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


TcInstDecls: Typechecking instance declarations
-}

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

module TcInstDcls ( tcInstDecls1, tcInstDeclsDeriv, tcInstDecls2 ) where

#include "HsVersions.h"

import GhcPrelude

import HsSyn
import TcBinds
import TcTyClsDecls
import TcTyDecls ( addTyConsToGblEnv )
import TcClassDcl( tcClassDecl2, tcATDefault,
                   HsSigFun, mkHsSigFun, badMethodErr,
                   findMethodBind, instantiateMethod )
import TcSigs
import TcRnMonad
import TcValidity
import TcHsSyn
import TcMType
import TcType
import BuildTyCl
import Inst
import ClsInst( AssocInstInfo(..), isNotAssociated )
import InstEnv
import FamInst
import FamInstEnv
import TcDeriv
import TcEnv
import TcHsType
import TcUnify
import CoreSyn    ( Expr(..), mkApps, mkVarApps, mkLams )
import MkCore     ( nO_METHOD_BINDING_ERROR_ID )
import CoreUnfold ( mkInlineUnfoldingWithArity, mkDFunUnfolding )
import Type
import TcEvidence
import TyCon
import CoAxiom
import DataCon
import ConLike
import Class
import Var
import VarEnv
import VarSet
import Bag
import BasicTypes
import DynFlags
import ErrUtils
import FastString
import Id
import ListSetOps
import Name
import NameSet
import Outputable
import SrcLoc
import Util
import BooleanFormula ( isUnsatisfied, pprBooleanFormulaNice )
import qualified GHC.LanguageExtensions as LangExt

import Control.Monad
import Maybes
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 SimplGently] in SimplUtils

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 CoreUnfold.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 MkId 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
Trac #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 (Trac #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 InstEnv).  But in *this* case it's wrong to
complain, because we just want to delegate to the op2 of this same
instance.

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

It might even be a bit disguised:

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

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

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

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


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

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

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



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

Gather up the instance declarations from their various sources
-}

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

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

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

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

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

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

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

addFamInsts :: [FamInst] -> TcM a -> TcM a
-- Extend (a) the family instance envt
--        (b) the type envt with stuff from data type decls
addFamInsts :: [FamInst] -> TcM a -> TcM a
addFamInsts fam_insts :: [FamInst]
fam_insts thing_inside :: 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 "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 (Trac #6005)
the scoping of the generated code inside the bracket does not seem to
work out.

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

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

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

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

tcLocalInstDecl (L _ (XInstDecl _)) = String -> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall a. String -> a
panic "tcLocalInstDecl"

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

        ; (subst :: TCvSubst
subst, skol_tvs :: [TyVar]
skol_tvs) <- [TyVar] -> TcM (TCvSubst, [TyVar])
tcInstSkolTyVars [TyVar]
tyvars
        ; let tv_skol_prs :: [(Name, TyVar)]
tv_skol_prs = [ (TyVar -> Name
tyVarName TyVar
tv, TyVar
skol_tv)
                            | (tv :: TyVar
tv, skol_tv :: TyVar
skol_tv) <- [TyVar]
tyvars [TyVar] -> [TyVar] -> [(TyVar, TyVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TyVar]
skol_tvs ]
              n_inferred :: Int
n_inferred = (VarBndr TyVar ArgFlag -> Bool) -> [VarBndr TyVar ArgFlag] -> Int
forall a. (a -> Bool) -> [a] -> Int
countWhile ((ArgFlag -> ArgFlag -> Bool
forall a. Eq a => a -> a -> Bool
== ArgFlag
Inferred) (ArgFlag -> Bool)
-> (VarBndr TyVar ArgFlag -> ArgFlag)
-> VarBndr TyVar ArgFlag
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. VarBndr TyVar ArgFlag -> ArgFlag
forall tv argf. VarBndr tv argf -> argf
binderArgFlag) ([VarBndr TyVar ArgFlag] -> Int) -> [VarBndr TyVar ArgFlag] -> Int
forall a b. (a -> b) -> a -> b
$
                           ([VarBndr TyVar ArgFlag], Type) -> [VarBndr TyVar ArgFlag]
forall a b. (a, b) -> a
fst (([VarBndr TyVar ArgFlag], Type) -> [VarBndr TyVar ArgFlag])
-> ([VarBndr TyVar ArgFlag], Type) -> [VarBndr TyVar ArgFlag]
forall a b. (a -> b) -> a -> b
$ Type -> ([VarBndr TyVar ArgFlag], Type)
splitForAllVarBndrs Type
dfun_ty
              visible_skol_tvs :: [TyVar]
visible_skol_tvs = Int -> [TyVar] -> [TyVar]
forall a. Int -> [a] -> [a]
drop Int
n_inferred [TyVar]
skol_tvs

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

        -- Next, process any associated types.
        ; (datafam_stuff :: [(FamInst, Maybe DerivInfo)]
datafam_stuff, tyfam_insts :: [FamInst]
tyfam_insts)
             <- [(Name, TyVar)]
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
tv_skol_prs (TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
 -> TcM ([(FamInst, Maybe DerivInfo)], [FamInst]))
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
-> TcM ([(FamInst, Maybe DerivInfo)], [FamInst])
forall a b. (a -> b) -> a -> b
$
                do  { let mini_env :: VarEnv Type
mini_env   = [(TyVar, Type)] -> VarEnv Type
forall a. [(TyVar, a)] -> VarEnv a
mkVarEnv (Class -> [TyVar]
classTyVars Class
clas [TyVar] -> [Type] -> [(TyVar, Type)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` HasCallStack => TCvSubst -> [Type] -> [Type]
TCvSubst -> [Type] -> [Type]
substTys TCvSubst
subst [Type]
inst_tys)
                          mini_subst :: TCvSubst
mini_subst = InScopeSet -> VarEnv Type -> TCvSubst
mkTvSubst (VarSet -> InScopeSet
mkInScopeSet ([TyVar] -> VarSet
mkVarSet [TyVar]
skol_tvs)) VarEnv Type
mini_env
                          mb_info :: AssocInstInfo
mb_info    = InClsInst :: Class -> [TyVar] -> VarEnv Type -> AssocInstInfo
InClsInst { ai_class :: Class
ai_class = Class
clas
                                                 , ai_tyvars :: [TyVar]
ai_tyvars = [TyVar]
visible_skol_tvs
                                                 , ai_inst_env :: VarEnv Type
ai_inst_env = VarEnv Type
mini_env }
                    ; [(FamInst, Maybe DerivInfo)]
df_stuff  <- (LDataFamInstDecl GhcRn -> TcM (FamInst, Maybe DerivInfo))
-> [LDataFamInstDecl GhcRn] -> TcRn [(FamInst, Maybe DerivInfo)]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndRecoverM (AssocInstInfo
-> LDataFamInstDecl GhcRn -> TcM (FamInst, Maybe DerivInfo)
tcDataFamInstDecl AssocInstInfo
mb_info) [LDataFamInstDecl GhcRn]
adts
                    ; [FamInst]
tf_insts1 <- (LTyFamInstDecl GhcRn -> TcM FamInst)
-> [LTyFamInstDecl GhcRn] -> TcRn [FamInst]
forall a b. (a -> TcRn b) -> [a] -> TcRn [b]
mapAndRecoverM (AssocInstInfo -> LTyFamInstDecl GhcRn -> TcM FamInst
tcTyFamInstDecl AssocInstInfo
mb_info)   [LTyFamInstDecl GhcRn]
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)
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
return ([(FamInst, Maybe DerivInfo)]
df_stuff, [FamInst]
tf_insts1 [FamInst] -> [FamInst] -> [FamInst]
forall a. [a] -> [a] -> [a]
++ [[FamInst]] -> [FamInst]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[FamInst]]
tf_insts2) }


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

        ; ClsInst
ispec <- Maybe OverlapMode
-> Name -> [TyVar] -> [Type] -> Class -> [Type] -> TcM ClsInst
newClsInst ((Located OverlapMode -> OverlapMode)
-> Maybe (Located OverlapMode) -> Maybe OverlapMode
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap Located OverlapMode -> OverlapMode
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc Maybe (Located OverlapMode)
overlap_mode) Name
dfun_name
                              [TyVar]
tyvars [Type]
theta Class
clas [Type]
inst_tys

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

              (datafam_insts :: [FamInst]
datafam_insts, m_deriv_infos :: [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 GhcRn -> Bool
forall idL idR. LHsBindsLR idL idR -> Bool
isEmptyLHsBinds LHsBinds GhcRn
binds Bool -> Bool -> Bool
&& [LSig GhcRn] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LSig GhcRn]
uprags
        ; Bool -> SDoc -> TcRn ()
failIfTc (Bool
is_boot Bool -> Bool -> Bool
&& Bool -> Bool
not Bool
no_binds) SDoc
badBootDeclErr

        ; ([InstInfo GhcRn], [FamInst], [DerivInfo])
-> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall (m :: * -> *) a. Monad m => a -> m a
return ( [InstInfo GhcRn
inst_info], [FamInst]
all_insts, [DerivInfo]
deriv_infos ) }
  where
    defined_ats :: NameSet
defined_ats = [Name] -> NameSet
mkNameSet ((LTyFamInstDecl GhcRn -> Name) -> [LTyFamInstDecl GhcRn] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (TyFamInstDecl GhcRn -> Name
forall pass. TyFamInstDecl pass -> IdP pass
tyFamInstDeclName (TyFamInstDecl GhcRn -> Name)
-> (LTyFamInstDecl GhcRn -> TyFamInstDecl GhcRn)
-> LTyFamInstDecl GhcRn
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LTyFamInstDecl GhcRn -> TyFamInstDecl GhcRn
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc) [LTyFamInstDecl GhcRn]
ats)
                  NameSet -> NameSet -> NameSet
`unionNameSet`
                  [Name] -> NameSet
mkNameSet ((LDataFamInstDecl GhcRn -> Name)
-> [LDataFamInstDecl GhcRn] -> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (Located Name -> Name
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc (Located Name -> Name)
-> (LDataFamInstDecl GhcRn -> Located Name)
-> LDataFamInstDecl GhcRn
-> Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn) -> Located Name
forall pass pats rhs. FamEqn pass pats rhs -> Located (IdP pass)
feqn_tycon
                                        (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn) -> Located Name)
-> (LDataFamInstDecl GhcRn
    -> FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
-> LDataFamInstDecl GhcRn
-> Located Name
forall b c a. (b -> c) -> (a -> b) -> a -> c
. HsImplicitBndrs
  GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
-> FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn)
forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body
                                        (HsImplicitBndrs
   GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
 -> FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
-> (LDataFamInstDecl GhcRn
    -> HsImplicitBndrs
         GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn)))
-> LDataFamInstDecl GhcRn
-> FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. DataFamInstDecl GhcRn
-> HsImplicitBndrs
     GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
forall pass.
DataFamInstDecl pass -> FamInstEqn pass (HsDataDefn pass)
dfid_eqn
                                        (DataFamInstDecl GhcRn
 -> HsImplicitBndrs
      GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn)))
-> (LDataFamInstDecl GhcRn -> DataFamInstDecl GhcRn)
-> LDataFamInstDecl GhcRn
-> HsImplicitBndrs
     GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LDataFamInstDecl GhcRn -> DataFamInstDecl GhcRn
forall a. HasSrcSpan a => a -> SrcSpanLess a
unLoc) [LDataFamInstDecl GhcRn]
adts)

tcClsInstDecl (L _ (XClsInstDecl _)) = String -> TcRn ([InstInfo GhcRn], [FamInst], [DerivInfo])
forall a. String -> a
panic "tcClsInstDecl"

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

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

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

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

         -- (1) do the work of verifying the synonym group
       ; KnotTied CoAxBranch
co_ax_branch <- TyCon
-> AssocInstInfo
-> LTyFamInstEqn GhcRn
-> TcM (KnotTied CoAxBranch)
tcTyFamInstEqn TyCon
fam_tc AssocInstInfo
mb_clsinfo
                                        (SrcSpan -> TyFamInstEqn GhcRn -> LTyFamInstEqn GhcRn
forall l e. l -> e -> GenLocated l e
L (Located Name -> SrcSpan
forall a. HasSrcSpan a => a -> SrcSpan
getLoc Located Name
Located (IdP GhcRn)
fam_lname) TyFamInstEqn GhcRn
eqn)


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

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


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

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

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

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

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

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


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

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

tcDataFamInstDecl :: AssocInstInfo
                  -> LDataFamInstDecl GhcRn -> TcM (FamInst, Maybe DerivInfo)
  -- "newtype instance" and "data instance"
tcDataFamInstDecl :: AssocInstInfo
-> LDataFamInstDecl GhcRn -> TcM (FamInst, Maybe DerivInfo)
tcDataFamInstDecl mb_clsinfo :: AssocInstInfo
mb_clsinfo
    (L loc :: SrcSpan
loc decl :: DataFamInstDecl GhcRn
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 GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
imp_vars
                                                   , hsib_body :: forall pass thing. HsImplicitBndrs pass thing -> thing
hsib_body =
      FamEqn { feqn_bndrs :: forall pass pats rhs.
FamEqn pass pats rhs -> Maybe [LHsTyVarBndr pass]
feqn_bndrs  = Maybe [LHsTyVarBndr GhcRn]
mb_bndrs
             , feqn_pats :: forall pass pats rhs. FamEqn pass pats rhs -> pats
feqn_pats   = HsTyPats GhcRn
hs_pats
             , feqn_tycon :: forall pass pats rhs. FamEqn pass pats rhs -> Located (IdP pass)
feqn_tycon  = lfam_name :: Located (IdP GhcRn)
lfam_name@(L _ fam_name :: IdP GhcRn
fam_name)
             , feqn_fixity :: forall pass pats rhs. FamEqn pass pats rhs -> LexicalFixity
feqn_fixity = LexicalFixity
fixity
             , feqn_rhs :: forall pass pats rhs. FamEqn pass pats 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 GhcRn
hs_ctxt
                                        , dd_cons :: forall pass. HsDataDefn pass -> [LConDecl pass]
dd_cons    = [LConDecl GhcRn]
hs_cons
                                        , dd_kindSig :: forall pass. HsDataDefn pass -> Maybe (LHsKind pass)
dd_kindSig = Maybe (LHsType GhcRn)
m_ksig
                                        , dd_derivs :: forall pass. HsDataDefn pass -> HsDeriving pass
dd_derivs  = HsDeriving GhcRn
derivs } }}}))
  = SrcSpan
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc             (TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo))
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a b. (a -> b) -> a -> b
$
    DataFamInstDecl GhcRn
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a. DataFamInstDecl GhcRn -> TcM a -> TcM a
tcAddDataFamInstCtxt DataFamInstDecl GhcRn
decl  (TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo))
-> TcM (FamInst, Maybe DerivInfo) -> TcM (FamInst, Maybe DerivInfo)
forall a b. (a -> b) -> a -> b
$
    do { TyCon
fam_tc <- Located Name -> TcM TyCon
tcLookupLocatedTyCon Located Name
Located (IdP GhcRn)
lfam_name

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

       -- Check that the family declaration is for the right kind
       ; Bool -> SDoc -> TcRn ()
checkTc (TyCon -> Bool
isDataFamilyTyCon TyCon
fam_tc) (TyCon -> SDoc
wrongKindOfFamily TyCon
fam_tc)
       ; Bool
gadt_syntax <- Name
-> NewOrData -> LHsContext GhcRn -> [LConDecl GhcRn] -> TcRn Bool
dataDeclChecks Name
IdP GhcRn
fam_name NewOrData
new_or_data LHsContext GhcRn
hs_ctxt [LConDecl GhcRn]
hs_cons
          -- Do /not/ check that the number of patterns = tyConArity fam_tc
          -- See [Arity of data families] in FamInstEnv

       ; (qtvs :: [TyVar]
qtvs, pats :: [Type]
pats, res_kind :: Type
res_kind, stupid_theta :: [Type]
stupid_theta)
             <- AssocInstInfo
-> TyCon
-> [Name]
-> Maybe [LHsTyVarBndr GhcRn]
-> LexicalFixity
-> LHsContext GhcRn
-> HsTyPats GhcRn
-> Maybe (LHsType GhcRn)
-> [LConDecl GhcRn]
-> TcM ([TyVar], [Type], Type, [Type])
tcDataFamHeader AssocInstInfo
mb_clsinfo TyCon
fam_tc [Name]
XHsIB GhcRn (FamEqn GhcRn (HsTyPats GhcRn) (HsDataDefn GhcRn))
imp_vars Maybe [LHsTyVarBndr GhcRn]
mb_bndrs
                                LexicalFixity
fixity LHsContext GhcRn
hs_ctxt HsTyPats GhcRn
hs_pats Maybe (LHsType GhcRn)
m_ksig [LConDecl GhcRn]
hs_cons

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

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

       -- Eta-expand the representation tycon until it has reult kind *
       -- See also Note [Arity of data families] in 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
       ; (extra_tcbs :: [TyConBinder]
extra_tcbs, final_res_kind :: Type
final_res_kind) <- [TyConBinder] -> Type -> TcM ([TyConBinder], Type)
etaExpandAlgTyCon [TyConBinder]
full_tcbs Type
res_kind
       ; Bool -> SDoc -> TcRn ()
checkTc (Type -> Bool
tcIsLiftedTypeKind Type
final_res_kind) (Bool -> Type -> SDoc
badKindSig Bool
True Type
res_kind)
       ; let extra_pats :: [Type]
extra_pats  = (TyConBinder -> Type) -> [TyConBinder] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map (TyVar -> Type
mkTyVarTy (TyVar -> Type) -> (TyConBinder -> TyVar) -> TyConBinder -> Type
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TyConBinder -> TyVar
forall tv argf. VarBndr tv argf -> tv
binderVar) [TyConBinder]
extra_tcbs
             all_pats :: [Type]
all_pats    = [Type]
pats [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
`chkAppend` [Type]
extra_pats
             orig_res_ty :: Type
orig_res_ty = TyCon -> [Type] -> Type
mkTyConApp TyCon
fam_tc [Type]
all_pats
             ty_binders :: [TyConBinder]
ty_binders  = [TyConBinder]
full_tcbs [TyConBinder] -> [TyConBinder] -> [TyConBinder]
forall a. [a] -> [a] -> [a]
`chkAppend` [TyConBinder]
extra_tcbs

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

       ; (rep_tc :: TyCon
rep_tc, axiom :: 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
$ \ ~(rec_rep_tc :: TyCon
rec_rep_tc, _) ->
           do { [DataCon]
data_cons <- [TyVar] -> TcM [DataCon] -> TcM [DataCon]
forall r. [TyVar] -> TcM r -> TcM r
tcExtendTyVarEnv [TyVar]
qtvs (TcM [DataCon] -> TcM [DataCon]) -> TcM [DataCon] -> TcM [DataCon]
forall a b. (a -> b) -> a -> b
$
                             -- For H98 decls, the tyvars scope
                             -- over the data constructors
                             TyCon -> [TyConBinder] -> Type -> [LConDecl GhcRn] -> TcM [DataCon]
tcConDecls TyCon
rec_rep_tc [TyConBinder]
ty_binders Type
orig_res_ty [LConDecl GhcRn]
hs_cons

              ; Name
rep_tc_name <- Located Name -> [Type] -> TcM Name
newFamInstTyConName Located Name
Located (IdP GhcRn)
lfam_name [Type]
pats
              ; Name
axiom_name  <- Located Name -> [[Type]] -> TcM Name
newFamInstAxiomName Located Name
Located (IdP GhcRn)
lfam_name [[Type]
pats]
              ; AlgTyConRhs
tc_rhs <- case NewOrData
new_or_data of
                     DataType -> AlgTyConRhs -> IOEnv (Env TcGblEnv TcLclEnv) AlgTyConRhs
forall (m :: * -> *) a. Monad m => a -> m a
return ([DataCon] -> AlgTyConRhs
mkDataTyConRhs [DataCon]
data_cons)
                     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
-> [TyVar]
-> [TyVar]
-> [TyVar]
-> TyCon
-> [Type]
-> Type
-> CoAxiom Unbranched
mkSingleCoAxiom Role
Representational Name
axiom_name
                                 [TyVar]
post_eta_qtvs [TyVar]
eta_tvs [] TyCon
fam_tc [Type]
eta_pats
                                 (TyCon -> [Type] -> Type
mkTyConApp TyCon
rep_tc ([TyVar] -> [Type]
mkTyVarTys [TyVar]
post_eta_qtvs))
                    parent :: AlgTyConFlav
parent = CoAxiom Unbranched -> TyCon -> [Type] -> AlgTyConFlav
DataFamInstTyCon CoAxiom Unbranched
axiom TyCon
fam_tc [Type]
all_pats

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

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

       ; let m_deriv_info :: Maybe DerivInfo
m_deriv_info = case HsDeriving GhcRn
derivs of
               L _ []    -> Maybe DerivInfo
forall a. Maybe a
Nothing
               L _ preds :: [LHsDerivingClause GhcRn]
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 -> [LHsDerivingClause GhcRn] -> SDoc -> DerivInfo
DerivInfo { di_rep_tc :: TyCon
di_rep_tc  = TyCon
rep_tc
                                  , di_clauses :: [LHsDerivingClause GhcRn]
di_clauses = [LHsDerivingClause GhcRn]
preds
                                  , di_ctxt :: SDoc
di_ctxt    = DataFamInstDecl GhcRn -> SDoc
tcMkDataFamInstCtxt DataFamInstDecl GhcRn
decl }

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

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

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

tcDataFamInstDecl _ _ = String -> TcM (FamInst, Maybe DerivInfo)
forall a. String -> a
panic "tcDataFamInstDecl"

-----------------------
tcDataFamHeader :: AssocInstInfo -> TyCon -> [Name] -> Maybe [LHsTyVarBndr GhcRn]
                -> LexicalFixity -> LHsContext GhcRn
                -> HsTyPats GhcRn -> Maybe (LHsKind GhcRn) -> [LConDecl GhcRn]
                -> TcM ([TyVar], [Type], Kind, ThetaType)
-- The "header" 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"
tcDataFamHeader :: AssocInstInfo
-> TyCon
-> [Name]
-> Maybe [LHsTyVarBndr GhcRn]
-> LexicalFixity
-> LHsContext GhcRn
-> HsTyPats GhcRn
-> Maybe (LHsType GhcRn)
-> [LConDecl GhcRn]
-> TcM ([TyVar], [Type], Type, [Type])
tcDataFamHeader mb_clsinfo :: AssocInstInfo
mb_clsinfo fam_tc :: TyCon
fam_tc imp_vars :: [Name]
imp_vars mb_bndrs :: Maybe [LHsTyVarBndr GhcRn]
mb_bndrs fixity :: LexicalFixity
fixity hs_ctxt :: LHsContext GhcRn
hs_ctxt hs_pats :: HsTyPats GhcRn
hs_pats m_ksig :: Maybe (LHsType GhcRn)
m_ksig hs_cons :: [LConDecl GhcRn]
hs_cons
  = do { (imp_tvs :: [TyVar]
imp_tvs, (exp_tvs :: [TyVar]
exp_tvs, (stupid_theta :: [Type]
stupid_theta, lhs_ty :: Type
lhs_ty, res_kind :: Type
res_kind)))
            <- TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
forall a. TcM a -> TcM a
pushTcLevelM_                                (TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
 -> TcM ([TyVar], ([TyVar], ([Type], Type, Type))))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
forall a b. (a -> b) -> a -> b
$
               TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
forall a. TcM a -> TcM a
solveEqualities                              (TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
 -> TcM ([TyVar], ([TyVar], ([Type], Type, Type))))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
forall a b. (a -> b) -> a -> b
$
               [Name]
-> TcM ([TyVar], ([Type], Type, Type))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
forall a. [Name] -> TcM a -> TcM ([TyVar], a)
bindImplicitTKBndrs_Q_Skol [Name]
imp_vars          (TcM ([TyVar], ([Type], Type, Type))
 -> TcM ([TyVar], ([TyVar], ([Type], Type, Type))))
-> TcM ([TyVar], ([Type], Type, Type))
-> TcM ([TyVar], ([TyVar], ([Type], Type, Type)))
forall a b. (a -> b) -> a -> b
$
               ContextKind
-> [LHsTyVarBndr GhcRn]
-> TcM ([Type], Type, Type)
-> TcM ([TyVar], ([Type], Type, Type))
forall a.
ContextKind -> [LHsTyVarBndr GhcRn] -> TcM a -> TcM ([TyVar], a)
bindExplicitTKBndrs_Q_Skol ContextKind
AnyKind [LHsTyVarBndr GhcRn]
exp_bndrs (TcM ([Type], Type, Type) -> TcM ([TyVar], ([Type], Type, Type)))
-> TcM ([Type], Type, Type) -> TcM ([TyVar], ([Type], Type, Type))
forall a b. (a -> b) -> a -> b
$
               do { [Type]
stupid_theta <- LHsContext GhcRn -> TcM [Type]
tcHsContext LHsContext GhcRn
hs_ctxt
                  ; (lhs_ty :: Type
lhs_ty, lhs_kind :: Type
lhs_kind) <- TyCon -> HsTyPats GhcRn -> TcM (Type, Type)
tcFamTyPats TyCon
fam_tc HsTyPats GhcRn
hs_pats
                    -- Ensure that the instance is consistent with its
                    -- parent class
                  ; AssocInstInfo -> Type -> TcRn ()
addConsistencyConstraints AssocInstInfo
mb_clsinfo Type
lhs_ty
                  ; (LConDecl GhcRn -> TcRn ()) -> [LConDecl GhcRn] -> TcRn ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ ((SrcSpanLess (LConDecl GhcRn) -> TcRn ())
-> LConDecl GhcRn -> TcRn ()
forall a.
HasSrcSpan a =>
(SrcSpanLess a -> TcRn ()) -> a -> TcRn ()
wrapLocM_ SrcSpanLess (LConDecl GhcRn) -> TcRn ()
ConDecl GhcRn -> TcRn ()
kcConDecl) [LConDecl GhcRn]
hs_cons
                  ; Type
res_kind <- Maybe (LHsType GhcRn) -> TcM Type
tc_kind_sig Maybe (LHsType GhcRn)
m_ksig
                  ; Type
lhs_ty <- HasDebugCallStack =>
RequireSaturation -> SDoc -> Type -> Type -> Type -> TcM Type
RequireSaturation -> SDoc -> Type -> Type -> Type -> TcM Type
checkExpectedKind RequireSaturation
YesSaturation SDoc
pp_lhs Type
lhs_ty Type
lhs_kind Type
res_kind
                  ; ([Type], Type, Type) -> TcM ([Type], Type, Type)
forall (m :: * -> *) a. Monad m => a -> m a
return ([Type]
stupid_theta, Type
lhs_ty, Type
res_kind) }

       -- See TcTyClsDecls Note [Generalising in tcFamTyPatsGuts]
       -- This code (and the stuff immediately above) is very similar
       -- to that in tcFamTyInstEqnGuts.  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 :: [TyVar]
scoped_tvs = [TyVar]
imp_tvs [TyVar] -> [TyVar] -> [TyVar]
forall a. [a] -> [a] -> [a]
++ [TyVar]
exp_tvs
       ; CandidatesQTvs
dvs  <- [Type] -> TcM CandidatesQTvs
candidateQTyVarsOfTypes (Type
lhs_ty Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: [TyVar] -> [Type]
mkTyVarTys [TyVar]
scoped_tvs)
       ; [TyVar]
qtvs <- VarSet -> CandidatesQTvs -> TcM [TyVar]
quantifyTyVars VarSet
emptyVarSet CandidatesQTvs
dvs

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

       -- Check that type patterns match the class instance head
       ; let pats :: [Type]
pats = Type -> [Type]
unravelFamInstPats Type
lhs_ty
       ; ([TyVar], [Type], Type, [Type])
-> TcM ([TyVar], [Type], Type, [Type])
forall (m :: * -> *) a. Monad m => a -> m a
return ([TyVar]
qtvs, [Type]
pats, Type
res_kind, [Type]
stupid_theta) }
  where
    fam_name :: Name
fam_name  = TyCon -> Name
tyConName TyCon
fam_tc
    data_ctxt :: UserTypeCtxt
data_ctxt = Name -> UserTypeCtxt
DataKindCtxt Name
fam_name
    pp_lhs :: SDoc
pp_lhs    = IdP GhcRn
-> Maybe [LHsTyVarBndr GhcRn]
-> HsTyPats GhcRn
-> LexicalFixity
-> LHsContext GhcRn
-> SDoc
forall (p :: Pass).
OutputableBndrId (GhcPass p) =>
IdP (GhcPass p)
-> Maybe [LHsTyVarBndr (GhcPass p)]
-> HsTyPats (GhcPass p)
-> LexicalFixity
-> LHsContext (GhcPass p)
-> SDoc
pprHsFamInstLHS Name
IdP GhcRn
fam_name Maybe [LHsTyVarBndr GhcRn]
mb_bndrs HsTyPats GhcRn
hs_pats LexicalFixity
fixity LHsContext GhcRn
hs_ctxt
    exp_bndrs :: [LHsTyVarBndr GhcRn]
exp_bndrs = Maybe [LHsTyVarBndr GhcRn]
mb_bndrs Maybe [LHsTyVarBndr GhcRn]
-> [LHsTyVarBndr GhcRn] -> [LHsTyVarBndr GhcRn]
forall a. Maybe a -> a -> a
`orElse` []

    -- See Note [Result kind signature for a data family instance]
    tc_kind_sig :: Maybe (LHsType GhcRn) -> TcM Type
tc_kind_sig Nothing
      = Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return Type
liftedTypeKind
    tc_kind_sig (Just hs_kind :: LHsType GhcRn
hs_kind)
      = do { Type
sig_kind <- UserTypeCtxt -> LHsType GhcRn -> TcM Type
tcLHsKindSig UserTypeCtxt
data_ctxt LHsType GhcRn
hs_kind
           ; let (tvs :: [TyVar]
tvs, inner_kind :: Type
inner_kind) = Type -> ([TyVar], Type)
tcSplitForAllTys Type
sig_kind
           ; TcLevel
lvl <- TcM TcLevel
getTcLevel
           ; (subst :: TCvSubst
subst, _tvs' :: [TyVar]
_tvs') <- TcLevel -> Bool -> TCvSubst -> [TyVar] -> TcM (TCvSubst, [TyVar])
tcInstSkolTyVarsAt TcLevel
lvl Bool
False TCvSubst
emptyTCvSubst [TyVar]
tvs
             -- Perhaps surprisingly, we don't need the skolemised tvs themselves
           ; Type -> TcM Type
forall (m :: * -> *) a. Monad m => a -> m a
return (HasCallStack => TCvSubst -> Type -> Type
TCvSubst -> Type -> Type
substTy TCvSubst
subst Type
inner_kind) }

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

Note [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
There are several fiddly subtleties lurking here

* The representation tycon Drep is parameerised 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-redcible, 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 takses 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

* 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 siganture and istantiate 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 the checkExpectedKind that immediately follows.

* 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 Trac #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 visibilty flags on an application of D may affected by the arguments
  themselves.  Heavy sigh.  But not truly hard; that's what tcbVisibilities
  does.

-}


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

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

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

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

          -- Done
        ; LHsBinds GhcTc -> TcM (LHsBinds GhcTc)
forall (m :: * -> *) a. Monad m => a -> m a
return (LHsBinds GhcTc
dm_binds LHsBinds GhcTc -> LHsBinds GhcTc -> LHsBinds GhcTc
forall a. Bag a -> Bag a -> Bag a
`unionBags` [LHsBinds GhcTc] -> LHsBinds GhcTc
forall a. [Bag a] -> Bag a
unionManyBags [LHsBinds GhcTc]
inst_binds_s) }

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

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

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

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

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

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

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

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

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

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

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

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

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

             app_to_meth :: HsExpr GhcTc -> Id -> HsExpr GhcTc
             app_to_meth :: HsExpr GhcTc -> TyVar -> HsExpr GhcTc
app_to_meth fun :: HsExpr GhcTc
fun meth_id :: TyVar
meth_id = XApp GhcTc -> LHsExpr GhcTc -> LHsExpr GhcTc -> HsExpr GhcTc
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp XApp GhcTc
NoExt
noExt (SrcSpan -> HsExpr GhcTc -> LHsExpr GhcTc
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsExpr GhcTc
fun)
                                            (SrcSpan -> HsExpr GhcTc -> LHsExpr GhcTc
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc (HsWrapper -> IdP GhcTc -> HsExpr GhcTc
forall (id :: Pass).
HsWrapper -> IdP (GhcPass id) -> HsExpr (GhcPass id)
wrapId HsWrapper
arg_wrapper TyVar
IdP GhcTc
meth_id))

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

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

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

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

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

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

wrapId :: HsWrapper -> IdP (GhcPass id) -> HsExpr (GhcPass id)
wrapId :: HsWrapper -> IdP (GhcPass id) -> HsExpr (GhcPass id)
wrapId wrapper :: HsWrapper
wrapper id :: IdP (GhcPass id)
id = HsWrapper -> HsExpr (GhcPass id) -> HsExpr (GhcPass id)
forall (id :: Pass).
HsWrapper -> HsExpr (GhcPass id) -> HsExpr (GhcPass id)
mkHsWrap HsWrapper
wrapper (XVar (GhcPass id)
-> Located (IdP (GhcPass id)) -> HsExpr (GhcPass id)
forall p. XVar p -> Located (IdP p) -> HsExpr p
HsVar XVar (GhcPass id)
NoExt
noExt (SrcSpanLess (Located (IdP (GhcPass id)))
-> Located (IdP (GhcPass id))
forall a. HasSrcSpan a => SrcSpanLess a -> a
noLoc SrcSpanLess (Located (IdP (GhcPass id)))
IdP (GhcPass 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 TcSimplify Note [Tracking redundant
   constraints]

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

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

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

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


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

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

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

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

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

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

{-
Note [Recursive superclasses]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See Trac #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 Trac #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 TcValidity.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 Trac #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 TcInteract.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 TcCanonical.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 neede
     a Functor dictionary. Yet these extra dictionaries were
     often never used.  Test T3064 compiled *far* faster after
     silent superclasses were eliminated.

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

This gives us:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

tcMethodBodyHelp :: HsSigFun -> Id -> TcId
                 -> LHsBind GhcRn -> TcM (LHsBinds GhcTcId)
tcMethodBodyHelp :: HsSigFun -> TyVar -> TyVar -> LHsBind GhcRn -> TcM (LHsBinds GhcTc)
tcMethodBodyHelp hs_sig_fn :: HsSigFun
hs_sig_fn sel_id :: TyVar
sel_id local_meth_id :: TyVar
local_meth_id meth_bind :: LHsBind GhcRn
meth_bind
  | Just hs_sig_ty :: LHsSigType GhcRn
hs_sig_ty <- HsSigFun
hs_sig_fn Name
sel_name
              -- There is a signature in the instance
              -- See Note [Instance method signatures]
  = do { let ctxt :: UserTypeCtxt
ctxt = Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
sel_name Bool
True
       ; (sig_ty :: Type
sig_ty, hs_wrap :: HsWrapper
hs_wrap)
             <- SrcSpan -> TcRn (Type, HsWrapper) -> TcRn (Type, HsWrapper)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan (LHsType GhcRn -> SrcSpan
forall a. HasSrcSpan a => a -> SrcSpan
getLoc (LHsSigType GhcRn -> LHsType GhcRn
forall pass. LHsSigType pass -> LHsType pass
hsSigType LHsSigType GhcRn
hs_sig_ty)) (TcRn (Type, HsWrapper) -> TcRn (Type, HsWrapper))
-> TcRn (Type, HsWrapper) -> TcRn (Type, HsWrapper)
forall a b. (a -> b) -> a -> b
$
                do { Bool
inst_sigs <- Extension -> TcRn Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.InstanceSigs
                   ; Bool -> SDoc -> TcRn ()
checkTc Bool
inst_sigs (Name -> LHsSigType GhcRn -> SDoc
misplacedInstSig Name
sel_name LHsSigType GhcRn
hs_sig_ty)
                   ; Type
sig_ty  <- UserTypeCtxt -> LHsSigType GhcRn -> TcM Type
tcHsSigType (Name -> Bool -> UserTypeCtxt
FunSigCtxt Name
sel_name Bool
False) LHsSigType GhcRn
hs_sig_ty
                   ; let local_meth_ty :: Type
local_meth_ty = TyVar -> Type
idType TyVar
local_meth_id
                   ; HsWrapper
hs_wrap <- (TidyEnv -> TcM (TidyEnv, SDoc)) -> TcM HsWrapper -> TcM HsWrapper
forall a. (TidyEnv -> TcM (TidyEnv, SDoc)) -> TcM a -> TcM a
addErrCtxtM (Name -> Type -> Type -> TidyEnv -> TcM (TidyEnv, SDoc)
methSigCtxt Name
sel_name Type
sig_ty Type
local_meth_ty) (TcM HsWrapper -> TcM HsWrapper) -> TcM HsWrapper -> TcM HsWrapper
forall a b. (a -> b) -> a -> b
$
                                UserTypeCtxt -> Type -> Type -> TcM HsWrapper
tcSubType_NC UserTypeCtxt
ctxt Type
sig_ty Type
local_meth_ty
                   ; (Type, HsWrapper) -> TcRn (Type, HsWrapper)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type
sig_ty, HsWrapper
hs_wrap) }

       ; Name
inner_meth_name <- OccName -> TcM Name
newName (Name -> OccName
nameOccName Name
sel_name)
       ; let inner_meth_id :: TyVar
inner_meth_id  = Name -> Type -> TyVar
mkLocalId Name
inner_meth_name Type
sig_ty
             inner_meth_sig :: TcIdSigInfo
inner_meth_sig = CompleteSig :: TyVar -> UserTypeCtxt -> SrcSpan -> TcIdSigInfo
CompleteSig { sig_bndr :: TyVar
sig_bndr = TyVar
inner_meth_id
                                          , sig_ctxt :: UserTypeCtxt
sig_ctxt = UserTypeCtxt
ctxt
                                          , sig_loc :: SrcSpan
sig_loc  = LHsType GhcRn -> SrcSpan
forall a. HasSrcSpan a => a -> SrcSpan
getLoc (LHsSigType GhcRn -> LHsType GhcRn
forall pass. LHsSigType pass -> LHsType pass
hsSigType LHsSigType GhcRn
hs_sig_ty) }


       ; (tc_bind :: LHsBinds GhcTc
tc_bind, [inner_id :: TyVar
inner_id]) <- TcPragEnv
-> TcIdSigInfo -> LHsBind GhcRn -> TcM (LHsBinds GhcTc, [TyVar])
tcPolyCheck TcPragEnv
no_prag_fn TcIdSigInfo
inner_meth_sig LHsBind GhcRn
meth_bind

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

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

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

       ; (tc_bind :: LHsBinds GhcTc
tc_bind, _) <- TcPragEnv
-> TcIdSigInfo -> LHsBind GhcRn -> TcM (LHsBinds GhcTc, [TyVar])
tcPolyCheck TcPragEnv
no_prag_fn TcIdSigInfo
tc_sig LHsBind GhcRn
meth_bind
       ; LHsBinds GhcTc -> TcM (LHsBinds GhcTc)
forall (m :: * -> *) a. Monad m => a -> m a
return LHsBinds GhcTc
tc_bind }

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


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

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

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

misplacedInstSig :: Name -> LHsSigType GhcRn -> SDoc
misplacedInstSig :: Name -> LHsSigType GhcRn -> SDoc
misplacedInstSig name :: Name
name hs_ty :: LHsSigType GhcRn
hs_ty
  = [SDoc] -> SDoc
vcat [ SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text "Illegal type signature in instance declaration:")
              2 (SDoc -> Int -> SDoc -> SDoc
hang (Name -> SDoc
forall a. NamedThing a => a -> SDoc
pprPrefixName Name
name)
                    2 (SDoc
dcolon SDoc -> SDoc -> SDoc
<+> LHsSigType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr LHsSigType GhcRn
hs_ty))
         , String -> SDoc
text "(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 TcBinds
mk_meth_spec_prags :: TyVar
-> [Located TcSpecPrag] -> [Located TcSpecPrag] -> TcSpecPrags
mk_meth_spec_prags meth_id :: TyVar
meth_id spec_inst_prags :: [Located TcSpecPrag]
spec_inst_prags spec_prags_for_me :: [Located TcSpecPrag]
spec_prags_for_me
  = [Located TcSpecPrag] -> TcSpecPrags
SpecPrags ([Located TcSpecPrag]
spec_prags_for_me [Located TcSpecPrag]
-> [Located TcSpecPrag] -> [Located TcSpecPrag]
forall a. [a] -> [a] -> [a]
++ [Located TcSpecPrag]
spec_prags_from_inst)
  where
    spec_prags_from_inst :: [Located TcSpecPrag]
spec_prags_from_inst
       | InlinePragma -> Bool
isInlinePragma (TyVar -> InlinePragma
idInlinePragma TyVar
meth_id)
       = []  -- Do not inherit SPECIALISE from the instance if the
             -- method is marked INLINE, because then it'll be inlined
             -- and the specialisation would do nothing. (Indeed it'll provoke
             -- a warning from the desugarer
       | Bool
otherwise
       = [ SrcSpan -> TcSpecPrag -> Located TcSpecPrag
forall l e. l -> e -> GenLocated l e
L SrcSpan
inst_loc (TyVar -> HsWrapper -> InlinePragma -> TcSpecPrag
SpecPrag TyVar
meth_id HsWrapper
wrap InlinePragma
inl)
         | L inst_loc :: SrcSpan
inst_loc (SpecPrag _       wrap :: HsWrapper
wrap inl :: 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
-> [Type] -> TyVar -> Name -> TcM (LHsBind GhcRn, [LSig GhcRn])
mkDefMethBind clas :: Class
clas inst_tys :: [Type]
inst_tys sel_id :: TyVar
sel_id dm_name :: Name
dm_name
  = do  { DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
        ; TyVar
dm_id <- Name -> TcM TyVar
tcLookupId Name
dm_name
        ; let inline_prag :: InlinePragma
inline_prag = TyVar -> InlinePragma
idInlinePragma TyVar
dm_id
              inline_prags :: [LSig GhcRn]
inline_prags | InlinePragma -> Bool
isAnyInlinePragma InlinePragma
inline_prag
                           = [SrcSpanLess (LSig GhcRn) -> LSig GhcRn
forall a. HasSrcSpan a => SrcSpanLess a -> a
noLoc (XInlineSig GhcRn
-> Located (IdP GhcRn) -> InlinePragma -> Sig GhcRn
forall pass.
XInlineSig pass -> Located (IdP pass) -> InlinePragma -> Sig pass
InlineSig XInlineSig GhcRn
NoExt
noExt Located Name
Located (IdP GhcRn)
fn InlinePragma
inline_prag)]
                           | Bool
otherwise
                           = []
                 -- Copy the inline pragma (if any) from the default method
                 -- to this version. Note [INLINE and default methods]

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

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

       ; (LHsBind GhcRn, [LSig GhcRn]) -> TcM (LHsBind GhcRn, [LSig GhcRn])
forall (m :: * -> *) a. Monad m => a -> m a
return (LHsBind GhcRn
bind, [LSig GhcRn]
inline_prags) }
  where
    mk_vta :: LHsExpr GhcRn -> Type -> LHsExpr GhcRn
    mk_vta :: LHsExpr GhcRn -> Type -> LHsExpr GhcRn
mk_vta fun :: LHsExpr GhcRn
fun ty :: Type
ty = SrcSpanLess (LHsExpr GhcRn) -> LHsExpr GhcRn
forall a. HasSrcSpan a => SrcSpanLess a -> a
noLoc (XAppTypeE GhcRn
-> LHsExpr GhcRn -> LHsWcType (NoGhcTc GhcRn) -> HsExpr GhcRn
forall p.
XAppTypeE p -> LHsExpr p -> LHsWcType (NoGhcTc p) -> HsExpr p
HsAppType XAppTypeE GhcRn
NoExt
noExt LHsExpr GhcRn
fun (LHsType GhcRn -> LHsWcType (NoGhcTc GhcRn)
forall thing. thing -> HsWildCardBndrs GhcRn thing
mkEmptyWildCardBndrs (LHsType GhcRn -> LHsWcType (NoGhcTc GhcRn))
-> LHsType GhcRn -> LHsWcType (NoGhcTc GhcRn)
forall a b. (a -> b) -> a -> b
$ LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass). LHsType (GhcPass p) -> LHsType (GhcPass p)
nlHsParTy
                                                (LHsType GhcRn -> LHsType GhcRn) -> LHsType GhcRn -> LHsType GhcRn
forall a b. (a -> b) -> a -> b
$ SrcSpanLess (LHsType GhcRn) -> LHsType GhcRn
forall a. HasSrcSpan a => SrcSpanLess a -> a
noLoc (SrcSpanLess (LHsType GhcRn) -> LHsType GhcRn)
-> SrcSpanLess (LHsType GhcRn) -> LHsType GhcRn
forall a b. (a -> b) -> a -> b
$ XXType GhcRn -> SrcSpanLess (LHsType GhcRn)
forall pass. XXType pass -> HsType pass
XHsType (XXType GhcRn -> SrcSpanLess (LHsType GhcRn))
-> XXType GhcRn -> SrcSpanLess (LHsType GhcRn)
forall a b. (a -> b) -> a -> b
$ Type -> NewHsTypeX
NHsCoreTy Type
ty))
       -- NB: use visible type application
       -- See Note [Default methods in instances]

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

warnUnsatisfiedMinimalDefinition :: ClassMinimalDef -> TcM ()
warnUnsatisfiedMinimalDefinition :: BooleanFormula Name -> TcRn ()
warnUnsatisfiedMinimalDefinition mindef :: 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 "No explicit implementation for"
                   ,Int -> SDoc -> SDoc
nest 2 (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$ BooleanFormula Name -> SDoc
forall a. Outputable a => BooleanFormula a -> SDoc
pprBooleanFormulaNice BooleanFormula Name
mindef
                   ]

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

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

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

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

   instance Baz Int Int

From the class decl we get

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

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

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

Lacking VTA we'd get ambiguity errors involving the default method.  This applies
equally to vanilla default methods (Trac #1061) and generic default methods
(Trac #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 Trac #7797.

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

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

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

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

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

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

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

instDeclCtxt1 :: LHsSigType GhcRn -> SDoc
instDeclCtxt1 :: LHsSigType GhcRn -> SDoc
instDeclCtxt1 hs_inst_ty :: LHsSigType GhcRn
hs_inst_ty
  = SDoc -> SDoc
inst_decl_ctxt (LHsType GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
ppr (LHsSigType GhcRn -> LHsType GhcRn
forall pass. LHsSigType pass -> LHsType pass
getLHsInstDeclHead LHsSigType GhcRn
hs_inst_ty))

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

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

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

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

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

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

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