass 'Renamed)
dm_name) [PredType]
visible_inst_tys
              bind :: GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
bind = HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
forall e. e -> Located e
noLoc (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
 -> GenLocated
      SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)))
-> HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
-> GenLocated
     SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
forall a b. (a -> b) -> a -> b
$ Origin
-> GenLocated SrcSpan Name
-> [LMatch (GhcPass 'Renamed) (LHsExpr (GhcPass 'Renamed))]
-> HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
mkTopFunBind Origin
Generated GenLocated SrcSpan Name
fn ([LMatch (GhcPass 'Renamed) (LHsExpr (GhcPass 'Renamed))]
 -> HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
-> [LMatch (GhcPass 'Renamed) (LHsExpr (GhcPass 'Renamed))]
-> HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)
forall a b. (a -> b) -> a -> b
$
                             [HsMatchContext (NoGhcTc (GhcPass 'Renamed))
-> [LPat (GhcPass 'Renamed)]
-> LHsExpr (GhcPass 'Renamed)
-> LMatch (GhcPass 'Renamed) (LHsExpr (GhcPass 'Renamed))
forall (p :: Pass) (body :: * -> *).
HsMatchContext (NoGhcTc (GhcPass p))
-> [LPat (GhcPass p)]
-> Located (body (GhcPass p))
-> LMatch (GhcPass p) (Located (body (GhcPass p)))
mkSimpleMatch (Located (IdP (GhcPass 'Renamed))
-> HsMatchContext (GhcPass 'Renamed)
forall p. LIdP p -> HsMatchContext p
mkPrefixFunRhs GenLocated SrcSpan Name
Located (IdP (GhcPass 'Renamed))
fn) [] LHsExpr (GhcPass 'Renamed)
rhs]

        ; IO () -> TcRn ()
forall (m :: * -> *) a. MonadIO m => IO a -> m a
External instance of the constraint type forall env. MonadIO (IOEnv env)
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
External instance of the constraint type Outputable Class
ppr Class
clas SDoc -> SDoc -> SDoc
<+> [PredType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable PredType
ppr [PredType]
inst_tys,
                          ConTag -> SDoc -> SDoc
nest ConTag
2 (Id -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Id
ppr Id
sel_id SDoc -> SDoc -> SDoc
<+> SDoc
equals SDoc -> SDoc -> SDoc
<+> LHsExpr (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (HsExpr (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr LHsExpr (GhcPass 'Renamed)
rhs)]))

       ; (GenLocated
   SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)),
 [LSig (GhcPass 'Renamed)])
-> TcM
     (GenLocated
        SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed)),
      [LSig (GhcPass 'Renamed)])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (GenLocated SrcSpan (HsBindLR (GhcPass 'Renamed) (GhcPass 'Renamed))
bind, [LSig (GhcPass 'Renamed)]
inline_prags) }
  where
    mk_vta :: LHsExpr GhcRn -> Type -> LHsExpr GhcRn
    mk_vta :: LHsExpr (GhcPass 'Renamed)
-> PredType -> LHsExpr (GhcPass 'Renamed)
mk_vta LHsExpr (GhcPass 'Renamed)
fun PredType
ty = HsExpr (GhcPass 'Renamed) -> LHsExpr (GhcPass 'Renamed)
forall e. e -> Located e
noLoc (XAppTypeE (GhcPass 'Renamed)
-> LHsExpr (GhcPass 'Renamed)
-> LHsWcType (NoGhcTc (GhcPass 'Renamed))
-> HsExpr (GhcPass 'Renamed)
forall p.
XAppTypeE p -> LHsExpr p -> LHsWcType (NoGhcTc p) -> HsExpr p
HsAppType XAppTypeE (GhcPass 'Renamed)
NoExtField
noExtField LHsExpr (GhcPass 'Renamed)
fun (LHsType (GhcPass 'Renamed)
-> HsWildCardBndrs (GhcPass 'Renamed) (LHsType (GhcPass 'Renamed))
forall thing. thing -> HsWildCardBndrs (GhcPass 'Renamed) thing
mkEmptyWildCardBndrs (LHsType (GhcPass 'Renamed)
 -> HsWildCardBndrs (GhcPass 'Renamed) (LHsType (GhcPass 'Renamed)))
-> LHsType (GhcPass 'Renamed)
-> HsWildCardBndrs (GhcPass 'Renamed) (LHsType (GhcPass 'Renamed))
forall a b. (a -> b) -> a -> b
$ LHsType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed)
forall (p :: Pass). LHsType (GhcPass p) -> LHsType (GhcPass p)
nlHsParTy
                                                (LHsType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed))
-> LHsType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed)
forall a b. (a -> b) -> a -> b
$ HsType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed)
forall e. e -> Located e
noLoc (HsType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed))
-> HsType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed)
forall a b. (a -> b) -> a -> b
$ XXType (GhcPass 'Renamed) -> HsType (GhcPass 'Renamed)
forall pass. XXType pass -> HsType pass
XHsType (XXType (GhcPass 'Renamed) -> HsType (GhcPass 'Renamed))
-> XXType (GhcPass 'Renamed) -> HsType (GhcPass 'Renamed)
forall a b. (a -> b) -> a -> b
$ PredType -> NewHsTypeX
NHsCoreTy PredType
ty))
       -- NB: use visible type application
       -- See Note [Default methods in instances]

----------------------
derivBindCtxt :: Id -> Class -> [Type ] -> SDoc
derivBindCtxt :: Id -> Class -> [PredType] -> SDoc
derivBindCtxt Id
sel_id Class
clas [PredType]
tys
   = [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"When typechecking the code for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Id -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Id
ppr Id
sel_id)
          , ConTag -> SDoc -> SDoc
nest ConTag
2 (String -> SDoc
text String
"in a derived instance for"
                    SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Class -> [PredType] -> SDoc
pprClassPred Class
clas [PredType]
tys) SDoc -> SDoc -> SDoc
<> SDoc
colon)
          , ConTag -> SDoc -> SDoc
nest ConTag
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"
                   ,ConTag -> SDoc -> SDoc
nest ConTag
2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ BooleanFormula Name -> SDoc
forall a. Outputable a => BooleanFormula a -> SDoc
External instance of the constraint type Outputable Name
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 :: Id
-> InstBindings (GhcPass 'Renamed)
-> TcM ([Located TcSpecPrag], TcPragEnv)
tcSpecInstPrags Id
dfun_id (InstBindings { ib_binds :: forall a. InstBindings a -> LHsBinds a
ib_binds = LHsBinds (GhcPass 'Renamed)
binds, ib_pragmas :: forall a. InstBindings a -> [LSig a]
ib_pragmas = [LSig (GhcPass 'Renamed)]
uprags })
  = do { [Located TcSpecPrag]
spec_inst_prags <- (LSig (GhcPass 'Renamed)
 -> IOEnv (Env TcGblEnv TcLclEnv) (Located TcSpecPrag))
-> [LSig (GhcPass 'Renamed)] -> TcM [Located TcSpecPrag]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
External instance of the constraint type forall m. Monad (IOEnv m)
External instance of the constraint type Traversable []
mapM ((Sig (GhcPass 'Renamed) -> TcM TcSpecPrag)
-> LSig (GhcPass 'Renamed)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located TcSpecPrag)
forall a b. (a -> TcM b) -> Located a -> TcM (Located b)
wrapLocM (Id -> Sig (GhcPass 'Renamed) -> TcM TcSpecPrag
tcSpecInst Id
dfun_id)) ([LSig (GhcPass 'Renamed)] -> TcM [Located TcSpecPrag])
-> [LSig (GhcPass 'Renamed)] -> TcM [Located TcSpecPrag]
forall a b. (a -> b) -> a -> b
$
                            (LSig (GhcPass 'Renamed) -> Bool)
-> [LSig (GhcPass 'Renamed)] -> [LSig (GhcPass 'Renamed)]
forall a. (a -> Bool) -> [a] -> [a]
filter LSig (GhcPass 'Renamed) -> Bool
forall name. LSig name -> Bool
isSpecInstLSig [LSig (GhcPass 'Renamed)]
uprags
             -- The filter removes the pragmas for methods
       ; ([Located TcSpecPrag], TcPragEnv)
-> TcM ([Located TcSpecPrag], TcPragEnv)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([Located TcSpecPrag]
spec_inst_prags, [LSig (GhcPass 'Renamed)]
-> LHsBinds (GhcPass 'Renamed) -> TcPragEnv
mkPragEnv [LSig (GhcPass 'Renamed)]
uprags LHsBinds (GhcPass 'Renamed)
binds) }

------------------------------
tcSpecInst :: Id -> Sig GhcRn -> TcM TcSpecPrag
tcSpecInst :: Id -> Sig (GhcPass 'Renamed) -> TcM TcSpecPrag
tcSpecInst Id
dfun_id prag :: Sig (GhcPass 'Renamed)
prag@(SpecInstSig XSpecInstSig (GhcPass 'Renamed)
_ SourceText
_ LHsSigType (GhcPass 'Renamed)
hs_ty)
  = SDoc -> TcM TcSpecPrag -> TcM TcSpecPrag
forall a. SDoc -> TcM a -> TcM a
addErrCtxt (Sig (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (Sig (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
spec_ctxt Sig (GhcPass 'Renamed)
prag) (TcM TcSpecPrag -> TcM TcSpecPrag)
-> TcM TcSpecPrag -> TcM TcSpecPrag
forall a b. (a -> b) -> a -> b
$
    do  { PredType
spec_dfun_ty <- UserTypeCtxt -> LHsSigType (GhcPass 'Renamed) -> TcM PredType
tcHsClsInstType UserTypeCtxt
SpecInstCtxt LHsSigType (GhcPass 'Renamed)
hs_ty
        ; HsWrapper
co_fn <- UserTypeCtxt -> PredType -> PredType -> TcM HsWrapper
tcSpecWrapper UserTypeCtxt
SpecInstCtxt (Id -> PredType
idType Id
dfun_id) PredType
spec_dfun_ty
        ; TcSpecPrag -> TcM TcSpecPrag
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (Id -> HsWrapper -> InlinePragma -> TcSpecPrag
SpecPrag Id
dfun_id HsWrapper
co_fn InlinePragma
defaultInlinePragma) }
  where
    spec_ctxt :: a -> SDoc
spec_ctxt a
prag = SDoc -> ConTag -> SDoc -> SDoc
hang (String -> SDoc
text String
"In the pragma:") ConTag
2 (a -> SDoc
forall a. Outputable a => a -> SDoc
Evidence bound by a type signature of the constraint type Outputable a
ppr a
prag)

tcSpecInst Id
_  Sig (GhcPass 'Renamed)
_ = String -> TcM TcSpecPrag
forall a. String -> a
panic String
"tcSpecInst"

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

instDeclCtxt1 :: LHsSigType GhcRn -> SDoc
instDeclCtxt1 :: LHsSigType (GhcPass 'Renamed) -> SDoc
instDeclCtxt1 LHsSigType (GhcPass 'Renamed)
hs_inst_ty
  = SDoc -> SDoc
inst_decl_ctxt (LHsType (GhcPass 'Renamed) -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (HsType (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr (LHsSigType (GhcPass 'Renamed) -> LHsType (GhcPass 'Renamed)
forall (p :: Pass). LHsSigType (GhcPass p) -> LHsType (GhcPass p)
getLHsInstDeclHead LHsSigType (GhcPass 'Renamed)
hs_inst_ty))

instDeclCtxt2 :: Type -> SDoc
instDeclCtxt2 :: PredType -> SDoc
instDeclCtxt2 PredType
dfun_ty
  = SDoc -> SDoc
inst_decl_ctxt (PredType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable PredType
ppr (Class -> [PredType] -> PredType
mkClassPred Class
cls [PredType]
tys))
  where
    ([Id]
_,[PredType]
_,Class
cls,[PredType]
tys) = PredType -> ([Id], [PredType], Class, [PredType])
tcSplitDFunTy PredType
dfun_ty

inst_decl_ctxt :: SDoc -> SDoc
inst_decl_ctxt :: SDoc -> SDoc
inst_decl_ctxt SDoc
doc = SDoc -> ConTag -> SDoc -> SDoc
hang (String -> SDoc
text String
"In the instance declaration for")
                        ConTag
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
External instance of the constraint type Outputable TyCon
ppr TyCon
tycon)
         , ConTag -> SDoc -> SDoc
nest ConTag
2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ SDoc -> SDoc
parens (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TyCon
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
External instance of the constraint type Outputable TyCon
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
External instance of the constraint type Outputable TyCon
ppr TyCon
tc_name)
         , ConTag -> SDoc -> SDoc
nest ConTag
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
External instance of the constraint type Outputable TyCon
ppr TyCon
tc)