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

-}

{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE ViewPatterns #-}

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

-- | Typechecking patterns
module GHC.Tc.Gen.Pat
   ( tcLetPat
   , newLetBndr
   , LetBndrSpec(..)
   , tcCheckPat, tcCheckPat_O, tcInferPat
   , tcPats
   , addDataConStupidTheta
   , badFieldCon
   , polyPatSig
   )
where

#include "HsVersions.h"

import GHC.Prelude

import {-# SOURCE #-}   GHC.Tc.Gen.Expr( tcSyntaxOp, tcSyntaxOpGen, tcInferSigma )

import GHC.Hs
import GHC.Tc.Utils.Zonk
import GHC.Tc.Gen.Sig( TcPragEnv, lookupPragEnv, addInlinePrags )
import GHC.Tc.Utils.Monad
import GHC.Tc.Utils.Instantiate
import GHC.Types.Id
import GHC.Types.Var
import GHC.Types.Name
import GHC.Types.Name.Reader
import GHC.Tc.Utils.Env
import GHC.Tc.Utils.TcMType
import GHC.Tc.Validity( arityErr )
import GHC.Core.TyCo.Ppr ( pprTyVars )
import GHC.Tc.Utils.TcType
import GHC.Tc.Utils.Unify
import GHC.Tc.Gen.HsType
import GHC.Builtin.Types
import GHC.Tc.Types.Evidence
import GHC.Tc.Types.Origin
import GHC.Core.TyCon
import GHC.Core.DataCon
import GHC.Core.PatSyn
import GHC.Core.ConLike
import GHC.Builtin.Names
import GHC.Types.Basic hiding (SuccessFlag(..))
import GHC.Driver.Session
import GHC.Types.SrcLoc
import GHC.Types.Var.Set
import GHC.Utils.Misc
import GHC.Utils.Outputable as Outputable
import qualified GHC.LanguageExtensions as LangExt
import Control.Arrow  ( second )
import Control.Monad  ( when )
import GHC.Data.List.SetOps ( getNth )

{-
************************************************************************
*                                                                      *
                External interface
*                                                                      *
************************************************************************
-}

tcLetPat :: (Name -> Maybe TcId)
         -> LetBndrSpec
         -> LPat GhcRn -> ExpSigmaType
         -> TcM a
         -> TcM (LPat GhcTcId, a)
tcLetPat :: (Name -> Maybe TyVar)
-> LetBndrSpec
-> LPat GhcRn
-> ExpSigmaType
-> TcM a
-> TcM (LPat GhcTcId, a)
tcLetPat Name -> Maybe TyVar
sig_fn LetBndrSpec
no_gen LPat GhcRn
pat ExpSigmaType
pat_ty TcM a
thing_inside
  = do { TcLevel
bind_lvl <- TcM TcLevel
getTcLevel
       ; let ctxt :: PatCtxt
ctxt = LetPat :: TcLevel -> (Name -> Maybe TyVar) -> LetBndrSpec -> PatCtxt
LetPat { pc_lvl :: TcLevel
pc_lvl    = TcLevel
bind_lvl
                           , pc_sig_fn :: Name -> Maybe TyVar
pc_sig_fn = Name -> Maybe TyVar
sig_fn
                           , pc_new :: LetBndrSpec
pc_new    = LetBndrSpec
no_gen }
             penv :: PatEnv
penv = PE :: Bool -> PatCtxt -> CtOrigin -> PatEnv
PE { pe_lazy :: Bool
pe_lazy = Bool
True
                       , pe_ctxt :: PatCtxt
pe_ctxt = PatCtxt
ctxt
                       , pe_orig :: CtOrigin
pe_orig = CtOrigin
PatOrigin }

       ; ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat ExpSigmaType
pat_ty PatEnv
penv LPat GhcRn
pat TcM a
thing_inside }

-----------------
tcPats :: HsMatchContext GhcRn
       -> [LPat GhcRn]            -- Patterns,
       -> [ExpSigmaType]         --   and their types
       -> TcM a                  --   and the checker for the body
       -> TcM ([LPat GhcTcId], a)

-- This is the externally-callable wrapper function
-- Typecheck the patterns, extend the environment to bind the variables,
-- do the thing inside, use any existentially-bound dictionaries to
-- discharge parts of the returning LIE, and deal with pattern type
-- signatures

--   1. Initialise the PatState
--   2. Check the patterns
--   3. Check the body
--   4. Check that no existentials escape

tcPats :: HsMatchContext GhcRn
-> [LPat GhcRn]
-> [ExpSigmaType]
-> TcM a
-> TcM ([LPat GhcTcId], a)
tcPats HsMatchContext GhcRn
ctxt [LPat GhcRn]
pats [ExpSigmaType]
pat_tys TcM a
thing_inside
  = [ExpSigmaType] -> Checker [LPat GhcRn] [LPat GhcTcId]
tc_lpats [ExpSigmaType]
pat_tys PatEnv
penv [LPat GhcRn]
pats TcM a
thing_inside
  where
    penv :: PatEnv
penv = PE :: Bool -> PatCtxt -> CtOrigin -> PatEnv
PE { pe_lazy :: Bool
pe_lazy = Bool
False, pe_ctxt :: PatCtxt
pe_ctxt = HsMatchContext GhcRn -> PatCtxt
LamPat HsMatchContext GhcRn
ctxt, pe_orig :: CtOrigin
pe_orig = CtOrigin
PatOrigin }

tcInferPat :: HsMatchContext GhcRn -> LPat GhcRn
           -> TcM a
           -> TcM ((LPat GhcTcId, a), TcSigmaType)
tcInferPat :: HsMatchContext GhcRn
-> LPat GhcRn -> TcM a -> TcM ((LPat GhcTcId, a), TcType)
tcInferPat HsMatchContext GhcRn
ctxt LPat GhcRn
pat TcM a
thing_inside
  = (ExpSigmaType -> TcM (Located (Pat GhcTcId), a))
-> TcM ((Located (Pat GhcTcId), a), TcType)
forall a. (ExpSigmaType -> TcM a) -> TcM (a, TcType)
tcInfer ((ExpSigmaType -> TcM (Located (Pat GhcTcId), a))
 -> TcM ((Located (Pat GhcTcId), a), TcType))
-> (ExpSigmaType -> TcM (Located (Pat GhcTcId), a))
-> TcM ((Located (Pat GhcTcId), a), TcType)
forall a b. (a -> b) -> a -> b
$ \ ExpSigmaType
exp_ty ->
    ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat ExpSigmaType
exp_ty PatEnv
penv LPat GhcRn
pat TcM a
thing_inside
 where
    penv :: PatEnv
penv = PE :: Bool -> PatCtxt -> CtOrigin -> PatEnv
PE { pe_lazy :: Bool
pe_lazy = Bool
False, pe_ctxt :: PatCtxt
pe_ctxt = HsMatchContext GhcRn -> PatCtxt
LamPat HsMatchContext GhcRn
ctxt, pe_orig :: CtOrigin
pe_orig = CtOrigin
PatOrigin }

tcCheckPat :: HsMatchContext GhcRn
           -> LPat GhcRn -> TcSigmaType
           -> TcM a                     -- Checker for body
           -> TcM (LPat GhcTcId, a)
tcCheckPat :: HsMatchContext GhcRn
-> LPat GhcRn -> TcType -> TcM a -> TcM (LPat GhcTcId, a)
tcCheckPat HsMatchContext GhcRn
ctxt = HsMatchContext GhcRn
-> CtOrigin
-> LPat GhcRn
-> TcType
-> TcM a
-> TcM (LPat GhcTcId, a)
forall a.
HsMatchContext GhcRn
-> CtOrigin
-> LPat GhcRn
-> TcType
-> TcM a
-> TcM (LPat GhcTcId, a)
tcCheckPat_O HsMatchContext GhcRn
ctxt CtOrigin
PatOrigin

-- | A variant of 'tcPat' that takes a custom origin
tcCheckPat_O :: HsMatchContext GhcRn
             -> CtOrigin              -- ^ origin to use if the type needs inst'ing
             -> LPat GhcRn -> TcSigmaType
             -> TcM a                 -- Checker for body
             -> TcM (LPat GhcTcId, a)
tcCheckPat_O :: HsMatchContext GhcRn
-> CtOrigin
-> LPat GhcRn
-> TcType
-> TcM a
-> TcM (LPat GhcTcId, a)
tcCheckPat_O HsMatchContext GhcRn
ctxt CtOrigin
orig LPat GhcRn
pat TcType
pat_ty TcM a
thing_inside
  = ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (TcType -> ExpSigmaType
mkCheckExpType TcType
pat_ty) PatEnv
penv LPat GhcRn
pat TcM a
thing_inside
  where
    penv :: PatEnv
penv = PE :: Bool -> PatCtxt -> CtOrigin -> PatEnv
PE { pe_lazy :: Bool
pe_lazy = Bool
False, pe_ctxt :: PatCtxt
pe_ctxt = HsMatchContext GhcRn -> PatCtxt
LamPat HsMatchContext GhcRn
ctxt, pe_orig :: CtOrigin
pe_orig = CtOrigin
orig }


{-
************************************************************************
*                                                                      *
                PatEnv, PatCtxt, LetBndrSpec
*                                                                      *
************************************************************************
-}

data PatEnv
  = PE { PatEnv -> Bool
pe_lazy :: Bool        -- True <=> lazy context, so no existentials allowed
       , PatEnv -> PatCtxt
pe_ctxt :: PatCtxt     -- Context in which the whole pattern appears
       , PatEnv -> CtOrigin
pe_orig :: CtOrigin    -- origin to use if the pat_ty needs inst'ing
       }

data PatCtxt
  = LamPat   -- Used for lambdas, case etc
       (HsMatchContext GhcRn)

  | LetPat   -- Used only for let(rec) pattern bindings
             -- See Note [Typing patterns in pattern bindings]
       { PatCtxt -> TcLevel
pc_lvl    :: TcLevel
                   -- Level of the binding group

       , PatCtxt -> Name -> Maybe TyVar
pc_sig_fn :: Name -> Maybe TcId
                   -- Tells the expected type
                   -- for binders with a signature

       , PatCtxt -> LetBndrSpec
pc_new :: LetBndrSpec
                -- How to make a new binder
       }        -- for binders without signatures

data LetBndrSpec
  = LetLclBndr            -- We are going to generalise, and wrap in an AbsBinds
                          -- so clone a fresh binder for the local monomorphic Id

  | LetGblBndr TcPragEnv  -- Generalisation plan is NoGen, so there isn't going
                          -- to be an AbsBinds; So we must bind the global version
                          -- of the binder right away.
                          -- And here is the inline-pragma information

instance Outputable LetBndrSpec where
  ppr :: LetBndrSpec -> SDoc
ppr LetBndrSpec
LetLclBndr      = String -> SDoc
text String
"LetLclBndr"
  ppr (LetGblBndr {}) = String -> SDoc
text String
"LetGblBndr"

makeLazy :: PatEnv -> PatEnv
makeLazy :: PatEnv -> PatEnv
makeLazy PatEnv
penv = PatEnv
penv { pe_lazy :: Bool
pe_lazy = Bool
True }

inPatBind :: PatEnv -> Bool
inPatBind :: PatEnv -> Bool
inPatBind (PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LetPat {} }) = Bool
True
inPatBind (PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LamPat {} }) = Bool
False

{- *********************************************************************
*                                                                      *
                Binders
*                                                                      *
********************************************************************* -}

tcPatBndr :: PatEnv -> Name -> ExpSigmaType -> TcM (HsWrapper, TcId)
-- (coi, xp) = tcPatBndr penv x pat_ty
-- Then coi : pat_ty ~ typeof(xp)
--
tcPatBndr :: PatEnv -> Name -> ExpSigmaType -> TcM (HsWrapper, TyVar)
tcPatBndr penv :: PatEnv
penv@(PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LetPat { pc_lvl :: PatCtxt -> TcLevel
pc_lvl    = TcLevel
bind_lvl
                                      , pc_sig_fn :: PatCtxt -> Name -> Maybe TyVar
pc_sig_fn = Name -> Maybe TyVar
sig_fn
                                      , pc_new :: PatCtxt -> LetBndrSpec
pc_new    = LetBndrSpec
no_gen } })
          Name
bndr_name ExpSigmaType
exp_pat_ty
  -- For the LetPat cases, see
  -- Note [Typechecking pattern bindings] in GHC.Tc.Gen.Bind

  | Just TyVar
bndr_id <- Name -> Maybe TyVar
sig_fn Name
bndr_name   -- There is a signature
  = do { HsWrapper
wrap <- PatEnv -> ExpSigmaType -> TcType -> TcM HsWrapper
tc_sub_type PatEnv
penv ExpSigmaType
exp_pat_ty (TyVar -> TcType
idType TyVar
bndr_id)
           -- See Note [Subsumption check at pattern variables]
       ; String -> SDoc -> TcRn ()
traceTc String
"tcPatBndr(sig)" (TyVar -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TyVar
ppr TyVar
bndr_id SDoc -> SDoc -> SDoc
$$ TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr (TyVar -> TcType
idType TyVar
bndr_id) SDoc -> SDoc -> SDoc
$$ ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable ExpSigmaType
ppr ExpSigmaType
exp_pat_ty)
       ; (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper
wrap, TyVar
bndr_id) }

  | Bool
otherwise                          -- No signature
  = do { (TcCoercion
co, TcType
bndr_ty) <- case ExpSigmaType
exp_pat_ty of
             Check TcType
pat_ty    -> TcLevel
-> TcType -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercion, TcType)
promoteTcType TcLevel
bind_lvl TcType
pat_ty
             Infer InferResult
infer_res -> ASSERT( bind_lvl == ir_lvl infer_res )
                                -- If we were under a constructor that bumped
                                -- the level, we'd be in checking mode
                                do { TcType
bndr_ty <- InferResult -> TcM TcType
inferResultToType InferResult
infer_res
                                   ; (TcCoercion, TcType)
-> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercion, TcType)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (TcType -> TcCoercion
mkTcNomReflCo TcType
bndr_ty, TcType
bndr_ty) }
       ; TyVar
bndr_id <- LetBndrSpec -> Name -> TcType -> TcM TyVar
newLetBndr LetBndrSpec
no_gen Name
bndr_name TcType
bndr_ty
       ; String -> SDoc -> TcRn ()
traceTc String
"tcPatBndr(nosig)" ([SDoc] -> SDoc
vcat [ TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcLevel
ppr TcLevel
bind_lvl
                                          , ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable ExpSigmaType
ppr ExpSigmaType
exp_pat_ty, TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
bndr_ty, TcCoercion -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcCoercion
ppr TcCoercion
co
                                          , TyVar -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TyVar
ppr TyVar
bndr_id ])
       ; (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (TcCoercion -> HsWrapper
mkWpCastN TcCoercion
co, TyVar
bndr_id) }

tcPatBndr PatEnv
_ Name
bndr_name ExpSigmaType
pat_ty
  = do { TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType ExpSigmaType
pat_ty
       ; String -> SDoc -> TcRn ()
traceTc String
"tcPatBndr(not let)" (Name -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Name
ppr Name
bndr_name SDoc -> SDoc -> SDoc
$$ TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
pat_ty)
       ; (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper
idHsWrapper, Name -> TcType -> TyVar
mkLocalIdOrCoVar Name
bndr_name TcType
pat_ty) }
               -- We should not have "OrCoVar" here, this is a bug (#17545)
               -- Whether or not there is a sig is irrelevant,
               -- as this is local

newLetBndr :: LetBndrSpec -> Name -> TcType -> TcM TcId
-- Make up a suitable Id for the pattern-binder.
-- See Note [Typechecking pattern bindings], item (4) in GHC.Tc.Gen.Bind
--
-- In the polymorphic case when we are going to generalise
--    (plan InferGen, no_gen = LetLclBndr), generate a "monomorphic version"
--    of the Id; the original name will be bound to the polymorphic version
--    by the AbsBinds
-- In the monomorphic case when we are not going to generalise
--    (plan NoGen, no_gen = LetGblBndr) there is no AbsBinds,
--    and we use the original name directly
newLetBndr :: LetBndrSpec -> Name -> TcType -> TcM TyVar
newLetBndr LetBndrSpec
LetLclBndr Name
name TcType
ty
  = do { Name
mono_name <- Name -> TcM Name
cloneLocalName Name
name
       ; TyVar -> TcM TyVar
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HasDebugCallStack => Name -> TcType -> TyVar
Name -> TcType -> TyVar
External instance of the constraint type HasDebugCallStack
mkLocalId Name
mono_name TcType
ty) }
newLetBndr (LetGblBndr TcPragEnv
prags) Name
name TcType
ty
  = TyVar -> [LSig GhcRn] -> TcM TyVar
addInlinePrags (HasDebugCallStack => Name -> TcType -> TyVar
Name -> TcType -> TyVar
External instance of the constraint type HasDebugCallStack
mkLocalId Name
name TcType
ty) (TcPragEnv -> Name -> [LSig GhcRn]
lookupPragEnv TcPragEnv
prags Name
name)

tc_sub_type :: PatEnv -> ExpSigmaType -> TcSigmaType -> TcM HsWrapper
-- tcSubTypeET with the UserTypeCtxt specialised to GenSigCtxt
-- Used during typechecking patterns
tc_sub_type :: PatEnv -> ExpSigmaType -> TcType -> TcM HsWrapper
tc_sub_type PatEnv
penv ExpSigmaType
t1 TcType
t2 = CtOrigin -> UserTypeCtxt -> ExpSigmaType -> TcType -> TcM HsWrapper
tcSubTypePat (PatEnv -> CtOrigin
pe_orig PatEnv
penv) UserTypeCtxt
GenSigCtxt ExpSigmaType
t1 TcType
t2

{- Note [Subsumption check at pattern variables]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we come across a variable with a type signature, we need to do a
subsumption, not equality, check against the context type.  e.g.

    data T = MkT (forall a. a->a)
      f :: forall b. [b]->[b]
      MkT f = blah

Since 'blah' returns a value of type T, its payload is a polymorphic
function of type (forall a. a->a).  And that's enough to bind the
less-polymorphic function 'f', but we need some impedance matching
to witness the instantiation.


************************************************************************
*                                                                      *
                The main worker functions
*                                                                      *
************************************************************************

Note [Nesting]
~~~~~~~~~~~~~~
tcPat takes a "thing inside" over which the pattern scopes.  This is partly
so that tcPat can extend the environment for the thing_inside, but also
so that constraints arising in the thing_inside can be discharged by the
pattern.

This does not work so well for the ErrCtxt carried by the monad: we don't
want the error-context for the pattern to scope over the RHS.
Hence the getErrCtxt/setErrCtxt stuff in tcMultiple
-}

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

type Checker inp out =  forall r.
                          PatEnv
                       -> inp
                       -> TcM r      -- Thing inside
                       -> TcM ( out
                              , r    -- Result of thing inside
                              )

tcMultiple :: Checker inp out -> Checker [inp] [out]
tcMultiple :: Checker inp out -> Checker [inp] [out]
tcMultiple Checker inp out
tc_pat PatEnv
penv [inp]
args TcM r
thing_inside
  = do  { [ErrCtxt]
err_ctxt <- TcM [ErrCtxt]
getErrCtxt
        ; let loop :: PatEnv -> [inp] -> TcM ([out], r)
loop PatEnv
_ []
                = do { r
res <- TcM r
thing_inside
                     ; ([out], r) -> TcM ([out], r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([], r
res) }

              loop PatEnv
penv (inp
arg:[inp]
args)
                = do { (out
p', ([out]
ps', r
res))
                                <- PatEnv -> inp -> TcM ([out], r) -> TcM (out, ([out], r))
Checker inp out
tc_pat PatEnv
penv inp
arg (TcM ([out], r) -> TcM (out, ([out], r)))
-> TcM ([out], r) -> TcM (out, ([out], r))
forall a b. (a -> b) -> a -> b
$
                                   [ErrCtxt] -> TcM ([out], r) -> TcM ([out], r)
forall a. [ErrCtxt] -> TcM a -> TcM a
setErrCtxt [ErrCtxt]
err_ctxt (TcM ([out], r) -> TcM ([out], r))
-> TcM ([out], r) -> TcM ([out], r)
forall a b. (a -> b) -> a -> b
$
                                   PatEnv -> [inp] -> TcM ([out], r)
loop PatEnv
penv [inp]
args
                -- setErrCtxt: restore context before doing the next pattern
                -- See note [Nesting] above

                     ; ([out], r) -> TcM ([out], r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (out
p'out -> [out] -> [out]
forall a. a -> [a] -> [a]
:[out]
ps', r
res) }

        ; PatEnv -> [inp] -> TcM ([out], r)
loop PatEnv
penv [inp]
args }

--------------------
tc_lpat :: ExpSigmaType
        -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat :: ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat ExpSigmaType
pat_ty PatEnv
penv (L SrcSpan
span Pat GhcRn
pat) TcM r
thing_inside
  = SrcSpan
-> TcRn (Located (Pat GhcTcId), r)
-> TcRn (Located (Pat GhcTcId), r)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
span (TcRn (Located (Pat GhcTcId), r)
 -> TcRn (Located (Pat GhcTcId), r))
-> TcRn (Located (Pat GhcTcId), r)
-> TcRn (Located (Pat GhcTcId), r)
forall a b. (a -> b) -> a -> b
$
    do  { (Pat GhcTcId
pat', r
res) <- Pat GhcRn
-> (TcM r -> TcM (Pat GhcTcId, r)) -> TcM r -> TcM (Pat GhcTcId, r)
forall a b. Pat GhcRn -> (TcM a -> TcM b) -> TcM a -> TcM b
maybeWrapPatCtxt Pat GhcRn
pat (ExpSigmaType -> Checker (Pat GhcRn) (Pat GhcTcId)
tc_pat ExpSigmaType
pat_ty PatEnv
penv Pat GhcRn
pat)
                                          TcM r
thing_inside
        ; (Located (Pat GhcTcId), r) -> TcRn (Located (Pat GhcTcId), r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (SrcSpan -> Pat GhcTcId -> Located (Pat GhcTcId)
forall l e. l -> e -> GenLocated l e
L SrcSpan
span Pat GhcTcId
pat', r
res) }

tc_lpats :: [ExpSigmaType]
         -> Checker [LPat GhcRn] [LPat GhcTcId]
tc_lpats :: [ExpSigmaType] -> Checker [LPat GhcRn] [LPat GhcTcId]
tc_lpats [ExpSigmaType]
tys PatEnv
penv [LPat GhcRn]
pats
  = ASSERT2( equalLength pats tys, ppr pats $$ ppr tys )
    Checker
  (GenLocated SrcSpan (Pat GhcRn), ExpSigmaType)
  (Located (Pat GhcTcId))
-> Checker
     [(GenLocated SrcSpan (Pat GhcRn), ExpSigmaType)]
     [Located (Pat GhcTcId)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple (\ PatEnv
penv' (GenLocated SrcSpan (Pat GhcRn)
p,ExpSigmaType
t) -> ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat ExpSigmaType
t PatEnv
penv' GenLocated SrcSpan (Pat GhcRn)
LPat GhcRn
p)
               PatEnv
penv
               (String
-> [GenLocated SrcSpan (Pat GhcRn)]
-> [ExpSigmaType]
-> [(GenLocated SrcSpan (Pat GhcRn), ExpSigmaType)]
forall a b. String -> [a] -> [b] -> [(a, b)]
zipEqual String
"tc_lpats" [GenLocated SrcSpan (Pat GhcRn)]
[LPat GhcRn]
pats [ExpSigmaType]
tys)

--------------------
tc_pat  :: ExpSigmaType
        -- ^ Fully refined result type
        -> Checker (Pat GhcRn) (Pat GhcTcId)
        -- ^ Translated pattern
tc_pat :: ExpSigmaType -> Checker (Pat GhcRn) (Pat GhcTcId)
tc_pat ExpSigmaType
pat_ty PatEnv
penv Pat GhcRn
ps_pat TcM r
thing_inside = case Pat GhcRn
ps_pat of

  VarPat XVarPat GhcRn
x (L SrcSpan
l IdP GhcRn
name) -> do
        { (HsWrapper
wrap, TyVar
id) <- PatEnv -> Name -> ExpSigmaType -> TcM (HsWrapper, TyVar)
tcPatBndr PatEnv
penv Name
IdP GhcRn
name ExpSigmaType
pat_ty
        ; r
res <- Name -> TyVar -> TcM r -> TcM r
forall a. Name -> TyVar -> TcM a -> TcM a
tcExtendIdEnv1 Name
IdP GhcRn
name TyVar
id TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
wrap (XVarPat GhcTcId -> Located (IdP GhcTcId) -> Pat GhcTcId
forall p. XVarPat p -> Located (IdP p) -> Pat p
VarPat XVarPat GhcRn
XVarPat GhcTcId
x (SrcSpan -> TyVar -> GenLocated SrcSpan TyVar
forall l e. l -> e -> GenLocated l e
L SrcSpan
l TyVar
id)) TcType
pat_ty, r
res) }

  ParPat XParPat GhcRn
x LPat GhcRn
pat -> do
        { (Located (Pat GhcTcId)
pat', r
res) <- ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat ExpSigmaType
pat_ty PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (XParPat GhcTcId -> LPat GhcTcId -> Pat GhcTcId
forall p. XParPat p -> LPat p -> Pat p
ParPat XParPat GhcRn
XParPat GhcTcId
x Located (Pat GhcTcId)
LPat GhcTcId
pat', r
res) }

  BangPat XBangPat GhcRn
x LPat GhcRn
pat -> do
        { (Located (Pat GhcTcId)
pat', r
res) <- ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat ExpSigmaType
pat_ty PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (XBangPat GhcTcId -> LPat GhcTcId -> Pat GhcTcId
forall p. XBangPat p -> LPat p -> Pat p
BangPat XBangPat GhcRn
XBangPat GhcTcId
x Located (Pat GhcTcId)
LPat GhcTcId
pat', r
res) }

  LazyPat XLazyPat GhcRn
x LPat GhcRn
pat -> do
        { (Located (Pat GhcTcId)
pat', (r
res, WantedConstraints
pat_ct))
                <- ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat ExpSigmaType
pat_ty (PatEnv -> PatEnv
makeLazy PatEnv
penv) LPat GhcRn
pat (TcM (r, WantedConstraints)
 -> TcM (LPat GhcTcId, (r, WantedConstraints)))
-> TcM (r, WantedConstraints)
-> TcM (LPat GhcTcId, (r, WantedConstraints))
forall a b. (a -> b) -> a -> b
$
                   TcM r -> TcM (r, WantedConstraints)
forall a. TcM a -> TcM (a, WantedConstraints)
captureConstraints TcM r
thing_inside
                -- Ignore refined penv', revert to penv

        ; WantedConstraints -> TcRn ()
emitConstraints WantedConstraints
pat_ct
        -- captureConstraints/extendConstraints:
        --   see Note [Hopping the LIE in lazy patterns]

        -- Check that the expected pattern type is itself lifted
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; TcCoercion
_ <- Maybe (HsExpr GhcRn) -> TcType -> TcType -> TcM TcCoercion
unifyType Maybe (HsExpr GhcRn)
forall a. Maybe a
Nothing (HasDebugCallStack => TcType -> TcType
TcType -> TcType
External instance of the constraint type HasDebugCallStack
tcTypeKind TcType
pat_ty) TcType
liftedTypeKind

        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (XLazyPat GhcTcId -> LPat GhcTcId -> Pat GhcTcId
forall p. XLazyPat p -> LPat p -> Pat p
LazyPat XLazyPat GhcRn
XLazyPat GhcTcId
x Located (Pat GhcTcId)
LPat GhcTcId
pat', r
res) }

  WildPat XWildPat GhcRn
_ -> do
        { r
res <- TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (XWildPat GhcTcId -> Pat GhcTcId
forall p. XWildPat p -> Pat p
WildPat TcType
XWildPat GhcTcId
pat_ty, r
res) }

  AsPat XAsPat GhcRn
x (L SrcSpan
nm_loc IdP GhcRn
name) LPat GhcRn
pat -> do
        { (HsWrapper
wrap, TyVar
bndr_id) <- SrcSpan -> TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
nm_loc (PatEnv -> Name -> ExpSigmaType -> TcM (HsWrapper, TyVar)
tcPatBndr PatEnv
penv Name
IdP GhcRn
name ExpSigmaType
pat_ty)
        ; (Located (Pat GhcTcId)
pat', r
res) <- Name
-> TyVar
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
forall a. Name -> TyVar -> TcM a -> TcM a
tcExtendIdEnv1 Name
IdP GhcRn
name TyVar
bndr_id (IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
 -> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r))
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
forall a b. (a -> b) -> a -> b
$
                         ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (TcType -> ExpSigmaType
mkCheckExpType (TcType -> ExpSigmaType) -> TcType -> ExpSigmaType
forall a b. (a -> b) -> a -> b
$ TyVar -> TcType
idType TyVar
bndr_id)
                                 PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
            -- NB: if we do inference on:
            --          \ (y@(x::forall a. a->a)) = e
            -- we'll fail.  The as-pattern infers a monotype for 'y', which then
            -- fails to unify with the polymorphic type for 'x'.  This could
            -- perhaps be fixed, but only with a bit more work.
            --
            -- If you fix it, don't forget the bindInstsOfPatIds!
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
wrap (XAsPat GhcTcId
-> Located (IdP GhcTcId) -> LPat GhcTcId -> Pat GhcTcId
forall p. XAsPat p -> Located (IdP p) -> LPat p -> Pat p
AsPat XAsPat GhcRn
XAsPat GhcTcId
x (SrcSpan -> TyVar -> GenLocated SrcSpan TyVar
forall l e. l -> e -> GenLocated l e
L SrcSpan
nm_loc TyVar
bndr_id) Located (Pat GhcTcId)
LPat GhcTcId
pat') TcType
pat_ty,
                  r
res) }

  ViewPat XViewPat GhcRn
_ LHsExpr GhcRn
expr LPat GhcRn
pat -> do
       {
         -- We use tcInferRho here.
         -- If we have a view function with types like:
         --    blah -> forall b. burble
         -- then simple-subsumption means that 'forall b' won't be instantiated
         -- so we can typecheck the inner pattern with that type
         -- An exotic example:
         --    pair :: forall a. a -> forall b. b -> (a,b)
         --    f (pair True -> x) = ...here (x :: forall b. b -> (Bool,b))
         --
         -- TEMPORARY: pending simple subsumption, use tcInferSigma
         -- When removing this, remove it from Expr.hs-boot too
        ; (LHsExpr GhcTcId
expr',TcType
expr_ty) <- LHsExpr GhcRn -> TcM (LHsExpr GhcTcId, TcType)
tcInferSigma LHsExpr GhcRn
expr

         -- Expression must be a function
        ; let expr_orig :: CtOrigin
expr_orig = LHsExpr GhcRn -> CtOrigin
lexprCtOrigin LHsExpr GhcRn
expr
              herald :: SDoc
herald    = String -> SDoc
text String
"A view pattern expression expects"
        ; (HsWrapper
expr_wrap1, [TcType
inf_arg_ty], TcType
inf_res_ty)
            <- SDoc
-> CtOrigin
-> Maybe (HsExpr GhcRn)
-> Int
-> TcType
-> TcM (HsWrapper, [TcType], TcType)
matchActualFunTys SDoc
herald CtOrigin
expr_orig (HsExpr GhcRn -> Maybe (HsExpr GhcRn)
forall a. a -> Maybe a
Just (LHsExpr GhcRn -> HsExpr GhcRn
forall l e. GenLocated l e -> e
unLoc LHsExpr GhcRn
expr)) Int
1 TcType
expr_ty
            -- expr_wrap1 :: expr_ty "->" (inf_arg_ty -> inf_res_ty)

         -- Check that overall pattern is more polymorphic than arg type
        ; HsWrapper
expr_wrap2 <- PatEnv -> ExpSigmaType -> TcType -> TcM HsWrapper
tc_sub_type PatEnv
penv ExpSigmaType
pat_ty TcType
inf_arg_ty
            -- expr_wrap2 :: pat_ty "->" inf_arg_ty

         -- Pattern must have inf_res_ty
        ; (Located (Pat GhcTcId)
pat', r
res) <- ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (TcType -> ExpSigmaType
mkCheckExpType TcType
inf_res_ty) PatEnv
penv LPat GhcRn
pat TcM r
thing_inside

        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; let expr_wrap2' :: HsWrapper
expr_wrap2' = HsWrapper -> HsWrapper -> TcType -> TcType -> SDoc -> HsWrapper
mkWpFun HsWrapper
expr_wrap2 HsWrapper
idHsWrapper
                                    TcType
pat_ty TcType
inf_res_ty SDoc
doc
               -- expr_wrap2' :: (inf_arg_ty -> inf_res_ty) "->"
               --                (pat_ty -> inf_res_ty)
              expr_wrap :: HsWrapper
expr_wrap = HsWrapper
expr_wrap2' HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
expr_wrap1
              doc :: SDoc
doc = String -> SDoc
text String
"When checking the view pattern function:" SDoc -> SDoc -> SDoc
<+> (LHsExpr GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (HsExpr (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr LHsExpr GhcRn
expr)
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (XViewPat GhcTcId -> LHsExpr GhcTcId -> LPat GhcTcId -> Pat GhcTcId
forall p. XViewPat p -> LHsExpr p -> LPat p -> Pat p
ViewPat TcType
XViewPat GhcTcId
pat_ty (HsWrapper -> LHsExpr GhcTcId -> LHsExpr GhcTcId
mkLHsWrap HsWrapper
expr_wrap LHsExpr GhcTcId
expr') Located (Pat GhcTcId)
LPat GhcTcId
pat', r
res)}

-- Type signatures in patterns
-- See Note [Pattern coercions] below
  SigPat XSigPat GhcRn
_ LPat GhcRn
pat HsPatSigType (NoGhcTc GhcRn)
sig_ty -> do
        { (TcType
inner_ty, [(Name, TyVar)]
tv_binds, [(Name, TyVar)]
wcs, HsWrapper
wrap) <- Bool
-> HsPatSigType GhcRn
-> ExpSigmaType
-> TcM (TcType, [(Name, TyVar)], [(Name, TyVar)], HsWrapper)
tcPatSig (PatEnv -> Bool
inPatBind PatEnv
penv)
                                                            HsPatSigType (NoGhcTc GhcRn)
HsPatSigType GhcRn
sig_ty ExpSigmaType
pat_ty
                -- Using tcExtendNameTyVarEnv is appropriate here
                -- because we're not really bringing fresh tyvars into scope.
                -- We're *naming* existing tyvars. Note that it is OK for a tyvar
                -- from an outer scope to mention one of these tyvars in its kind.
        ; (Located (Pat GhcTcId)
pat', r
res) <- [(Name, TyVar)]
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
wcs      (IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
 -> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r))
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
forall a b. (a -> b) -> a -> b
$
                         [(Name, TyVar)]
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
tv_binds (IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
 -> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r))
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
-> IOEnv (Env TcGblEnv TcLclEnv) (Located (Pat GhcTcId), r)
forall a b. (a -> b) -> a -> b
$
                         ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (TcType -> ExpSigmaType
mkCheckExpType TcType
inner_ty) PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
wrap (XSigPat GhcTcId
-> LPat GhcTcId -> HsPatSigType (NoGhcTc GhcTcId) -> Pat GhcTcId
forall p. XSigPat p -> LPat p -> HsPatSigType (NoGhcTc p) -> Pat p
SigPat TcType
XSigPat GhcTcId
inner_ty Located (Pat GhcTcId)
LPat GhcTcId
pat' HsPatSigType (NoGhcTc GhcRn)
HsPatSigType (NoGhcTc GhcTcId)
sig_ty) TcType
pat_ty, r
res) }

------------------------
-- Lists, tuples, arrays
  ListPat Maybe SyntaxExprRn
XListPat GhcRn
Nothing [LPat GhcRn]
pats -> do
        { (HsWrapper
coi, TcType
elt_ty) <- (TcType -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercion, TcType))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, TcType)
forall a.
(TcType -> TcM (TcCoercion, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy TcType -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercion, TcType)
matchExpectedListTy PatEnv
penv ExpSigmaType
pat_ty
        ; ([Located (Pat GhcTcId)]
pats', r
res) <- Checker (GenLocated SrcSpan (Pat GhcRn)) (Located (Pat GhcTcId))
-> Checker [GenLocated SrcSpan (Pat GhcRn)] [Located (Pat GhcTcId)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple (ExpSigmaType
-> PatEnv -> LPat GhcRn -> TcM r -> TcM (LPat GhcTcId, r)
ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (ExpSigmaType
 -> PatEnv -> LPat GhcRn -> TcM r -> TcM (LPat GhcTcId, r))
-> ExpSigmaType
-> PatEnv
-> LPat GhcRn
-> TcM r
-> TcM (LPat GhcTcId, r)
forall a b. (a -> b) -> a -> b
$ TcType -> ExpSigmaType
mkCheckExpType TcType
elt_ty)
                                     PatEnv
penv [GenLocated SrcSpan (Pat GhcRn)]
[LPat GhcRn]
pats TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
coi
                         (XListPat GhcTcId -> [LPat GhcTcId] -> Pat GhcTcId
forall p. XListPat p -> [LPat p] -> Pat p
ListPat (TcType -> Maybe (TcType, SyntaxExpr GhcTcId) -> ListPatTc
ListPatTc TcType
elt_ty Maybe (TcType, SyntaxExpr GhcTcId)
forall a. Maybe a
Nothing) [Located (Pat GhcTcId)]
[LPat GhcTcId]
pats') TcType
pat_ty, r
res)
}

  ListPat (Just SyntaxExprRn
e) [LPat GhcRn]
pats -> do
        { TcType
tau_pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType ExpSigmaType
pat_ty
        ; (([Located (Pat GhcTcId)]
pats', r
res, TcType
elt_ty), SyntaxExprTc
e')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType] -> TcM ([Located (Pat GhcTcId)], r, TcType))
-> TcM (([Located (Pat GhcTcId)], r, TcType), SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOpGen CtOrigin
ListOrigin SyntaxExprRn
e [ExpSigmaType -> SyntaxOpType
SynType (TcType -> ExpSigmaType
mkCheckExpType TcType
tau_pat_ty)]
                                          SyntaxOpType
SynList (([TcType] -> TcM ([Located (Pat GhcTcId)], r, TcType))
 -> TcM (([Located (Pat GhcTcId)], r, TcType), SyntaxExprTc))
-> ([TcType] -> TcM ([Located (Pat GhcTcId)], r, TcType))
-> TcM (([Located (Pat GhcTcId)], r, TcType), SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
                 \ [TcType
elt_ty] ->
                 do { ([Located (Pat GhcTcId)]
pats', r
res) <- Checker (GenLocated SrcSpan (Pat GhcRn)) (Located (Pat GhcTcId))
-> Checker [GenLocated SrcSpan (Pat GhcRn)] [Located (Pat GhcTcId)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple (ExpSigmaType
-> PatEnv -> LPat GhcRn -> TcM r -> TcM (LPat GhcTcId, r)
ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (ExpSigmaType
 -> PatEnv -> LPat GhcRn -> TcM r -> TcM (LPat GhcTcId, r))
-> ExpSigmaType
-> PatEnv
-> LPat GhcRn
-> TcM r
-> TcM (LPat GhcTcId, r)
forall a b. (a -> b) -> a -> b
$ TcType -> ExpSigmaType
mkCheckExpType TcType
elt_ty)
                                                 PatEnv
penv [GenLocated SrcSpan (Pat GhcRn)]
[LPat GhcRn]
pats TcM r
thing_inside
                    ; ([Located (Pat GhcTcId)], r, TcType)
-> TcM ([Located (Pat GhcTcId)], r, TcType)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([Located (Pat GhcTcId)]
pats', r
res, TcType
elt_ty) }
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (XListPat GhcTcId -> [LPat GhcTcId] -> Pat GhcTcId
forall p. XListPat p -> [LPat p] -> Pat p
ListPat (TcType -> Maybe (TcType, SyntaxExpr GhcTcId) -> ListPatTc
ListPatTc TcType
elt_ty ((TcType, SyntaxExprTc) -> Maybe (TcType, SyntaxExprTc)
forall a. a -> Maybe a
Just (TcType
tau_pat_ty,SyntaxExprTc
e'))) [Located (Pat GhcTcId)]
[LPat GhcTcId]
pats', r
res)
}

  TuplePat XTuplePat GhcRn
_ [LPat GhcRn]
pats Boxity
boxity -> do
        { let arity :: Int
arity = [GenLocated SrcSpan (Pat GhcRn)] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
External instance of the constraint type Foldable []
length [GenLocated SrcSpan (Pat GhcRn)]
[LPat GhcRn]
pats
              tc :: TyCon
tc = Boxity -> Int -> TyCon
tupleTyCon Boxity
boxity Int
arity
              -- NB: tupleTyCon does not flatten 1-tuples
              -- See Note [Don't flatten tuples from HsSyn] in GHC.Core.Make
        ; (HsWrapper
coi, [TcType]
arg_tys) <- (TcType -> TcM (TcCoercion, [TcType]))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, [TcType])
forall a.
(TcType -> TcM (TcCoercion, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy (TyCon -> TcType -> TcM (TcCoercion, [TcType])
matchExpectedTyConApp TyCon
tc)
                                               PatEnv
penv ExpSigmaType
pat_ty
                     -- Unboxed tuples have RuntimeRep vars, which we discard:
                     -- See Note [Unboxed tuple RuntimeRep vars] in GHC.Core.TyCon
        ; let con_arg_tys :: [TcType]
con_arg_tys = case Boxity
boxity of Boxity
Unboxed -> Int -> [TcType] -> [TcType]
forall a. Int -> [a] -> [a]
drop Int
arity [TcType]
arg_tys
                                           Boxity
Boxed   -> [TcType]
arg_tys
        ; ([Located (Pat GhcTcId)]
pats', r
res) <- [ExpSigmaType] -> Checker [LPat GhcRn] [LPat GhcTcId]
tc_lpats ((TcType -> ExpSigmaType) -> [TcType] -> [ExpSigmaType]
forall a b. (a -> b) -> [a] -> [b]
map TcType -> ExpSigmaType
mkCheckExpType [TcType]
con_arg_tys)
                                   PatEnv
penv [LPat GhcRn]
pats TcM r
thing_inside

        ; DynFlags
dflags <- IOEnv (Env TcGblEnv TcLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
External instance of the constraint type forall env. ContainsDynFlags env => HasDynFlags (IOEnv env)
External instance of the constraint type forall gbl lcl. ContainsDynFlags (Env gbl lcl)
getDynFlags

        -- Under flag control turn a pattern (x,y,z) into ~(x,y,z)
        -- so that we can experiment with lazy tuple-matching.
        -- This is a pretty odd place to make the switch, but
        -- it was easy to do.
        ; let
              unmangled_result :: Pat GhcTcId
unmangled_result = XTuplePat GhcTcId -> [LPat GhcTcId] -> Boxity -> Pat GhcTcId
forall p. XTuplePat p -> [LPat p] -> Boxity -> Pat p
TuplePat [TcType]
XTuplePat GhcTcId
con_arg_tys [Located (Pat GhcTcId)]
[LPat GhcTcId]
pats' Boxity
boxity
                                 -- pat_ty /= pat_ty iff coi /= IdCo
              possibly_mangled_result :: Pat GhcTcId
possibly_mangled_result
                | GeneralFlag -> DynFlags -> Bool
gopt GeneralFlag
Opt_IrrefutableTuples DynFlags
dflags Bool -> Bool -> Bool
&&
                  Boxity -> Bool
isBoxed Boxity
boxity      = XLazyPat GhcTcId -> LPat GhcTcId -> Pat GhcTcId
forall p. XLazyPat p -> LPat p -> Pat p
LazyPat XLazyPat GhcTcId
NoExtField
noExtField (Pat GhcTcId -> Located (Pat GhcTcId)
forall e. e -> Located e
noLoc Pat GhcTcId
unmangled_result)
                | Bool
otherwise           = Pat GhcTcId
unmangled_result

        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; ASSERT( con_arg_tys `equalLength` pats ) -- Syntactically enforced
          (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
coi Pat GhcTcId
possibly_mangled_result TcType
pat_ty, r
res)
        }

  SumPat XSumPat GhcRn
_ LPat GhcRn
pat Int
alt Int
arity  -> do
        { let tc :: TyCon
tc = Int -> TyCon
sumTyCon Int
arity
        ; (HsWrapper
coi, [TcType]
arg_tys) <- (TcType -> TcM (TcCoercion, [TcType]))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, [TcType])
forall a.
(TcType -> TcM (TcCoercion, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy (TyCon -> TcType -> TcM (TcCoercion, [TcType])
matchExpectedTyConApp TyCon
tc)
                                               PatEnv
penv ExpSigmaType
pat_ty
        ; -- Drop levity vars, we don't care about them here
          let con_arg_tys :: [TcType]
con_arg_tys = Int -> [TcType] -> [TcType]
forall a. Int -> [a] -> [a]
drop Int
arity [TcType]
arg_tys
        ; (Located (Pat GhcTcId)
pat', r
res) <- ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (TcType -> ExpSigmaType
mkCheckExpType ([TcType]
con_arg_tys [TcType] -> Int -> TcType
forall a. Outputable a => [a] -> Int -> a
External instance of the constraint type Outputable TcType
`getNth` (Int
alt Int -> Int -> Int
forall a. Num a => a -> a -> a
External instance of the constraint type Num Int
- Int
1)))
                                 PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
coi (XSumPat GhcTcId -> LPat GhcTcId -> Int -> Int -> Pat GhcTcId
forall p. XSumPat p -> LPat p -> Int -> Int -> Pat p
SumPat [TcType]
XSumPat GhcTcId
con_arg_tys Located (Pat GhcTcId)
LPat GhcTcId
pat' Int
alt Int
arity) TcType
pat_ty
                 , r
res)
        }

------------------------
-- Data constructors
  ConPat XConPat GhcRn
NoExtField
NoExtField Located (ConLikeP GhcRn)
con HsConPatDetails GhcRn
arg_pats ->
    PatEnv
-> Located Name
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM r
-> TcM (Pat GhcTcId, r)
forall a.
PatEnv
-> Located Name
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
tcConPat PatEnv
penv Located Name
Located (ConLikeP GhcRn)
con ExpSigmaType
pat_ty HsConPatDetails GhcRn
arg_pats TcM r
thing_inside

------------------------
-- Literal patterns
  LitPat XLitPat GhcRn
x HsLit GhcRn
simple_lit -> do
        { let lit_ty :: TcType
lit_ty = HsLit GhcRn -> TcType
forall (p :: Pass). HsLit (GhcPass p) -> TcType
hsLitType HsLit GhcRn
simple_lit
        ; HsWrapper
wrap   <- PatEnv -> ExpSigmaType -> TcType -> TcM HsWrapper
tc_sub_type PatEnv
penv ExpSigmaType
pat_ty TcType
lit_ty
        ; r
res    <- TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ( HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
wrap (XLitPat GhcTcId -> HsLit GhcTcId -> Pat GhcTcId
forall p. XLitPat p -> HsLit p -> Pat p
LitPat XLitPat GhcRn
XLitPat GhcTcId
x (HsLit GhcRn -> HsLit GhcTcId
forall (p1 :: Pass) (p2 :: Pass).
HsLit (GhcPass p1) -> HsLit (GhcPass p2)
convertLit HsLit GhcRn
simple_lit)) TcType
pat_ty
                 , r
res) }

------------------------
-- Overloaded patterns: n, and n+k

-- In the case of a negative literal (the more complicated case),
-- we get
--
--   case v of (-5) -> blah
--
-- becoming
--
--   if v == (negate (fromInteger 5)) then blah else ...
--
-- There are two bits of rebindable syntax:
--   (==)   :: pat_ty -> neg_lit_ty -> Bool
--   negate :: lit_ty -> neg_lit_ty
-- where lit_ty is the type of the overloaded literal 5.
--
-- When there is no negation, neg_lit_ty and lit_ty are the same
  NPat XNPat GhcRn
_ (L SrcSpan
l HsOverLit GhcRn
over_lit) Maybe (SyntaxExpr GhcRn)
mb_neg SyntaxExpr GhcRn
eq -> do
        { let orig :: CtOrigin
orig = HsOverLit GhcRn -> CtOrigin
LiteralOrigin HsOverLit GhcRn
over_lit
        ; ((HsOverLit GhcTcId
lit', Maybe SyntaxExprTc
mb_neg'), SyntaxExprTc
eq')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> TcM (HsOverLit GhcTcId, Maybe SyntaxExprTc))
-> TcM ((HsOverLit GhcTcId, Maybe SyntaxExprTc), SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
eq [ExpSigmaType -> SyntaxOpType
SynType ExpSigmaType
pat_ty, SyntaxOpType
SynAny]
                          (TcType -> ExpSigmaType
mkCheckExpType TcType
boolTy) (([TcType] -> TcM (HsOverLit GhcTcId, Maybe SyntaxExprTc))
 -> TcM ((HsOverLit GhcTcId, Maybe SyntaxExprTc), SyntaxExprTc))
-> ([TcType] -> TcM (HsOverLit GhcTcId, Maybe SyntaxExprTc))
-> TcM ((HsOverLit GhcTcId, Maybe SyntaxExprTc), SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [TcType
neg_lit_ty] ->
               let new_over_lit :: TcType -> TcM (HsOverLit GhcTcId)
new_over_lit TcType
lit_ty = HsOverLit GhcRn -> ExpSigmaType -> TcM (HsOverLit GhcTcId)
newOverloadedLit HsOverLit GhcRn
over_lit
                                           (TcType -> ExpSigmaType
mkCheckExpType TcType
lit_ty)
               in case Maybe (SyntaxExpr GhcRn)
mb_neg of
                 Maybe (SyntaxExpr GhcRn)
Nothing  -> (, Maybe SyntaxExprTc
forall a. Maybe a
Nothing) (HsOverLit GhcTcId -> (HsOverLit GhcTcId, Maybe SyntaxExprTc))
-> TcM (HsOverLit GhcTcId)
-> TcM (HsOverLit GhcTcId, Maybe SyntaxExprTc)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
External instance of the constraint type forall env. Functor (IOEnv env)
<$> TcType -> TcM (HsOverLit GhcTcId)
new_over_lit TcType
neg_lit_ty
                 Just SyntaxExpr GhcRn
neg -> -- Negative literal
                             -- The 'negate' is re-mappable syntax
                   (SyntaxExprTc -> Maybe SyntaxExprTc)
-> (HsOverLit GhcTcId, SyntaxExprTc)
-> (HsOverLit GhcTcId, Maybe SyntaxExprTc)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> a (d, b) (d, c)
External instance of the constraint type Arrow (->)
second SyntaxExprTc -> Maybe SyntaxExprTc
forall a. a -> Maybe a
Just ((HsOverLit GhcTcId, SyntaxExprTc)
 -> (HsOverLit GhcTcId, Maybe SyntaxExprTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTcId, SyntaxExprTc)
-> TcM (HsOverLit GhcTcId, Maybe SyntaxExprTc)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
External instance of the constraint type forall env. Functor (IOEnv env)
<$>
                   (CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> TcM (HsOverLit GhcTcId))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTcId, SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
neg [SyntaxOpType
SynRho] (TcType -> ExpSigmaType
mkCheckExpType TcType
neg_lit_ty) (([TcType] -> TcM (HsOverLit GhcTcId))
 -> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTcId, SyntaxExprTc))
-> ([TcType] -> TcM (HsOverLit GhcTcId))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTcId, SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
                    \ [TcType
lit_ty] -> TcType -> TcM (HsOverLit GhcTcId)
new_over_lit TcType
lit_ty)

        ; r
res <- TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (XNPat GhcTcId
-> Located (HsOverLit GhcTcId)
-> Maybe (SyntaxExpr GhcTcId)
-> SyntaxExpr GhcTcId
-> Pat GhcTcId
forall p.
XNPat p
-> Located (HsOverLit p)
-> Maybe (SyntaxExpr p)
-> SyntaxExpr p
-> Pat p
NPat TcType
XNPat GhcTcId
pat_ty (SrcSpan -> HsOverLit GhcTcId -> Located (HsOverLit GhcTcId)
forall l e. l -> e -> GenLocated l e
L SrcSpan
l HsOverLit GhcTcId
lit') Maybe (SyntaxExpr GhcTcId)
Maybe SyntaxExprTc
mb_neg' SyntaxExpr GhcTcId
SyntaxExprTc
eq', r
res) }

{-
Note [NPlusK patterns]
~~~~~~~~~~~~~~~~~~~~~~
From

  case v of x + 5 -> blah

we get

  if v >= 5 then (\x -> blah) (v - 5) else ...

There are two bits of rebindable syntax:
  (>=) :: pat_ty -> lit1_ty -> Bool
  (-)  :: pat_ty -> lit2_ty -> var_ty

lit1_ty and lit2_ty could conceivably be different.
var_ty is the type inferred for x, the variable in the pattern.

If the pushed-down pattern type isn't a tau-type, the two pat_ty's above
could conceivably be different specializations. But this is very much
like the situation in Note [Case branches must be taus] in GHC.Tc.Gen.Match.
So we tauify the pat_ty before proceeding.

Note that we need to type-check the literal twice, because it is used
twice, and may be used at different types. The second HsOverLit stored in the
AST is used for the subtraction operation.
-}

-- See Note [NPlusK patterns]
  NPlusKPat XNPlusKPat GhcRn
_ (L SrcSpan
nm_loc IdP GhcRn
name)
               (L SrcSpan
loc HsOverLit GhcRn
lit) HsOverLit GhcRn
_ SyntaxExpr GhcRn
ge SyntaxExpr GhcRn
minus -> do
        { TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType ExpSigmaType
pat_ty
        ; let orig :: CtOrigin
orig = HsOverLit GhcRn -> CtOrigin
LiteralOrigin HsOverLit GhcRn
lit
        ; (HsOverLit GhcTcId
lit1', SyntaxExprTc
ge')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> TcM (HsOverLit GhcTcId))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTcId, SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
ge [TcType -> SyntaxOpType
synKnownType TcType
pat_ty, SyntaxOpType
SynRho]
                                  (TcType -> ExpSigmaType
mkCheckExpType TcType
boolTy) (([TcType] -> TcM (HsOverLit GhcTcId))
 -> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTcId, SyntaxExprTc))
-> ([TcType] -> TcM (HsOverLit GhcTcId))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTcId, SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [TcType
lit1_ty] ->
               HsOverLit GhcRn -> ExpSigmaType -> TcM (HsOverLit GhcTcId)
newOverloadedLit HsOverLit GhcRn
lit (TcType -> ExpSigmaType
mkCheckExpType TcType
lit1_ty)
        ; ((HsOverLit GhcTcId
lit2', HsWrapper
minus_wrap, TyVar
bndr_id), SyntaxExprTc
minus')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType] -> TcM (HsOverLit GhcTcId, HsWrapper, TyVar))
-> TcM ((HsOverLit GhcTcId, HsWrapper, TyVar), SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOpGen CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
minus [TcType -> SyntaxOpType
synKnownType TcType
pat_ty, SyntaxOpType
SynRho] SyntaxOpType
SynAny (([TcType] -> TcM (HsOverLit GhcTcId, HsWrapper, TyVar))
 -> TcM ((HsOverLit GhcTcId, HsWrapper, TyVar), SyntaxExprTc))
-> ([TcType] -> TcM (HsOverLit GhcTcId, HsWrapper, TyVar))
-> TcM ((HsOverLit GhcTcId, HsWrapper, TyVar), SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [TcType
lit2_ty, TcType
var_ty] ->
               do { HsOverLit GhcTcId
lit2' <- HsOverLit GhcRn -> ExpSigmaType -> TcM (HsOverLit GhcTcId)
newOverloadedLit HsOverLit GhcRn
lit (TcType -> ExpSigmaType
mkCheckExpType TcType
lit2_ty)
                  ; (HsWrapper
wrap, TyVar
bndr_id) <- SrcSpan -> TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
nm_loc (TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar))
-> TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall a b. (a -> b) -> a -> b
$
                                     PatEnv -> Name -> ExpSigmaType -> TcM (HsWrapper, TyVar)
tcPatBndr PatEnv
penv Name
IdP GhcRn
name (TcType -> ExpSigmaType
mkCheckExpType TcType
var_ty)
                           -- co :: var_ty ~ idType bndr_id

                           -- minus_wrap is applicable to minus'
                  ; (HsOverLit GhcTcId, HsWrapper, TyVar)
-> TcM (HsOverLit GhcTcId, HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsOverLit GhcTcId
lit2', HsWrapper
wrap, TyVar
bndr_id) }

        -- The Report says that n+k patterns must be in Integral
        -- but it's silly to insist on this in the RebindableSyntax case
        ; IOEnv (Env TcGblEnv TcLclEnv) Bool -> TcRn () -> TcRn ()
forall (m :: * -> *). Monad m => m Bool -> m () -> m ()
External instance of the constraint type forall m. Monad (IOEnv m)
unlessM (Extension -> IOEnv (Env TcGblEnv TcLclEnv) Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.RebindableSyntax) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
          do { Class
icls <- Name -> TcM Class
tcLookupClass Name
integralClassName
             ; CtOrigin -> [TcType] -> TcRn ()
instStupidTheta CtOrigin
orig [Class -> [TcType] -> TcType
mkClassPred Class
icls [TcType
pat_ty]] }

        ; r
res <- Name -> TyVar -> TcM r -> TcM r
forall a. Name -> TyVar -> TcM a -> TcM a
tcExtendIdEnv1 Name
IdP GhcRn
name TyVar
bndr_id TcM r
thing_inside

        ; let minus'' :: SyntaxExprTc
minus'' = case SyntaxExprTc
minus' of
                          SyntaxExprTc
NoSyntaxExprTc -> String -> SDoc -> SyntaxExprTc
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tc_pat NoSyntaxExprTc" (SyntaxExprTc -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable SyntaxExprTc
ppr SyntaxExprTc
minus')
                                   -- this should be statically avoidable
                                   -- Case (3) from Note [NoSyntaxExpr] in Hs.Expr
                          SyntaxExprTc { syn_expr :: SyntaxExprTc -> HsExpr GhcTcId
syn_expr = HsExpr GhcTcId
minus'_expr
                                       , syn_arg_wraps :: SyntaxExprTc -> [HsWrapper]
syn_arg_wraps = [HsWrapper]
minus'_arg_wraps
                                       , syn_res_wrap :: SyntaxExprTc -> HsWrapper
syn_res_wrap = HsWrapper
minus'_res_wrap }
                            -> SyntaxExprTc :: HsExpr GhcTcId -> [HsWrapper] -> HsWrapper -> SyntaxExprTc
SyntaxExprTc { syn_expr :: HsExpr GhcTcId
syn_expr = HsExpr GhcTcId
minus'_expr
                                            , syn_arg_wraps :: [HsWrapper]
syn_arg_wraps = [HsWrapper]
minus'_arg_wraps
                                            , syn_res_wrap :: HsWrapper
syn_res_wrap = HsWrapper
minus_wrap HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
minus'_res_wrap }
                             -- Oy. This should really be a record update, but
                             -- we get warnings if we try. #17783
              pat' :: Pat GhcTcId
pat' = XNPlusKPat GhcTcId
-> Located (IdP GhcTcId)
-> Located (HsOverLit GhcTcId)
-> HsOverLit GhcTcId
-> SyntaxExpr GhcTcId
-> SyntaxExpr GhcTcId
-> Pat GhcTcId
forall p.
XNPlusKPat p
-> Located (IdP p)
-> Located (HsOverLit p)
-> HsOverLit p
-> SyntaxExpr p
-> SyntaxExpr p
-> Pat p
NPlusKPat TcType
XNPlusKPat GhcTcId
pat_ty (SrcSpan -> TyVar -> GenLocated SrcSpan TyVar
forall l e. l -> e -> GenLocated l e
L SrcSpan
nm_loc TyVar
bndr_id) (SrcSpan -> HsOverLit GhcTcId -> Located (HsOverLit GhcTcId)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsOverLit GhcTcId
lit1') HsOverLit GhcTcId
lit2'
                               SyntaxExpr GhcTcId
SyntaxExprTc
ge' SyntaxExpr GhcTcId
SyntaxExprTc
minus''
        ; (Pat GhcTcId, r) -> TcM (Pat GhcTcId, r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (Pat GhcTcId
pat', r
res) }

-- HsSpliced is an annotation produced by 'GHC.Rename.Splice.rnSplicePat'.
-- Here we get rid of it and add the finalizers to the global environment.
--
-- See Note [Delaying modFinalizers in untyped splices] in GHC.Rename.Splice.
  SplicePat XSplicePat GhcRn
_ HsSplice GhcRn
splice -> case HsSplice GhcRn
splice of
    (HsSpliced XSpliced GhcRn
_ ThModFinalizers
mod_finalizers (HsSplicedPat Pat GhcRn
pat)) -> do
      { ThModFinalizers -> TcRn ()
addModFinalizersWithLclEnv ThModFinalizers
mod_finalizers
      ; ExpSigmaType -> Checker (Pat GhcRn) (Pat GhcTcId)
tc_pat ExpSigmaType
pat_ty PatEnv
penv Pat GhcRn
pat TcM r
thing_inside }
    HsSplice GhcRn
_ -> String -> TcM (Pat GhcTcId, r)
forall a. String -> a
panic String
"invalid splice in splice pat"


{-
Note [Hopping the LIE in lazy patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In a lazy pattern, we must *not* discharge constraints from the RHS
from dictionaries bound in the pattern.  E.g.
        f ~(C x) = 3
We can't discharge the Num constraint from dictionaries bound by
the pattern C!

So we have to make the constraints from thing_inside "hop around"
the pattern.  Hence the captureConstraints and emitConstraints.

The same thing ensures that equality constraints in a lazy match
are not made available in the RHS of the match. For example
        data T a where { T1 :: Int -> T Int; ... }
        f :: T a -> Int -> a
        f ~(T1 i) y = y
It's obviously not sound to refine a to Int in the right
hand side, because the argument might not match T1 at all!

Finally, a lazy pattern should not bind any existential type variables
because they won't be in scope when we do the desugaring


************************************************************************
*                                                                      *
            Pattern signatures   (pat :: type)
*                                                                      *
************************************************************************
-}

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

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

                -- A pattern binding cannot bind scoped type variables
                -- It is more convenient to make the test here
                -- than in the renamer
        { Bool -> TcRn () -> TcRn ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
External instance of the constraint type forall m. Applicative (IOEnv m)
when Bool
in_pat_bind (SDoc -> TcRn ()
addErr ([(Name, TyVar)] -> SDoc
patBindSigErr [(Name, TyVar)]
sig_tvs))

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

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

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


{- *********************************************************************
*                                                                      *
        Most of the work for constructors is here
        (the rest is in the ConPatIn case of tc_pat)
*                                                                      *
************************************************************************

[Pattern matching indexed data types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider the following declarations:

  data family Map k :: * -> *
  data instance Map (a, b) v = MapPair (Map a (Pair b v))

and a case expression

  case x :: Map (Int, c) w of MapPair m -> ...

As explained by [Wrappers for data instance tycons] in GHC.Types.Id.Make, the
worker/wrapper types for MapPair are

  $WMapPair :: forall a b v. Map a (Map a b v) -> Map (a, b) v
  $wMapPair :: forall a b v. Map a (Map a b v) -> :R123Map a b v

So, the type of the scrutinee is Map (Int, c) w, but the tycon of MapPair is
:R123Map, which means the straight use of boxySplitTyConApp would give a type
error.  Hence, the smart wrapper function boxySplitTyConAppWithFamily calls
boxySplitTyConApp with the family tycon Map instead, which gives us the family
type list {(Int, c), w}.  To get the correct split for :R123Map, we need to
unify the family type list {(Int, c), w} with the instance types {(a, b), v}
(provided by tyConFamInst_maybe together with the family tycon).  This
unification yields the substitution [a -> Int, b -> c, v -> w], which gives us
the split arguments for the representation tycon :R123Map as {Int, c, w}

In other words, boxySplitTyConAppWithFamily implicitly takes the coercion

  Co123Map a b v :: {Map (a, b) v ~ :R123Map a b v}

moving between representation and family type into account.  To produce type
correct Core, this coercion needs to be used to case the type of the scrutinee
from the family to the representation type.  This is achieved by
unwrapFamInstScrutinee using a CoPat around the result pattern.

Now it might appear seem as if we could have used the previous GADT type
refinement infrastructure of refineAlt and friends instead of the explicit
unification and CoPat generation.  However, that would be wrong.  Why?  The
whole point of GADT refinement is that the refinement is local to the case
alternative.  In contrast, the substitution generated by the unification of
the family type list and instance types needs to be propagated to the outside.
Imagine that in the above example, the type of the scrutinee would have been
(Map x w), then we would have unified {x, w} with {(a, b), v}, yielding the
substitution [x -> (a, b), v -> w].  In contrast to GADT matching, the
instantiation of x with (a, b) must be global; ie, it must be valid in *all*
alternatives of the case expression, whereas in the GADT case it might vary
between alternatives.

RIP GADT refinement: refinements have been replaced by the use of explicit
equality constraints that are used in conjunction with implication constraints
to express the local scope of GADT refinements.
-}

--      Running example:
-- MkT :: forall a b c. (a~[b]) => b -> c -> T a
--       with scrutinee of type (T ty)

tcConPat :: PatEnv -> Located Name
         -> ExpSigmaType           -- Type of the pattern
         -> HsConPatDetails GhcRn -> TcM a
         -> TcM (Pat GhcTcId, a)
tcConPat :: PatEnv
-> Located Name
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
tcConPat PatEnv
penv con_lname :: Located Name
con_lname@(L SrcSpan
_ Name
con_name) ExpSigmaType
pat_ty HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
  = do  { ConLike
con_like <- Name -> TcM ConLike
tcLookupConLike Name
con_name
        ; case ConLike
con_like of
            RealDataCon DataCon
data_con -> PatEnv
-> Located Name
-> DataCon
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
forall a.
PatEnv
-> Located Name
-> DataCon
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
tcDataConPat PatEnv
penv Located Name
con_lname DataCon
data_con
                                                 ExpSigmaType
pat_ty HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
            PatSynCon PatSyn
pat_syn -> PatEnv
-> Located Name
-> PatSyn
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
forall a.
PatEnv
-> Located Name
-> PatSyn
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
tcPatSynPat PatEnv
penv Located Name
con_lname PatSyn
pat_syn
                                             ExpSigmaType
pat_ty HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
        }

tcDataConPat :: PatEnv -> Located Name -> DataCon
             -> ExpSigmaType               -- Type of the pattern
             -> HsConPatDetails GhcRn -> TcM a
             -> TcM (Pat GhcTcId, a)
tcDataConPat :: PatEnv
-> Located Name
-> DataCon
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
tcDataConPat PatEnv
penv (L SrcSpan
con_span Name
con_name) DataCon
data_con ExpSigmaType
pat_ty
             HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
  = do  { let tycon :: TyCon
tycon = DataCon -> TyCon
dataConTyCon DataCon
data_con
                  -- For data families this is the representation tycon
              ([TyVar]
univ_tvs, [TyVar]
ex_tvs, [EqSpec]
eq_spec, [TcType]
theta, [TcType]
arg_tys, TcType
_)
                = DataCon -> ([TyVar], [TyVar], [EqSpec], [TcType], [TcType], TcType)
dataConFullSig DataCon
data_con
              header :: GenLocated SrcSpan ConLike
header = SrcSpan -> ConLike -> GenLocated SrcSpan ConLike
forall l e. l -> e -> GenLocated l e
L SrcSpan
con_span (DataCon -> ConLike
RealDataCon DataCon
data_con)

          -- Instantiate the constructor type variables [a->ty]
          -- This may involve doing a family-instance coercion,
          -- and building a wrapper
        ; (HsWrapper
wrap, [TcType]
ctxt_res_tys) <- PatEnv -> TyCon -> ExpSigmaType -> TcM (HsWrapper, [TcType])
matchExpectedConTy PatEnv
penv TyCon
tycon ExpSigmaType
pat_ty
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty

          -- Add the stupid theta
        ; SrcSpan -> TcRn () -> TcRn ()
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
con_span (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$ DataCon -> [TcType] -> TcRn ()
addDataConStupidTheta DataCon
data_con [TcType]
ctxt_res_tys

        ; let all_arg_tys :: [TcType]
all_arg_tys = [EqSpec] -> [TcType]
eqSpecPreds [EqSpec]
eq_spec [TcType] -> [TcType] -> [TcType]
forall a. [a] -> [a] -> [a]
++ [TcType]
theta [TcType] -> [TcType] -> [TcType]
forall a. [a] -> [a] -> [a]
++ [TcType]
arg_tys
        ; [TyVar] -> [TcType] -> PatEnv -> TcRn ()
checkExistentials [TyVar]
ex_tvs [TcType]
all_arg_tys PatEnv
penv

        ; TCvSubst
tenv <- CtOrigin -> [TyVar] -> [TcType] -> TcM TCvSubst
instTyVarsWith CtOrigin
PatOrigin [TyVar]
univ_tvs [TcType]
ctxt_res_tys
                  -- NB: Do not use zipTvSubst!  See #14154
                  -- We want to create a well-kinded substitution, so
                  -- that the instantiated type is well-kinded

        ; (TCvSubst
tenv, [TyVar]
ex_tvs') <- TCvSubst -> [TyVar] -> TcM (TCvSubst, [TyVar])
tcInstSuperSkolTyVarsX TCvSubst
tenv [TyVar]
ex_tvs
                     -- Get location from monad, not from ex_tvs

        ; let -- pat_ty' = mkTyConApp tycon ctxt_res_tys
              -- pat_ty' is type of the actual constructor application
              -- pat_ty' /= pat_ty iff coi /= IdCo

              arg_tys' :: [TcType]
arg_tys' = HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTys TCvSubst
tenv [TcType]
arg_tys

        ; String -> SDoc -> TcRn ()
traceTc String
"tcConPat" ([SDoc] -> SDoc
vcat [ Name -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable Name
ppr Name
con_name
                                   , [TyVar] -> SDoc
pprTyVars [TyVar]
univ_tvs
                                   , [TyVar] -> SDoc
pprTyVars [TyVar]
ex_tvs
                                   , [EqSpec] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable EqSpec
ppr [EqSpec]
eq_spec
                                   , [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
theta
                                   , [TyVar] -> SDoc
pprTyVars [TyVar]
ex_tvs'
                                   , [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
ctxt_res_tys
                                   , [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
arg_tys'
                                   , HsConDetails
  (GenLocated SrcSpan (Pat GhcRn))
  (HsRecFields GhcRn (GenLocated SrcSpan (Pat GhcRn)))
-> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall arg rec.
(Outputable arg, Outputable rec) =>
Outputable (HsConDetails arg rec)
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (Pat (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
External instance of the constraint type forall arg p. Outputable arg => Outputable (HsRecFields p arg)
External instance of the constraint type forall l e.
(Outputable l, Outputable e) =>
Outputable (GenLocated l e)
External instance of the constraint type Outputable SrcSpan
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (Pat (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr HsConDetails
  (GenLocated SrcSpan (Pat GhcRn))
  (HsRecFields GhcRn (GenLocated SrcSpan (Pat GhcRn)))
HsConPatDetails GhcRn
arg_pats ])
        ; if [TyVar] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
External instance of the constraint type Foldable []
null [TyVar]
ex_tvs Bool -> Bool -> Bool
&& [EqSpec] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
External instance of the constraint type Foldable []
null [EqSpec]
eq_spec Bool -> Bool -> Bool
&& [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
External instance of the constraint type Foldable []
null [TcType]
theta
          then do { -- The common case; no class bindings etc
                    -- (see Note [Arrows and patterns])
                    (HsConDetails
  (Located (Pat GhcTcId))
  (HsRecFields GhcTcId (Located (Pat GhcTcId)))
arg_pats', a
res) <- ConLike
-> [TcType]
-> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTcId)
tcConArgs (DataCon -> ConLike
RealDataCon DataCon
data_con) [TcType]
arg_tys'
                                                  PatEnv
penv HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
                  ; let res_pat :: Pat GhcTcId
res_pat = ConPat :: forall p.
XConPat p -> Located (ConLikeP p) -> HsConPatDetails p -> Pat p
ConPat { pat_con :: Located (ConLikeP GhcTcId)
pat_con = GenLocated SrcSpan ConLike
Located (ConLikeP GhcTcId)
header
                                         , pat_args :: HsConPatDetails GhcTcId
pat_args = HsConDetails
  (Located (Pat GhcTcId))
  (HsRecFields GhcTcId (Located (Pat GhcTcId)))
HsConPatDetails GhcTcId
arg_pats'
                                         , pat_con_ext :: XConPat GhcTcId
pat_con_ext = ConPatTc :: [TcType]
-> [TyVar] -> [TyVar] -> TcEvBinds -> HsWrapper -> ConPatTc
ConPatTc
                                           { cpt_tvs :: [TyVar]
cpt_tvs = [], cpt_dicts :: [TyVar]
cpt_dicts = []
                                           , cpt_binds :: TcEvBinds
cpt_binds = TcEvBinds
emptyTcEvBinds
                                           , cpt_arg_tys :: [TcType]
cpt_arg_tys = [TcType]
ctxt_res_tys
                                           , cpt_wrap :: HsWrapper
cpt_wrap = HsWrapper
idHsWrapper
                                           }
                                         }

                  ; (Pat GhcTcId, a) -> TcM (Pat GhcTcId, a)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
wrap Pat GhcTcId
res_pat TcType
pat_ty, a
res) }

          else do   -- The general case, with existential,
                    -- and local equality constraints
        { let theta' :: [TcType]
theta'     = HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTheta TCvSubst
tenv ([EqSpec] -> [TcType]
eqSpecPreds [EqSpec]
eq_spec [TcType] -> [TcType] -> [TcType]
forall a. [a] -> [a] -> [a]
++ [TcType]
theta)
                           -- order is *important* as we generate the list of
                           -- dictionary binders from theta'
              no_equalities :: Bool
no_equalities = [EqSpec] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
External instance of the constraint type Foldable []
null [EqSpec]
eq_spec Bool -> Bool -> Bool
&& Bool -> Bool
not ((TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
External instance of the constraint type Foldable []
any TcType -> Bool
isEqPred [TcType]
theta)
              skol_info :: SkolemInfo
skol_info = ConLike -> HsMatchContext GhcRn -> SkolemInfo
PatSkol (DataCon -> ConLike
RealDataCon DataCon
data_con) HsMatchContext GhcRn
mc
              mc :: HsMatchContext GhcRn
mc = case PatEnv -> PatCtxt
pe_ctxt PatEnv
penv of
                     LamPat HsMatchContext GhcRn
mc -> HsMatchContext GhcRn
mc
                     LetPat {} -> HsMatchContext GhcRn
forall p. HsMatchContext p
PatBindRhs

        ; Bool
gadts_on    <- Extension -> IOEnv (Env TcGblEnv TcLclEnv) Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.GADTs
        ; Bool
families_on <- Extension -> IOEnv (Env TcGblEnv TcLclEnv) Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.TypeFamilies
        ; Bool -> SDoc -> TcRn ()
checkTc (Bool
no_equalities Bool -> Bool -> Bool
|| Bool
gadts_on Bool -> Bool -> Bool
|| Bool
families_on)
                  (String -> SDoc
text String
"A pattern match on a GADT requires the" SDoc -> SDoc -> SDoc
<+>
                   String -> SDoc
text String
"GADTs or TypeFamilies language extension")
                  -- #2905 decided that a *pattern-match* of a GADT
                  -- should require the GADT language flag.
                  -- Re TypeFamilies see also #7156

        ; [TyVar]
given <- [TcType] -> TcM [TyVar]
newEvVars [TcType]
theta'
        ; (TcEvBinds
ev_binds, (HsConDetails
  (Located (Pat GhcTcId))
  (HsRecFields GhcTcId (Located (Pat GhcTcId)))
arg_pats', a
res))
             <- SkolemInfo
-> [TyVar]
-> [TyVar]
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (Located (Pat GhcTcId))
        (HsRecFields GhcTcId (Located (Pat GhcTcId))),
      a)
-> TcM
     (TcEvBinds,
      (HsConDetails
         (Located (Pat GhcTcId))
         (HsRecFields GhcTcId (Located (Pat GhcTcId))),
       a))
forall result.
SkolemInfo
-> [TyVar] -> [TyVar] -> TcM result -> TcM (TcEvBinds, result)
checkConstraints SkolemInfo
skol_info [TyVar]
ex_tvs' [TyVar]
given (IOEnv
   (Env TcGblEnv TcLclEnv)
   (HsConDetails
      (Located (Pat GhcTcId))
      (HsRecFields GhcTcId (Located (Pat GhcTcId))),
    a)
 -> TcM
      (TcEvBinds,
       (HsConDetails
          (Located (Pat GhcTcId))
          (HsRecFields GhcTcId (Located (Pat GhcTcId))),
        a)))
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (Located (Pat GhcTcId))
        (HsRecFields GhcTcId (Located (Pat GhcTcId))),
      a)
-> TcM
     (TcEvBinds,
      (HsConDetails
         (Located (Pat GhcTcId))
         (HsRecFields GhcTcId (Located (Pat GhcTcId))),
       a))
forall a b. (a -> b) -> a -> b
$
                ConLike
-> [TcType]
-> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTcId)
tcConArgs (DataCon -> ConLike
RealDataCon DataCon
data_con) [TcType]
arg_tys' PatEnv
penv HsConPatDetails GhcRn
arg_pats TcM a
thing_inside

        ; let res_pat :: Pat GhcTcId
res_pat = ConPat :: forall p.
XConPat p -> Located (ConLikeP p) -> HsConPatDetails p -> Pat p
ConPat
                { pat_con :: Located (ConLikeP GhcTcId)
pat_con   = GenLocated SrcSpan ConLike
Located (ConLikeP GhcTcId)
header
                , pat_args :: HsConPatDetails GhcTcId
pat_args  = HsConDetails
  (Located (Pat GhcTcId))
  (HsRecFields GhcTcId (Located (Pat GhcTcId)))
HsConPatDetails GhcTcId
arg_pats'
                , pat_con_ext :: XConPat GhcTcId
pat_con_ext = ConPatTc :: [TcType]
-> [TyVar] -> [TyVar] -> TcEvBinds -> HsWrapper -> ConPatTc
ConPatTc
                  { cpt_tvs :: [TyVar]
cpt_tvs   = [TyVar]
ex_tvs'
                  , cpt_dicts :: [TyVar]
cpt_dicts = [TyVar]
given
                  , cpt_binds :: TcEvBinds
cpt_binds = TcEvBinds
ev_binds
                  , cpt_arg_tys :: [TcType]
cpt_arg_tys = [TcType]
ctxt_res_tys
                  , cpt_wrap :: HsWrapper
cpt_wrap  = HsWrapper
idHsWrapper
                  }
                }
        ; (Pat GhcTcId, a) -> TcM (Pat GhcTcId, a)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
wrap Pat GhcTcId
res_pat TcType
pat_ty, a
res)
        } }

tcPatSynPat :: PatEnv -> Located Name -> PatSyn
            -> ExpSigmaType                -- Type of the pattern
            -> HsConPatDetails GhcRn -> TcM a
            -> TcM (Pat GhcTcId, a)
tcPatSynPat :: PatEnv
-> Located Name
-> PatSyn
-> ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTcId, a)
tcPatSynPat PatEnv
penv (L SrcSpan
con_span Name
_) PatSyn
pat_syn ExpSigmaType
pat_ty HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
  = do  { let ([TyVar]
univ_tvs, [TcType]
req_theta, [TyVar]
ex_tvs, [TcType]
prov_theta, [TcType]
arg_tys, TcType
ty) = PatSyn -> ([TyVar], [TcType], [TyVar], [TcType], [TcType], TcType)
patSynSig PatSyn
pat_syn

        ; (TCvSubst
subst, [TyVar]
univ_tvs') <- [TyVar] -> TcM (TCvSubst, [TyVar])
newMetaTyVars [TyVar]
univ_tvs

        ; let all_arg_tys :: [TcType]
all_arg_tys = TcType
ty TcType -> [TcType] -> [TcType]
forall a. a -> [a] -> [a]
: [TcType]
prov_theta [TcType] -> [TcType] -> [TcType]
forall a. [a] -> [a] -> [a]
++ [TcType]
arg_tys
        ; [TyVar] -> [TcType] -> PatEnv -> TcRn ()
checkExistentials [TyVar]
ex_tvs [TcType]
all_arg_tys PatEnv
penv
        ; (TCvSubst
tenv, [TyVar]
ex_tvs') <- TCvSubst -> [TyVar] -> TcM (TCvSubst, [TyVar])
tcInstSuperSkolTyVarsX TCvSubst
subst [TyVar]
ex_tvs
        ; let ty' :: TcType
ty'         = HasCallStack => TCvSubst -> TcType -> TcType
TCvSubst -> TcType -> TcType
substTy TCvSubst
tenv TcType
ty
              arg_tys' :: [TcType]
arg_tys'    = HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTys TCvSubst
tenv [TcType]
arg_tys
              prov_theta' :: [TcType]
prov_theta' = HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTheta TCvSubst
tenv [TcType]
prov_theta
              req_theta' :: [TcType]
req_theta'  = HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTheta TCvSubst
tenv [TcType]
req_theta

        ; HsWrapper
wrap <- PatEnv -> ExpSigmaType -> TcType -> TcM HsWrapper
tc_sub_type PatEnv
penv ExpSigmaType
pat_ty TcType
ty'
        ; String -> SDoc -> TcRn ()
traceTc String
"tcPatSynPat" (PatSyn -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable PatSyn
ppr PatSyn
pat_syn SDoc -> SDoc -> SDoc
$$
                                 ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable ExpSigmaType
ppr ExpSigmaType
pat_ty SDoc -> SDoc -> SDoc
$$
                                 TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
ty' SDoc -> SDoc -> SDoc
$$
                                 [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TyVar
ppr [TyVar]
ex_tvs' SDoc -> SDoc -> SDoc
$$
                                 [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
prov_theta' SDoc -> SDoc -> SDoc
$$
                                 [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
req_theta' SDoc -> SDoc -> SDoc
$$
                                 [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
arg_tys')

        ; [TyVar]
prov_dicts' <- [TcType] -> TcM [TyVar]
newEvVars [TcType]
prov_theta'

        ; let skol_info :: SkolemInfo
skol_info = case PatEnv -> PatCtxt
pe_ctxt PatEnv
penv of
                            LamPat HsMatchContext GhcRn
mc -> ConLike -> HsMatchContext GhcRn -> SkolemInfo
PatSkol (PatSyn -> ConLike
PatSynCon PatSyn
pat_syn) HsMatchContext GhcRn
mc
                            LetPat {} -> SkolemInfo
UnkSkol -- Doesn't matter

        ; HsWrapper
req_wrap <- CtOrigin -> [TcType] -> [TcType] -> TcM HsWrapper
instCall CtOrigin
PatOrigin ([TyVar] -> [TcType]
mkTyVarTys [TyVar]
univ_tvs') [TcType]
req_theta'
        ; String -> SDoc -> TcRn ()
traceTc String
"instCall" (HsWrapper -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable HsWrapper
ppr HsWrapper
req_wrap)

        ; String -> SDoc -> TcRn ()
traceTc String
"checkConstraints {" SDoc
Outputable.empty
        ; (TcEvBinds
ev_binds, (HsConDetails
  (Located (Pat GhcTcId))
  (HsRecFields GhcTcId (Located (Pat GhcTcId)))
arg_pats', a
res))
             <- SkolemInfo
-> [TyVar]
-> [TyVar]
-> TcM
     (HsConDetails
        (Located (Pat GhcTcId))
        (HsRecFields GhcTcId (Located (Pat GhcTcId))),
      a)
-> TcM
     (TcEvBinds,
      (HsConDetails
         (Located (Pat GhcTcId))
         (HsRecFields GhcTcId (Located (Pat GhcTcId))),
       a))
forall result.
SkolemInfo
-> [TyVar] -> [TyVar] -> TcM result -> TcM (TcEvBinds, result)
checkConstraints SkolemInfo
skol_info [TyVar]
ex_tvs' [TyVar]
prov_dicts' (TcM
   (HsConDetails
      (Located (Pat GhcTcId))
      (HsRecFields GhcTcId (Located (Pat GhcTcId))),
    a)
 -> TcM
      (TcEvBinds,
       (HsConDetails
          (Located (Pat GhcTcId))
          (HsRecFields GhcTcId (Located (Pat GhcTcId))),
        a)))
-> TcM
     (HsConDetails
        (Located (Pat GhcTcId))
        (HsRecFields GhcTcId (Located (Pat GhcTcId))),
      a)
-> TcM
     (TcEvBinds,
      (HsConDetails
         (Located (Pat GhcTcId))
         (HsRecFields GhcTcId (Located (Pat GhcTcId))),
       a))
forall a b. (a -> b) -> a -> b
$
                ConLike
-> [TcType]
-> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTcId)
tcConArgs (PatSyn -> ConLike
PatSynCon PatSyn
pat_syn) [TcType]
arg_tys' PatEnv
penv HsConPatDetails GhcRn
arg_pats TcM a
thing_inside

        ; String -> SDoc -> TcRn ()
traceTc String
"checkConstraints }" (TcEvBinds -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcEvBinds
ppr TcEvBinds
ev_binds)
        ; let res_pat :: Pat GhcTcId
res_pat = ConPat :: forall p.
XConPat p -> Located (ConLikeP p) -> HsConPatDetails p -> Pat p
ConPat { pat_con :: Located (ConLikeP GhcTcId)
pat_con   = SrcSpan -> ConLike -> GenLocated SrcSpan ConLike
forall l e. l -> e -> GenLocated l e
L SrcSpan
con_span (ConLike -> GenLocated SrcSpan ConLike)
-> ConLike -> GenLocated SrcSpan ConLike
forall a b. (a -> b) -> a -> b
$ PatSyn -> ConLike
PatSynCon PatSyn
pat_syn
                               , pat_args :: HsConPatDetails GhcTcId
pat_args  = HsConDetails
  (Located (Pat GhcTcId))
  (HsRecFields GhcTcId (Located (Pat GhcTcId)))
HsConPatDetails GhcTcId
arg_pats'
                               , pat_con_ext :: XConPat GhcTcId
pat_con_ext = ConPatTc :: [TcType]
-> [TyVar] -> [TyVar] -> TcEvBinds -> HsWrapper -> ConPatTc
ConPatTc
                                 { cpt_tvs :: [TyVar]
cpt_tvs   = [TyVar]
ex_tvs'
                                 , cpt_dicts :: [TyVar]
cpt_dicts = [TyVar]
prov_dicts'
                                 , cpt_binds :: TcEvBinds
cpt_binds = TcEvBinds
ev_binds
                                 , cpt_arg_tys :: [TcType]
cpt_arg_tys = [TyVar] -> [TcType]
mkTyVarTys [TyVar]
univ_tvs'
                                 , cpt_wrap :: HsWrapper
cpt_wrap  = HsWrapper
req_wrap
                                 }
                               }
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_ty
        ; (Pat GhcTcId, a) -> TcM (Pat GhcTcId, a)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsWrapper -> Pat GhcTcId -> TcType -> Pat GhcTcId
mkHsWrapPat HsWrapper
wrap Pat GhcTcId
res_pat TcType
pat_ty, a
res) }

----------------------------
-- | Convenient wrapper for calling a matchExpectedXXX function
matchExpectedPatTy :: (TcRhoType -> TcM (TcCoercionN, a))
                    -> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
-- See Note [Matching polytyped patterns]
-- Returns a wrapper : pat_ty ~R inner_ty
matchExpectedPatTy :: (TcType -> TcM (TcCoercion, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy TcType -> TcM (TcCoercion, a)
inner_match (PE { pe_orig :: PatEnv -> CtOrigin
pe_orig = CtOrigin
orig }) ExpSigmaType
pat_ty
  = do { TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType ExpSigmaType
pat_ty
       ; (HsWrapper
wrap, TcType
pat_rho) <- CtOrigin -> TcType -> TcM (HsWrapper, TcType)
topInstantiate CtOrigin
orig TcType
pat_ty
       ; (TcCoercion
co, a
res) <- TcType -> TcM (TcCoercion, a)
inner_match TcType
pat_rho
       ; String -> SDoc -> TcRn ()
traceTc String
"matchExpectedPatTy" (TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
pat_ty SDoc -> SDoc -> SDoc
$$ HsWrapper -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable HsWrapper
ppr HsWrapper
wrap)
       ; (HsWrapper, a) -> TcM (HsWrapper, a)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (TcCoercion -> HsWrapper
mkWpCastN (TcCoercion -> TcCoercion
mkTcSymCo TcCoercion
co) HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
wrap, a
res) }

----------------------------
matchExpectedConTy :: PatEnv
                   -> TyCon      -- The TyCon that this data
                                 -- constructor actually returns
                                 -- In the case of a data family this is
                                 -- the /representation/ TyCon
                   -> ExpSigmaType  -- The type of the pattern; in the case
                                    -- of a data family this would mention
                                    -- the /family/ TyCon
                   -> TcM (HsWrapper, [TcSigmaType])
-- See Note [Matching constructor patterns]
-- Returns a wrapper : pat_ty "->" T ty1 ... tyn
matchExpectedConTy :: PatEnv -> TyCon -> ExpSigmaType -> TcM (HsWrapper, [TcType])
matchExpectedConTy (PE { pe_orig :: PatEnv -> CtOrigin
pe_orig = CtOrigin
orig }) TyCon
data_tc ExpSigmaType
exp_pat_ty
  | Just (TyCon
fam_tc, [TcType]
fam_args, CoAxiom Unbranched
co_tc) <- TyCon -> Maybe (TyCon, [TcType], CoAxiom Unbranched)
tyConFamInstSig_maybe TyCon
data_tc
         -- Comments refer to Note [Matching constructor patterns]
         -- co_tc :: forall a. T [a] ~ T7 a
  = do { TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType ExpSigmaType
exp_pat_ty
       ; (HsWrapper
wrap, TcType
pat_rho) <- CtOrigin -> TcType -> TcM (HsWrapper, TcType)
topInstantiate CtOrigin
orig TcType
pat_ty

       ; (TCvSubst
subst, [TyVar]
tvs') <- [TyVar] -> TcM (TCvSubst, [TyVar])
newMetaTyVars (TyCon -> [TyVar]
tyConTyVars TyCon
data_tc)
             -- tys = [ty1,ty2]

       ; String -> SDoc -> TcRn ()
traceTc String
"matchExpectedConTy" ([SDoc] -> SDoc
vcat [TyCon -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TyCon
ppr TyCon
data_tc,
                                             [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TyVar
ppr (TyCon -> [TyVar]
tyConTyVars TyCon
data_tc),
                                             TyCon -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TyCon
ppr TyCon
fam_tc, [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
fam_args,
                                             ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable ExpSigmaType
ppr ExpSigmaType
exp_pat_ty,
                                             TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
pat_ty,
                                             TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
pat_rho, HsWrapper -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable HsWrapper
ppr HsWrapper
wrap])
       ; TcCoercion
co1 <- Maybe (HsExpr GhcRn) -> TcType -> TcType -> TcM TcCoercion
unifyType Maybe (HsExpr GhcRn)
forall a. Maybe a
Nothing (TyCon -> [TcType] -> TcType
mkTyConApp TyCon
fam_tc (HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTys TCvSubst
subst [TcType]
fam_args)) TcType
pat_rho
             -- co1 : T (ty1,ty2) ~N pat_rho
             -- could use tcSubType here... but it's the wrong way round
             -- for actual vs. expected in error messages.

       ; let tys' :: [TcType]
tys' = [TyVar] -> [TcType]
mkTyVarTys [TyVar]
tvs'
             co2 :: TcCoercion
co2 = CoAxiom Unbranched -> [TcType] -> [TcCoercion] -> TcCoercion
mkTcUnbranchedAxInstCo CoAxiom Unbranched
co_tc [TcType]
tys' []
             -- co2 : T (ty1,ty2) ~R T7 ty1 ty2

             full_co :: TcCoercion
full_co = TcCoercion -> TcCoercion
mkTcSubCo (TcCoercion -> TcCoercion
mkTcSymCo TcCoercion
co1) TcCoercion -> TcCoercion -> TcCoercion
`mkTcTransCo` TcCoercion
co2
             -- full_co :: pat_rho ~R T7 ty1 ty2

       ; (HsWrapper, [TcType]) -> TcM (HsWrapper, [TcType])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ( TcCoercion -> HsWrapper
mkWpCastR TcCoercion
full_co HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
wrap, [TcType]
tys') }

  | Bool
otherwise
  = do { TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType ExpSigmaType
exp_pat_ty
       ; (HsWrapper
wrap, TcType
pat_rho) <- CtOrigin -> TcType -> TcM (HsWrapper, TcType)
topInstantiate CtOrigin
orig TcType
pat_ty
       ; (TcCoercion
coi, [TcType]
tys) <- TyCon -> TcType -> TcM (TcCoercion, [TcType])
matchExpectedTyConApp TyCon
data_tc TcType
pat_rho
       ; (HsWrapper, [TcType]) -> TcM (HsWrapper, [TcType])
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (TcCoercion -> HsWrapper
mkWpCastN (TcCoercion -> TcCoercion
mkTcSymCo TcCoercion
coi) HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
wrap, [TcType]
tys) }

{-
Note [Matching constructor patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose (coi, tys) = matchExpectedConType data_tc pat_ty

 * In the simple case, pat_ty = tc tys

 * If pat_ty is a polytype, we want to instantiate it
   This is like part of a subsumption check.  Eg
      f :: (forall a. [a]) -> blah
      f [] = blah

 * In a type family case, suppose we have
          data family T a
          data instance T (p,q) = A p | B q
       Then we'll have internally generated
              data T7 p q = A p | B q
              axiom coT7 p q :: T (p,q) ~ T7 p q

       So if pat_ty = T (ty1,ty2), we return (coi, [ty1,ty2]) such that
           coi = coi2 . coi1 : T7 t ~ pat_ty
           coi1 : T (ty1,ty2) ~ pat_ty
           coi2 : T7 ty1 ty2 ~ T (ty1,ty2)

   For families we do all this matching here, not in the unifier,
   because we never want a whisper of the data_tycon to appear in
   error messages; it's a purely internal thing
-}

tcConArgs :: ConLike -> [TcSigmaType]
          -> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)

tcConArgs :: ConLike
-> [TcType]
-> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTcId)
tcConArgs ConLike
con_like [TcType]
arg_tys PatEnv
penv HsConPatDetails GhcRn
con_args TcM r
thing_inside = case HsConPatDetails GhcRn
con_args of
  PrefixCon [LPat GhcRn]
arg_pats -> do
        { Bool -> SDoc -> TcRn ()
checkTc (Int
con_arity Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
External instance of the constraint type Eq Int
== Int
no_of_args)     -- Check correct arity
                  (SDoc -> ConLike -> Int -> Int -> SDoc
forall a. Outputable a => SDoc -> a -> Int -> Int -> SDoc
External instance of the constraint type Outputable ConLike
arityErr (String -> SDoc
text String
"constructor") ConLike
con_like Int
con_arity Int
no_of_args)
        ; let pats_w_tys :: [(GenLocated SrcSpan (Pat GhcRn), TcType)]
pats_w_tys = String
-> [GenLocated SrcSpan (Pat GhcRn)]
-> [TcType]
-> [(GenLocated SrcSpan (Pat GhcRn), TcType)]
forall a b. String -> [a] -> [b] -> [(a, b)]
zipEqual String
"tcConArgs" [GenLocated SrcSpan (Pat GhcRn)]
[LPat GhcRn]
arg_pats [TcType]
arg_tys
        ; ([Located (Pat GhcTcId)]
arg_pats', r
res) <- Checker
  (GenLocated SrcSpan (Pat GhcRn), TcType) (Located (Pat GhcTcId))
-> Checker
     [(GenLocated SrcSpan (Pat GhcRn), TcType)] [Located (Pat GhcTcId)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple Checker
  (GenLocated SrcSpan (Pat GhcRn), TcType) (Located (Pat GhcTcId))
Checker (LPat GhcRn, TcType) (LPat GhcTcId)
tcConArg PatEnv
penv [(GenLocated SrcSpan (Pat GhcRn), TcType)]
pats_w_tys
                                              TcM r
thing_inside
        ; (HsConDetails
   (Located (Pat GhcTcId))
   (HsRecFields GhcTcId (Located (Pat GhcTcId))),
 r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (Located (Pat GhcTcId))
        (HsRecFields GhcTcId (Located (Pat GhcTcId))),
      r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ([Located (Pat GhcTcId)]
-> HsConDetails
     (Located (Pat GhcTcId))
     (HsRecFields GhcTcId (Located (Pat GhcTcId)))
forall arg rec. [arg] -> HsConDetails arg rec
PrefixCon [Located (Pat GhcTcId)]
arg_pats', r
res) }
    where
      con_arity :: Int
con_arity  = ConLike -> Int
conLikeArity ConLike
con_like
      no_of_args :: Int
no_of_args = [GenLocated SrcSpan (Pat GhcRn)] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
External instance of the constraint type Foldable []
length [GenLocated SrcSpan (Pat GhcRn)]
[LPat GhcRn]
arg_pats

  InfixCon LPat GhcRn
p1 LPat GhcRn
p2 -> do
        { Bool -> SDoc -> TcRn ()
checkTc (Int
con_arity Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
External instance of the constraint type Eq Int
== Int
2)      -- Check correct arity
                  (SDoc -> ConLike -> Int -> Int -> SDoc
forall a. Outputable a => SDoc -> a -> Int -> Int -> SDoc
External instance of the constraint type Outputable ConLike
arityErr (String -> SDoc
text String
"constructor") ConLike
con_like Int
con_arity Int
2)
        ; let [TcType
arg_ty1,TcType
arg_ty2] = [TcType]
arg_tys       -- This can't fail after the arity check
        ; ([Located (Pat GhcTcId)
p1',Located (Pat GhcTcId)
p2'], r
res) <- Checker
  (GenLocated SrcSpan (Pat GhcRn), TcType) (Located (Pat GhcTcId))
-> Checker
     [(GenLocated SrcSpan (Pat GhcRn), TcType)] [Located (Pat GhcTcId)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple Checker
  (GenLocated SrcSpan (Pat GhcRn), TcType) (Located (Pat GhcTcId))
Checker (LPat GhcRn, TcType) (LPat GhcTcId)
tcConArg PatEnv
penv [(GenLocated SrcSpan (Pat GhcRn)
LPat GhcRn
p1,TcType
arg_ty1),(GenLocated SrcSpan (Pat GhcRn)
LPat GhcRn
p2,TcType
arg_ty2)]
                                                  TcM r
thing_inside
        ; (HsConDetails
   (Located (Pat GhcTcId))
   (HsRecFields GhcTcId (Located (Pat GhcTcId))),
 r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (Located (Pat GhcTcId))
        (HsRecFields GhcTcId (Located (Pat GhcTcId))),
      r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (Located (Pat GhcTcId)
-> Located (Pat GhcTcId)
-> HsConDetails
     (Located (Pat GhcTcId))
     (HsRecFields GhcTcId (Located (Pat GhcTcId)))
forall arg rec. arg -> arg -> HsConDetails arg rec
InfixCon Located (Pat GhcTcId)
p1' Located (Pat GhcTcId)
p2', r
res) }
    where
      con_arity :: Int
con_arity  = ConLike -> Int
conLikeArity ConLike
con_like

  RecCon (HsRecFields [LHsRecField GhcRn (LPat GhcRn)]
rpats Maybe (Located Int)
dd) -> do
        { ([LHsRecField GhcTcId (Located (Pat GhcTcId))]
rpats', r
res) <- Checker
  (LHsRecField GhcRn (GenLocated SrcSpan (Pat GhcRn)))
  (LHsRecField GhcTcId (Located (Pat GhcTcId)))
-> Checker
     [LHsRecField GhcRn (GenLocated SrcSpan (Pat GhcRn))]
     [LHsRecField GhcTcId (Located (Pat GhcTcId))]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple Checker
  (LHsRecField GhcRn (GenLocated SrcSpan (Pat GhcRn)))
  (LHsRecField GhcTcId (Located (Pat GhcTcId)))
Checker
  (LHsRecField GhcRn (LPat GhcRn))
  (LHsRecField GhcTcId (LPat GhcTcId))
tc_field PatEnv
penv [LHsRecField GhcRn (GenLocated SrcSpan (Pat GhcRn))]
[LHsRecField GhcRn (LPat GhcRn)]
rpats TcM r
thing_inside
        ; (HsConDetails
   (Located (Pat GhcTcId))
   (HsRecFields GhcTcId (Located (Pat GhcTcId))),
 r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (Located (Pat GhcTcId))
        (HsRecFields GhcTcId (Located (Pat GhcTcId))),
      r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (HsRecFields GhcTcId (Located (Pat GhcTcId))
-> HsConDetails
     (Located (Pat GhcTcId))
     (HsRecFields GhcTcId (Located (Pat GhcTcId)))
forall arg rec. rec -> HsConDetails arg rec
RecCon ([LHsRecField GhcTcId (Located (Pat GhcTcId))]
-> Maybe (Located Int)
-> HsRecFields GhcTcId (Located (Pat GhcTcId))
forall p arg.
[LHsRecField p arg] -> Maybe (Located Int) -> HsRecFields p arg
HsRecFields [LHsRecField GhcTcId (Located (Pat GhcTcId))]
rpats' Maybe (Located Int)
dd), r
res) }
    where
      tc_field :: Checker (LHsRecField GhcRn (LPat GhcRn))
                          (LHsRecField GhcTcId (LPat GhcTcId))
      tc_field :: PatEnv
-> LHsRecField GhcRn (LPat GhcRn)
-> TcM r
-> TcM (LHsRecField GhcTcId (LPat GhcTcId), r)
tc_field PatEnv
penv
               (L SrcSpan
l (HsRecField (L SrcSpan
loc (FieldOcc XCFieldOcc GhcRn
sel (L SrcSpan
lr RdrName
rdr))) LPat GhcRn
pat Bool
pun))
               TcM r
thing_inside
        = do { TyVar
sel'   <- Name -> TcM TyVar
tcLookupId Name
XCFieldOcc GhcRn
sel
             ; TcType
pat_ty <- SrcSpan -> TcM TcType -> TcM TcType
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcM TcType -> TcM TcType) -> TcM TcType -> TcM TcType
forall a b. (a -> b) -> a -> b
$ Name -> FieldLabelString -> TcM TcType
find_field_ty Name
XCFieldOcc GhcRn
sel
                                            (OccName -> FieldLabelString
occNameFS (OccName -> FieldLabelString) -> OccName -> FieldLabelString
forall a b. (a -> b) -> a -> b
$ RdrName -> OccName
rdrNameOcc RdrName
rdr)
             ; (Located (Pat GhcTcId)
pat', r
res) <- PatEnv -> (LPat GhcRn, TcType) -> TcM r -> TcM (LPat GhcTcId, r)
Checker (LPat GhcRn, TcType) (LPat GhcTcId)
tcConArg PatEnv
penv (LPat GhcRn
pat, TcType
pat_ty) TcM r
thing_inside
             ; (LHsRecField GhcTcId (Located (Pat GhcTcId)), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (LHsRecField GhcTcId (Located (Pat GhcTcId)), r)
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return (SrcSpan
-> HsRecField' (FieldOcc GhcTcId) (Located (Pat GhcTcId))
-> LHsRecField GhcTcId (Located (Pat GhcTcId))
forall l e. l -> e -> GenLocated l e
L SrcSpan
l (Located (FieldOcc GhcTcId)
-> Located (Pat GhcTcId)
-> Bool
-> HsRecField' (FieldOcc GhcTcId) (Located (Pat GhcTcId))
forall id arg. Located id -> arg -> Bool -> HsRecField' id arg
HsRecField (SrcSpan -> FieldOcc GhcTcId -> Located (FieldOcc GhcTcId)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc (XCFieldOcc GhcTcId
-> GenLocated SrcSpan RdrName -> FieldOcc GhcTcId
forall pass.
XCFieldOcc pass -> GenLocated SrcSpan RdrName -> FieldOcc pass
FieldOcc TyVar
XCFieldOcc GhcTcId
sel' (SrcSpan -> RdrName -> GenLocated SrcSpan RdrName
forall l e. l -> e -> GenLocated l e
L SrcSpan
lr RdrName
rdr))) Located (Pat GhcTcId)
pat'
                                                                      Bool
pun), r
res) }


      find_field_ty :: Name -> FieldLabelString -> TcM TcType
      find_field_ty :: Name -> FieldLabelString -> TcM TcType
find_field_ty Name
sel FieldLabelString
lbl
        = case [TcType
ty | (FieldLabel
fl, TcType
ty) <- [(FieldLabel, TcType)]
field_tys, FieldLabel -> Name
forall a. FieldLbl a -> a
flSelector FieldLabel
fl Name -> Name -> Bool
forall a. Eq a => a -> a -> Bool
External instance of the constraint type Eq Name
== Name
sel ] of

                -- No matching field; chances are this field label comes from some
                -- other record type (or maybe none).  If this happens, just fail,
                -- otherwise we get crashes later (#8570), and similar:
                --      f (R { foo = (a,b) }) = a+b
                -- If foo isn't one of R's fields, we don't want to crash when
                -- typechecking the "a+b".
           [] -> SDoc -> TcM TcType
forall a. SDoc -> TcRn a
failWith (ConLike -> FieldLabelString -> SDoc
badFieldCon ConLike
con_like FieldLabelString
lbl)

                -- The normal case, when the field comes from the right constructor
           (TcType
pat_ty : [TcType]
extras) -> do
                String -> SDoc -> TcRn ()
traceTc String
"find_field" (TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
pat_ty SDoc -> SDoc -> SDoc
<+> [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall a. Outputable a => Outputable [a]
External instance of the constraint type Outputable TcType
ppr [TcType]
extras)
                ASSERT( null extras ) (return pat_ty)

      field_tys :: [(FieldLabel, TcType)]
      field_tys :: [(FieldLabel, TcType)]
field_tys = [FieldLabel] -> [TcType] -> [(FieldLabel, TcType)]
forall a b. [a] -> [b] -> [(a, b)]
zip (ConLike -> [FieldLabel]
conLikeFieldLabels ConLike
con_like) [TcType]
arg_tys
          -- Don't use zipEqual! If the constructor isn't really a record, then
          -- dataConFieldLabels will be empty (and each field in the pattern
          -- will generate an error below).

tcConArg :: Checker (LPat GhcRn, TcSigmaType) (LPat GhcTc)
tcConArg :: PatEnv -> (LPat GhcRn, TcType) -> TcM r -> TcM (LPat GhcTcId, r)
tcConArg PatEnv
penv (LPat GhcRn
arg_pat, TcType
arg_ty) = ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTcId)
tc_lpat (TcType -> ExpSigmaType
mkCheckExpType TcType
arg_ty) PatEnv
penv LPat GhcRn
arg_pat

addDataConStupidTheta :: DataCon -> [TcType] -> TcM ()
-- Instantiate the "stupid theta" of the data con, and throw
-- the constraints into the constraint set
addDataConStupidTheta :: DataCon -> [TcType] -> TcRn ()
addDataConStupidTheta DataCon
data_con [TcType]
inst_tys
  | [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
External instance of the constraint type Foldable []
null [TcType]
stupid_theta = () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ()
  | Bool
otherwise         = CtOrigin -> [TcType] -> TcRn ()
instStupidTheta CtOrigin
origin [TcType]
inst_theta
  where
    origin :: CtOrigin
origin = Name -> CtOrigin
OccurrenceOf (DataCon -> Name
dataConName DataCon
data_con)
        -- The origin should always report "occurrence of C"
        -- even when C occurs in a pattern
    stupid_theta :: [TcType]
stupid_theta = DataCon -> [TcType]
dataConStupidTheta DataCon
data_con
    univ_tvs :: [TyVar]
univ_tvs     = DataCon -> [TyVar]
dataConUnivTyVars DataCon
data_con
    tenv :: TCvSubst
tenv = [TyVar] -> [TcType] -> TCvSubst
HasDebugCallStack => [TyVar] -> [TcType] -> TCvSubst
External instance of the constraint type HasDebugCallStack
zipTvSubst [TyVar]
univ_tvs ([TyVar] -> [TcType] -> [TcType]
forall b a. [b] -> [a] -> [a]
takeList [TyVar]
univ_tvs [TcType]
inst_tys)
         -- NB: inst_tys can be longer than the univ tyvars
         --     because the constructor might have existentials
    inst_theta :: [TcType]
inst_theta = HasCallStack => TCvSubst -> [TcType] -> [TcType]
TCvSubst -> [TcType] -> [TcType]
substTheta TCvSubst
tenv [TcType]
stupid_theta

{-
Note [Arrows and patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~
(Oct 07) Arrow notation has the odd property that it involves
"holes in the scope". For example:
  expr :: Arrow a => a () Int
  expr = proc (y,z) -> do
          x <- term -< y
          expr' -< x

Here the 'proc (y,z)' binding scopes over the arrow tails but not the
arrow body (e.g 'term').  As things stand (bogusly) all the
constraints from the proc body are gathered together, so constraints
from 'term' will be seen by the tcPat for (y,z).  But we must *not*
bind constraints from 'term' here, because the desugarer will not make
these bindings scope over 'term'.

The Right Thing is not to confuse these constraints together. But for
now the Easy Thing is to ensure that we do not have existential or
GADT constraints in a 'proc', and to short-cut the constraint
simplification for such vanilla patterns so that it binds no
constraints. Hence the 'fast path' in tcConPat; but it's also a good
plan for ordinary vanilla patterns to bypass the constraint
simplification step.

************************************************************************
*                                                                      *
                Note [Pattern coercions]
*                                                                      *
************************************************************************

In principle, these program would be reasonable:

        f :: (forall a. a->a) -> Int
        f (x :: Int->Int) = x 3

        g :: (forall a. [a]) -> Bool
        g [] = True

In both cases, the function type signature restricts what arguments can be passed
in a call (to polymorphic ones).  The pattern type signature then instantiates this
type.  For example, in the first case,  (forall a. a->a) <= Int -> Int, and we
generate the translated term
        f = \x' :: (forall a. a->a).  let x = x' Int in x 3

From a type-system point of view, this is perfectly fine, but it's *very* seldom useful.
And it requires a significant amount of code to implement, because we need to decorate
the translated pattern with coercion functions (generated from the subsumption check
by tcSub).

So for now I'm just insisting on type *equality* in patterns.  No subsumption.

Old notes about desugaring, at a time when pattern coercions were handled:

A SigPat is a type coercion and must be handled one at a time.  We can't
combine them unless the type of the pattern inside is identical, and we don't
bother to check for that.  For example:

        data T = T1 Int | T2 Bool
        f :: (forall a. a -> a) -> T -> t
        f (g::Int->Int)   (T1 i) = T1 (g i)
        f (g::Bool->Bool) (T2 b) = T2 (g b)

We desugar this as follows:

        f = \ g::(forall a. a->a) t::T ->
            let gi = g Int
            in case t of { T1 i -> T1 (gi i)
                           other ->
            let gb = g Bool
            in case t of { T2 b -> T2 (gb b)
                           other -> fail }}

Note that we do not treat the first column of patterns as a
column of variables, because the coerced variables (gi, gb)
would be of different types.  So we get rather grotty code.
But I don't think this is a common case, and if it was we could
doubtless improve it.

Meanwhile, the strategy is:
        * treat each SigPat coercion (always non-identity coercions)
                as a separate block
        * deal with the stuff inside, and then wrap a binding round
                the result to bind the new variable (gi, gb, etc)


************************************************************************
*                                                                      *
\subsection{Errors and contexts}
*                                                                      *
************************************************************************

Note [Existential check]
~~~~~~~~~~~~~~~~~~~~~~~~
Lazy patterns can't bind existentials.  They arise in two ways:
  * Let bindings      let { C a b = e } in b
  * Twiddle patterns  f ~(C a b) = e
The pe_lazy field of PatEnv says whether we are inside a lazy
pattern (perhaps deeply)

See also Note [Typechecking pattern bindings] in GHC.Tc.Gen.Bind
-}

maybeWrapPatCtxt :: Pat GhcRn -> (TcM a -> TcM b) -> TcM a -> TcM b
-- Not all patterns are worth pushing a context
maybeWrapPatCtxt :: Pat GhcRn -> (TcM a -> TcM b) -> TcM a -> TcM b
maybeWrapPatCtxt Pat GhcRn
pat TcM a -> TcM b
tcm TcM a
thing_inside
  | Bool -> Bool
not (Pat GhcRn -> Bool
forall {p}. Pat p -> Bool
worth_wrapping Pat GhcRn
pat) = TcM a -> TcM b
tcm TcM a
thing_inside
  | Bool
otherwise                = SDoc -> TcM b -> TcM b
forall a. SDoc -> TcM a -> TcM a
addErrCtxt SDoc
msg (TcM b -> TcM b) -> TcM b -> TcM b
forall a b. (a -> b) -> a -> b
$ TcM a -> TcM b
tcm (TcM a -> TcM b) -> TcM a -> TcM b
forall a b. (a -> b) -> a -> b
$ TcM a -> TcM a
forall a. TcM a -> TcM a
popErrCtxt TcM a
thing_inside
                               -- Remember to pop before doing thing_inside
  where
   worth_wrapping :: Pat p -> Bool
worth_wrapping (VarPat {}) = Bool
False
   worth_wrapping (ParPat {}) = Bool
False
   worth_wrapping (AsPat {})  = Bool
False
   worth_wrapping Pat p
_           = Bool
True
   msg :: SDoc
msg = SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"In the pattern:") Int
2 (Pat GhcRn -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type forall (p :: Pass).
OutputableBndrId p =>
Outputable (Pat (GhcPass p))
External instance of the constraint type OutputableBndr Name
External instance of the constraint type OutputableBndr Name
External instance of the constraint type IsPass 'Renamed
ppr Pat GhcRn
pat)

-----------------------------------------------
checkExistentials :: [TyVar]   -- existentials
                  -> [Type]    -- argument types
                  -> PatEnv -> TcM ()
    -- See Note [Existential check]]
    -- See Note [Arrows and patterns]
checkExistentials :: [TyVar] -> [TcType] -> PatEnv -> TcRn ()
checkExistentials [TyVar]
ex_tvs [TcType]
tys PatEnv
_
  | (TyVar -> Bool) -> [TyVar] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
External instance of the constraint type Foldable []
all (Bool -> Bool
not (Bool -> Bool) -> (TyVar -> Bool) -> TyVar -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (TyVar -> VarSet -> Bool
`elemVarSet` [TcType] -> VarSet
tyCoVarsOfTypes [TcType]
tys)) [TyVar]
ex_tvs = () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ()
checkExistentials [TyVar]
_ [TcType]
_ (PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LetPat {}})         = () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ()
checkExistentials [TyVar]
_ [TcType]
_ (PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LamPat HsMatchContext GhcRn
ProcExpr })  = SDoc -> TcRn ()
forall a. SDoc -> TcRn a
failWithTc SDoc
existentialProcPat
checkExistentials [TyVar]
_ [TcType]
_ (PE { pe_lazy :: PatEnv -> Bool
pe_lazy = Bool
True })             = SDoc -> TcRn ()
forall a. SDoc -> TcRn a
failWithTc SDoc
existentialLazyPat
checkExistentials [TyVar]
_ [TcType]
_ PatEnv
_                                   = () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
External instance of the constraint type forall m. Monad (IOEnv m)
return ()

existentialLazyPat :: SDoc
existentialLazyPat :: SDoc
existentialLazyPat
  = SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"An existential or GADT data constructor cannot be used")
       Int
2 (String -> SDoc
text String
"inside a lazy (~) pattern")

existentialProcPat :: SDoc
existentialProcPat :: SDoc
existentialProcPat
  = String -> SDoc
text String
"Proc patterns cannot use existential or GADT data constructors"

badFieldCon :: ConLike -> FieldLabelString -> SDoc
badFieldCon :: ConLike -> FieldLabelString -> SDoc
badFieldCon ConLike
con FieldLabelString
field
  = [SDoc] -> SDoc
hsep [String -> SDoc
text String
"Constructor" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (ConLike -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable ConLike
ppr ConLike
con),
          String -> SDoc
text String
"does not have field", SDoc -> SDoc
quotes (FieldLabelString -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable FieldLabelString
ppr FieldLabelString
field)]

polyPatSig :: TcType -> SDoc
polyPatSig :: TcType -> SDoc
polyPatSig TcType
sig_ty
  = SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"Illegal polymorphic type signature in pattern:")
       Int
2 (TcType -> SDoc
forall a. Outputable a => a -> SDoc
External instance of the constraint type Outputable TcType
ppr TcType
sig_ty)