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

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

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

-}

-- | 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, tcInferRho )

import GHC.Hs
import GHC.Rename.Utils
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.Core.Multiplicity
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.Type
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 GHC.Utils.Panic
import qualified GHC.LanguageExtensions as LangExt
import Control.Arrow  ( second )
import Control.Monad
import GHC.Data.List.SetOps ( getNth )

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

tcLetPat :: (Name -> Maybe TcId)
         -> LetBndrSpec
         -> LPat GhcRn -> Scaled ExpSigmaType
         -> TcM a
         -> TcM (LPat GhcTc, a)
tcLetPat :: forall a.
(Name -> Maybe TyVar)
-> LetBndrSpec
-> LPat GhcRn
-> Scaled ExpSigmaType
-> TcM a
-> TcM (LPat GhcTc, a)
tcLetPat Name -> Maybe TyVar
sig_fn LetBndrSpec
no_gen LPat GhcRn
pat Scaled ExpSigmaType
pat_ty TcM a
thing_inside
  = do { TcLevel
bind_lvl <- TcM TcLevel
getTcLevel
       ; let ctxt :: PatCtxt
ctxt = 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 { pe_lazy :: Bool
pe_lazy = Bool
True
                       , pe_ctxt :: PatCtxt
pe_ctxt = PatCtxt
ctxt
                       , pe_orig :: CtOrigin
pe_orig = CtOrigin
PatOrigin }

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

-----------------
tcPats :: HsMatchContext GhcRn
       -> [LPat GhcRn]            -- Patterns,
       -> [Scaled ExpSigmaType]         --   and their types
       -> TcM a                  --   and the checker for the body
       -> TcM ([LPat GhcTc], 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 :: forall a.
HsMatchContext GhcRn
-> [LPat GhcRn]
-> [Scaled ExpSigmaType]
-> TcM a
-> TcM ([LPat GhcTc], a)
tcPats HsMatchContext GhcRn
ctxt [LPat GhcRn]
pats [Scaled ExpSigmaType]
pat_tys TcM a
thing_inside
  = [Scaled ExpSigmaType] -> Checker [LPat GhcRn] [LPat GhcTc]
tc_lpats [Scaled ExpSigmaType]
pat_tys PatEnv
penv [LPat GhcRn]
pats TcM a
thing_inside
  where
    penv :: PatEnv
penv = 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 GhcTc, a), TcSigmaType)
tcInferPat :: forall a.
HsMatchContext GhcRn
-> LPat GhcRn -> TcM a -> TcM ((LPat GhcTc, a), TcType)
tcInferPat HsMatchContext GhcRn
ctxt LPat GhcRn
pat TcM a
thing_inside
  = (ExpSigmaType -> TcM (LPat GhcTc, a))
-> TcM ((LPat GhcTc, a), TcType)
forall a. (ExpSigmaType -> TcM a) -> TcM (a, TcType)
tcInfer ((ExpSigmaType -> TcM (LPat GhcTc, a))
 -> TcM ((LPat GhcTc, a), TcType))
-> (ExpSigmaType -> TcM (LPat GhcTc, a))
-> TcM ((LPat GhcTc, a), TcType)
forall a b. (a -> b) -> a -> b
$ \ ExpSigmaType
exp_ty ->
    Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (ExpSigmaType -> Scaled ExpSigmaType
forall a. a -> Scaled a
unrestricted ExpSigmaType
exp_ty) PatEnv
penv LPat GhcRn
pat TcM a
thing_inside
 where
    penv :: PatEnv
penv = 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 -> Scaled TcSigmaType
           -> TcM a                     -- Checker for body
           -> TcM (LPat GhcTc, a)
tcCheckPat :: forall a.
HsMatchContext GhcRn
-> LPat GhcRn -> Scaled TcType -> TcM a -> TcM (LPat GhcTc, a)
tcCheckPat HsMatchContext GhcRn
ctxt = HsMatchContext GhcRn
-> CtOrigin
-> LPat GhcRn
-> Scaled TcType
-> TcM a
-> TcM (LPat GhcTc, a)
forall a.
HsMatchContext GhcRn
-> CtOrigin
-> LPat GhcRn
-> Scaled TcType
-> TcM a
-> TcM (LPat GhcTc, 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 -> Scaled TcSigmaType
             -> TcM a                 -- Checker for body
             -> TcM (LPat GhcTc, a)
tcCheckPat_O :: forall a.
HsMatchContext GhcRn
-> CtOrigin
-> LPat GhcRn
-> Scaled TcType
-> TcM a
-> TcM (LPat GhcTc, a)
tcCheckPat_O HsMatchContext GhcRn
ctxt CtOrigin
orig LPat GhcRn
pat (Scaled TcType
pat_mult TcType
pat_ty) TcM a
thing_inside
  = Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (TcType -> ExpSigmaType -> Scaled ExpSigmaType
forall a. TcType -> a -> Scaled a
Scaled TcType
pat_mult (TcType -> ExpSigmaType
mkCheckExpType TcType
pat_ty)) PatEnv
penv LPat GhcRn
pat TcM a
thing_inside
  where
    penv :: PatEnv
penv = 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 -> Scaled ExpSigmaType -> TcM (HsWrapper, TcId)
-- (coi, xp) = tcPatBndr penv x pat_ty
-- Then coi : pat_ty ~ typeof(xp)
--
tcPatBndr :: PatEnv -> Name -> Scaled 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 Scaled 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 (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled 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
ppr TyVar
bndr_id SDoc -> SDoc -> SDoc
$$ TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyVar -> TcType
idType TyVar
bndr_id) SDoc -> SDoc -> SDoc
$$ Scaled ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
ppr Scaled ExpSigmaType
exp_pat_ty)
       ; (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper
wrap, TyVar
bndr_id) }

  | Bool
otherwise                          -- No signature
  = do { (TcCoercionN
co, TcType
bndr_ty) <- case Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
exp_pat_ty of
             Check TcType
pat_ty    -> TcLevel
-> TcType -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, 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 (see tcConArg)
                                -- hence this assertion
                                do { TcType
bndr_ty <- InferResult -> TcM TcType
inferResultToType InferResult
infer_res
                                   ; (TcCoercionN, TcType)
-> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, TcType)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcType -> TcCoercionN
mkTcNomReflCo TcType
bndr_ty, TcType
bndr_ty) }
       ; let bndr_mult :: TcType
bndr_mult = Scaled ExpSigmaType -> TcType
forall a. Scaled a -> TcType
scaledMult Scaled ExpSigmaType
exp_pat_ty
       ; TyVar
bndr_id <- LetBndrSpec -> Name -> TcType -> TcType -> TcM TyVar
newLetBndr LetBndrSpec
no_gen Name
bndr_name TcType
bndr_mult TcType
bndr_ty
       ; String -> SDoc -> TcRn ()
traceTc String
"tcPatBndr(nosig)" ([SDoc] -> SDoc
vcat [ TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
bind_lvl
                                          , Scaled ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
ppr Scaled ExpSigmaType
exp_pat_ty, TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
bndr_ty, TcCoercionN -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcCoercionN
co
                                          , TyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyVar
bndr_id ])
       ; (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcCoercionN -> HsWrapper
mkWpCastN TcCoercionN
co, TyVar
bndr_id) }

tcPatBndr PatEnv
_ Name
bndr_name Scaled ExpSigmaType
pat_ty
  = do { let pat_mult :: TcType
pat_mult = Scaled ExpSigmaType -> TcType
forall a. Scaled a -> TcType
scaledMult Scaled ExpSigmaType
pat_ty
       ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
       ; String -> SDoc -> TcRn ()
traceTc String
"tcPatBndr(not let)" (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
bndr_name SDoc -> SDoc -> SDoc
$$ TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
pat_ty)
       ; (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper
idHsWrapper, Name -> TcType -> TcType -> TyVar
mkLocalIdOrCoVar Name
bndr_name TcType
pat_mult 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 -> Mult -> 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 -> TcType -> TcM TyVar
newLetBndr LetBndrSpec
LetLclBndr Name
name TcType
w TcType
ty
  = do { Name
mono_name <- Name -> TcM Name
cloneLocalName Name
name
       ; TyVar -> TcM TyVar
forall (m :: * -> *) a. Monad m => a -> m a
return (HasDebugCallStack => Name -> TcType -> TcType -> TyVar
Name -> TcType -> TcType -> TyVar
mkLocalId Name
mono_name TcType
w TcType
ty) }
newLetBndr (LetGblBndr TcPragEnv
prags) Name
name TcType
w TcType
ty
  = TyVar -> [LSig GhcRn] -> TcM TyVar
addInlinePrags (HasDebugCallStack => Name -> TcType -> TcType -> TyVar
Name -> TcType -> TcType -> TyVar
mkLocalId Name
name TcType
w 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 :: forall inp out. 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
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
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 :: Scaled ExpSigmaType
        -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat :: Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaType
pat_ty PatEnv
penv (L SrcSpanAnnA
span Pat GhcRn
pat) TcM r
thing_inside
  = SrcSpanAnnA -> TcRn (LPat GhcTc, r) -> TcRn (LPat GhcTc, r)
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnA
span (TcRn (LPat GhcTc, r) -> TcRn (LPat GhcTc, r))
-> TcRn (LPat GhcTc, r) -> TcRn (LPat GhcTc, r)
forall a b. (a -> b) -> a -> b
$
    do  { (Pat GhcTc
pat', r
res) <- Pat GhcRn
-> (TcM r -> TcM (Pat GhcTc, r)) -> TcM r -> TcM (Pat GhcTc, r)
forall a b. Pat GhcRn -> (TcM a -> TcM b) -> TcM a -> TcM b
maybeWrapPatCtxt Pat GhcRn
pat (Scaled ExpSigmaType -> Checker (Pat GhcRn) (Pat GhcTc)
tc_pat Scaled ExpSigmaType
pat_ty PatEnv
penv Pat GhcRn
pat)
                                          TcM r
thing_inside
        ; (GenLocated SrcSpanAnnA (Pat GhcTc), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
forall (m :: * -> *) a. Monad m => a -> m a
return (SrcSpanAnnA -> Pat GhcTc -> GenLocated SrcSpanAnnA (Pat GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnA
span Pat GhcTc
pat', r
res) }

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

--------------------
-- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
checkManyPattern :: Scaled a -> TcM HsWrapper
checkManyPattern :: forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled a
pat_ty = CtOrigin -> TcType -> TcType -> TcM HsWrapper
tcSubMult CtOrigin
NonLinearPatternOrigin TcType
Many (Scaled a -> TcType
forall a. Scaled a -> TcType
scaledMult Scaled a
pat_ty)

tc_pat  :: Scaled ExpSigmaType
        -- ^ Fully refined result type
        -> Checker (Pat GhcRn) (Pat GhcTc)
        -- ^ Translated pattern

tc_pat :: Scaled ExpSigmaType -> Checker (Pat GhcRn) (Pat GhcTc)
tc_pat Scaled ExpSigmaType
pat_ty PatEnv
penv Pat GhcRn
ps_pat TcM r
thing_inside = case Pat GhcRn
ps_pat of

  VarPat XVarPat GhcRn
x (L SrcSpanAnnN
l Name
name) -> do
        { (HsWrapper
wrap, TyVar
id) <- PatEnv -> Name -> Scaled ExpSigmaType -> TcM (HsWrapper, TyVar)
tcPatBndr PatEnv
penv Name
name Scaled ExpSigmaType
pat_ty
        ; (r
res, HsWrapper
mult_wrap) <- Name -> TcType -> TcM r -> TcM (r, HsWrapper)
forall a. Name -> TcType -> TcM a -> TcM (a, HsWrapper)
tcCheckUsage Name
name (Scaled ExpSigmaType -> TcType
forall a. Scaled a -> TcType
scaledMult Scaled ExpSigmaType
pat_ty) (TcM r -> TcM (r, HsWrapper)) -> TcM r -> TcM (r, HsWrapper)
forall a b. (a -> b) -> a -> b
$
                              Name -> TyVar -> TcM r -> TcM r
forall a. Name -> TyVar -> TcM a -> TcM a
tcExtendIdEnv1 Name
name TyVar
id TcM r
thing_inside
            -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat (HsWrapper
wrap HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
mult_wrap) (XVarPat GhcTc -> LIdP GhcTc -> Pat GhcTc
forall p. XVarPat p -> LIdP p -> Pat p
VarPat XVarPat GhcRn
XVarPat GhcTc
x (SrcSpanAnnN -> TyVar -> GenLocated SrcSpanAnnN TyVar
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
l TyVar
id)) TcType
pat_ty, r
res) }

  ParPat XParPat GhcRn
x LPat GhcRn
pat -> do
        { (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', r
res) <- Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaType
pat_ty PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (XParPat GhcTc -> LPat GhcTc -> Pat GhcTc
forall p. XParPat p -> LPat p -> Pat p
ParPat XParPat GhcRn
XParPat GhcTc
x GenLocated SrcSpanAnnA (Pat GhcTc)
LPat GhcTc
pat', r
res) }

  BangPat XBangPat GhcRn
x LPat GhcRn
pat -> do
        { (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', r
res) <- Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaType
pat_ty PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (XBangPat GhcTc -> LPat GhcTc -> Pat GhcTc
forall p. XBangPat p -> LPat p -> Pat p
BangPat XBangPat GhcRn
XBangPat GhcTc
x GenLocated SrcSpanAnnA (Pat GhcTc)
LPat GhcTc
pat', r
res) }

  LazyPat XLazyPat GhcRn
x LPat GhcRn
pat -> do
        { HsWrapper
mult_wrap <- Scaled ExpSigmaType -> TcM HsWrapper
forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled ExpSigmaType
pat_ty
            -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
        ; (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', (r
res, WantedConstraints
pat_ct))
                <- Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaType
pat_ty (PatEnv -> PatEnv
makeLazy PatEnv
penv) LPat GhcRn
pat (TcM (r, WantedConstraints)
 -> TcM (LPat GhcTc, (r, WantedConstraints)))
-> TcM (r, WantedConstraints)
-> TcM (LPat GhcTc, (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 (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; TcCoercionN
_ <- Maybe SDoc -> TcType -> TcType -> TcM TcCoercionN
unifyType Maybe SDoc
forall a. Maybe a
Nothing (HasDebugCallStack => TcType -> TcType
TcType -> TcType
tcTypeKind TcType
pat_ty) TcType
liftedTypeKind

        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
mult_wrap (XLazyPat GhcTc -> LPat GhcTc -> Pat GhcTc
forall p. XLazyPat p -> LPat p -> Pat p
LazyPat XLazyPat GhcRn
XLazyPat GhcTc
x GenLocated SrcSpanAnnA (Pat GhcTc)
LPat GhcTc
pat') TcType
pat_ty, r
res) }

  WildPat XWildPat GhcRn
_ -> do
        { HsWrapper
mult_wrap <- Scaled ExpSigmaType -> TcM HsWrapper
forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled ExpSigmaType
pat_ty
            -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
        ; r
res <- TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
mult_wrap (XWildPat GhcTc -> Pat GhcTc
forall p. XWildPat p -> Pat p
WildPat TcType
XWildPat GhcTc
pat_ty) TcType
pat_ty, r
res) }

  AsPat XAsPat GhcRn
x (L SrcSpanAnnN
nm_loc Name
name) LPat GhcRn
pat -> do
        { HsWrapper
mult_wrap <- Scaled ExpSigmaType -> TcM HsWrapper
forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled ExpSigmaType
pat_ty
            -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
        ; (HsWrapper
wrap, TyVar
bndr_id) <- SrcSpanAnnN -> TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnN
nm_loc (PatEnv -> Name -> Scaled ExpSigmaType -> TcM (HsWrapper, TyVar)
tcPatBndr PatEnv
penv Name
name Scaled ExpSigmaType
pat_ty)
        ; (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', r
res) <- Name
-> TyVar
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
forall a. Name -> TyVar -> TcM a -> TcM a
tcExtendIdEnv1 Name
name TyVar
bndr_id (IOEnv
   (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
forall a b. (a -> b) -> a -> b
$
                         Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Scaled ExpSigmaType
pat_ty Scaled ExpSigmaType -> ExpSigmaType -> Scaled ExpSigmaType
forall a b. Scaled a -> b -> Scaled b
`scaledSet`(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 (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat (HsWrapper
wrap HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
mult_wrap) (XAsPat GhcTc -> LIdP GhcTc -> LPat GhcTc -> Pat GhcTc
forall p. XAsPat p -> LIdP p -> LPat p -> Pat p
AsPat XAsPat GhcRn
XAsPat GhcTc
x (SrcSpanAnnN -> TyVar -> GenLocated SrcSpanAnnN TyVar
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
nm_loc TyVar
bndr_id) GenLocated SrcSpanAnnA (Pat GhcTc)
LPat GhcTc
pat') TcType
pat_ty, r
res) }

  ViewPat XViewPat GhcRn
_ LHsExpr GhcRn
expr LPat GhcRn
pat -> do
        { HsWrapper
mult_wrap <- Scaled ExpSigmaType -> TcM HsWrapper
forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled ExpSigmaType
pat_ty
         -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
         --
         -- It should be possible to have view patterns at linear (or otherwise
         -- non-Many) multiplicity. But it is not clear at the moment what
         -- restriction need to be put in place, if any, for linear view
         -- patterns to desugar to type-correct Core.

        ; (GenLocated SrcSpanAnnA (HsExpr GhcTc)
expr',TcType
expr_ty) <- LHsExpr GhcRn -> TcM (LHsExpr GhcTc, TcType)
tcInferRho LHsExpr GhcRn
expr
               -- Note [View patterns and polymorphism]

         -- Expression must be a function
        ; let herald :: SDoc
herald = String -> SDoc
text String
"A view pattern expression expects"
        ; (HsWrapper
expr_wrap1, Scaled TcType
_mult TcType
inf_arg_ty, TcType
inf_res_sigma)
            <- SDoc
-> Maybe SDoc
-> (Int, [Scaled TcType])
-> TcType
-> TcM (HsWrapper, Scaled TcType, TcType)
matchActualFunTySigma SDoc
herald (SDoc -> Maybe SDoc
forall a. a -> Maybe a
Just (GenLocated SrcSpanAnnA (HsExpr GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsExpr GhcRn)
LHsExpr GhcRn
expr)) (Int
1,[]) TcType
expr_ty
               -- See Note [View patterns and polymorphism]
               -- expr_wrap1 :: expr_ty "->" (inf_arg_ty -> inf_res_sigma)

         -- Check that overall pattern is more polymorphic than arg type
        ; HsWrapper
expr_wrap2 <- PatEnv -> ExpSigmaType -> TcType -> TcM HsWrapper
tc_sub_type PatEnv
penv (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty) TcType
inf_arg_ty
            -- expr_wrap2 :: pat_ty "->" inf_arg_ty

         -- Pattern must have inf_res_sigma
        ; (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', r
res) <- Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Scaled ExpSigmaType
pat_ty Scaled ExpSigmaType -> ExpSigmaType -> Scaled ExpSigmaType
forall a b. Scaled a -> b -> Scaled b
`scaledSet` TcType -> ExpSigmaType
mkCheckExpType TcType
inf_res_sigma) PatEnv
penv LPat GhcRn
pat TcM r
thing_inside

        ; let Scaled TcType
w ExpSigmaType
h_pat_ty = Scaled ExpSigmaType
pat_ty
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
h_pat_ty
        ; let expr_wrap2' :: HsWrapper
expr_wrap2' = HsWrapper
-> HsWrapper -> Scaled TcType -> TcType -> SDoc -> HsWrapper
mkWpFun HsWrapper
expr_wrap2 HsWrapper
idHsWrapper
                                    (TcType -> TcType -> Scaled TcType
forall a. TcType -> a -> Scaled a
Scaled TcType
w TcType
pat_ty) TcType
inf_res_sigma SDoc
doc
               -- expr_wrap2' :: (inf_arg_ty -> inf_res_sigma) "->"
               --                (pat_ty -> inf_res_sigma)
              expr_wrap :: HsWrapper
expr_wrap = HsWrapper
expr_wrap2' HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
expr_wrap1 HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
mult_wrap
              doc :: SDoc
doc = String -> SDoc
text String
"When checking the view pattern function:" SDoc -> SDoc -> SDoc
<+> (GenLocated SrcSpanAnnA (HsExpr GhcRn) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpanAnnA (HsExpr GhcRn)
LHsExpr GhcRn
expr)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (XViewPat GhcTc -> LHsExpr GhcTc -> LPat GhcTc -> Pat GhcTc
forall p. XViewPat p -> LHsExpr p -> LPat p -> Pat p
ViewPat TcType
XViewPat GhcTc
pat_ty (HsWrapper -> LHsExpr GhcTc -> LHsExpr GhcTc
mkLHsWrap HsWrapper
expr_wrap GenLocated SrcSpanAnnA (HsExpr GhcTc)
LHsExpr GhcTc
expr') GenLocated SrcSpanAnnA (Pat GhcTc)
LPat GhcTc
pat', r
res)}

{- Note [View patterns and polymorphism]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this exotic example:
   pair :: forall a. Bool -> a -> forall b. b -> (a,b)

   f :: Int -> blah
   f (pair True -> x) = ...here (x :: forall b. b -> (Int,b))

The expression (pair True) should have type
    pair True :: Int -> forall b. b -> (Int,b)
so that it is ready to consume the incoming Int. It should be an
arrow type (t1 -> t2); hence using (tcInferRho expr).

Then, when taking that arrow apart we want to get a *sigma* type
(forall b. b->(Int,b)), because that's what we want to bind 'x' to.
Fortunately that's what matchExpectedFunTySigma returns anyway.
-}

-- 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 (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled 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.
        ; (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', r
res) <- [(Name, TyVar)]
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
wcs      (IOEnv
   (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
forall a b. (a -> b) -> a -> b
$
                         [(Name, TyVar)]
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
tv_binds (IOEnv
   (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
 -> IOEnv
      (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r))
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
forall a b. (a -> b) -> a -> b
$
                         Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Scaled ExpSigmaType
pat_ty Scaled ExpSigmaType -> ExpSigmaType -> Scaled ExpSigmaType
forall a b. Scaled a -> b -> Scaled b
`scaledSet` TcType -> ExpSigmaType
mkCheckExpType TcType
inner_ty) PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
wrap (XSigPat GhcTc
-> LPat GhcTc -> HsPatSigType (NoGhcTc GhcTc) -> Pat GhcTc
forall p. XSigPat p -> LPat p -> HsPatSigType (NoGhcTc p) -> Pat p
SigPat TcType
XSigPat GhcTc
inner_ty GenLocated SrcSpanAnnA (Pat GhcTc)
LPat GhcTc
pat' HsPatSigType (NoGhcTc GhcRn)
HsPatSigType (NoGhcTc GhcTc)
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) (TcCoercionN, TcType))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, TcType)
forall a.
(TcType -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy TcType -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, TcType)
matchExpectedListTy PatEnv
penv (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; ([GenLocated SrcSpanAnnA (Pat GhcTc)]
pats', r
res) <- Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
-> Checker
     [GenLocated SrcSpanAnnA (Pat GhcRn)]
     [GenLocated SrcSpanAnnA (Pat GhcTc)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple (Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Scaled ExpSigmaType
pat_ty Scaled ExpSigmaType -> ExpSigmaType -> Scaled ExpSigmaType
forall a b. Scaled a -> b -> Scaled b
`scaledSet` TcType -> ExpSigmaType
mkCheckExpType TcType
elt_ty))
                                     PatEnv
penv [GenLocated SrcSpanAnnA (Pat GhcRn)]
[LPat GhcRn]
pats TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
coi
                         (XListPat GhcTc -> [LPat GhcTc] -> Pat GhcTc
forall p. XListPat p -> [LPat p] -> Pat p
ListPat (TcType -> Maybe (TcType, SyntaxExpr GhcTc) -> ListPatTc
ListPatTc TcType
elt_ty Maybe (TcType, SyntaxExpr GhcTc)
forall a. Maybe a
Nothing) [GenLocated SrcSpanAnnA (Pat GhcTc)]
[LPat GhcTc]
pats') TcType
pat_ty, r
res)
}

  ListPat (Just SyntaxExprRn
e) [LPat GhcRn]
pats -> do
        { TcType
tau_pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (([GenLocated SrcSpanAnnA (Pat GhcTc)]
pats', r
res, TcType
elt_ty), SyntaxExprTc
e')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType]
    -> [TcType]
    -> TcM ([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType))
-> TcM
     (([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType), SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType] -> [TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOpGen CtOrigin
ListOrigin SyntaxExprRn
e [ExpSigmaType -> SyntaxOpType
SynType (TcType -> ExpSigmaType
mkCheckExpType TcType
tau_pat_ty)]
                                          SyntaxOpType
SynList (([TcType]
  -> [TcType]
  -> TcM ([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType))
 -> TcM
      (([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType), SyntaxExprTc))
-> ([TcType]
    -> [TcType]
    -> TcM ([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType))
-> TcM
     (([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType), SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
                 \ [TcType
elt_ty] [TcType]
_ ->
                 do { ([GenLocated SrcSpanAnnA (Pat GhcTc)]
pats', r
res) <- Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
-> Checker
     [GenLocated SrcSpanAnnA (Pat GhcRn)]
     [GenLocated SrcSpanAnnA (Pat GhcTc)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple (Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Scaled ExpSigmaType
pat_ty Scaled ExpSigmaType -> ExpSigmaType -> Scaled ExpSigmaType
forall a b. Scaled a -> b -> Scaled b
`scaledSet` TcType -> ExpSigmaType
mkCheckExpType TcType
elt_ty))
                                                 PatEnv
penv [GenLocated SrcSpanAnnA (Pat GhcRn)]
[LPat GhcRn]
pats TcM r
thing_inside
                    ; ([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType)
-> TcM ([GenLocated SrcSpanAnnA (Pat GhcTc)], r, TcType)
forall (m :: * -> *) a. Monad m => a -> m a
return ([GenLocated SrcSpanAnnA (Pat GhcTc)]
pats', r
res, TcType
elt_ty) }
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (XListPat GhcTc -> [LPat GhcTc] -> Pat GhcTc
forall p. XListPat p -> [LPat p] -> Pat p
ListPat (TcType -> Maybe (TcType, SyntaxExpr GhcTc) -> ListPatTc
ListPatTc TcType
elt_ty ((TcType, SyntaxExprTc) -> Maybe (TcType, SyntaxExprTc)
forall a. a -> Maybe a
Just (TcType
tau_pat_ty,SyntaxExprTc
e'))) [GenLocated SrcSpanAnnA (Pat GhcTc)]
[LPat GhcTc]
pats', r
res)
}

  TuplePat XTuplePat GhcRn
_ [LPat GhcRn]
pats Boxity
boxity -> do
        { let arity :: Int
arity = [GenLocated SrcSpanAnnA (Pat GhcRn)] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [GenLocated SrcSpanAnnA (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
        ; Int -> TcRn ()
checkTupSize Int
arity
        ; (HsWrapper
coi, [TcType]
arg_tys) <- (TcType -> TcM (TcCoercionN, [TcType]))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, [TcType])
forall a.
(TcType -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy (TyCon -> TcType -> TcM (TcCoercionN, [TcType])
matchExpectedTyConApp TyCon
tc)
                                               PatEnv
penv (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled 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
        ; ([GenLocated SrcSpanAnnA (Pat GhcTc)]
pats', r
res) <- [Scaled ExpSigmaType] -> Checker [LPat GhcRn] [LPat GhcTc]
tc_lpats ((TcType -> Scaled ExpSigmaType)
-> [TcType] -> [Scaled ExpSigmaType]
forall a b. (a -> b) -> [a] -> [b]
map (Scaled ExpSigmaType -> ExpSigmaType -> Scaled ExpSigmaType
forall a b. Scaled a -> b -> Scaled b
scaledSet Scaled ExpSigmaType
pat_ty (ExpSigmaType -> Scaled ExpSigmaType)
-> (TcType -> ExpSigmaType) -> TcType -> Scaled ExpSigmaType
forall b c a. (b -> c) -> (a -> b) -> a -> c
. 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
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 GhcTc
unmangled_result = XTuplePat GhcTc -> [LPat GhcTc] -> Boxity -> Pat GhcTc
forall p. XTuplePat p -> [LPat p] -> Boxity -> Pat p
TuplePat [TcType]
XTuplePat GhcTc
con_arg_tys [GenLocated SrcSpanAnnA (Pat GhcTc)]
[LPat GhcTc]
pats' Boxity
boxity
                                 -- pat_ty /= pat_ty iff coi /= IdCo
              possibly_mangled_result :: Pat GhcTc
possibly_mangled_result
                | GeneralFlag -> DynFlags -> Bool
gopt GeneralFlag
Opt_IrrefutableTuples DynFlags
dflags Bool -> Bool -> Bool
&&
                  Boxity -> Bool
isBoxed Boxity
boxity   = XLazyPat GhcTc -> LPat GhcTc -> Pat GhcTc
forall p. XLazyPat p -> LPat p -> Pat p
LazyPat NoExtField
XLazyPat GhcTc
noExtField (Pat GhcTc -> GenLocated SrcSpanAnnA (Pat GhcTc)
forall a an. a -> LocatedAn an a
noLocA Pat GhcTc
unmangled_result)
                | Bool
otherwise        = Pat GhcTc
unmangled_result

        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; ASSERT( con_arg_tys `equalLength` pats ) -- Syntactically enforced
          (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
coi Pat GhcTc
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 (TcCoercionN, [TcType]))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, [TcType])
forall a.
(TcType -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy (TyCon -> TcType -> TcM (TcCoercionN, [TcType])
matchExpectedTyConApp TyCon
tc)
                                               PatEnv
penv (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled 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
        ; (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', r
res) <- Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Scaled ExpSigmaType
pat_ty Scaled ExpSigmaType -> ExpSigmaType -> Scaled ExpSigmaType
forall a b. Scaled a -> b -> Scaled b
`scaledSet` TcType -> ExpSigmaType
mkCheckExpType ([TcType]
con_arg_tys [TcType] -> Int -> TcType
forall a. Outputable a => [a] -> Int -> a
`getNth` (Int
alt Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1)))
                                 PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
coi (XSumPat GhcTc -> LPat GhcTc -> Int -> Int -> Pat GhcTc
forall p. XSumPat p -> LPat p -> Int -> Int -> Pat p
SumPat [TcType]
XSumPat GhcTc
con_arg_tys GenLocated SrcSpanAnnA (Pat GhcTc)
LPat GhcTc
pat' Int
alt Int
arity) TcType
pat_ty
                 , r
res)
        }

------------------------
-- Data constructors
  ConPat XConPat GhcRn
_ XRec GhcRn (ConLikeP GhcRn)
con HsConPatDetails GhcRn
arg_pats ->
    PatEnv
-> GenLocated SrcSpanAnnN Name
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM r
-> TcM (Pat GhcTc, r)
forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
tcConPat PatEnv
penv GenLocated SrcSpanAnnN Name
XRec GhcRn (ConLikeP GhcRn)
con Scaled 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 (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty) TcType
lit_ty
        ; r
res    <- TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return ( HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
wrap (XLitPat GhcTc -> HsLit GhcTc -> Pat GhcTc
forall p. XLitPat p -> HsLit p -> Pat p
LitPat XLitPat GhcRn
XLitPat GhcTc
x (HsLit GhcRn -> HsLit GhcTc
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
        { HsWrapper
mult_wrap <- Scaled ExpSigmaType -> TcM HsWrapper
forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled ExpSigmaType
pat_ty
          -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
          --
          -- It may be possible to refine linear pattern so that they work in
          -- linear environments. But it is not clear how useful this is.
        ; let orig :: CtOrigin
orig = HsOverLit GhcRn -> CtOrigin
LiteralOrigin HsOverLit GhcRn
over_lit
        ; ((HsOverLit GhcTc
lit', Maybe SyntaxExprTc
mb_neg'), SyntaxExprTc
eq')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType]
    -> [TcType] -> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc))
-> TcM ((HsOverLit GhcTc, Maybe SyntaxExprTc), SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> [TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
eq [ExpSigmaType -> SyntaxOpType
SynType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty), SyntaxOpType
SynAny]
                          (TcType -> ExpSigmaType
mkCheckExpType TcType
boolTy) (([TcType]
  -> [TcType] -> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc))
 -> TcM ((HsOverLit GhcTc, Maybe SyntaxExprTc), SyntaxExprTc))
-> ([TcType]
    -> [TcType] -> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc))
-> TcM ((HsOverLit GhcTc, Maybe SyntaxExprTc), SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [TcType
neg_lit_ty] [TcType]
_ ->
               let new_over_lit :: TcType -> TcM (HsOverLit GhcTc)
new_over_lit TcType
lit_ty = HsOverLit GhcRn -> ExpSigmaType -> TcM (HsOverLit GhcTc)
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 GhcTc -> (HsOverLit GhcTc, Maybe SyntaxExprTc))
-> TcM (HsOverLit GhcTc)
-> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> TcType -> TcM (HsOverLit GhcTc)
new_over_lit TcType
neg_lit_ty
                 Just SyntaxExpr GhcRn
neg -> -- Negative literal
                             -- The 'negate' is re-mappable syntax
                   (SyntaxExprTc -> Maybe SyntaxExprTc)
-> (HsOverLit GhcTc, SyntaxExprTc)
-> (HsOverLit GhcTc, Maybe SyntaxExprTc)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> a (d, b) (d, c)
second SyntaxExprTc -> Maybe SyntaxExprTc
forall a. a -> Maybe a
Just ((HsOverLit GhcTc, SyntaxExprTc)
 -> (HsOverLit GhcTc, Maybe SyntaxExprTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
-> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$>
                   (CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> [TcType] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> [TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
neg [SyntaxOpType
SynRho] (TcType -> ExpSigmaType
mkCheckExpType TcType
neg_lit_ty) (([TcType] -> [TcType] -> TcM (HsOverLit GhcTc))
 -> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc))
-> ([TcType] -> [TcType] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
                    \ [TcType
lit_ty] [TcType]
_ -> TcType -> TcM (HsOverLit GhcTc)
new_over_lit TcType
lit_ty)
                     -- applied to a closed literal: linearity doesn't matter as
                     -- literals are typed in an empty environment, hence have
                     -- all multiplicities.

        ; r
res <- TcM r
thing_inside
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
mult_wrap (XNPat GhcTc
-> XRec GhcTc (HsOverLit GhcTc)
-> Maybe (SyntaxExpr GhcTc)
-> SyntaxExpr GhcTc
-> Pat GhcTc
forall p.
XNPat p
-> XRec p (HsOverLit p)
-> Maybe (SyntaxExpr p)
-> SyntaxExpr p
-> Pat p
NPat TcType
XNPat GhcTc
pat_ty (SrcSpan -> HsOverLit GhcTc -> GenLocated SrcSpan (HsOverLit GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
l HsOverLit GhcTc
lit') Maybe (SyntaxExpr GhcTc)
Maybe SyntaxExprTc
mb_neg' SyntaxExpr GhcTc
SyntaxExprTc
eq') TcType
pat_ty, 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.

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 SrcSpanAnnN
nm_loc Name
name)
               (L SrcSpan
loc HsOverLit GhcRn
lit) HsOverLit GhcRn
_ SyntaxExpr GhcRn
ge SyntaxExpr GhcRn
minus -> do
        { HsWrapper
mult_wrap <- Scaled ExpSigmaType -> TcM HsWrapper
forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled ExpSigmaType
pat_ty
            -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
        ; let pat_exp_ty :: ExpSigmaType
pat_exp_ty = Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty
              orig :: CtOrigin
orig = HsOverLit GhcRn -> CtOrigin
LiteralOrigin HsOverLit GhcRn
lit
        ; (HsOverLit GhcTc
lit1', SyntaxExprTc
ge')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> [TcType] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaType
-> ([TcType] -> [TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
ge [ExpSigmaType -> SyntaxOpType
SynType ExpSigmaType
pat_exp_ty, SyntaxOpType
SynRho]
                                  (TcType -> ExpSigmaType
mkCheckExpType TcType
boolTy) (([TcType] -> [TcType] -> TcM (HsOverLit GhcTc))
 -> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc))
-> ([TcType] -> [TcType] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [TcType
lit1_ty] [TcType]
_ ->
               HsOverLit GhcRn -> ExpSigmaType -> TcM (HsOverLit GhcTc)
newOverloadedLit HsOverLit GhcRn
lit (TcType -> ExpSigmaType
mkCheckExpType TcType
lit1_ty)
        ; ((HsOverLit GhcTc
lit2', HsWrapper
minus_wrap, TyVar
bndr_id), SyntaxExprTc
minus')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType]
    -> [TcType] -> TcM (HsOverLit GhcTc, HsWrapper, TyVar))
-> TcM ((HsOverLit GhcTc, HsWrapper, TyVar), SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> SyntaxOpType
-> ([TcType] -> [TcType] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOpGen CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
minus [ExpSigmaType -> SyntaxOpType
SynType ExpSigmaType
pat_exp_ty, SyntaxOpType
SynRho] SyntaxOpType
SynAny (([TcType] -> [TcType] -> TcM (HsOverLit GhcTc, HsWrapper, TyVar))
 -> TcM ((HsOverLit GhcTc, HsWrapper, TyVar), SyntaxExprTc))
-> ([TcType]
    -> [TcType] -> TcM (HsOverLit GhcTc, HsWrapper, TyVar))
-> TcM ((HsOverLit GhcTc, HsWrapper, TyVar), SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [TcType
lit2_ty, TcType
var_ty] [TcType]
_ ->
               do { HsOverLit GhcTc
lit2' <- HsOverLit GhcRn -> ExpSigmaType -> TcM (HsOverLit GhcTc)
newOverloadedLit HsOverLit GhcRn
lit (TcType -> ExpSigmaType
mkCheckExpType TcType
lit2_ty)
                  ; (HsWrapper
wrap, TyVar
bndr_id) <- SrcSpanAnnN -> TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnN
nm_loc (TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar))
-> TcM (HsWrapper, TyVar) -> TcM (HsWrapper, TyVar)
forall a b. (a -> b) -> a -> b
$
                                     PatEnv -> Name -> Scaled ExpSigmaType -> TcM (HsWrapper, TyVar)
tcPatBndr PatEnv
penv Name
name (ExpSigmaType -> Scaled ExpSigmaType
forall a. a -> Scaled a
unrestricted (ExpSigmaType -> Scaled ExpSigmaType)
-> ExpSigmaType -> Scaled ExpSigmaType
forall a b. (a -> b) -> a -> b
$ TcType -> ExpSigmaType
mkCheckExpType TcType
var_ty)
                           -- co :: var_ty ~ idType bndr_id

                           -- minus_wrap is applicable to minus'
                  ; (HsOverLit GhcTc, HsWrapper, TyVar)
-> TcM (HsOverLit GhcTc, HsWrapper, TyVar)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsOverLit GhcTc
lit2', HsWrapper
wrap, TyVar
bndr_id) }

        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType ExpSigmaType
pat_exp_ty
        -- 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 ()
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
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
ppr SyntaxExprTc
minus')
                                   -- this should be statically avoidable
                                   -- Case (3) from Note [NoSyntaxExpr] in "GHC.Hs.Expr"
                          SyntaxExprTc { syn_expr :: SyntaxExprTc -> HsExpr GhcTc
syn_expr = HsExpr GhcTc
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 { syn_expr :: HsExpr GhcTc
syn_expr = HsExpr GhcTc
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 GhcTc
pat' = XNPlusKPat GhcTc
-> LIdP GhcTc
-> XRec GhcTc (HsOverLit GhcTc)
-> HsOverLit GhcTc
-> SyntaxExpr GhcTc
-> SyntaxExpr GhcTc
-> Pat GhcTc
forall p.
XNPlusKPat p
-> LIdP p
-> XRec p (HsOverLit p)
-> HsOverLit p
-> SyntaxExpr p
-> SyntaxExpr p
-> Pat p
NPlusKPat TcType
XNPlusKPat GhcTc
pat_ty (SrcSpanAnnN -> TyVar -> GenLocated SrcSpanAnnN TyVar
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
nm_loc TyVar
bndr_id) (SrcSpan -> HsOverLit GhcTc -> GenLocated SrcSpan (HsOverLit GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc HsOverLit GhcTc
lit1') HsOverLit GhcTc
lit2'
                               SyntaxExpr GhcTc
SyntaxExprTc
ge' SyntaxExpr GhcTc
SyntaxExprTc
minus''
        ; (Pat GhcTc, r) -> TcM (Pat GhcTc, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
mult_wrap Pat GhcTc
pat' TcType
pat_ty, 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
      ; Scaled ExpSigmaType -> Checker (Pat GhcRn) (Pat GhcTc)
tc_pat Scaled ExpSigmaType
pat_ty PatEnv
penv Pat GhcRn
pat TcM r
thing_inside }
    HsSplice GhcRn
_ -> String -> TcM (Pat GhcTc, 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
-> HoleMode
-> HsPatSigType GhcRn
-> ContextKind
-> TcM ([(Name, TyVar)], [(Name, TyVar)], TcType)
tcHsPatSigType UserTypeCtxt
PatSigCtxt HoleMode
HM_Sig HsPatSigType GhcRn
sig ContextKind
OpenKind
        -- 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
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
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 ()
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
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
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
ppr TcType
res_ty)) ]
            ; (TidyEnv, SDoc) -> TcM (TidyEnv, SDoc)
forall (m :: * -> *) a. Monad m => a -> m a
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
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.

Note [Freshen existentials]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is essential that these existentials are freshened.
Otherwise, if we have something like
  case (a :: Ex, b :: Ex) of (MkEx ..., MkEx ...) -> ...
we'll give both unpacked existential variables the
same name, leading to shadowing.

-}

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

tcConPat :: PatEnv -> LocatedN Name
         -> Scaled ExpSigmaType    -- Type of the pattern
         -> HsConPatDetails GhcRn -> TcM a
         -> TcM (Pat GhcTc, a)
tcConPat :: forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
tcConPat PatEnv
penv con_lname :: GenLocated SrcSpanAnnN Name
con_lname@(L SrcSpanAnnN
_ Name
con_name) Scaled 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
-> GenLocated SrcSpanAnnN Name
-> DataCon
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> DataCon
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
tcDataConPat PatEnv
penv GenLocated SrcSpanAnnN Name
con_lname DataCon
data_con
                                                 Scaled ExpSigmaType
pat_ty HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
            PatSynCon PatSyn
pat_syn -> PatEnv
-> GenLocated SrcSpanAnnN Name
-> PatSyn
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> PatSyn
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
tcPatSynPat PatEnv
penv GenLocated SrcSpanAnnN Name
con_lname PatSyn
pat_syn
                                             Scaled ExpSigmaType
pat_ty HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
        }

tcDataConPat :: PatEnv -> LocatedN Name -> DataCon
             -> Scaled ExpSigmaType        -- Type of the pattern
             -> HsConPatDetails GhcRn -> TcM a
             -> TcM (Pat GhcTc, a)
tcDataConPat :: forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> DataCon
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
tcDataConPat PatEnv
penv (L SrcSpanAnnN
con_span Name
con_name) DataCon
data_con Scaled ExpSigmaType
pat_ty_scaled
             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, [Scaled TcType]
arg_tys, TcType
_)
                = DataCon
-> ([TyVar], [TyVar], [EqSpec], [TcType], [Scaled TcType], TcType)
dataConFullSig DataCon
data_con
              header :: GenLocated SrcSpanAnnN ConLike
header = SrcSpanAnnN -> ConLike -> GenLocated SrcSpanAnnN ConLike
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
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 -> Scaled ExpSigmaType -> TcM (HsWrapper, [TcType])
matchExpectedConTy PatEnv
penv TyCon
tycon Scaled ExpSigmaType
pat_ty_scaled
        ; TcType
pat_ty <- ExpSigmaType -> TcM TcType
readExpType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty_scaled)

          -- Add the stupid theta
        ; SrcSpanAnnN -> TcRn () -> TcRn ()
forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnN
con_span (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$ DataCon -> [TcType] -> TcRn ()
addDataConStupidTheta DataCon
data_con [TcType]
ctxt_res_tys

        -- Check that this isn't a GADT pattern match
        -- in situations in which that isn't allowed.
        ; 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]
++ ((Scaled TcType -> TcType) -> [Scaled TcType] -> [TcType]
forall a b. (a -> b) -> [a] -> [b]
map Scaled TcType -> TcType
forall a. Scaled a -> a
scaledThing [Scaled TcType]
arg_tys)
        ; ConLike -> [TyVar] -> [TcType] -> PatEnv -> TcRn ()
checkGADT (DataCon -> ConLike
RealDataCon DataCon
data_con) [TyVar]
ex_tvs [TcType]
all_arg_tys PatEnv
penv

        ; TCvSubst
tenv1 <- 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
tenv1 [TyVar]
ex_tvs
                     -- Get location from monad, not from ex_tvs
                     -- This freshens: See Note [Freshen existentials]
                     -- Why "super"? See Note [Binding when lookup up instances]
                     -- in GHC.Core.InstEnv.

        ; let arg_tys' :: [Scaled TcType]
arg_tys' = HasCallStack => TCvSubst -> [Scaled TcType] -> [Scaled TcType]
TCvSubst -> [Scaled TcType] -> [Scaled TcType]
substScaledTys TCvSubst
tenv [Scaled TcType]
arg_tys
              pat_mult :: TcType
pat_mult = Scaled ExpSigmaType -> TcType
forall a. Scaled a -> TcType
scaledMult Scaled ExpSigmaType
pat_ty_scaled
              arg_tys_scaled :: [Scaled TcType]
arg_tys_scaled = (Scaled TcType -> Scaled TcType)
-> [Scaled TcType] -> [Scaled TcType]
forall a b. (a -> b) -> [a] -> [b]
map (TcType -> Scaled TcType -> Scaled TcType
forall a. TcType -> Scaled a -> Scaled a
scaleScaled TcType
pat_mult) [Scaled TcType]
arg_tys'

        ; String -> SDoc -> TcRn ()
traceTc String
"tcConPat" ([SDoc] -> SDoc
vcat [ Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
con_name
                                   , [TyVar] -> SDoc
pprTyVars [TyVar]
univ_tvs
                                   , [TyVar] -> SDoc
pprTyVars [TyVar]
ex_tvs
                                   , [EqSpec] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [EqSpec]
eq_spec
                                   , [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TcType]
theta
                                   , [TyVar] -> SDoc
pprTyVars [TyVar]
ex_tvs'
                                   , [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TcType]
ctxt_res_tys
                                   , [Scaled TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Scaled TcType]
arg_tys'
                                   , HsConDetails
  (HsPatSigType GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcRn))
  (HsRecFields GhcRn (GenLocated SrcSpanAnnA (Pat GhcRn)))
-> SDoc
forall a. Outputable a => a -> SDoc
ppr HsConPatDetails GhcRn
HsConDetails
  (HsPatSigType GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcRn))
  (HsRecFields GhcRn (GenLocated SrcSpanAnnA (Pat GhcRn)))
arg_pats ])
        ; if [TyVar] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TyVar]
ex_tvs Bool -> Bool -> Bool
&& [EqSpec] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EqSpec]
eq_spec Bool -> Bool -> Bool
&& [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TcType]
theta
          then do { -- The common case; no class bindings etc
                    -- (see Note [Arrows and patterns])
                    (HsConDetails
  (HsPatSigType GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
arg_pats', a
res) <- ConLike
-> [Scaled TcType]
-> TCvSubst
-> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)
tcConArgs (DataCon -> ConLike
RealDataCon DataCon
data_con) [Scaled TcType]
arg_tys_scaled
                                                  TCvSubst
tenv PatEnv
penv HsConPatDetails GhcRn
arg_pats TcM a
thing_inside
                  ; let res_pat :: Pat GhcTc
res_pat = ConPat { pat_con :: XRec GhcTc (ConLikeP GhcTc)
pat_con = GenLocated SrcSpanAnnN ConLike
XRec GhcTc (ConLikeP GhcTc)
header
                                         , pat_args :: HsConPatDetails GhcTc
pat_args = HsConPatDetails GhcTc
HsConDetails
  (HsPatSigType GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
arg_pats'
                                         , pat_con_ext :: XConPat GhcTc
pat_con_ext = 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 GhcTc, a) -> TcM (Pat GhcTc, a)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
wrap Pat GhcTc
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
null [EqSpec]
eq_spec Bool -> Bool -> Bool
&& Bool -> Bool
not ((TcType -> Bool) -> [TcType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
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
  (HsPatSigType GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
arg_pats', a
res))
             <- SkolemInfo
-> [TyVar]
-> [TyVar]
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (HsPatSigType GhcRn)
        (GenLocated SrcSpanAnnA (Pat GhcTc))
        (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
      a)
-> TcM
     (TcEvBinds,
      (HsConDetails
         (HsPatSigType GhcRn)
         (GenLocated SrcSpanAnnA (Pat GhcTc))
         (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
       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
      (HsPatSigType GhcRn)
      (GenLocated SrcSpanAnnA (Pat GhcTc))
      (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
    a)
 -> TcM
      (TcEvBinds,
       (HsConDetails
          (HsPatSigType GhcRn)
          (GenLocated SrcSpanAnnA (Pat GhcTc))
          (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
        a)))
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (HsPatSigType GhcRn)
        (GenLocated SrcSpanAnnA (Pat GhcTc))
        (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
      a)
-> TcM
     (TcEvBinds,
      (HsConDetails
         (HsPatSigType GhcRn)
         (GenLocated SrcSpanAnnA (Pat GhcTc))
         (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
       a))
forall a b. (a -> b) -> a -> b
$
                ConLike
-> [Scaled TcType]
-> TCvSubst
-> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)
tcConArgs (DataCon -> ConLike
RealDataCon DataCon
data_con) [Scaled TcType]
arg_tys_scaled TCvSubst
tenv PatEnv
penv HsConPatDetails GhcRn
arg_pats TcM a
thing_inside

        ; let res_pat :: Pat GhcTc
res_pat = ConPat
                { pat_con :: XRec GhcTc (ConLikeP GhcTc)
pat_con   = GenLocated SrcSpanAnnN ConLike
XRec GhcTc (ConLikeP GhcTc)
header
                , pat_args :: HsConPatDetails GhcTc
pat_args  = HsConPatDetails GhcTc
HsConDetails
  (HsPatSigType GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
arg_pats'
                , pat_con_ext :: XConPat GhcTc
pat_con_ext = 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 GhcTc, a) -> TcM (Pat GhcTc, a)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat HsWrapper
wrap Pat GhcTc
res_pat TcType
pat_ty, a
res)
        } }

tcPatSynPat :: PatEnv -> LocatedN Name -> PatSyn
            -> Scaled ExpSigmaType         -- Type of the pattern
            -> HsConPatDetails GhcRn -> TcM a
            -> TcM (Pat GhcTc, a)
tcPatSynPat :: forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> PatSyn
-> Scaled ExpSigmaType
-> HsConPatDetails GhcRn
-> TcM a
-> TcM (Pat GhcTc, a)
tcPatSynPat PatEnv
penv (L SrcSpanAnnN
con_span Name
con_name) PatSyn
pat_syn Scaled 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, [Scaled TcType]
arg_tys, TcType
ty) = PatSyn
-> ([TyVar], [TcType], [TyVar], [TcType], [Scaled TcType], TcType)
patSynSig PatSyn
pat_syn

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

        -- Check that we aren't matching on a GADT-like pattern synonym
        -- in situations in which that isn't allowed.
        ; 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]
++ ((Scaled TcType -> TcType) -> [Scaled TcType] -> [TcType]
forall a b. (a -> b) -> [a] -> [b]
map Scaled TcType -> TcType
forall a. Scaled a -> a
scaledThing [Scaled TcType]
arg_tys)
        ; ConLike -> [TyVar] -> [TcType] -> PatEnv -> TcRn ()
checkGADT (PatSyn -> ConLike
PatSynCon PatSyn
pat_syn) [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
           -- This freshens: Note [Freshen existentials]

        ; let ty' :: TcType
ty'         = HasCallStack => TCvSubst -> TcType -> TcType
TCvSubst -> TcType -> TcType
substTy TCvSubst
tenv TcType
ty
              arg_tys' :: [Scaled TcType]
arg_tys'    = HasCallStack => TCvSubst -> [Scaled TcType] -> [Scaled TcType]
TCvSubst -> [Scaled TcType] -> [Scaled TcType]
substScaledTys TCvSubst
tenv [Scaled TcType]
arg_tys
              pat_mult :: TcType
pat_mult    = Scaled ExpSigmaType -> TcType
forall a. Scaled a -> TcType
scaledMult Scaled ExpSigmaType
pat_ty
              arg_tys_scaled :: [Scaled TcType]
arg_tys_scaled = (Scaled TcType -> Scaled TcType)
-> [Scaled TcType] -> [Scaled TcType]
forall a b. (a -> b) -> [a] -> [b]
map (TcType -> Scaled TcType -> Scaled TcType
forall a. TcType -> Scaled a -> Scaled a
scaleScaled TcType
pat_mult) [Scaled 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
mult_wrap <- Scaled ExpSigmaType -> TcM HsWrapper
forall a. Scaled a -> TcM HsWrapper
checkManyPattern Scaled ExpSigmaType
pat_ty
            -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.

        ; HsWrapper
wrap <- PatEnv -> ExpSigmaType -> TcType -> TcM HsWrapper
tc_sub_type PatEnv
penv (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty) TcType
ty'
        ; String -> SDoc -> TcRn ()
traceTc String
"tcPatSynPat" (PatSyn -> SDoc
forall a. Outputable a => a -> SDoc
ppr PatSyn
pat_syn SDoc -> SDoc -> SDoc
$$
                                 Scaled ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
ppr Scaled ExpSigmaType
pat_ty SDoc -> SDoc -> SDoc
$$
                                 TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
ty' SDoc -> SDoc -> SDoc
$$
                                 [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TyVar]
ex_tvs' SDoc -> SDoc -> SDoc
$$
                                 [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TcType]
prov_theta' SDoc -> SDoc -> SDoc
$$
                                 [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TcType]
req_theta' SDoc -> SDoc -> SDoc
$$
                                 [Scaled TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Scaled 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 (Name -> CtOrigin
OccurrenceOf Name
con_name) ([TyVar] -> [TcType]
mkTyVarTys [TyVar]
univ_tvs') [TcType]
req_theta'
                      -- Origin (OccurrenceOf con_name):
                      -- see Note [Call-stack tracing of pattern synonyms]
        ; String -> SDoc -> TcRn ()
traceTc String
"instCall" (HsWrapper -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsWrapper
req_wrap)

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

        ; String -> SDoc -> TcRn ()
traceTc String
"checkConstraints }" (TcEvBinds -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcEvBinds
ev_binds)
        ; let res_pat :: Pat GhcTc
res_pat = ConPat { pat_con :: XRec GhcTc (ConLikeP GhcTc)
pat_con   = SrcSpanAnnN -> ConLike -> GenLocated SrcSpanAnnN ConLike
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
con_span (ConLike -> GenLocated SrcSpanAnnN ConLike)
-> ConLike -> GenLocated SrcSpanAnnN ConLike
forall a b. (a -> b) -> a -> b
$ PatSyn -> ConLike
PatSynCon PatSyn
pat_syn
                               , pat_args :: HsConPatDetails GhcTc
pat_args  = HsConPatDetails GhcTc
HsConDetails
  (HsPatSigType GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
arg_pats'
                               , pat_con_ext :: XConPat GhcTc
pat_con_ext = 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 (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
pat_ty)
        ; (Pat GhcTc, a) -> TcM (Pat GhcTc, a)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
mkHsWrapPat (HsWrapper
wrap HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
mult_wrap) Pat GhcTc
res_pat TcType
pat_ty, a
res) }

{- Note [Call-stack tracing of pattern synonyms]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   f :: HasCallStack => blah

   pattern Annotated :: HasCallStack => (CallStack, a) -> a
   pattern Annotated x <- (f -> x)

When we pattern-match against `Annotated` we will call `f`, and must
pass a call-stack.  We may want `Annotated` itself to propagate the call
stack, so we give it a HasCallStack constraint too.  But then we expect
to see `Annotated` in the call stack.

This is achieve easily, but a bit trickily.  When we instantiate
Annotated's "required" constraints, in tcPatSynPat, give them a
CtOrigin of (OccurrenceOf "Annotated"). That way the special magic
in GHC.Tc.Solver.Canonical.canClassNC which deals with CallStack
constraints will kick in: that logic only fires on constraints
whose Origin is (OccurrenceOf f).

See also Note [Overview of implicit CallStacks] in GHC.Tc.Types.Evidence
and Note [Solving CallStack constraints] in GHC.Tc.Solver.Monad
-}
----------------------------
-- | 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 :: forall a.
(TcType -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
matchExpectedPatTy TcType -> TcM (TcCoercionN, 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
       ; (TcCoercionN
co, a
res) <- TcType -> TcM (TcCoercionN, a)
inner_match TcType
pat_rho
       ; String -> SDoc -> TcRn ()
traceTc String
"matchExpectedPatTy" (TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
pat_ty SDoc -> SDoc -> SDoc
$$ HsWrapper -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsWrapper
wrap)
       ; (HsWrapper, a) -> TcM (HsWrapper, a)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcCoercionN -> HsWrapper
mkWpCastN (TcCoercionN -> TcCoercionN
mkTcSymCo TcCoercionN
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
                   -> Scaled 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 -> Scaled ExpSigmaType -> TcM (HsWrapper, [TcType])
matchExpectedConTy (PE { pe_orig :: PatEnv -> CtOrigin
pe_orig = CtOrigin
orig }) TyCon
data_tc Scaled 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 (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled 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
ppr TyCon
data_tc,
                                             [TyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [TyVar]
tyConTyVars TyCon
data_tc),
                                             TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
fam_tc, [TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TcType]
fam_args,
                                             Scaled ExpSigmaType -> SDoc
forall a. Outputable a => a -> SDoc
ppr Scaled ExpSigmaType
exp_pat_ty,
                                             TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
pat_ty,
                                             TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcType
pat_rho, HsWrapper -> SDoc
forall a. Outputable a => a -> SDoc
ppr HsWrapper
wrap])
       ; TcCoercionN
co1 <- Maybe SDoc -> TcType -> TcType -> TcM TcCoercionN
unifyType Maybe SDoc
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 :: TcCoercionN
co2 = CoAxiom Unbranched -> [TcType] -> [TcCoercionN] -> TcCoercionN
mkTcUnbranchedAxInstCo CoAxiom Unbranched
co_tc [TcType]
tys' []
             -- co2 : T (ty1,ty2) ~R T7 ty1 ty2

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

       ; (HsWrapper, [TcType]) -> TcM (HsWrapper, [TcType])
forall (m :: * -> *) a. Monad m => a -> m a
return ( TcCoercionN -> HsWrapper
mkWpCastR TcCoercionN
full_co HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
wrap, [TcType]
tys') }

  | Bool
otherwise
  = do { TcType
pat_ty <- ExpSigmaType -> TcM TcType
expTypeToType (Scaled ExpSigmaType -> ExpSigmaType
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaType
exp_pat_ty)
       ; (HsWrapper
wrap, TcType
pat_rho) <- CtOrigin -> TcType -> TcM (HsWrapper, TcType)
topInstantiate CtOrigin
orig TcType
pat_ty
       ; (TcCoercionN
coi, [TcType]
tys) <- TyCon -> TcType -> TcM (TcCoercionN, [TcType])
matchExpectedTyConApp TyCon
data_tc TcType
pat_rho
       ; (HsWrapper, [TcType]) -> TcM (HsWrapper, [TcType])
forall (m :: * -> *) a. Monad m => a -> m a
return (TcCoercionN -> HsWrapper
mkWpCastN (TcCoercionN -> TcCoercionN
mkTcSymCo TcCoercionN
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
-}

{-
Note [Typechecking type applications in patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
How should we typecheck type applications in patterns, such as
   f :: Either (Maybe a) [b] -> blah
   f (Left @x @[y] (v::Maybe x)) = blah

It's quite straightforward, and very similar to the treatment of
pattern signatures.

* Step 1: bind the newly-in-scope type variables x and y to fresh
  unification variables, say x0 and y0.

* Step 2: typecheck those type arguments, @x and @[y], to get the
  types x0 and [y0].

* Step 3: Unify those types with the type arguments we expect,
  in this case (Maybe a) and [b].  These unifications will
  (perhaps after the constraint solver has done its work)
  unify   x0 := Maybe a
          y0 := b
  Thus we learn that x stands for (Maybe a) and y for b.

Wrinkles:

* Surprisingly, we can discard the coercions arising from
  these unifications.  The *only* thing the unification does is
  to side-effect those unification variables, so that we know
  what type x and y stand for; and cause an error if the equality
  is not soluble.  It's a bit like a Derived constraint arising
  from a functional dependency.

* Exactly the same works for existential arguments
     data T where
        MkT :: a -> a -> T
     f :: T -> blah
     f (MkT @x v w) = ...
   Here we create a fresh unification variable x0 for x, and
   unify it with the fresh existential variable bound by the pattern.

* Note that both here and in pattern signatures the unification may
  not even end up unifying the variable.  For example
     type S a b = a
     f :: Maybe a -> Bool
     f (Just @(S a b) x) = True :: b
   In Step 3 we will unify (S a0 b0 ~ a), which succeeds, but has no
   effect on the unification variable b0, to which 'b' is bound.
   Later, in the RHS, we find that b0 must be Bool, and unify it there.
   All is fine.
-}

tcConArgs :: ConLike
          -> [Scaled TcSigmaType]
          -> TCvSubst            -- Instantiating substitution for constructor type
          -> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)
tcConArgs :: ConLike
-> [Scaled TcType]
-> TCvSubst
-> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)
tcConArgs ConLike
con_like [Scaled TcType]
arg_tys TCvSubst
tenv PatEnv
penv HsConPatDetails GhcRn
con_args TcM r
thing_inside = case HsConPatDetails GhcRn
con_args of
  PrefixCon [HsPatSigType (NoGhcTc GhcRn)]
type_args [LPat GhcRn]
arg_pats -> do
        { Bool -> SDoc -> TcRn ()
checkTc (Int
con_arity Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
no_of_args)     -- Check correct arity
                  (SDoc -> ConLike -> Int -> Int -> SDoc
forall a. Outputable a => SDoc -> a -> Int -> Int -> SDoc
arityErr (String -> SDoc
text String
"constructor") ConLike
con_like Int
con_arity Int
no_of_args)

        ; let con_binders :: [InvisTVBinder]
con_binders = ConLike -> [InvisTVBinder]
conLikeUserTyVarBinders ConLike
con_like
        ; Bool -> SDoc -> TcRn ()
checkTc ([HsPatSigType (NoGhcTc GhcRn)]
[HsPatSigType GhcRn]
type_args [HsPatSigType GhcRn] -> [InvisTVBinder] -> Bool
forall a b. [a] -> [b] -> Bool
`leLength` [InvisTVBinder]
con_binders)
                  (ConLike -> Int -> Int -> SDoc
conTyArgArityErr ConLike
con_like ([InvisTVBinder] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [InvisTVBinder]
con_binders) ([HsPatSigType GhcRn] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [HsPatSigType (NoGhcTc GhcRn)]
[HsPatSigType GhcRn]
type_args))

        ; let pats_w_tys :: [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)]
pats_w_tys = String
-> [GenLocated SrcSpanAnnA (Pat GhcRn)]
-> [Scaled TcType]
-> [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)]
forall a b. String -> [a] -> [b] -> [(a, b)]
zipEqual String
"tcConArgs" [GenLocated SrcSpanAnnA (Pat GhcRn)]
[LPat GhcRn]
arg_pats [Scaled TcType]
arg_tys
        ; ([TcType]
type_args', ([GenLocated SrcSpanAnnA (Pat GhcTc)]
arg_pats', r
res))
            <- Checker (HsPatSigType GhcRn) TcType
-> Checker [HsPatSigType GhcRn] [TcType]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple Checker (HsPatSigType GhcRn) TcType
tcConTyArg PatEnv
penv [HsPatSigType (NoGhcTc GhcRn)]
[HsPatSigType GhcRn]
type_args (TcM ([GenLocated SrcSpanAnnA (Pat GhcTc)], r)
 -> TcM ([TcType], ([GenLocated SrcSpanAnnA (Pat GhcTc)], r)))
-> TcM ([GenLocated SrcSpanAnnA (Pat GhcTc)], r)
-> TcM ([TcType], ([GenLocated SrcSpanAnnA (Pat GhcTc)], r))
forall a b. (a -> b) -> a -> b
$
               Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
-> Checker
     [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)]
     [GenLocated SrcSpanAnnA (Pat GhcTc)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
Checker (LPat GhcRn, Scaled TcType) (LPat GhcTc)
tcConArg PatEnv
penv [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)]
pats_w_tys TcM r
thing_inside

          -- This unification is straight from Figure 7 of
          -- "Type Variables in Patterns", Haskell'18
        ; [TcCoercionN]
_ <- (TcType -> TcType -> TcM TcCoercionN)
-> [TcType]
-> [TcType]
-> IOEnv (Env TcGblEnv TcLclEnv) [TcCoercionN]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (Maybe SDoc -> TcType -> TcType -> TcM TcCoercionN
unifyType Maybe SDoc
forall a. Maybe a
Nothing) [TcType]
type_args' (TCvSubst -> [TyVar] -> [TcType]
substTyVars TCvSubst
tenv ([TyVar] -> [TcType]) -> [TyVar] -> [TcType]
forall a b. (a -> b) -> a -> b
$
                                                        [InvisTVBinder] -> [TyVar]
forall tv argf. [VarBndr tv argf] -> [tv]
binderVars [InvisTVBinder]
con_binders)
          -- OK to drop coercions here. These unifications are all about
          -- guiding inference based on a user-written type annotation
          -- See Note [Typechecking type applications in patterns]

        ; (HsConDetails
   (HsPatSigType GhcRn)
   (GenLocated SrcSpanAnnA (Pat GhcTc))
   (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
 r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (HsPatSigType GhcRn)
        (GenLocated SrcSpanAnnA (Pat GhcTc))
        (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
      r)
forall (m :: * -> *) a. Monad m => a -> m a
return ([HsPatSigType GhcRn]
-> [GenLocated SrcSpanAnnA (Pat GhcTc)]
-> HsConDetails
     (HsPatSigType GhcRn)
     (GenLocated SrcSpanAnnA (Pat GhcTc))
     (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
forall tyarg arg rec.
[tyarg] -> [arg] -> HsConDetails tyarg arg rec
PrefixCon [HsPatSigType (NoGhcTc GhcRn)]
[HsPatSigType GhcRn]
type_args [GenLocated SrcSpanAnnA (Pat GhcTc)]
arg_pats', r
res) }
    where
      con_arity :: Int
con_arity  = ConLike -> Int
conLikeArity ConLike
con_like
      no_of_args :: Int
no_of_args = [GenLocated SrcSpanAnnA (Pat GhcRn)] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [GenLocated SrcSpanAnnA (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
== Int
2)      -- Check correct arity
                  (SDoc -> ConLike -> Int -> Int -> SDoc
forall a. Outputable a => SDoc -> a -> Int -> Int -> SDoc
arityErr (String -> SDoc
text String
"constructor") ConLike
con_like Int
con_arity Int
2)
        ; let [Scaled TcType
arg_ty1,Scaled TcType
arg_ty2] = [Scaled TcType]
arg_tys       -- This can't fail after the arity check
        ; ([GenLocated SrcSpanAnnA (Pat GhcTc)
p1',GenLocated SrcSpanAnnA (Pat GhcTc)
p2'], r
res) <- Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
-> Checker
     [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)]
     [GenLocated SrcSpanAnnA (Pat GhcTc)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled TcType)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
Checker (LPat GhcRn, Scaled TcType) (LPat GhcTc)
tcConArg PatEnv
penv [(GenLocated SrcSpanAnnA (Pat GhcRn)
LPat GhcRn
p1,Scaled TcType
arg_ty1),(GenLocated SrcSpanAnnA (Pat GhcRn)
LPat GhcRn
p2,Scaled TcType
arg_ty2)]
                                                  TcM r
thing_inside
        ; (HsConDetails
   (HsPatSigType GhcRn)
   (GenLocated SrcSpanAnnA (Pat GhcTc))
   (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
 r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (HsPatSigType GhcRn)
        (GenLocated SrcSpanAnnA (Pat GhcTc))
        (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
      r)
forall (m :: * -> *) a. Monad m => a -> m a
return (GenLocated SrcSpanAnnA (Pat GhcTc)
-> GenLocated SrcSpanAnnA (Pat GhcTc)
-> HsConDetails
     (HsPatSigType GhcRn)
     (GenLocated SrcSpanAnnA (Pat GhcTc))
     (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
forall tyarg arg rec. arg -> arg -> HsConDetails tyarg arg rec
InfixCon GenLocated SrcSpanAnnA (Pat GhcTc)
p1' GenLocated SrcSpanAnnA (Pat GhcTc)
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
        { ([GenLocated
   SrcSpanAnnA
   (HsRecField'
      (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc)))]
rpats', r
res) <- Checker
  (GenLocated
     SrcSpanAnnA
     (HsRecField GhcRn (GenLocated SrcSpanAnnA (Pat GhcRn))))
  (GenLocated
     SrcSpanAnnA
     (HsRecField'
        (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc))))
-> Checker
     [GenLocated
        SrcSpanAnnA
        (HsRecField GhcRn (GenLocated SrcSpanAnnA (Pat GhcRn)))]
     [GenLocated
        SrcSpanAnnA
        (HsRecField'
           (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc)))]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple Checker
  (GenLocated
     SrcSpanAnnA
     (HsRecField GhcRn (GenLocated SrcSpanAnnA (Pat GhcRn))))
  (GenLocated
     SrcSpanAnnA
     (HsRecField'
        (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc))))
Checker
  (LHsRecField GhcRn (LPat GhcRn)) (LHsRecField GhcTc (LPat GhcTc))
tc_field PatEnv
penv [GenLocated
   SrcSpanAnnA
   (HsRecField GhcRn (GenLocated SrcSpanAnnA (Pat GhcRn)))]
[LHsRecField GhcRn (LPat GhcRn)]
rpats TcM r
thing_inside
        ; (HsConDetails
   (HsPatSigType GhcRn)
   (GenLocated SrcSpanAnnA (Pat GhcTc))
   (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
 r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (HsConDetails
        (HsPatSigType GhcRn)
        (GenLocated SrcSpanAnnA (Pat GhcTc))
        (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
      r)
forall (m :: * -> *) a. Monad m => a -> m a
return (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))
-> HsConDetails
     (HsPatSigType GhcRn)
     (GenLocated SrcSpanAnnA (Pat GhcTc))
     (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
forall tyarg arg rec. rec -> HsConDetails tyarg arg rec
RecCon ([LHsRecField GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))]
-> Maybe (Located Int)
-> HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))
forall p arg.
[LHsRecField p arg] -> Maybe (Located Int) -> HsRecFields p arg
HsRecFields [GenLocated
   SrcSpanAnnA
   (HsRecField'
      (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc)))]
[LHsRecField GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))]
rpats' Maybe (Located Int)
dd), r
res) }
    where
      tc_field :: Checker (LHsRecField GhcRn (LPat GhcRn))
                          (LHsRecField GhcTc (LPat GhcTc))
      tc_field :: Checker
  (LHsRecField GhcRn (LPat GhcRn)) (LHsRecField GhcTc (LPat GhcTc))
tc_field PatEnv
penv
               (L SrcSpanAnnA
l (HsRecField XHsRecField (FieldOcc GhcRn)
ann (L SrcSpan
loc (FieldOcc XCFieldOcc GhcRn
sel (L SrcSpanAnnN
lr RdrName
rdr))) GenLocated SrcSpanAnnA (Pat GhcRn)
pat Bool
pun))
               TcM r
thing_inside
        = do { TyVar
sel'   <- Name -> TcM TyVar
tcLookupId Name
XCFieldOcc GhcRn
sel
             ; Scaled TcType
pat_ty <- SrcSpan -> TcRn (Scaled TcType) -> TcRn (Scaled TcType)
forall a. SrcSpan -> TcRn a -> TcRn a
setSrcSpan SrcSpan
loc (TcRn (Scaled TcType) -> TcRn (Scaled TcType))
-> TcRn (Scaled TcType) -> TcRn (Scaled TcType)
forall a b. (a -> b) -> a -> b
$ Name -> FieldLabelString -> TcRn (Scaled 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)
             ; (GenLocated SrcSpanAnnA (Pat GhcTc)
pat', r
res) <- PatEnv
-> (LPat GhcRn, Scaled TcType) -> TcM r -> TcM (LPat GhcTc, r)
Checker (LPat GhcRn, Scaled TcType) (LPat GhcTc)
tcConArg PatEnv
penv (GenLocated SrcSpanAnnA (Pat GhcRn)
LPat GhcRn
pat, Scaled TcType
pat_ty) TcM r
thing_inside
             ; (GenLocated
   SrcSpanAnnA
   (HsRecField'
      (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc))),
 r)
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (GenLocated
        SrcSpanAnnA
        (HsRecField'
           (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc))),
      r)
forall (m :: * -> *) a. Monad m => a -> m a
return (SrcSpanAnnA
-> HsRecField'
     (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc))
-> GenLocated
     SrcSpanAnnA
     (HsRecField' (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc)))
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnA
l (XHsRecField (FieldOcc GhcTc)
-> Located (FieldOcc GhcTc)
-> GenLocated SrcSpanAnnA (Pat GhcTc)
-> Bool
-> HsRecField'
     (FieldOcc GhcTc) (GenLocated SrcSpanAnnA (Pat GhcTc))
forall id arg.
XHsRecField id -> Located id -> arg -> Bool -> HsRecField' id arg
HsRecField XHsRecField (FieldOcc GhcRn)
XHsRecField (FieldOcc GhcTc)
ann (SrcSpan -> FieldOcc GhcTc -> Located (FieldOcc GhcTc)
forall l e. l -> e -> GenLocated l e
L SrcSpan
loc (XCFieldOcc GhcTc
-> GenLocated SrcSpanAnnN RdrName -> FieldOcc GhcTc
forall pass.
XCFieldOcc pass -> GenLocated SrcSpanAnnN RdrName -> FieldOcc pass
FieldOcc TyVar
XCFieldOcc GhcTc
sel' (SrcSpanAnnN -> RdrName -> GenLocated SrcSpanAnnN RdrName
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
lr RdrName
rdr))) GenLocated SrcSpanAnnA (Pat GhcTc)
pat'
                                                                        Bool
pun), r
res) }


      find_field_ty :: Name -> FieldLabelString -> TcM (Scaled TcType)
      find_field_ty :: Name -> FieldLabelString -> TcRn (Scaled TcType)
find_field_ty Name
sel FieldLabelString
lbl
        = case [Scaled TcType
ty | (FieldLabel
fl, Scaled TcType
ty) <- [(FieldLabel, Scaled TcType)]
field_tys, FieldLabel -> Name
flSelector FieldLabel
fl Name -> Name -> Bool
forall a. Eq a => a -> a -> Bool
== 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 -> TcRn (Scaled 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
           (Scaled TcType
pat_ty : [Scaled TcType]
extras) -> do
                String -> SDoc -> TcRn ()
traceTc String
"find_field" (Scaled TcType -> SDoc
forall a. Outputable a => a -> SDoc
ppr Scaled TcType
pat_ty SDoc -> SDoc -> SDoc
<+> [Scaled TcType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Scaled TcType]
extras)
                ASSERT( null extras ) (return pat_ty)

      field_tys :: [(FieldLabel, Scaled TcType)]
      field_tys :: [(FieldLabel, Scaled TcType)]
field_tys = [FieldLabel] -> [Scaled TcType] -> [(FieldLabel, Scaled TcType)]
forall a b. [a] -> [b] -> [(a, b)]
zip (ConLike -> [FieldLabel]
conLikeFieldLabels ConLike
con_like) [Scaled 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).

tcConTyArg :: Checker (HsPatSigType GhcRn) TcType
tcConTyArg :: Checker (HsPatSigType GhcRn) TcType
tcConTyArg PatEnv
penv HsPatSigType GhcRn
rn_ty TcM r
thing_inside
  = do { ([(Name, TyVar)]
sig_wcs, [(Name, TyVar)]
sig_ibs, TcType
arg_ty) <- UserTypeCtxt
-> HoleMode
-> HsPatSigType GhcRn
-> ContextKind
-> TcM ([(Name, TyVar)], [(Name, TyVar)], TcType)
tcHsPatSigType UserTypeCtxt
TypeAppCtxt HoleMode
HM_TyAppPat HsPatSigType GhcRn
rn_ty ContextKind
AnyKind
               -- AnyKind is a bit suspect: it really should be the kind gotten
               -- from instantiating the constructor type. But this would be
               -- hard to get right, because earlier type patterns might influence
               -- the kinds of later patterns. In any case, it all gets checked
               -- by the calls to unifyType in tcConArgs, which will also unify
               -- kinds.
       ; Bool -> TcRn () -> TcRn ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Bool -> Bool
not ([(Name, TyVar)] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [(Name, TyVar)]
sig_ibs) Bool -> Bool -> Bool
&& PatEnv -> Bool
inPatBind PatEnv
penv) (TcRn () -> TcRn ()) -> TcRn () -> TcRn ()
forall a b. (a -> b) -> a -> b
$
           SDoc -> TcRn ()
addErr (String -> SDoc
text String
"Binding type variables is not allowed in pattern bindings")
       ; r
result <- [(Name, TyVar)] -> TcM r -> TcM r
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
sig_wcs (TcM r -> TcM r) -> TcM r -> TcM r
forall a b. (a -> b) -> a -> b
$
                   [(Name, TyVar)] -> TcM r -> TcM r
forall r. [(Name, TyVar)] -> TcM r -> TcM r
tcExtendNameTyVarEnv [(Name, TyVar)]
sig_ibs (TcM r -> TcM r) -> TcM r -> TcM r
forall a b. (a -> b) -> a -> b
$
                   TcM r
thing_inside
       ; (TcType, r) -> TcM (TcType, r)
forall (m :: * -> *) a. Monad m => a -> m a
return (TcType
arg_ty, r
result) }

tcConArg :: Checker (LPat GhcRn, Scaled TcSigmaType) (LPat GhcTc)
tcConArg :: Checker (LPat GhcRn, Scaled TcType) (LPat GhcTc)
tcConArg PatEnv
penv (LPat GhcRn
arg_pat, Scaled TcType
arg_mult TcType
arg_ty)
  = Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (TcType -> ExpSigmaType -> Scaled ExpSigmaType
forall a. TcType -> a -> Scaled a
Scaled TcType
arg_mult (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
null [TcType]
stupid_theta = () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
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
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

conTyArgArityErr :: ConLike
                 -> Int   -- expected # of arguments
                 -> Int   -- actual # of arguments
                 -> SDoc
conTyArgArityErr :: ConLike -> Int -> Int -> SDoc
conTyArgArityErr ConLike
con_like Int
expected_number Int
actual_number
  = String -> SDoc
text String
"Too many type arguments in constructor pattern for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (ConLike -> SDoc
forall a. Outputable a => a -> SDoc
ppr ConLike
con_like) SDoc -> SDoc -> SDoc
$$
    String -> SDoc
text String
"Expected no more than" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr Int
expected_number SDoc -> SDoc -> SDoc
<> SDoc
semi SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"got" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr Int
actual_number

{-
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', which we do by disallowing any
non-vanilla pattern match (i.e. one that introduces existential
variables or provided constraints), in tcDataConPat and tcPatSynPat.

We also short-cut the constraint simplification for such vanilla patterns,
so that we bind no constraints. Hence the 'fast path' in tcDataConPat;
which applies more generally (not just within 'proc'), as it's a good
plan in general to bypass the constraint simplification step entirely
when it's not needed.

************************************************************************
*                                                                      *
                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 :: forall a b. 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
ppr Pat GhcRn
pat)

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

-- | Check that a pattern isn't a GADT, or doesn't have existential variables,
-- in a situation in which that is not permitted (inside a lazy pattern, or
-- in arrow notation).
checkGADT :: ConLike
          -> [TyVar] -- ^ existentials
          -> [Type]  -- ^ argument types
          -> PatEnv
          -> TcM ()
checkGADT :: ConLike -> [TyVar] -> [TcType] -> PatEnv -> TcRn ()
checkGADT ConLike
conlike [TyVar]
ex_tvs [TcType]
arg_tys = \case
  PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LetPat {} }
    -> () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LamPat (ArrowMatchCtxt {}) }
    | Bool -> Bool
not (Bool -> Bool) -> Bool -> Bool
forall a b. (a -> b) -> a -> b
$ ConLike -> Bool
isVanillaConLike ConLike
conlike
    -- See Note [Arrows and patterns]
    -> SDoc -> TcRn ()
forall a. SDoc -> TcRn a
failWithTc SDoc
existentialProcPat
  PE { pe_lazy :: PatEnv -> Bool
pe_lazy = Bool
True }
    | Bool
has_existentials
    -- See Note [Existential check]
    -> SDoc -> TcRn ()
forall a. SDoc -> TcRn a
failWithTc SDoc
existentialLazyPat
  PatEnv
_ -> () -> TcRn ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  where
    has_existentials :: Bool
    has_existentials :: Bool
has_existentials = (TyVar -> Bool) -> [TyVar] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (TyVar -> VarSet -> Bool
`elemVarSet` [TcType] -> VarSet
tyCoVarsOfTypes [TcType]
arg_tys) [TyVar]
ex_tvs

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
ppr ConLike
con),
          String -> SDoc
text String
"does not have field", SDoc -> SDoc
quotes (FieldLabelString -> SDoc
forall a. Outputable a => a -> SDoc
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
ppr TcType
sig_ty)