{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# 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
   , tcMatchPats
   , addDataConStupidTheta
   )
where

import GHC.Prelude

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

import GHC.Hs
import GHC.Hs.Syn.Type
import GHC.Rename.Utils
import GHC.Tc.Errors.Types
import GHC.Tc.Gen.Sig( TcPragEnv, lookupPragEnv, addInlinePrags )
import GHC.Tc.Utils.Monad
import GHC.Tc.Utils.Instantiate
import GHC.Types.FieldLabel
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.Concrete ( hasFixedRuntimeRep_syntactic )
import GHC.Tc.Utils.Env
import GHC.Tc.Utils.TcMType
import GHC.Tc.Zonk.TcType
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.Coercion
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.DynFlags
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.FastString
import qualified Data.List.NonEmpty as NE

import GHC.Data.List.SetOps ( getNth )
import Language.Haskell.Syntax.Basic (FieldLabelString(..))

import Data.List( partition )
import Control.Monad.Trans.Writer.CPS
import Control.Monad.Trans.Class

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

tcLetPat :: (Name -> Maybe TcId)
         -> LetBndrSpec
         -> LPat GhcRn -> Scaled ExpSigmaTypeFRR
         -> TcM a
         -> TcM (LPat GhcTc, a)
tcLetPat :: forall a.
(Name -> Maybe TyCoVar)
-> LetBndrSpec
-> LPat GhcRn
-> Scaled ExpSigmaTypeFRR
-> TcM a
-> TcM (LPat GhcTc, a)
tcLetPat Name -> Maybe TyCoVar
sig_fn LetBndrSpec
no_gen LPat GhcRn
pat Scaled ExpSigmaTypeFRR
pat_ty TcM a
thing_inside
  = do { bind_lvl <- TcM TcLevel
getTcLevel
       ; let ctxt = LetPat { pc_lvl :: TcLevel
pc_lvl    = TcLevel
bind_lvl
                           , pc_sig_fn :: Name -> Maybe TyCoVar
pc_sig_fn = Name -> Maybe TyCoVar
sig_fn
                           , pc_new :: LetBndrSpec
pc_new    = LetBndrSpec
no_gen }
             penv = PE { pe_lazy :: Bool
pe_lazy = Bool
True
                       , pe_ctxt :: PatCtxt
pe_ctxt = PatCtxt
ctxt
                       , pe_orig :: CtOrigin
pe_orig = CtOrigin
PatOrigin }
       ; dflags <- getDynFlags
       ; manyIfLazy dflags pat
       ; tc_lpat pat_ty penv pat thing_inside }
  where
    -- The logic is partly duplicated from decideBangHood in
    -- GHC.HsToCore.Utils. Ugh…
    manyIfLazy :: DynFlags -> GenLocated SrcSpanAnnA (Pat GhcRn) -> TcM ()
manyIfLazy DynFlags
dflags GenLocated SrcSpanAnnA (Pat GhcRn)
lpat
      | Extension -> DynFlags -> Bool
xopt Extension
LangExt.Strict DynFlags
dflags = GenLocated SrcSpanAnnA (Pat GhcRn) -> TcM ()
xstrict GenLocated SrcSpanAnnA (Pat GhcRn)
lpat
      | Bool
otherwise = GenLocated SrcSpanAnnA (Pat GhcRn) -> TcM ()
not_xstrict GenLocated SrcSpanAnnA (Pat GhcRn)
lpat
      where
        xstrict :: GenLocated SrcSpanAnnA (Pat GhcRn) -> TcM ()
xstrict p :: GenLocated SrcSpanAnnA (Pat GhcRn)
p@(L SrcSpanAnnA
_ (LazyPat XLazyPat GhcRn
_ LPat GhcRn
_)) = NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
LazyPatternReason LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
p Scaled ExpSigmaTypeFRR
pat_ty
        xstrict (L SrcSpanAnnA
_ (ParPat XParPat GhcRn
_ LPat GhcRn
p)) = GenLocated SrcSpanAnnA (Pat GhcRn) -> TcM ()
xstrict LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
p
        xstrict GenLocated SrcSpanAnnA (Pat GhcRn)
_ = () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()

        not_xstrict :: GenLocated SrcSpanAnnA (Pat GhcRn) -> TcM ()
not_xstrict (L SrcSpanAnnA
_ (BangPat XBangPat GhcRn
_ LPat GhcRn
_)) = () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
        not_xstrict (L SrcSpanAnnA
_ (VarPat XVarPat GhcRn
_ LIdP GhcRn
_)) = () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
        not_xstrict (L SrcSpanAnnA
_ (ParPat XParPat GhcRn
_ LPat GhcRn
p)) = GenLocated SrcSpanAnnA (Pat GhcRn) -> TcM ()
not_xstrict LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
p
        not_xstrict GenLocated SrcSpanAnnA (Pat GhcRn)
p = NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
LazyPatternReason LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
p Scaled ExpSigmaTypeFRR
pat_ty

-----------------
tcMatchPats :: forall a.
               HsMatchContextRn
            -> [LPat GhcRn]          -- ^ patterns
            -> [ExpPatType]             -- ^ types of the patterns
            -> TcM a                    -- ^ checker for the body
            -> TcM ([LPat GhcTc], a)
-- See Note [tcMatchPats]
--
-- PRECONDITION:
--    number of visible pats::[LPat GhcRn]   (p is visible, @p is invisible)
--      ==
--    number of visible pat_tys::[ExpPatType]   (ExpFunPatTy is visible,
--                                               ExpForAllPatTy b is visible iff b is Required)
--
-- POSTCONDITION:
--   Returns only the /value/ patterns; see Note [tcMatchPats]

tcMatchPats :: forall a.
HsMatchContextRn
-> [LPat GhcRn] -> [ExpPatType] -> TcM a -> TcM ([LPat GhcTc], a)
tcMatchPats HsMatchContextRn
match_ctxt [LPat GhcRn]
pats [ExpPatType]
pat_tys TcM a
thing_inside
  = Bool -> SDoc -> TcM ([LPat GhcTc], a) -> TcM ([LPat GhcTc], a)
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr ((ExpPatType -> Bool) -> [ExpPatType] -> Int
forall a. (a -> Bool) -> [a] -> Int
count ExpPatType -> Bool
isVisibleExpPatType [ExpPatType]
pat_tys Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== (GenLocated SrcSpanAnnA (Pat GhcRn) -> Bool)
-> [GenLocated SrcSpanAnnA (Pat GhcRn)] -> Int
forall a. (a -> Bool) -> [a] -> Int
count (Pat GhcRn -> Bool
forall p. Pat p -> Bool
isVisArgPat (Pat GhcRn -> Bool)
-> (GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn)
-> GenLocated SrcSpanAnnA (Pat GhcRn)
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn
forall l e. GenLocated l e -> e
unLoc) [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats)
              ([GenLocated SrcSpanAnnA (Pat GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ [ExpPatType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [ExpPatType]
pat_tys) (TcM ([LPat GhcTc], a) -> TcM ([LPat GhcTc], a))
-> TcM ([LPat GhcTc], a) -> TcM ([LPat GhcTc], a)
forall a b. (a -> b) -> a -> b
$
       -- Check PRECONDITION
       -- When we get @patterns the (length pats) will change
    do { err_ctxt <- TcM [ErrCtxt]
getErrCtxt
       ; let loop :: [LPat GhcRn] -> [ExpPatType] -> TcM ([LPat GhcTc], a)

             -- No more patterns.  Discard excess pat_tys;
             -- they should all be invisible.  Example:
             --    f :: Int -> forall a b. blah
             --    f x @p = rhs
             -- We will call tcMatchPats with
             --   pats = [x, @p]
             --   pat_tys = [Int, @a, @b]
             loop [] [ExpPatType]
pat_tys
               = Bool -> SDoc -> TcM ([LPat GhcTc], a) -> TcM ([LPat GhcTc], a)
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (Bool -> Bool
not ((ExpPatType -> Bool) -> [ExpPatType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any ExpPatType -> Bool
isVisibleExpPatType [ExpPatType]
pat_tys)) ([GenLocated SrcSpanAnnA (Pat GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ [ExpPatType] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [ExpPatType]
pat_tys) (TcM ([LPat GhcTc], a) -> TcM ([LPat GhcTc], a))
-> TcM ([LPat GhcTc], a) -> TcM ([LPat GhcTc], a)
forall a b. (a -> b) -> a -> b
$
                 do { res <- [ErrCtxt] -> TcM a -> TcM a
forall a. [ErrCtxt] -> TcM a -> TcM a
setErrCtxt [ErrCtxt]
err_ctxt TcM a
thing_inside
                    ; return ([], res) }

             -- ExpForAllPat: expecting a type pattern
             loop all_pats :: [LPat GhcRn]
all_pats@(LPat GhcRn
pat : [LPat GhcRn]
pats) (ExpForAllPatTy (Bndr TyCoVar
tv ForAllTyFlag
vis) : [ExpPatType]
pat_tys)
               | ForAllTyFlag -> Bool
isVisibleForAllTyFlag ForAllTyFlag
vis
               = do { (_p, (ps, res)) <- TyCoVar -> Checker (LPat GhcRn) (LPat GhcTc)
tc_forall_lpat TyCoVar
tv PatEnv
penv LPat GhcRn
pat (TcM ([LPat GhcTc], a) -> TcM (LPat GhcTc, ([LPat GhcTc], a)))
-> TcM ([LPat GhcTc], a) -> TcM (LPat GhcTc, ([LPat GhcTc], a))
forall a b. (a -> b) -> a -> b
$
                                         [LPat GhcRn] -> [ExpPatType] -> TcM ([LPat GhcTc], a)
loop [LPat GhcRn]
pats [ExpPatType]
pat_tys

                    ; return (ps, res) }
                    -- This VisPat is Erased.
                    -- See Note [Invisible binders in functions] in GHC.Hs.Pat

               -- Invisible (Specified) forall in type, and an @a type pattern
               -- E.g.    f :: forall a. Bool -> a -> blah
               --         f @b True  x = rhs1  -- b is bound to skolem a
               --         f @c False y = rhs2  -- c is bound to skolem a
               -- Also handles invisible (Inferred) case originating from type
               -- class deriving; see Note [Inferred invisible patterns]
               | L SrcSpanAnnA
_ (InvisPat XInvisPat GhcRn
pat_spec HsTyPat (NoGhcTc GhcRn)
tp) <- LPat GhcRn
pat
               , Invisible Specificity
spec <- ForAllTyFlag
vis
               , XInvisPat GhcRn
Specificity
pat_spec Specificity -> Specificity -> Bool
forall a. Eq a => a -> a -> Bool
== Specificity
spec
               = do { (_p, (ps, res)) <- HsTyPat GhcRn
-> TyCoVar
-> TcM ([LPat GhcTc], a)
-> TcM (Type, ([LPat GhcTc], a))
forall r. HsTyPat GhcRn -> TyCoVar -> TcM r -> TcM (Type, r)
tc_ty_pat HsTyPat (NoGhcTc GhcRn)
HsTyPat GhcRn
tp TyCoVar
tv (TcM ([LPat GhcTc], a) -> TcM (Type, ([LPat GhcTc], a)))
-> TcM ([LPat GhcTc], a) -> TcM (Type, ([LPat GhcTc], a))
forall a b. (a -> b) -> a -> b
$
                                         [LPat GhcRn] -> [ExpPatType] -> TcM ([LPat GhcTc], a)
loop [LPat GhcRn]
pats [ExpPatType]
pat_tys
                    ; return (ps, res) }

               | Bool
otherwise  -- Discard invisible pat_ty
               = [LPat GhcRn] -> [ExpPatType] -> TcM ([LPat GhcTc], a)
loop [LPat GhcRn]
all_pats [ExpPatType]
pat_tys

             -- This case handles the user error when an InvisPat is used
             -- without a corresponding invisible (Specified) forall in the type
             -- E.g. 1.  f :: Int
             --          f @a = ...   -- loop (InvisPat{} : _) []
             --      2.  f :: Int -> Int
             --          f @a x = ... -- loop (InvisPat{} : _) (ExpFunPatTy{} : _)
             --      3.  f :: forall a -> Int
             --          f @a t = ... -- loop (InvisPat{} : _) (ExpForAllPatTy (Bndr _ Required) : _)
             --      4.  f :: forall {a}. Int
             --          f @a t = ... -- loop (InvisPat{} : _) (ExpForAllPatTy (Bndr _ Inferred) : _)
             loop (L SrcSpanAnnA
loc (InvisPat XInvisPat GhcRn
_ HsTyPat (NoGhcTc GhcRn)
tp) : [LPat GhcRn]
_) [ExpPatType]
_ =
                SrcSpan
-> TcRnMessage
-> IOEnv
     (Env TcGblEnv TcLclEnv) ([GenLocated SrcSpanAnnA (Pat GhcTc)], a)
forall a. SrcSpan -> TcRnMessage -> TcRn a
failAt (SrcSpanAnnA -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA SrcSpanAnnA
loc) (HsTyPat GhcRn -> TcRnMessage
TcRnInvisPatWithNoForAll HsTyPat (NoGhcTc GhcRn)
HsTyPat GhcRn
tp)

             -- ExpFunPatTy: expecting a value pattern
             -- tc_lpat will error if it sees a @t type pattern
             loop (LPat GhcRn
pat : [LPat GhcRn]
pats) (ExpFunPatTy Scaled ExpSigmaTypeFRR
pat_ty : [ExpPatType]
pat_tys)
               = do { (p, (ps, res)) <- Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaTypeFRR
pat_ty PatEnv
penv LPat GhcRn
pat (TcM ([LPat GhcTc], a) -> TcM (LPat GhcTc, ([LPat GhcTc], a)))
-> TcM ([LPat GhcTc], a) -> TcM (LPat GhcTc, ([LPat GhcTc], a))
forall a b. (a -> b) -> a -> b
$
                                        [LPat GhcRn] -> [ExpPatType] -> TcM ([LPat GhcTc], a)
loop [LPat GhcRn]
pats [ExpPatType]
pat_tys
                    ; return (p : ps, res) }
                    -- This VisPat is Retained.
                    -- See Note [Invisible binders in functions] in GHC.Hs.Pat

             loop pats :: [LPat GhcRn]
pats@(LPat GhcRn
_:[LPat GhcRn]
_) [] = String
-> SDoc
-> IOEnv
     (Env TcGblEnv TcLclEnv) ([GenLocated SrcSpanAnnA (Pat GhcTc)], a)
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tcMatchPats" ([GenLocated SrcSpanAnnA (Pat GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats)
                    -- Failure of PRECONDITION

       ; loop pats pat_tys }
  where
    penv :: PatEnv
penv = PE { pe_lazy :: Bool
pe_lazy = Bool
False, pe_ctxt :: PatCtxt
pe_ctxt = HsMatchContextRn -> PatCtxt
LamPat HsMatchContextRn
match_ctxt, pe_orig :: CtOrigin
pe_orig = CtOrigin
PatOrigin }


tcInferPat :: FixedRuntimeRepContext
           -> HsMatchContextRn
           -> LPat GhcRn
           -> TcM a
           -> TcM ((LPat GhcTc, a), TcSigmaTypeFRR)
tcInferPat :: forall a.
FixedRuntimeRepContext
-> HsMatchContextRn
-> LPat GhcRn
-> TcM a
-> TcM ((LPat GhcTc, a), Type)
tcInferPat FixedRuntimeRepContext
frr_orig HsMatchContextRn
ctxt LPat GhcRn
pat TcM a
thing_inside
  = FixedRuntimeRepContext
-> (ExpSigmaTypeFRR -> TcM (LPat GhcTc, a))
-> TcM ((LPat GhcTc, a), Type)
forall a.
FixedRuntimeRepContext
-> (ExpSigmaTypeFRR -> TcM a) -> TcM (a, Type)
tcInferFRR FixedRuntimeRepContext
frr_orig ((ExpSigmaTypeFRR -> TcM (LPat GhcTc, a))
 -> TcM ((LPat GhcTc, a), Type))
-> (ExpSigmaTypeFRR -> TcM (LPat GhcTc, a))
-> TcM ((LPat GhcTc, a), Type)
forall a b. (a -> b) -> a -> b
$ \ ExpSigmaTypeFRR
exp_ty ->
    Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (ExpSigmaTypeFRR -> Scaled ExpSigmaTypeFRR
forall a. a -> Scaled a
unrestricted ExpSigmaTypeFRR
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 = HsMatchContextRn -> PatCtxt
LamPat HsMatchContextRn
ctxt, pe_orig :: CtOrigin
pe_orig = CtOrigin
PatOrigin }

tcCheckPat :: HsMatchContextRn
           -> LPat GhcRn -> Scaled TcSigmaTypeFRR
           -> TcM a                     -- Checker for body
           -> TcM (LPat GhcTc, a)
tcCheckPat :: forall a.
HsMatchContextRn
-> LPat GhcRn -> Scaled Type -> TcM a -> TcM (LPat GhcTc, a)
tcCheckPat HsMatchContextRn
ctxt = HsMatchContextRn
-> CtOrigin
-> LPat GhcRn
-> Scaled Type
-> TcM a
-> TcM (LPat GhcTc, a)
forall a.
HsMatchContextRn
-> CtOrigin
-> LPat GhcRn
-> Scaled Type
-> TcM a
-> TcM (LPat GhcTc, a)
tcCheckPat_O HsMatchContextRn
ctxt CtOrigin
PatOrigin

-- | A variant of 'tcPat' that takes a custom origin
tcCheckPat_O :: HsMatchContextRn
             -> CtOrigin              -- ^ origin to use if the type needs inst'ing
             -> LPat GhcRn -> Scaled TcSigmaTypeFRR
             -> TcM a                 -- Checker for body
             -> TcM (LPat GhcTc, a)
tcCheckPat_O :: forall a.
HsMatchContextRn
-> CtOrigin
-> LPat GhcRn
-> Scaled Type
-> TcM a
-> TcM (LPat GhcTc, a)
tcCheckPat_O HsMatchContextRn
ctxt CtOrigin
orig LPat GhcRn
pat (Scaled Type
pat_mult Type
pat_ty) TcM a
thing_inside
  = Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Type -> ExpSigmaTypeFRR -> Scaled ExpSigmaTypeFRR
forall a. Type -> a -> Scaled a
Scaled Type
pat_mult (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
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 = HsMatchContextRn -> PatCtxt
LamPat HsMatchContextRn
ctxt, pe_orig :: CtOrigin
pe_orig = CtOrigin
orig }


{- Note [tcMatchPats]
~~~~~~~~~~~~~~~~~~~~~
tcMatchPats is the externally-callable wrapper function for
  function definitions  f p1 .. pn = rhs
  lambdas               \p1 .. pn -> body
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

It takes the list of patterns writen by the user, but it returns only the
/value/ patterns.  For example:
     f :: forall a. forall b -> a -> Mabye b -> blah
     f @a w x (Just y) = ....
tcMatchPats returns only the /value/ patterns [x, Just y].  Why?  The
desugarer expects only value patterns.  (We could change that, but we would
have to do so carefullly.)  However, distinguishing value patterns from type
patterns is a bit tricky; e.g. the `w` in this example.  So it's very
convenient to filter them out right here.


************************************************************************
*                                                                      *
                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
      HsMatchContextRn

  | 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 TyCoVar
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
forall doc. IsLine doc => String -> doc
text String
"LetLclBndr"
  ppr (LetGblBndr {}) = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"LetGblBndr"

makeLazy :: PatEnv -> PatEnv
makeLazy :: PatEnv -> PatEnv
makeLazy PatEnv
penv = PatEnv
penv { pe_lazy = 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 ExpSigmaTypeFRR -> TcM (HsWrapper, TcId)
-- (coi, xp) = tcPatBndr penv x pat_ty
-- Then coi : pat_ty ~ typeof(xp)
--
tcPatBndr :: PatEnv
-> Name -> Scaled ExpSigmaTypeFRR -> TcM (HsWrapper, TyCoVar)
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 TyCoVar
pc_sig_fn = Name -> Maybe TyCoVar
sig_fn
                                      , pc_new :: PatCtxt -> LetBndrSpec
pc_new    = LetBndrSpec
no_gen } })
          Name
bndr_name Scaled ExpSigmaTypeFRR
exp_pat_ty
  -- For the LetPat cases, see
  -- Note [Typechecking pattern bindings] in GHC.Tc.Gen.Bind

  | Just TyCoVar
bndr_id <- Name -> Maybe TyCoVar
sig_fn Name
bndr_name   -- There is a signature
  = do { wrap <- PatEnv -> ExpSigmaTypeFRR -> Type -> TcM HsWrapper
tc_sub_type PatEnv
penv (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
exp_pat_ty) (TyCoVar -> Type
idType TyCoVar
bndr_id)
           -- See Note [Subsumption check at pattern variables]
       ; traceTc "tcPatBndr(sig)" (ppr bndr_id $$ ppr (idType bndr_id) $$ ppr exp_pat_ty)
       ; return (wrap, bndr_id) }

  | Bool
otherwise                          -- No signature
  = do { (co, bndr_ty) <- case Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
exp_pat_ty of
             Check Type
pat_ty    -> TcLevel
-> Type -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type)
promoteTcType TcLevel
bind_lvl Type
pat_ty
             Infer InferResult
infer_res -> Bool
-> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type)
-> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type)
forall a. HasCallStack => Bool -> a -> a
assert (TcLevel
bind_lvl TcLevel -> TcLevel -> Bool
`sameDepthAs` InferResult -> TcLevel
ir_lvl InferResult
infer_res) (IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type)
 -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type))
-> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type)
-> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type)
forall a b. (a -> b) -> a -> b
$
                                -- If we were under a constructor that bumped the
                                -- level, we'd be in checking mode (see tcConArg)
                                -- hence this assertion
                                do { bndr_ty <- InferResult -> TcM Type
inferResultToType InferResult
infer_res
                                   ; return (mkNomReflCo bndr_ty, bndr_ty) }
       ; let bndr_mult = Scaled ExpSigmaTypeFRR -> Type
forall a. Scaled a -> Type
scaledMult Scaled ExpSigmaTypeFRR
exp_pat_ty
       ; bndr_id <- newLetBndr no_gen bndr_name bndr_mult bndr_ty
       ; traceTc "tcPatBndr(nosig)" (vcat [ ppr bind_lvl
                                          , ppr exp_pat_ty, ppr bndr_ty, ppr co
                                          , ppr bndr_id ])
       ; return (mkWpCastN co, bndr_id) }

tcPatBndr PatEnv
_ Name
bndr_name Scaled ExpSigmaTypeFRR
pat_ty
  = do { let pat_mult :: Type
pat_mult = Scaled ExpSigmaTypeFRR -> Type
forall a. Scaled a -> Type
scaledMult Scaled ExpSigmaTypeFRR
pat_ty
       ; pat_ty <- ExpSigmaTypeFRR -> TcM Type
expTypeToType (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
pat_ty)
       ; traceTc "tcPatBndr(not let)" (ppr bndr_name $$ ppr pat_ty)
       ; return (idHsWrapper, mkLocalIdOrCoVar bndr_name pat_mult 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 -> Type -> Type -> TcM TyCoVar
newLetBndr LetBndrSpec
LetLclBndr Name
name Type
w Type
ty
  = do { mono_name <- Name -> TcM Name
cloneLocalName Name
name
       ; return (mkLocalId mono_name w ty) }
newLetBndr (LetGblBndr TcPragEnv
prags) Name
name Type
w Type
ty
  = TyCoVar -> [LSig GhcRn] -> TcM TyCoVar
addInlinePrags (HasDebugCallStack => Name -> Type -> Type -> TyCoVar
Name -> Type -> Type -> TyCoVar
mkLocalId Name
name Type
w Type
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 -> ExpSigmaTypeFRR -> Type -> TcM HsWrapper
tc_sub_type PatEnv
penv ExpSigmaTypeFRR
t1 Type
t2 = CtOrigin
-> UserTypeCtxt -> ExpSigmaTypeFRR -> Type -> TcM HsWrapper
tcSubTypePat (PatEnv -> CtOrigin
pe_orig PatEnv
penv) UserTypeCtxt
GenSigCtxt ExpSigmaTypeFRR
t1 Type
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 () -> PatEnv -> [inp] -> TcM r -> TcM r
tcMultiple_ :: forall inp r. Checker inp () -> PatEnv -> [inp] -> TcM r -> TcM r
tcMultiple_ Checker inp ()
tc_pat PatEnv
penv [inp]
args TcM r
thing_inside
  = do { (_, res) <- Checker inp () -> Checker [inp] [()]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple PatEnv -> inp -> TcM r -> TcM ((), r)
Checker inp ()
tc_pat PatEnv
penv [inp]
args TcM r
thing_inside
       ; return res }

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  { err_ctxt <- TcM [ErrCtxt]
getErrCtxt
        ; let loop []
                = do { res <- TcM r
thing_inside
                     ; return ([], res) }

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

                     ; return (p':ps', res) }

        ; loop args }

--------------------
tc_lpat :: Scaled ExpSigmaTypeFRR
        -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat :: Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaTypeFRR
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. EpAnn 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', 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 ExpSigmaTypeFRR -> Checker (Pat GhcRn) (Pat GhcTc)
tc_pat Scaled ExpSigmaTypeFRR
pat_ty PatEnv
penv Pat GhcRn
pat)
                                          TcM r
thing_inside
        ; return (L span pat', res) }

tc_lpats :: [Scaled ExpSigmaTypeFRR]
         -> Checker [LPat GhcRn] [LPat GhcTc]
tc_lpats :: [Scaled ExpSigmaTypeFRR] -> Checker [LPat GhcRn] [LPat GhcTc]
tc_lpats [Scaled ExpSigmaTypeFRR]
tys PatEnv
penv [LPat GhcRn]
pats
  = Bool
-> SDoc
-> (TcM r -> TcM ([LPat GhcTc], r))
-> TcM r
-> TcM ([LPat GhcTc], r)
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr ([GenLocated SrcSpanAnnA (Pat GhcRn)]
-> [Scaled ExpSigmaTypeFRR] -> Bool
forall a b. [a] -> [b] -> Bool
equalLength [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats [Scaled ExpSigmaTypeFRR]
tys) ([GenLocated SrcSpanAnnA (Pat GhcRn)] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ [Scaled ExpSigmaTypeFRR] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Scaled ExpSigmaTypeFRR]
tys) ((TcM r -> TcM ([LPat GhcTc], r))
 -> TcM r -> TcM ([LPat GhcTc], r))
-> (TcM r -> TcM ([LPat GhcTc], r))
-> TcM r
-> TcM ([LPat GhcTc], r)
forall a b. (a -> b) -> a -> b
$
    Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled ExpSigmaTypeFRR)
  (LPat GhcTc)
-> Checker
     [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled ExpSigmaTypeFRR)]
     [LPat GhcTc]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple (\ PatEnv
penv' (GenLocated SrcSpanAnnA (Pat GhcRn)
p,Scaled ExpSigmaTypeFRR
t) -> Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaTypeFRR
t PatEnv
penv' LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
p)
               PatEnv
penv
               (String
-> [GenLocated SrcSpanAnnA (Pat GhcRn)]
-> [Scaled ExpSigmaTypeFRR]
-> [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled ExpSigmaTypeFRR)]
forall a b. HasDebugCallStack => String -> [a] -> [b] -> [(a, b)]
zipEqual String
"tc_lpats" [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats [Scaled ExpSigmaTypeFRR]
tys)

--------------------
checkManyPattern :: NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern :: forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
reason LPat GhcRn
pat Scaled a
pat_ty = CtOrigin -> Type -> Type -> TcM ()
tcSubMult (NonLinearPatternReason -> LPat GhcRn -> CtOrigin
NonLinearPatternOrigin NonLinearPatternReason
reason LPat GhcRn
pat) Type
ManyTy (Scaled a -> Type
forall a. Scaled a -> Type
scaledMult Scaled a
pat_ty)


tc_forall_lpat :: TcTyVar -> Checker (LPat GhcRn) (LPat GhcTc)
tc_forall_lpat :: TyCoVar -> Checker (LPat GhcRn) (LPat GhcTc)
tc_forall_lpat TyCoVar
tv PatEnv
penv (L SrcSpanAnnA
span Pat GhcRn
pat) TcM r
thing_inside
  = SrcSpanAnnA -> TcRn (LPat GhcTc, r) -> TcRn (LPat GhcTc, r)
forall ann a. EpAnn 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', 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 (TyCoVar -> Checker (Pat GhcRn) (Pat GhcTc)
tc_forall_pat TyCoVar
tv PatEnv
penv Pat GhcRn
pat)
                                          TcM r
thing_inside
        ; return (L span pat', res) }

tc_forall_pat :: TcTyVar -> Checker (Pat GhcRn) (Pat GhcTc)
tc_forall_pat :: TyCoVar -> Checker (Pat GhcRn) (Pat GhcTc)
tc_forall_pat TyCoVar
tv PatEnv
penv (ParPat XParPat GhcRn
x LPat GhcRn
lpat) TcM r
thing_inside
  = do { (lpat', res) <- TyCoVar -> Checker (LPat GhcRn) (LPat GhcTc)
tc_forall_lpat TyCoVar
tv PatEnv
penv LPat GhcRn
lpat TcM r
thing_inside
       ; return (ParPat x lpat', res) }

tc_forall_pat TyCoVar
tv PatEnv
_ (EmbTyPat XEmbTyPat GhcRn
_ HsTyPat (NoGhcTc GhcRn)
tp) TcM r
thing_inside
  -- The entire type pattern is guarded with the `type` herald:
  --    f (type t) (x :: t) = ...
  -- This special case is not necessary for correctness but avoids
  -- a redundant `ExpansionPat` node.
  = do { (arg_ty, result) <- HsTyPat GhcRn -> TyCoVar -> TcM r -> TcM (Type, r)
forall r. HsTyPat GhcRn -> TyCoVar -> TcM r -> TcM (Type, r)
tc_ty_pat HsTyPat (NoGhcTc GhcRn)
HsTyPat GhcRn
tp TyCoVar
tv TcM r
thing_inside
       ; return (EmbTyPat arg_ty tp, result) }

tc_forall_pat TyCoVar
tv PatEnv
_ Pat GhcRn
pat TcM r
thing_inside
  -- The type pattern is not guarded with the `type` herald, or perhaps
  -- only parts of it are, e.g.
  --    f (t :: Type)        (x :: t) = ...    -- no `type` herald
  --    f ((type t) :: Type) (x :: t) = ...    -- nested `type` herald
  -- Apply a recursive T2T transformation.
  = do { tp <- Pat GhcRn -> TcM (HsTyPat GhcRn)
pat_to_type_pat Pat GhcRn
pat
       ; (arg_ty, result) <- tc_ty_pat tp tv thing_inside
       ; let pat' = XXPat GhcTc -> Pat GhcTc
forall p. XXPat p -> Pat p
XPat (XXPat GhcTc -> Pat GhcTc) -> XXPat GhcTc -> Pat GhcTc
forall a b. (a -> b) -> a -> b
$ Pat GhcRn -> Pat GhcTc -> XXPatGhcTc
ExpansionPat Pat GhcRn
pat (XEmbTyPat GhcTc -> HsTyPat (NoGhcTc GhcTc) -> Pat GhcTc
forall p. XEmbTyPat p -> HsTyPat (NoGhcTc p) -> Pat p
EmbTyPat XEmbTyPat GhcTc
Type
arg_ty HsTyPat (NoGhcTc GhcTc)
HsTyPat GhcRn
tp)
       ; return (pat', result) }


-- Convert a Pat into the equivalent HsTyPat.
-- See `expr_to_type` (GHC.Tc.Gen.App) for the HsExpr counterpart.
-- The `TcM` monad is only used to fail on ill-formed type patterns.
pat_to_type_pat :: Pat GhcRn -> TcM (HsTyPat GhcRn)
pat_to_type_pat :: Pat GhcRn -> TcM (HsTyPat GhcRn)
pat_to_type_pat Pat GhcRn
pat = do
  (ty, x) <- WriterT
  HsTyPatRnBuilder
  (IOEnv (Env TcGblEnv TcLclEnv))
  (GenLocated SrcSpanAnnA (HsType GhcRn))
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (GenLocated SrcSpanAnnA (HsType GhcRn), HsTyPatRnBuilder)
forall w (m :: * -> *) a. Monoid w => WriterT w m a -> m (a, w)
runWriterT (Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
pat_to_type Pat GhcRn
pat)
  pure (HsTP (buildHsTyPatRn x) ty)

pat_to_type :: Pat GhcRn -> WriterT HsTyPatRnBuilder TcM (LHsType GhcRn)
pat_to_type :: Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
pat_to_type (EmbTyPat XEmbTyPat GhcRn
_ (HsTP XHsTP (NoGhcTc GhcRn)
x LHsType (NoGhcTc GhcRn)
t)) =
  do { HsTyPatRnBuilder
-> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) ()
forall w (m :: * -> *). (Monoid w, Monad m) => w -> WriterT w m ()
tell (HsTyPatRn -> HsTyPatRnBuilder
builderFromHsTyPatRn XHsTP (NoGhcTc GhcRn)
HsTyPatRn
x)
     ; GenLocated SrcSpanAnnA (HsType GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall a.
a -> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) a
forall (m :: * -> *) a. Monad m => a -> m a
return LHsType (NoGhcTc GhcRn)
GenLocated SrcSpanAnnA (HsType GhcRn)
t }
pat_to_type (VarPat XVarPat GhcRn
_ LIdP GhcRn
lname)  =
  do { HsTyPatRnBuilder
-> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) ()
forall w (m :: * -> *). (Monoid w, Monad m) => w -> WriterT w m ()
tell (Name -> HsTyPatRnBuilder
tpBuilderExplicitTV (GenLocated SrcSpanAnnN Name -> Name
forall l e. GenLocated l e -> e
unLoc LIdP GhcRn
GenLocated SrcSpanAnnN Name
lname))
     ; GenLocated SrcSpanAnnA (HsType GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall a.
a -> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) a
forall (m :: * -> *) a. Monad m => a -> m a
return GenLocated SrcSpanAnnA (HsType GhcRn)
b }
  where b :: GenLocated SrcSpanAnnA (HsType GhcRn)
b = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XTyVar GhcRn -> PromotionFlag -> LIdP GhcRn -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> LIdP pass -> HsType pass
HsTyVar XTyVar GhcRn
forall a. NoAnn a => a
noAnn PromotionFlag
NotPromoted LIdP GhcRn
lname)
pat_to_type (WildPat XWildPat GhcRn
_) = GenLocated SrcSpanAnnA (HsType GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall a.
a -> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) a
forall (m :: * -> *) a. Monad m => a -> m a
return GenLocated SrcSpanAnnA (HsType GhcRn)
b
  where b :: GenLocated SrcSpanAnnA (HsType GhcRn)
b = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XWildCardTy GhcRn -> HsType GhcRn
forall pass. XWildCardTy pass -> HsType pass
HsWildCardTy XWildCardTy GhcRn
NoExtField
noExtField)
pat_to_type (SigPat XSigPat GhcRn
_ LPat GhcRn
pat HsPatSigType (NoGhcTc GhcRn)
sig_ty)
  = do { t <- Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
pat_to_type (GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn
forall l e. GenLocated l e -> e
unLoc LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
pat)
       ; let { !(HsPS x_hsps k) = sig_ty
             ; b = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XKindSig GhcRn -> LHsType GhcRn -> LHsType GhcRn -> HsType GhcRn
forall pass.
XKindSig pass -> LHsType pass -> LHsType pass -> HsType pass
HsKindSig XKindSig GhcRn
TokDcolon
forall a. NoAnn a => a
noAnn LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
t LHsType (NoGhcTc GhcRn)
LHsType GhcRn
k) }
       ; tell (tpBuilderPatSig x_hsps)
       ; return b }
pat_to_type (ParPat XParPat GhcRn
_ LPat GhcRn
pat)
  = do { t <- Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
pat_to_type (GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn
forall l e. GenLocated l e -> e
unLoc LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
pat)
       ; return (noLocA (HsParTy noAnn t)) }
pat_to_type (SplicePat (HsUntypedSpliceTop ThModFinalizers
mod_finalizers Pat GhcRn
pat) HsUntypedSplice GhcRn
splice) = do
      { t <- Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
pat_to_type Pat GhcRn
pat
      ; return (noLocA (HsSpliceTy (HsUntypedSpliceTop mod_finalizers t) splice)) }

pat_to_type (TuplePat XTuplePat GhcRn
_ [LPat GhcRn]
pats Boxity
Boxed)
  = do { tys <- (GenLocated SrcSpanAnnA (Pat GhcRn)
 -> WriterT
      HsTyPatRnBuilder
      (IOEnv (Env TcGblEnv TcLclEnv))
      (GenLocated SrcSpanAnnA (HsType GhcRn)))
-> [GenLocated SrcSpanAnnA (Pat GhcRn)]
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     [GenLocated SrcSpanAnnA (HsType GhcRn)]
forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
forall (f :: * -> *) a b.
Applicative f =>
(a -> f b) -> [a] -> f [b]
traverse (Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
Pat GhcRn
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
pat_to_type (Pat GhcRn
 -> WriterT
      HsTyPatRnBuilder
      (IOEnv (Env TcGblEnv TcLclEnv))
      (GenLocated SrcSpanAnnA (HsType GhcRn)))
-> (GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn)
-> GenLocated SrcSpanAnnA (Pat GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn
forall l e. GenLocated l e -> e
unLoc) [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats
       ; let t = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XExplicitTupleTy GhcRn
-> PromotionFlag -> [LHsType GhcRn] -> HsType GhcRn
forall pass.
XExplicitTupleTy pass
-> PromotionFlag -> [LHsType pass] -> HsType pass
HsExplicitTupleTy XExplicitTupleTy GhcRn
NoExtField
noExtField PromotionFlag
NotPromoted [LHsType GhcRn]
[GenLocated SrcSpanAnnA (HsType GhcRn)]
tys)
       ; pure t }
pat_to_type (ListPat XListPat GhcRn
_ [LPat GhcRn]
pats)
  = do { tys <- (GenLocated SrcSpanAnnA (Pat GhcRn)
 -> WriterT
      HsTyPatRnBuilder
      (IOEnv (Env TcGblEnv TcLclEnv))
      (GenLocated SrcSpanAnnA (HsType GhcRn)))
-> [GenLocated SrcSpanAnnA (Pat GhcRn)]
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     [GenLocated SrcSpanAnnA (HsType GhcRn)]
forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
forall (f :: * -> *) a b.
Applicative f =>
(a -> f b) -> [a] -> f [b]
traverse (Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
Pat GhcRn
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
pat_to_type (Pat GhcRn
 -> WriterT
      HsTyPatRnBuilder
      (IOEnv (Env TcGblEnv TcLclEnv))
      (GenLocated SrcSpanAnnA (HsType GhcRn)))
-> (GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn)
-> GenLocated SrcSpanAnnA (Pat GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn
forall l e. GenLocated l e -> e
unLoc) [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats
       ; let t = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XExplicitListTy GhcRn
-> PromotionFlag -> [LHsType GhcRn] -> HsType GhcRn
forall pass.
XExplicitListTy pass
-> PromotionFlag -> [LHsType pass] -> HsType pass
HsExplicitListTy XExplicitListTy GhcRn
NoExtField
NoExtField PromotionFlag
NotPromoted [LHsType GhcRn]
[GenLocated SrcSpanAnnA (HsType GhcRn)]
tys)
       ; pure t }

pat_to_type (LitPat XLitPat GhcRn
_ HsLit GhcRn
lit)
  | Just HsTyLit GhcRn
ty_lit <- HsLit GhcRn -> Maybe (HsTyLit GhcRn)
tyLitFromLit HsLit GhcRn
lit
  = do { let t :: GenLocated SrcSpanAnnA (HsType GhcRn)
t = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XTyLit GhcRn -> HsTyLit GhcRn -> HsType GhcRn
forall pass. XTyLit pass -> HsTyLit pass -> HsType pass
HsTyLit XTyLit GhcRn
NoExtField
noExtField HsTyLit GhcRn
ty_lit)
      ; GenLocated SrcSpanAnnA (HsType GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall a.
a -> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) a
forall (f :: * -> *) a. Applicative f => a -> f a
pure GenLocated SrcSpanAnnA (HsType GhcRn)
t }
pat_to_type (NPat XNPat GhcRn
_ (L EpAnnCO
_ HsOverLit GhcRn
lit) Maybe (SyntaxExpr GhcRn)
_ SyntaxExpr GhcRn
_)
  | Just HsTyLit GhcRn
ty_lit <- OverLitVal -> Maybe (HsTyLit GhcRn)
tyLitFromOverloadedLit (HsOverLit GhcRn -> OverLitVal
forall p. HsOverLit p -> OverLitVal
ol_val HsOverLit GhcRn
lit)
  = do { let t :: GenLocated SrcSpanAnnA (HsType GhcRn)
t = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XTyLit GhcRn -> HsTyLit GhcRn -> HsType GhcRn
forall pass. XTyLit pass -> HsTyLit pass -> HsType pass
HsTyLit XTyLit GhcRn
NoExtField
noExtField HsTyLit GhcRn
ty_lit)
       ; GenLocated SrcSpanAnnA (HsType GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall a.
a -> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) a
forall (f :: * -> *) a. Applicative f => a -> f a
pure GenLocated SrcSpanAnnA (HsType GhcRn)
t}

pat_to_type (ConPat XConPat GhcRn
_ XRec GhcRn (ConLikeP GhcRn)
lname (InfixCon LPat GhcRn
left LPat GhcRn
right))
  = do { lty <- Pat GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
pat_to_type (GenLocated SrcSpanAnnA (Pat GhcRn) -> Pat GhcRn
forall l e. GenLocated l e -> e
unLoc LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
left)
       ; rty <- pat_to_type (unLoc right)
       ; let { t = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XOpTy GhcRn
-> PromotionFlag
-> LHsType GhcRn
-> LIdP GhcRn
-> LHsType GhcRn
-> HsType GhcRn
forall pass.
XOpTy pass
-> PromotionFlag
-> LHsType pass
-> LIdP pass
-> LHsType pass
-> HsType pass
HsOpTy XOpTy GhcRn
NoExtField
noExtField PromotionFlag
NotPromoted LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
lty LIdP GhcRn
XRec GhcRn (ConLikeP GhcRn)
lname LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
rty)}
       ; pure t }
pat_to_type (ConPat XConPat GhcRn
_ XRec GhcRn (ConLikeP GhcRn)
lname (PrefixCon [HsConPatTyArg (NoGhcTc GhcRn)]
invis_args [LPat GhcRn]
vis_args))
  = do { let { appHead :: GenLocated SrcSpanAnnA (HsType GhcRn)
appHead = HsType GhcRn -> GenLocated SrcSpanAnnA (HsType GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (XTyVar GhcRn -> PromotionFlag -> LIdP GhcRn -> HsType GhcRn
forall pass.
XTyVar pass -> PromotionFlag -> LIdP pass -> HsType pass
HsTyVar XTyVar GhcRn
forall a. NoAnn a => a
noAnn PromotionFlag
NotPromoted LIdP GhcRn
XRec GhcRn (ConLikeP GhcRn)
lname)}
       ; ty_invis <- (GenLocated SrcSpanAnnA (HsType GhcRn)
 -> HsConPatTyArg GhcRn
 -> WriterT
      HsTyPatRnBuilder
      (IOEnv (Env TcGblEnv TcLclEnv))
      (GenLocated SrcSpanAnnA (HsType GhcRn)))
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> [HsConPatTyArg GhcRn]
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall (t :: * -> *) (m :: * -> *) b a.
(Foldable t, Monad m) =>
(b -> a -> m b) -> b -> t a -> m b
foldM LHsType GhcRn
-> HsConPatTyArg GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
GenLocated SrcSpanAnnA (HsType GhcRn)
-> HsConPatTyArg GhcRn
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
apply_invis_arg GenLocated SrcSpanAnnA (HsType GhcRn)
appHead [HsConPatTyArg (NoGhcTc GhcRn)]
[HsConPatTyArg GhcRn]
invis_args
       ; tys_vis <- traverse (pat_to_type . unLoc) vis_args
       ; let t = (GenLocated SrcSpanAnnA (HsType GhcRn)
 -> GenLocated SrcSpanAnnA (HsType GhcRn)
 -> GenLocated SrcSpanAnnA (HsType GhcRn))
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> [GenLocated SrcSpanAnnA (HsType GhcRn)]
-> GenLocated SrcSpanAnnA (HsType GhcRn)
forall b a. (b -> a -> b) -> b -> [a] -> b
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
GenLocated SrcSpanAnnA (HsType GhcRn)
-> GenLocated SrcSpanAnnA (HsType GhcRn)
-> GenLocated SrcSpanAnnA (HsType GhcRn)
forall (p :: Pass).
LHsType (GhcPass p) -> LHsType (GhcPass p) -> LHsType (GhcPass p)
mkHsAppTy GenLocated SrcSpanAnnA (HsType GhcRn)
ty_invis [GenLocated SrcSpanAnnA (HsType GhcRn)]
tys_vis
       ; pure t }
      where
        apply_invis_arg :: LHsType GhcRn -> HsConPatTyArg GhcRn -> WriterT HsTyPatRnBuilder TcM (LHsType GhcRn)
        apply_invis_arg :: LHsType GhcRn
-> HsConPatTyArg GhcRn
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
apply_invis_arg !LHsType GhcRn
t (HsConPatTyArg XConPatTyArg GhcRn
_ (HsTP XHsTP GhcRn
argx LHsType GhcRn
arg))
          = do { HsTyPatRnBuilder
-> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) ()
forall w (m :: * -> *). (Monoid w, Monad m) => w -> WriterT w m ()
tell (HsTyPatRn -> HsTyPatRnBuilder
builderFromHsTyPatRn XHsTP GhcRn
HsTyPatRn
argx)
               ; GenLocated SrcSpanAnnA (HsType GhcRn)
-> WriterT
     HsTyPatRnBuilder
     (IOEnv (Env TcGblEnv TcLclEnv))
     (GenLocated SrcSpanAnnA (HsType GhcRn))
forall a.
a -> WriterT HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) a
forall (f :: * -> *) a. Applicative f => a -> f a
pure (XAppKindTy GhcRn -> LHsType GhcRn -> LHsType GhcRn -> LHsType GhcRn
forall (p :: Pass).
XAppKindTy (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
-> LHsType (GhcPass p)
mkHsAppKindTy XAppKindTy GhcRn
NoExtField
noExtField LHsType GhcRn
t LHsType GhcRn
arg)}

pat_to_type Pat GhcRn
pat = TcM (LHsType GhcRn)
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
forall (m :: * -> *) a.
Monad m =>
m a -> WriterT HsTyPatRnBuilder m a
forall (t :: (* -> *) -> * -> *) (m :: * -> *) a.
(MonadTrans t, Monad m) =>
m a -> t m a
lift (TcM (LHsType GhcRn)
 -> WriterT
      HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn))
-> TcM (LHsType GhcRn)
-> WriterT
     HsTyPatRnBuilder (IOEnv (Env TcGblEnv TcLclEnv)) (LHsType GhcRn)
forall a b. (a -> b) -> a -> b
$
  TcRnMessage -> TcM (LHsType GhcRn)
forall a. TcRnMessage -> TcRn a
failWith (TcRnMessage -> TcM (LHsType GhcRn))
-> TcRnMessage -> TcM (LHsType GhcRn)
forall a b. (a -> b) -> a -> b
$ Pat GhcRn -> TcRnMessage
TcRnIllformedTypePattern Pat GhcRn
pat
  -- This failure is the only use of the TcM monad in `pat_to_type_pat`

{-
Note [Pattern to type (P2T) conversion]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this:

  data T a b where
    MkT :: forall a. forall b -> a -> b -> T a b
    -- NB: `a` is invisible, but `b` is required

  f (MkT @[Int] (Maybe Bool) x y) = ...

The second type argument of `MkT` is Required, so we write it without
an `@` sign in the pattern match.  So the (Maybe Bool) will be
  * parsed and renamed as a term pattern
  * converted to a type when typechecking the pattern-match: the P2T conversion

This is the only place we have P2T. In type-lambdas, the "pattern" is always a
type variable:

   f :: forall a -> a -> blah
   f b (x::b) = ...

The `b` argument must be a simple variable; we can't pattern-match on types.

The function `pat_to_type` does the P2T conversion:
   pat_to_type :: Pat GhcRn -> WriterT HsTyPatRnBuilder TcM (LHsType GhcRn)

It is arranged as a writer monad, where the `HsTyPatRnBuilder` accumulates the
binders bound by the type.  (We could discover these binders by a subsequent
traversal, that would mean writing another traversal.)
-}

tc_ty_pat :: HsTyPat GhcRn -> TcTyVar -> TcM r -> TcM (TcType, r)
tc_ty_pat :: forall r. HsTyPat GhcRn -> TyCoVar -> TcM r -> TcM (Type, r)
tc_ty_pat HsTyPat GhcRn
tp TyCoVar
tv TcM r
thing_inside
  = do { (sig_wcs, sig_ibs, arg_ty) <- HsTyPat GhcRn
-> Type -> TcM ([(Name, TyCoVar)], [(Name, TyCoVar)], Type)
tcHsTyPat HsTyPat GhcRn
tp (TyCoVar -> Type
varType TyCoVar
tv)
       ; _ <- unifyType Nothing arg_ty (mkTyVarTy tv)
       ; result <- tcExtendNameTyVarEnv sig_wcs $
                   tcExtendNameTyVarEnv sig_ibs $
                   thing_inside
       ; return (arg_ty, result) }

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

tc_pat :: Scaled ExpSigmaTypeFRR -> Checker (Pat GhcRn) (Pat GhcTc)
tc_pat Scaled ExpSigmaTypeFRR
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
        { (wrap, id) <- PatEnv
-> Name -> Scaled ExpSigmaTypeFRR -> TcM (HsWrapper, TyCoVar)
tcPatBndr PatEnv
penv Name
name Scaled ExpSigmaTypeFRR
pat_ty
        ; res <- tcCheckUsage name (scaledMult pat_ty) $
                              tcExtendIdEnv1 name id thing_inside
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return (mkHsWrapPat wrap (VarPat x (L l id)) pat_ty, res) }

  ParPat XParPat GhcRn
x LPat GhcRn
pat -> do
        { (pat', res) <- Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaTypeFRR
pat_ty PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; return (ParPat x pat', res) }

  BangPat XBangPat GhcRn
x LPat GhcRn
pat -> do
        { (pat', res) <- Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaTypeFRR
pat_ty PatEnv
penv LPat GhcRn
pat TcM r
thing_inside
        ; return (BangPat x pat', res) }

  OrPat XOrPat GhcRn
_ NonEmpty (LPat GhcRn)
pats -> do -- See Note [Implementation of OrPatterns], Typechecker (1)
    { let pats_list :: [GenLocated SrcSpanAnnA (Pat GhcRn)]
pats_list = NonEmpty (GenLocated SrcSpanAnnA (Pat GhcRn))
-> [GenLocated SrcSpanAnnA (Pat GhcRn)]
forall a. NonEmpty a -> [a]
NE.toList NonEmpty (LPat GhcRn)
NonEmpty (GenLocated SrcSpanAnnA (Pat GhcRn))
pats
    ; (pats_list', (res, pat_ct)) <- [Scaled ExpSigmaTypeFRR] -> Checker [LPat GhcRn] [LPat GhcTc]
tc_lpats ((GenLocated SrcSpanAnnA (Pat GhcRn) -> Scaled ExpSigmaTypeFRR)
-> [GenLocated SrcSpanAnnA (Pat GhcRn)] -> [Scaled ExpSigmaTypeFRR]
forall a b. (a -> b) -> [a] -> [b]
map (Scaled ExpSigmaTypeFRR
-> GenLocated SrcSpanAnnA (Pat GhcRn) -> Scaled ExpSigmaTypeFRR
forall a b. a -> b -> a
const Scaled ExpSigmaTypeFRR
pat_ty) [GenLocated SrcSpanAnnA (Pat GhcRn)]
pats_list) PatEnv
penv [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
pats_list (TcM r -> TcM (r, WantedConstraints)
forall a. TcM a -> TcM (a, WantedConstraints)
captureConstraints TcM r
thing_inside)
    ; let pats' = [GenLocated SrcSpanAnnA (Pat GhcTc)]
-> NonEmpty (GenLocated SrcSpanAnnA (Pat GhcTc))
forall a. HasCallStack => [a] -> NonEmpty a
NE.fromList [GenLocated SrcSpanAnnA (Pat GhcTc)]
pats_list' -- tc_lpats preserves non-emptiness
    ; emitConstraints pat_ct
        -- captureConstraints/extendConstraints:
        --   like in Note [Hopping the LIE in lazy patterns]
    ; pat_ty <- expTypeToType (scaledThing pat_ty)
    ; return (OrPat pat_ty pats', res) }

  LazyPat XLazyPat GhcRn
x LPat GhcRn
pat -> do
        { NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
LazyPatternReason (Pat GhcRn -> GenLocated SrcSpanAnnA (Pat GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Pat GhcRn
ps_pat) Scaled ExpSigmaTypeFRR
pat_ty
        ; (pat', (res, pat_ct))
                <- Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat Scaled ExpSigmaTypeFRR
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

        ; emitConstraints pat_ct
        -- captureConstraints/extendConstraints:
        --   see Note [Hopping the LIE in lazy patterns]

        -- Check that the expected pattern type is itself lifted
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; _ <- unifyType Nothing (typeKind pat_ty) liftedTypeKind

        ; return ((LazyPat x pat'), res) }

  WildPat XWildPat GhcRn
_ -> do
        { NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
OtherPatternReason (Pat GhcRn -> GenLocated SrcSpanAnnA (Pat GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Pat GhcRn
ps_pat) Scaled ExpSigmaTypeFRR
pat_ty
        ; res <- TcM r
thing_inside
        ; pat_ty <- expTypeToType (scaledThing pat_ty)
        ; return (WildPat pat_ty, res) }

  AsPat XAsPat GhcRn
x (L SrcSpanAnnN
nm_loc Name
name) LPat GhcRn
pat -> do
        { NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
OtherPatternReason (Pat GhcRn -> GenLocated SrcSpanAnnA (Pat GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Pat GhcRn
ps_pat) Scaled ExpSigmaTypeFRR
pat_ty
        ; (wrap, bndr_id) <- SrcSpanAnnN -> TcM (HsWrapper, TyCoVar) -> TcM (HsWrapper, TyCoVar)
forall ann a. EpAnn ann -> TcRn a -> TcRn a
setSrcSpanA SrcSpanAnnN
nm_loc (PatEnv
-> Name -> Scaled ExpSigmaTypeFRR -> TcM (HsWrapper, TyCoVar)
tcPatBndr PatEnv
penv Name
name Scaled ExpSigmaTypeFRR
pat_ty)
        ; (pat', res) <- tcExtendIdEnv1 name bndr_id $
                         tc_lpat (pat_ty `scaledSet`(mkCheckExpType $ idType bndr_id))
                                 penv pat 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!
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return (mkHsWrapPat wrap (AsPat x (L nm_loc bndr_id) pat') pat_ty, res) }

  ViewPat XViewPat GhcRn
_ LHsExpr GhcRn
expr LPat GhcRn
pat -> do
        { NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
ViewPatternReason (Pat GhcRn -> GenLocated SrcSpanAnnA (Pat GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Pat GhcRn
ps_pat) Scaled ExpSigmaTypeFRR
pat_ty
         --
         -- 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.

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

         -- Expression must be a function
        ; let herald = HsExpr GhcRn -> ExpectedFunTyOrigin
ExpectedFunTyViewPat (HsExpr GhcRn -> ExpectedFunTyOrigin)
-> HsExpr GhcRn -> ExpectedFunTyOrigin
forall a b. (a -> b) -> a -> b
$ GenLocated SrcSpanAnnA (HsExpr GhcRn) -> HsExpr GhcRn
forall l e. GenLocated l e -> e
unLoc LHsExpr GhcRn
GenLocated SrcSpanAnnA (HsExpr GhcRn)
expr
        ; (expr_wrap1, Scaled _mult inf_arg_ty, inf_res_sigma)
            <- matchActualFunTy herald (Just . HsExprRnThing $ unLoc expr) (1,expr_ty) 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
        ; expr_wrap2 <- tc_sub_type penv (scaledThing pat_ty) inf_arg_ty
            -- expr_wrap2 :: pat_ty "->" inf_arg_ty

         -- Pattern must have inf_res_sigma
        ; (pat', res) <- tc_lpat (pat_ty `scaledSet` mkCheckExpType inf_res_sigma) penv pat thing_inside

        ; let Scaled w h_pat_ty = pat_ty
        ; pat_ty <- readExpType h_pat_ty
        ; let expr_wrap2' = HsWrapper -> HsWrapper -> Scaled Type -> Type -> HsWrapper
mkWpFun HsWrapper
expr_wrap2 HsWrapper
idHsWrapper
                              (Type -> Type -> Scaled Type
forall a. Type -> a -> Scaled a
Scaled Type
w Type
pat_ty) Type
inf_res_sigma
          -- expr_wrap2' :: (inf_arg_ty -> inf_res_sigma) "->"
          --                (pat_ty -> inf_res_sigma)
          -- NB: pat_ty comes from matchActualFunTy, so it has a
          -- fixed RuntimeRep, as needed to call mkWpFun.
        ; let
              expr_wrap = HsWrapper
expr_wrap2' HsWrapper -> HsWrapper -> HsWrapper
<.> HsWrapper
expr_wrap1

        ; return $ (ViewPat pat_ty (mkLHsWrap expr_wrap expr') pat', 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 matchActualFunTy returns anyway.
-}

-- Type signatures in patterns
-- See Note [Pattern coercions] below
  SigPat XSigPat GhcRn
_ LPat GhcRn
pat HsPatSigType (NoGhcTc GhcRn)
sig_ty -> do
        { (inner_ty, tv_binds, wcs, wrap) <- Bool
-> HsPatSigType GhcRn
-> ExpSigmaTypeFRR
-> TcM (Type, [(Name, TyCoVar)], [(Name, TyCoVar)], HsWrapper)
tcPatSig (PatEnv -> Bool
inPatBind PatEnv
penv)
                                                            HsPatSigType (NoGhcTc GhcRn)
HsPatSigType GhcRn
sig_ty (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
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.
        ; (pat', res) <- tcExtendNameTyVarEnv wcs      $
                         tcExtendNameTyVarEnv tv_binds $
                         tc_lpat (pat_ty `scaledSet` mkCheckExpType inner_ty) penv pat thing_inside
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return (mkHsWrapPat wrap (SigPat inner_ty pat' sig_ty) pat_ty, res) }

------------------------
-- Lists, tuples, arrays

  -- Necessarily a built-in list pattern, not an overloaded list pattern.
  -- See Note [Desugaring overloaded list patterns].
  ListPat XListPat GhcRn
_ [LPat GhcRn]
pats -> do
        { (coi, elt_ty) <- (Type -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type))
-> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, Type)
forall a.
(Type -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, a)
matchExpectedPatTy Type -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, Type)
matchExpectedListTy PatEnv
penv (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
pat_ty)
        ; (pats', res) <- tcMultiple (tc_lpat (pat_ty `scaledSet` mkCheckExpType elt_ty))
                                     penv pats thing_inside
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return (mkHsWrapPat coi
                         (ListPat elt_ty pats') pat_ty, res)
}

  TuplePat XTuplePat GhcRn
_ [LPat GhcRn]
pats Boxity
boxity -> do
        { let arity :: Int
arity = [GenLocated SrcSpanAnnA (Pat GhcRn)] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat 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 -> TcM ()
checkTupSize Int
arity
        ; (coi, arg_tys) <- (Type -> TcM (TcCoercionN, [Type]))
-> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, [Type])
forall a.
(Type -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, a)
matchExpectedPatTy (TyCon -> Type -> TcM (TcCoercionN, [Type])
matchExpectedTyConApp TyCon
tc)
                                               PatEnv
penv (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
pat_ty)
                     -- Unboxed tuples have RuntimeRep vars, which we discard:
                     -- See Note [Unboxed tuple RuntimeRep vars] in GHC.Core.TyCon
        ; let con_arg_tys = case Boxity
boxity of Boxity
Unboxed -> Int -> [Type] -> [Type]
forall a. Int -> [a] -> [a]
drop Int
arity [Type]
arg_tys
                                           Boxity
Boxed   -> [Type]
arg_tys
        ; (pats', res) <- tc_lpats (map (scaledSet pat_ty . mkCheckExpType) con_arg_tys)
                                   penv pats thing_inside

        ; dflags <- 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 = XTuplePat GhcTc -> [LPat GhcTc] -> Boxity -> Pat GhcTc
forall p. XTuplePat p -> [LPat p] -> Boxity -> Pat p
TuplePat [Type]
XTuplePat GhcTc
con_arg_tys [LPat GhcTc]
[GenLocated SrcSpanAnnA (Pat GhcTc)]
pats' Boxity
boxity
                                 -- pat_ty /= pat_ty iff coi /= IdCo
              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 XLazyPat GhcTc
NoExtField
noExtField (Pat GhcTc -> GenLocated SrcSpanAnnA (Pat GhcTc)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Pat GhcTc
unmangled_result)
                | Bool
otherwise        = Pat GhcTc
unmangled_result

        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; massert (con_arg_tys `equalLength` pats) -- Syntactically enforced
        ; return (mkHsWrapPat coi possibly_mangled_result pat_ty, res)
        }

  SumPat XSumPat GhcRn
_ LPat GhcRn
pat Int
alt Int
arity  -> do
        { let tc :: TyCon
tc = Int -> TyCon
sumTyCon Int
arity
        ; (coi, arg_tys) <- (Type -> TcM (TcCoercionN, [Type]))
-> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, [Type])
forall a.
(Type -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, a)
matchExpectedPatTy (TyCon -> Type -> TcM (TcCoercionN, [Type])
matchExpectedTyConApp TyCon
tc)
                                               PatEnv
penv (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
pat_ty)
        ; -- Drop levity vars, we don't care about them here
          let con_arg_tys = Int -> [Type] -> [Type]
forall a. Int -> [a] -> [a]
drop Int
arity [Type]
arg_tys
        ; (pat', res) <- tc_lpat (pat_ty `scaledSet` mkCheckExpType (con_arg_tys `getNth` (alt - 1)))
                                 penv pat thing_inside
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return (mkHsWrapPat coi (SumPat con_arg_tys pat' alt arity) pat_ty
                 , res)
        }

------------------------
-- Data constructors
  ConPat XConPat GhcRn
_ XRec GhcRn (ConLikeP GhcRn)
con HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
arg_pats ->
    PatEnv
-> GenLocated SrcSpanAnnN Name
-> Scaled ExpSigmaTypeFRR
-> HsConDetails
     (HsConPatTyArg (NoGhcTc GhcRn))
     (LPat GhcRn)
     (HsRecFields GhcRn (LPat GhcRn))
-> TcM r
-> TcM (Pat GhcTc, r)
forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> Scaled ExpSigmaTypeFRR
-> HsConDetails
     (HsConPatTyArg (NoGhcTc GhcRn))
     (LPat GhcRn)
     (HsRecFields GhcRn (LPat GhcRn))
-> TcM a
-> TcM (Pat GhcTc, a)
tcConPat PatEnv
penv XRec GhcRn (ConLikeP GhcRn)
GenLocated SrcSpanAnnN Name
con Scaled ExpSigmaTypeFRR
pat_ty HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
arg_pats TcM r
thing_inside

------------------------
-- Literal patterns
  LitPat XLitPat GhcRn
x HsLit GhcRn
simple_lit -> do
        { let lit_ty :: Type
lit_ty = HsLit GhcRn -> Type
forall (p :: Pass). IsPass p => HsLit (GhcPass p) -> Type
hsLitType HsLit GhcRn
simple_lit
        ; wrap   <- PatEnv -> ExpSigmaTypeFRR -> Type -> TcM HsWrapper
tc_sub_type PatEnv
penv (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
pat_ty) Type
lit_ty
        ; res    <- thing_inside
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return ( mkHsWrapPat wrap (LitPat x (convertLit simple_lit)) pat_ty
                 , 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 EpAnnCO
l HsOverLit GhcRn
over_lit) Maybe (SyntaxExpr GhcRn)
mb_neg SyntaxExpr GhcRn
eq -> do
        { NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
OtherPatternReason (Pat GhcRn -> GenLocated SrcSpanAnnA (Pat GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Pat GhcRn
ps_pat) Scaled ExpSigmaTypeFRR
pat_ty
          -- 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
        ; ((lit', mb_neg'), eq')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaTypeFRR
-> ([Type] -> [Type] -> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc))
-> TcM ((HsOverLit GhcTc, Maybe SyntaxExprTc), SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaTypeFRR
-> ([Type] -> [Type] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
eq [ExpSigmaTypeFRR -> SyntaxOpType
SynType (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
pat_ty), SyntaxOpType
SynAny]
                          (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
boolTy) (([Type] -> [Type] -> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc))
 -> TcM ((HsOverLit GhcTc, Maybe SyntaxExprTc), SyntaxExprTc))
-> ([Type] -> [Type] -> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc))
-> TcM ((HsOverLit GhcTc, Maybe SyntaxExprTc), SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [Type
neg_lit_ty] [Type]
_ ->
               let new_over_lit :: Type -> TcM (HsOverLit GhcTc)
new_over_lit Type
lit_ty = HsOverLit GhcRn -> ExpSigmaTypeFRR -> TcM (HsOverLit GhcTc)
newOverloadedLit HsOverLit GhcRn
over_lit
                                           (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
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
<$> Type -> TcM (HsOverLit GhcTc)
new_over_lit Type
neg_lit_ty
                 Just SyntaxExpr GhcRn
neg -> -- Negative literal
                             -- The 'negate' is re-mappable syntax
                   (SyntaxExprTc -> Maybe SyntaxExprTc)
-> (HsOverLit GhcTc, SyntaxExprTc)
-> (HsOverLit GhcTc, Maybe SyntaxExprTc)
forall b c d. (b -> c) -> (d, b) -> (d, c)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> a (d, b) (d, c)
second SyntaxExprTc -> Maybe SyntaxExprTc
forall a. a -> Maybe a
Just ((HsOverLit GhcTc, SyntaxExprTc)
 -> (HsOverLit GhcTc, Maybe SyntaxExprTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
-> TcM (HsOverLit GhcTc, Maybe SyntaxExprTc)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$>
                   (CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaTypeFRR
-> ([Type] -> [Type] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaTypeFRR
-> ([Type] -> [Type] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
neg [SyntaxOpType
SynRho] (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
neg_lit_ty) (([Type] -> [Type] -> TcM (HsOverLit GhcTc))
 -> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc))
-> ([Type] -> [Type] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
                    \ [Type
lit_ty] [Type]
_ -> Type -> TcM (HsOverLit GhcTc)
new_over_lit Type
lit_ty)
                     -- applied to a closed literal: linearity doesn't matter as
                     -- literals are typed in an empty environment, hence have
                     -- all multiplicities.

        ; res <- thing_inside
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return (NPat pat_ty (L l lit') mb_neg' eq', 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 EpAnnCO
loc HsOverLit GhcRn
lit) HsOverLit GhcRn
_ SyntaxExpr GhcRn
ge SyntaxExpr GhcRn
minus -> do
        { NonLinearPatternReason
-> LPat GhcRn -> Scaled ExpSigmaTypeFRR -> TcM ()
forall a.
NonLinearPatternReason -> LPat GhcRn -> Scaled a -> TcM ()
checkManyPattern NonLinearPatternReason
OtherPatternReason (Pat GhcRn -> GenLocated SrcSpanAnnA (Pat GhcRn)
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA Pat GhcRn
ps_pat) Scaled ExpSigmaTypeFRR
pat_ty
        ; let pat_exp_ty :: ExpSigmaTypeFRR
pat_exp_ty = Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
pat_ty
              orig :: CtOrigin
orig = HsOverLit GhcRn -> CtOrigin
LiteralOrigin HsOverLit GhcRn
lit
        ; (lit1', ge')
            <- CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaTypeFRR
-> ([Type] -> [Type] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a.
CtOrigin
-> SyntaxExprRn
-> [SyntaxOpType]
-> ExpSigmaTypeFRR
-> ([Type] -> [Type] -> TcM a)
-> TcM (a, SyntaxExprTc)
tcSyntaxOp CtOrigin
orig SyntaxExpr GhcRn
SyntaxExprRn
ge [ExpSigmaTypeFRR -> SyntaxOpType
SynType ExpSigmaTypeFRR
pat_exp_ty, SyntaxOpType
SynRho]
                                  (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
boolTy) (([Type] -> [Type] -> TcM (HsOverLit GhcTc))
 -> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc))
-> ([Type] -> [Type] -> TcM (HsOverLit GhcTc))
-> IOEnv (Env TcGblEnv TcLclEnv) (HsOverLit GhcTc, SyntaxExprTc)
forall a b. (a -> b) -> a -> b
$
               \ [Type
lit1_ty] [Type]
_ ->
               HsOverLit GhcRn -> ExpSigmaTypeFRR -> TcM (HsOverLit GhcTc)
newOverloadedLit HsOverLit GhcRn
lit (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
lit1_ty)
        ; ((lit2', minus_wrap, bndr_id), minus')
            <- tcSyntaxOpGen orig minus [SynType pat_exp_ty, SynRho] SynAny $
               \ [Type
lit2_ty, Type
var_ty] [Type]
_ ->
               do { lit2' <- HsOverLit GhcRn -> ExpSigmaTypeFRR -> TcM (HsOverLit GhcTc)
newOverloadedLit HsOverLit GhcRn
lit (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
lit2_ty)
                  ; (wrap, bndr_id) <- setSrcSpanA nm_loc $
                                     tcPatBndr penv name (unrestricted $ mkCheckExpType var_ty)
                           -- co :: var_ty ~ idType bndr_id

                           -- minus_wrap is applicable to minus'
                  ; return (lit2', wrap, bndr_id) }

        ; pat_ty <- readExpType 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
        ; unlessM (xoptM LangExt.RebindableSyntax) $
          do { icls <- tcLookupClass integralClassName
             ; instStupidTheta orig [mkClassPred icls [pat_ty]] }

        ; res <- tcExtendIdEnv1 name bndr_id thing_inside

        ; let 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' = 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 XNPlusKPat GhcTc
Type
pat_ty (SrcSpanAnnN -> TyCoVar -> GenLocated SrcSpanAnnN TyCoVar
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
nm_loc TyCoVar
bndr_id) (EpAnnCO -> HsOverLit GhcTc -> GenLocated EpAnnCO (HsOverLit GhcTc)
forall l e. l -> e -> GenLocated l e
L EpAnnCO
loc HsOverLit GhcTc
lit1') HsOverLit GhcTc
lit2'
                               SyntaxExpr GhcTc
SyntaxExprTc
ge' SyntaxExpr GhcTc
SyntaxExprTc
minus''
        ; return (pat', res) }

-- 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 (HsUntypedSpliceTop ThModFinalizers
mod_finalizers Pat GhcRn
pat) HsUntypedSplice GhcRn
_ -> do
      { ThModFinalizers -> TcM ()
addModFinalizersWithLclEnv ThModFinalizers
mod_finalizers
      ; Scaled ExpSigmaTypeFRR -> Checker (Pat GhcRn) (Pat GhcTc)
tc_pat Scaled ExpSigmaTypeFRR
pat_ty PatEnv
penv Pat GhcRn
pat TcM r
thing_inside }

  SplicePat (HsUntypedSpliceNested Name
_) HsUntypedSplice GhcRn
_ -> String -> TcM (Pat GhcTc, r)
forall a. HasCallStack => String -> a
panic String
"tc_pat: nested splice in splice pat"

  EmbTyPat XEmbTyPat GhcRn
_ HsTyPat (NoGhcTc GhcRn)
_ -> TcRnMessage -> TcM (Pat GhcTc, r)
forall a. TcRnMessage -> TcRn a
failWith TcRnMessage
TcRnIllegalTypePattern

  InvisPat XInvisPat GhcRn
_ HsTyPat (NoGhcTc GhcRn)
_ -> String -> TcM (Pat GhcTc, r)
forall a. HasCallStack => String -> a
panic String
"tc_pat: invisible pattern appears recursively in the pattern"

  XPat (HsPatExpanded Pat GhcRn
lpat Pat GhcRn
rpat) -> do
    { (rpat', res) <- Scaled ExpSigmaTypeFRR -> Checker (Pat GhcRn) (Pat GhcTc)
tc_pat Scaled ExpSigmaTypeFRR
pat_ty PatEnv
penv Pat GhcRn
rpat TcM r
thing_inside
    ; return (XPat $ ExpansionPat lpat rpat', res) }

{-
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
-> ExpSigmaTypeFRR
-> TcM (Type, [(Name, TyCoVar)], [(Name, TyCoVar)], HsWrapper)
tcPatSig Bool
in_pat_bind HsPatSigType GhcRn
sig ExpSigmaTypeFRR
res_ty
 = do  { (sig_wcs, sig_tvs, sig_ty) <- UserTypeCtxt
-> HoleMode
-> HsPatSigType GhcRn
-> ContextKind
-> TcM ([(Name, TyCoVar)], [(Name, TyCoVar)], Type)
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

        ; case NE.nonEmpty sig_tvs of
            Maybe (NonEmpty (Name, TyCoVar))
Nothing -> do {
                -- Just do the subsumption check and return
                  wrap <- (TidyEnv -> ZonkM (TidyEnv, SDoc))
-> TcM HsWrapper -> TcM HsWrapper
forall a. (TidyEnv -> ZonkM (TidyEnv, SDoc)) -> TcM a -> TcM a
addErrCtxtM (Type -> TidyEnv -> ZonkM (TidyEnv, SDoc)
mk_msg Type
sig_ty) (TcM HsWrapper -> TcM HsWrapper) -> TcM HsWrapper -> TcM HsWrapper
forall a b. (a -> b) -> a -> b
$
                          CtOrigin
-> UserTypeCtxt -> ExpSigmaTypeFRR -> Type -> TcM HsWrapper
tcSubTypePat CtOrigin
PatSigOrigin UserTypeCtxt
PatSigCtxt ExpSigmaTypeFRR
res_ty Type
sig_ty
                ; return (sig_ty, [], sig_wcs, wrap)
                }
            Just NonEmpty (Name, TyCoVar)
sig_tvs_ne -> 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 -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
in_pat_bind
                (TcRnMessage -> TcM ()
addErr (NonEmpty (Name, TyCoVar) -> TcRnMessage
TcRnCannotBindScopedTyVarInPatSig NonEmpty (Name, TyCoVar)
sig_tvs_ne))

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

              -- Phew!
              return (sig_ty, sig_tvs, sig_wcs, wrap)
       }
  where
    mk_msg :: Type -> TidyEnv -> ZonkM (TidyEnv, SDoc)
mk_msg Type
sig_ty TidyEnv
tidy_env
       = do { (tidy_env, sig_ty) <- TidyEnv -> Type -> ZonkM (TidyEnv, Type)
zonkTidyTcType TidyEnv
tidy_env Type
sig_ty
            ; res_ty <- readExpType res_ty   -- should be filled in by now
            ; (tidy_env, res_ty) <- zonkTidyTcType tidy_env res_ty
            ; let msg = [SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [ SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"When checking that the pattern signature:")
                                  Int
4 (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
sig_ty)
                             , Int -> SDoc -> SDoc
nest Int
2 (SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"fits the type of its context:")
                                          Int
2 (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
res_ty)) ]
            ; return (tidy_env, msg) }


{- *********************************************************************
*                                                                      *
        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 ExpSigmaTypeFRR    -- Type of the pattern
         -> HsConPatDetails GhcRn -> TcM a
         -> TcM (Pat GhcTc, a)
tcConPat :: forall a.
PatEnv
-> GenLocated SrcSpanAnnN Name
-> Scaled ExpSigmaTypeFRR
-> HsConDetails
     (HsConPatTyArg (NoGhcTc GhcRn))
     (LPat GhcRn)
     (HsRecFields GhcRn (LPat GhcRn))
-> TcM a
-> TcM (Pat GhcTc, a)
tcConPat PatEnv
penv con_lname :: GenLocated SrcSpanAnnN Name
con_lname@(L SrcSpanAnnN
_ Name
con_name) Scaled ExpSigmaTypeFRR
pat_ty HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
arg_pats TcM a
thing_inside
  = do  { con_like <- Name -> TcM ConLike
tcLookupConLike Name
con_name
        ; case con_like of
            RealDataCon DataCon
data_con -> GenLocated SrcSpanAnnN Name
-> DataCon
-> Scaled ExpSigmaTypeFRR
-> Checker
     (HsConDetails
        (HsConPatTyArg (NoGhcTc GhcRn))
        (LPat GhcRn)
        (HsRecFields GhcRn (LPat GhcRn)))
     (Pat GhcTc)
tcDataConPat GenLocated SrcSpanAnnN Name
con_lname DataCon
data_con Scaled ExpSigmaTypeFRR
pat_ty
                                                 PatEnv
penv HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
arg_pats TcM a
thing_inside
            PatSynCon PatSyn
pat_syn -> GenLocated SrcSpanAnnN Name
-> PatSyn
-> Scaled ExpSigmaTypeFRR
-> Checker
     (HsConDetails
        (HsConPatTyArg (NoGhcTc GhcRn))
        (LPat GhcRn)
        (HsRecFields GhcRn (LPat GhcRn)))
     (Pat GhcTc)
tcPatSynPat GenLocated SrcSpanAnnN Name
con_lname PatSyn
pat_syn Scaled ExpSigmaTypeFRR
pat_ty
                                             PatEnv
penv HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
arg_pats TcM a
thing_inside
        }

-- Warn when pattern matching on a GADT or a pattern synonym
-- when MonoLocalBinds is off.
warnMonoLocalBinds :: TcM ()
warnMonoLocalBinds :: TcM ()
warnMonoLocalBinds
  = do { mono_local_binds <- Extension -> IOEnv (Env TcGblEnv TcLclEnv) Bool
forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.MonoLocalBinds
       ; unless mono_local_binds $
           addDiagnostic TcRnGADTMonoLocalBinds
           -- We used to require the GADTs or TypeFamilies extension
           -- to pattern match on a GADT (#2905, #7156)
           --
           -- In #20485 this was made into a warning.
       }

tcDataConPat :: LocatedN Name -> DataCon
             -> Scaled ExpSigmaTypeFRR        -- Type of the pattern
             -> Checker (HsConPatDetails GhcRn) (Pat GhcTc)
tcDataConPat :: GenLocated SrcSpanAnnN Name
-> DataCon
-> Scaled ExpSigmaTypeFRR
-> Checker
     (HsConDetails
        (HsConPatTyArg (NoGhcTc GhcRn))
        (LPat GhcRn)
        (HsRecFields GhcRn (LPat GhcRn)))
     (Pat GhcTc)
tcDataConPat (L SrcSpanAnnN
con_span Name
con_name) DataCon
data_con Scaled ExpSigmaTypeFRR
pat_ty_scaled
             PatEnv
penv HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
arg_pats TcM r
thing_inside
  = do  { let tycon :: TyCon
tycon = DataCon -> TyCon
dataConTyCon DataCon
data_con
                  -- For data families this is the representation tycon
              ([TyCoVar]
univ_tvs, [TyCoVar]
ex_tvs, [EqSpec]
eq_spec, [Type]
theta, [Scaled Type]
arg_tys, Type
_)
                = DataCon
-> ([TyCoVar], [TyCoVar], [EqSpec], [Type], [Scaled Type], Type)
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
        ; (wrap, ctxt_res_tys) <- PatEnv
-> TyCon -> Scaled ExpSigmaTypeFRR -> TcM (HsWrapper, [Type])
matchExpectedConTy PatEnv
penv TyCon
tycon Scaled ExpSigmaTypeFRR
pat_ty_scaled
        ; pat_ty <- readExpType (scaledThing pat_ty_scaled)

          -- Add the stupid theta
        ; setSrcSpanA con_span $ addDataConStupidTheta data_con ctxt_res_tys

        -- Check that this isn't a GADT pattern match
        -- in situations in which that isn't allowed.
        ; let all_arg_tys = [EqSpec] -> [Type]
eqSpecPreds [EqSpec]
eq_spec [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
theta [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ ((Scaled Type -> Type) -> [Scaled Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map Scaled Type -> Type
forall a. Scaled a -> a
scaledThing [Scaled Type]
arg_tys)
        ; checkGADT (RealDataCon data_con) ex_tvs all_arg_tys penv

        ; tenv1 <- instTyVarsWith PatOrigin univ_tvs 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

        ; let mc = case PatEnv -> PatCtxt
pe_ctxt PatEnv
penv of
                     LamPat HsMatchContextRn
mc -> HsMatchContextRn
mc
                     LetPat {} -> HsMatchContextRn
HsMatchContext (GenLocated SrcSpanAnnN Name)
forall fn. HsMatchContext fn
PatBindRhs
        ; skol_info <- mkSkolemInfo (PatSkol (RealDataCon data_con) mc)
        ; (tenv, ex_tvs') <- tcInstSuperSkolTyVarsX skol_info tenv1 ex_tvs
                     -- Get location from monad, not from ex_tvs
                     -- This freshens: See Note [Freshen existentials]
                     -- Why "super"? See Note [Binding when looking up instances]
                     -- in GHC.Core.InstEnv.

        ; let arg_tys'       = HasDebugCallStack => Subst -> [Scaled Type] -> [Scaled Type]
Subst -> [Scaled Type] -> [Scaled Type]
substScaledTys Subst
tenv [Scaled Type]
arg_tys
              pat_mult       = Scaled ExpSigmaTypeFRR -> Type
forall a. Scaled a -> Type
scaledMult Scaled ExpSigmaTypeFRR
pat_ty_scaled
              arg_tys_scaled = (Scaled Type -> Scaled Type) -> [Scaled Type] -> [Scaled Type]
forall a b. (a -> b) -> [a] -> [b]
map (Type -> Scaled Type -> Scaled Type
forall a. Type -> Scaled a -> Scaled a
scaleScaled Type
pat_mult) [Scaled Type]
arg_tys'
              con_like       = DataCon -> ConLike
RealDataCon DataCon
data_con

        -- This check is necessary to uphold the invariant that 'tcConArgs'
        -- is given argument types with a fixed runtime representation.
        -- See test case T20363.
        ; checkFixedRuntimeRep data_con arg_tys'

        ; traceTc "tcConPat" (vcat [ text "con_name:" <+> ppr con_name
                                   , text "univ_tvs:" <+> pprTyVars univ_tvs
                                   , text "ex_tvs:" <+> pprTyVars ex_tvs
                                   , text "eq_spec:" <+> ppr eq_spec
                                   , text "theta:" <+> ppr theta
                                   , text "ex_tvs':" <+> pprTyVars ex_tvs'
                                   , text "ctxt_res_tys:" <+> ppr ctxt_res_tys
                                   , text "pat_ty:" <+> ppr pat_ty
                                   , text "arg_tys':" <+> ppr arg_tys'
                                   , text "arg_pats" <+> ppr arg_pats ])

        ; (univ_ty_args, ex_ty_args) <- splitConTyArgs con_like arg_pats

        ; if null ex_tvs && null eq_spec && null theta
          then do { -- The common case; no class bindings etc
                    -- (see Note [Arrows and patterns])
                    (arg_pats', res) <- tcConTyArgs tenv penv univ_ty_args $
                                        tcConValArgs con_like arg_tys_scaled
                                                     penv arg_pats thing_inside
                  ; let res_pat = ConPat { pat_con :: XRec GhcTc (ConLikeP GhcTc)
pat_con = XRec GhcTc (ConLikeP GhcTc)
GenLocated SrcSpanAnnN ConLike
header
                                         , pat_args :: HsConPatDetails GhcTc
pat_args = HsConPatDetails GhcTc
HsConDetails
  (HsConPatTyArg GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
arg_pats'
                                         , pat_con_ext :: XConPat GhcTc
pat_con_ext = ConPatTc
                                           { cpt_tvs :: [TyCoVar]
cpt_tvs = [], cpt_dicts :: [TyCoVar]
cpt_dicts = []
                                           , cpt_binds :: TcEvBinds
cpt_binds = TcEvBinds
emptyTcEvBinds
                                           , cpt_arg_tys :: [Type]
cpt_arg_tys = [Type]
ctxt_res_tys
                                           , cpt_wrap :: HsWrapper
cpt_wrap = HsWrapper
idHsWrapper
                                           }
                                         }

                  ; return (mkHsWrapPat wrap res_pat pat_ty, res) }

          else do   -- The general case, with existential,
                    -- and local equality constraints
        { let theta'     = HasDebugCallStack => Subst -> [Type] -> [Type]
Subst -> [Type] -> [Type]
substTheta Subst
tenv ([EqSpec] -> [Type]
eqSpecPreds [EqSpec]
eq_spec [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ [Type]
theta)
                           -- order is *important* as we generate the list of
                           -- dictionary binders from theta'

        ; when (not (null eq_spec) || any isEqClassPred theta) warnMonoLocalBinds

        ; given <- newEvVars theta'
        ; (ev_binds, (arg_pats', res))
             <- -- See Note [Type applications in patterns] (W4)
                tcConTyArgs tenv penv univ_ty_args                       $
                checkConstraints (getSkolemInfo skol_info) ex_tvs' given $
                tcConTyArgs tenv penv ex_ty_args                         $
                tcConValArgs con_like arg_tys_scaled penv arg_pats thing_inside

        ; let res_pat = ConPat
                { pat_con :: XRec GhcTc (ConLikeP GhcTc)
pat_con   = XRec GhcTc (ConLikeP GhcTc)
GenLocated SrcSpanAnnN ConLike
header
                , pat_args :: HsConPatDetails GhcTc
pat_args  = HsConPatDetails GhcTc
HsConDetails
  (HsConPatTyArg GhcRn)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
arg_pats'
                , pat_con_ext :: XConPat GhcTc
pat_con_ext = ConPatTc
                  { cpt_tvs :: [TyCoVar]
cpt_tvs   = [TyCoVar]
ex_tvs'
                  , cpt_dicts :: [TyCoVar]
cpt_dicts = [TyCoVar]
given
                  , cpt_binds :: TcEvBinds
cpt_binds = TcEvBinds
ev_binds
                  , cpt_arg_tys :: [Type]
cpt_arg_tys = [Type]
ctxt_res_tys
                  , cpt_wrap :: HsWrapper
cpt_wrap  = HsWrapper
idHsWrapper
                  }
                }
        ; return (mkHsWrapPat wrap res_pat pat_ty, res)
        } }

tcPatSynPat :: LocatedN Name -> PatSyn
            -> Scaled ExpSigmaType         -- ^ Type of the pattern
            -> Checker (HsConPatDetails GhcRn) (Pat GhcTc)
tcPatSynPat :: GenLocated SrcSpanAnnN Name
-> PatSyn
-> Scaled ExpSigmaTypeFRR
-> Checker
     (HsConDetails
        (HsConPatTyArg (NoGhcTc GhcRn))
        (LPat GhcRn)
        (HsRecFields GhcRn (LPat GhcRn)))
     (Pat GhcTc)
tcPatSynPat (L SrcSpanAnnN
con_span Name
con_name) PatSyn
pat_syn Scaled ExpSigmaTypeFRR
pat_ty PatEnv
penv HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
arg_pats TcM r
thing_inside
  = do  { let ([TyCoVar]
univ_tvs, [Type]
req_theta, [TyCoVar]
ex_tvs, [Type]
prov_theta, [Scaled Type]
arg_tys, Type
ty) = PatSyn
-> ([TyCoVar], [Type], [TyCoVar], [Type], [Scaled Type], Type)
patSynSig PatSyn
pat_syn

        ; (subst, univ_tvs') <- [TyCoVar] -> TcM (Subst, [TyCoVar])
newMetaTyVars [TyCoVar]
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 = Type
ty Type -> [Type] -> [Type]
forall a. a -> [a] -> [a]
: [Type]
prov_theta [Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++ ((Scaled Type -> Type) -> [Scaled Type] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map Scaled Type -> Type
forall a. Scaled a -> a
scaledThing [Scaled Type]
arg_tys)
        ; checkGADT (PatSynCon pat_syn) ex_tvs all_arg_tys penv

        ; skol_info <- case pe_ctxt penv of
                            LamPat HsMatchContextRn
mc -> SkolemInfoAnon -> IOEnv (Env TcGblEnv TcLclEnv) SkolemInfo
forall (m :: * -> *). MonadIO m => SkolemInfoAnon -> m SkolemInfo
mkSkolemInfo (ConLike -> HsMatchContextRn -> SkolemInfoAnon
PatSkol (PatSyn -> ConLike
PatSynCon PatSyn
pat_syn) HsMatchContextRn
mc)
                            LetPat {} -> SkolemInfo -> IOEnv (Env TcGblEnv TcLclEnv) SkolemInfo
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return SkolemInfo
HasDebugCallStack => SkolemInfo
unkSkol -- Doesn't matter

        ; (tenv, ex_tvs') <- tcInstSuperSkolTyVarsX skol_info subst ex_tvs
           -- This freshens: Note [Freshen existentials]

        ; let ty'         = HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
tenv Type
ty
              arg_tys'    = HasDebugCallStack => Subst -> [Scaled Type] -> [Scaled Type]
Subst -> [Scaled Type] -> [Scaled Type]
substScaledTys Subst
tenv [Scaled Type]
arg_tys
              pat_mult    = Scaled ExpSigmaTypeFRR -> Type
forall a. Scaled a -> Type
scaledMult Scaled ExpSigmaTypeFRR
pat_ty
              arg_tys_scaled = (Scaled Type -> Scaled Type) -> [Scaled Type] -> [Scaled Type]
forall a b. (a -> b) -> [a] -> [b]
map (Type -> Scaled Type -> Scaled Type
forall a. Type -> Scaled a -> Scaled a
scaleScaled Type
pat_mult) [Scaled Type]
arg_tys'
              prov_theta' = HasDebugCallStack => Subst -> [Type] -> [Type]
Subst -> [Type] -> [Type]
substTheta Subst
tenv [Type]
prov_theta
              req_theta'  = HasDebugCallStack => Subst -> [Type] -> [Type]
Subst -> [Type] -> [Type]
substTheta Subst
tenv [Type]
req_theta
              con_like    = PatSyn -> ConLike
PatSynCon PatSyn
pat_syn

        ; when (any isEqClassPred prov_theta) warnMonoLocalBinds

        ; checkManyPattern PatternSynonymReason nlWildPatName pat_ty

        ; (univ_ty_args, ex_ty_args) <- splitConTyArgs con_like arg_pats

        ; wrap <- tc_sub_type penv (scaledThing pat_ty) ty'

        ; traceTc "tcPatSynPat" $
          vcat [ text "Pat syn:" <+> ppr pat_syn
               , text "Expected type:" <+> ppr pat_ty
               , text "Pat res ty:" <+> ppr ty'
               , text "ex_tvs':" <+> pprTyVars ex_tvs'
               , text "prov_theta':" <+> ppr prov_theta'
               , text "req_theta':" <+> ppr req_theta'
               , text "arg_tys':" <+> ppr arg_tys'
               , text "univ_ty_args:" <+> ppr univ_ty_args
               , text "ex_ty_args:" <+> ppr ex_ty_args ]

        ; req_wrap <- instCall (OccurrenceOf con_name) (mkTyVarTys univ_tvs') req_theta'
                      -- Origin (OccurrenceOf con_name):
                      -- see Note [Call-stack tracing of pattern synonyms]
        ; traceTc "instCall" (ppr req_wrap)

          -- Pattern synonyms can never have representation-polymorphic argument types,
          -- as checked in 'GHC.Tc.Gen.Sig.tcPatSynSig' (see use of 'FixedRuntimeRepPatSynSigArg')
          -- and 'GHC.Tc.TyCl.PatSyn.tcInferPatSynDecl'.
          -- (If you want to lift this restriction, use 'hasFixedRuntimeRep' here, to match
          -- 'tcDataConPat'.)
        ; let
            bad_arg_tys :: [(Int, Scaled Type)]
            bad_arg_tys = ((Int, Scaled Type) -> Bool)
-> [(Int, Scaled Type)] -> [(Int, Scaled Type)]
forall a. (a -> Bool) -> [a] -> [a]
filter (\ (Int
_, Scaled Type
_ Type
arg_ty) -> Bool -> Bool
not (HasDebugCallStack => Type -> Bool
Type -> Bool
typeHasFixedRuntimeRep Type
arg_ty))
                        ([(Int, Scaled Type)] -> [(Int, Scaled Type)])
-> [(Int, Scaled Type)] -> [(Int, Scaled Type)]
forall a b. (a -> b) -> a -> b
$ [Int] -> [Scaled Type] -> [(Int, Scaled Type)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Int
0..] [Scaled Type]
arg_tys'
        ; massertPpr (null bad_arg_tys) $
            vcat [ text "tcPatSynPat: pattern arguments do not have a fixed RuntimeRep"
                 , text "bad_arg_tys:" <+> ppr bad_arg_tys ]

        ; traceTc "checkConstraints {" Outputable.empty
        ; prov_dicts' <- newEvVars prov_theta'
        ; (ev_binds, (arg_pats', res))
             <- -- See Note [Type applications in patterns] (W4)
                tcConTyArgs tenv penv univ_ty_args                             $
                checkConstraints (getSkolemInfo skol_info) ex_tvs' prov_dicts' $
                tcConTyArgs tenv penv ex_ty_args                               $
                tcConValArgs con_like arg_tys_scaled penv arg_pats             $
                thing_inside
        ; traceTc "checkConstraints }" (ppr ev_binds)

        ; let 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
arg_pats'
                               , pat_con_ext :: XConPat GhcTc
pat_con_ext = ConPatTc
                                 { cpt_tvs :: [TyCoVar]
cpt_tvs   = [TyCoVar]
ex_tvs'
                                 , cpt_dicts :: [TyCoVar]
cpt_dicts = [TyCoVar]
prov_dicts'
                                 , cpt_binds :: TcEvBinds
cpt_binds = TcEvBinds
ev_binds
                                 , cpt_arg_tys :: [Type]
cpt_arg_tys = [TyCoVar] -> [Type]
mkTyVarTys [TyCoVar]
univ_tvs'
                                 , cpt_wrap :: HsWrapper
cpt_wrap  = HsWrapper
req_wrap
                                 }
                               }
        ; pat_ty <- readExpType (scaledThing pat_ty)
        ; return (mkHsWrapPat wrap res_pat pat_ty, res) }

checkFixedRuntimeRep :: DataCon -> [Scaled TcSigmaTypeFRR] -> TcM ()
checkFixedRuntimeRep :: DataCon -> [Scaled Type] -> TcM ()
checkFixedRuntimeRep DataCon
data_con [Scaled Type]
arg_tys
  = (Int -> Scaled Type -> TcM ()) -> [Int] -> [Scaled Type] -> TcM ()
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m ()
zipWithM_ Int -> Scaled Type -> TcM ()
check_one [Int
1..] [Scaled Type]
arg_tys
  where
    check_one :: Int -> Scaled Type -> TcM ()
check_one Int
i Scaled Type
arg_ty = HasDebugCallStack => FixedRuntimeRepContext -> Type -> TcM ()
FixedRuntimeRepContext -> Type -> TcM ()
hasFixedRuntimeRep_syntactic
                            (DataCon -> Int -> FixedRuntimeRepContext
FRRDataConPatArg DataCon
data_con Int
i)
                            (Scaled Type -> Type
forall a. Scaled a -> a
scaledThing Scaled Type
arg_ty)

{- 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.Dict.solveCallStack 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.Types
-}
----------------------------
-- | Convenient wrapper for calling a matchExpectedXXX function
matchExpectedPatTy :: (TcRhoType -> TcM (TcCoercionN, a))
                    -> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, a)
-- See Note [Matching polytyped patterns]
-- Returns a wrapper : pat_ty ~R inner_ty
matchExpectedPatTy :: forall a.
(Type -> TcM (TcCoercionN, a))
-> PatEnv -> ExpSigmaTypeFRR -> TcM (HsWrapper, a)
matchExpectedPatTy Type -> TcM (TcCoercionN, a)
inner_match (PE { pe_orig :: PatEnv -> CtOrigin
pe_orig = CtOrigin
orig }) ExpSigmaTypeFRR
pat_ty
  = do { pat_ty <- ExpSigmaTypeFRR -> TcM Type
expTypeToType ExpSigmaTypeFRR
pat_ty
       ; (wrap, pat_rho) <- topInstantiate orig pat_ty
       ; (co, res) <- inner_match pat_rho
       ; traceTc "matchExpectedPatTy" (ppr pat_ty $$ ppr wrap)
       ; return (mkWpCastN (mkSymCo co) <.> wrap, 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 ExpSigmaTypeFRR
                       -- ^ 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 ExpSigmaTypeFRR -> TcM (HsWrapper, [Type])
matchExpectedConTy (PE { pe_orig :: PatEnv -> CtOrigin
pe_orig = CtOrigin
orig }) TyCon
data_tc Scaled ExpSigmaTypeFRR
exp_pat_ty
  | Just (TyCon
fam_tc, [Type]
fam_args, CoAxiom Unbranched
co_tc) <- TyCon -> Maybe (TyCon, [Type], CoAxiom Unbranched)
tyConFamInstSig_maybe TyCon
data_tc
         -- Comments refer to Note [Matching constructor patterns]
         -- co_tc :: forall a. T [a] ~ T7 a
  = do { pat_ty <- ExpSigmaTypeFRR -> TcM Type
expTypeToType (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
exp_pat_ty)
       ; (wrap, pat_rho) <- topInstantiate orig pat_ty

       ; (subst, tvs') <- newMetaTyVars (tyConTyVars data_tc)
             -- tys = [ty1,ty2]

       ; traceTc "matchExpectedConTy" (vcat [ppr data_tc,
                                             ppr (tyConTyVars data_tc),
                                             ppr fam_tc, ppr fam_args,
                                             ppr exp_pat_ty,
                                             ppr pat_ty,
                                             ppr pat_rho, ppr wrap])
       ; co1 <- unifyType Nothing (mkTyConApp fam_tc (substTys subst fam_args)) 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' = [TyCoVar] -> [Type]
mkTyVarTys [TyCoVar]
tvs'
             co2 = Role
-> CoAxiom Unbranched -> [Type] -> [TcCoercionN] -> TcCoercionN
mkUnbranchedAxInstCo Role
Representational CoAxiom Unbranched
co_tc [Type]
tys' []
             -- co2 : T (ty1,ty2) ~R T7 ty1 ty2

             full_co = HasDebugCallStack => TcCoercionN -> TcCoercionN
TcCoercionN -> TcCoercionN
mkSubCo (TcCoercionN -> TcCoercionN
mkSymCo TcCoercionN
co1) HasDebugCallStack => TcCoercionN -> TcCoercionN -> TcCoercionN
TcCoercionN -> TcCoercionN -> TcCoercionN
`mkTransCo` TcCoercionN
co2
             -- full_co :: pat_rho ~R T7 ty1 ty2

       ; return ( mkWpCastR full_co <.> wrap, tys') }

  | Bool
otherwise
  = do { pat_ty <- ExpSigmaTypeFRR -> TcM Type
expTypeToType (Scaled ExpSigmaTypeFRR -> ExpSigmaTypeFRR
forall a. Scaled a -> a
scaledThing Scaled ExpSigmaTypeFRR
exp_pat_ty)
       ; (wrap, pat_rho) <- topInstantiate orig pat_ty
       ; (coi, tys) <- matchExpectedTyConApp data_tc pat_rho
       ; return (mkWpCastN (mkSymCo coi) <.> wrap, 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 [Type applications in patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Type applications in patterns are enabled by -XTypeAbstractions.
For example:
   f :: Either (Maybe a) [b] -> blah
   f (Left @x @[y] (v::Maybe x)) = blah

How should we typecheck them?  The basic plan is pretty simple, and is
all done in tcConTyArgs. For each type argument:

* Step 1:
    * bind the newly-in-scope type variables (here `x` or `y`) to
      unification variables, say `x0` or `y0`

    * typecheck the type argument, `@x` or `@[y]` to get the
      types `x0` or `[y0]`.

    This step is done by `tcHsPatSigType`, similar to the way we
    deal with pattern signatures.

* Step 2: Unify those types with the type arguments we expect from
  the context, 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.

* Step 3: Extend the lexical context to bind `x` to `x0` and
  `y` to `y0`, and typecheck the body of the pattern match.

However there are several quite tricky wrinkles.

(W1) 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 constraint arising
     from a functional dependency, where we don't use the evidence.

(W2) 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 2 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.

(W3) The order of the arguments to the /data constructor/ may differ from
     the order of the arguments to the /type constructor/. Example
         data T a b where { MkT :: forall c d. (c,d) -> T d c }
         f :: T Int Bool -> blah
         f (MkT @x @y p) = ...
     The /first/ type argument to `MkT`, namely `@x` corresponds to the
     /second/ argument to `T` in the type `T Int Bool`.  So `x` is bound
     to `Bool` -- not to `Int`!.  That is why splitConTyArgs uses
     conLikeUserTyVarBinders to match up with the user-supplied type arguments
     in the pattern, not dataConUnivTyVars/dataConExTyVars.

(W4) A similar story works for existentials, but it is subtly different
     (#19847).  Consider
         data T a where { MkT :: forall a b. a -> b -> T a }
         f :: T Int -> blah
         f (MkT @x @y v w) = blah
     Here we create a fresh unification variables x0,y0 for x,y and
     unify x0~Int, y0~b, where b is the fresh existential variable bound by
     the pattern. But
       * (x0~Int) must be /outside/ the implication constraint
       * (y0~b)   must be /inside/ it
     (and hence x0 and y0 themselves must have different levels).
     Thus:
         x0[1]~Int,  (forall[2] b. (y0[2]~b, ...constraints-from-blah...))

     We need (x0~Int) /outside/ so that it can influence the type of the
     pattern in an inferred setting, e.g.
         g :: T _ -> blah
         g (MkT @Int @y v w) = blah
     Here we want to infer `g` to have type `T Int -> blah`. If the
     (x0~Int) was inside the implication, and the the constructor bound
     equality constraints, `x0` would be untouchable. This was the root
     cause of #19847.

     We need (y0~b) to be /inside/ the implication, so that `b` is in
     scope.  In fact, we may actually /need/ equalities bound by the
     implication to prove the equality constraint we generate.
     Example   data T a where
                 MkT :: forall p q. T (p,q)
               f :: T (Int,Bool) -> blah
               f (MkT @Int @Bool) = ...
     We get the implication
        forall[2] p q. (p,q)~(Int,Bool) => (p ~ Int, q ~ Bool, ...)
     where the Given comes from the GADT match, while (p~Int, q~Bool)
     comes from matching the type arguments.

     Wow.  That's all quite subtle! See the long discussion on #19847.  We
     must treat universal and existential arguments separately, even though
     they are all mixed up (W3).  The function splitConTyArgs separates the
     universals from existentials; and we build the implication between
     typechecking the two sets:
           tcConTyArgs ... univ_ty_args    $
           checkConstraints ...            $
           tcConTyArgs ... ex_ty_args      $
           ..typecheck body..
     You can see this code shape in tcDataConPat and tcPatSynPat.

     Where pattern synonyms are involved, this two-level split may not be
     enough.  See #22328 for the story.
-}

{- Note [Omitted record fields and linearity]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider

  data T = MkT {a:A, b:B}
  f :: T -> A
  f (MkT{a=a}) = a

The pattern in f is equivalent to

  f (MkT a _) = a

Evidently, the b field isn't used linearly here, it must be typed as a wildcard
pattern. However, this is *the only check* for omitted record fields: if it
weren't for linearity checking, the type checker could ignore b altogether. So
we have a function check_omitted_fields_multiplicity, whose purpose is to do the
linearity checking on the omitted fields.
-}

tcConValArgs :: ConLike
             -> [Scaled TcSigmaTypeFRR]
             -> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)
tcConValArgs :: ConLike
-> [Scaled Type]
-> Checker
     (HsConDetails
        (HsConPatTyArg (NoGhcTc GhcRn))
        (LPat GhcRn)
        (HsRecFields GhcRn (LPat GhcRn)))
     (HsConPatDetails GhcTc)
tcConValArgs ConLike
con_like [Scaled Type]
arg_tys PatEnv
penv HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
con_args TcM r
thing_inside = case HsConDetails
  (HsConPatTyArg (NoGhcTc GhcRn))
  (LPat GhcRn)
  (HsRecFields GhcRn (LPat GhcRn))
con_args of
  PrefixCon [HsConPatTyArg (NoGhcTc GhcRn)]
type_args [LPat GhcRn]
arg_pats -> do
        -- NB: type_args already dealt with
        -- See Note [Type applications in patterns]
        { Bool -> TcRnMessage -> TcM ()
checkTc (Int
con_arity Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
no_of_args)     -- Check correct arity
                  (TyThing -> Int -> Int -> TcRnMessage
TcRnArityMismatch (ConLike -> TyThing
AConLike ConLike
con_like) Int
con_arity Int
no_of_args)

        ; let pats_w_tys :: [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)]
pats_w_tys = String
-> [GenLocated SrcSpanAnnA (Pat GhcRn)]
-> [Scaled Type]
-> [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)]
forall a b. HasDebugCallStack => String -> [a] -> [b] -> [(a, b)]
zipEqual String
"tcConArgs" [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
arg_pats [Scaled Type]
arg_tys
        ; (arg_pats', res) <- Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
-> Checker
     [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)]
     [GenLocated SrcSpanAnnA (Pat GhcTc)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple PatEnv -> (LPat GhcRn, Scaled Type) -> TcM r -> TcM (LPat GhcTc, r)
PatEnv
-> (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)
-> TcM r
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
Checker (LPat GhcRn, Scaled Type) (LPat GhcTc)
Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
tcConArg PatEnv
penv [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)]
pats_w_tys TcM r
thing_inside

        ; return (PrefixCon type_args arg_pats', 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 a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [LPat GhcRn]
[GenLocated SrcSpanAnnA (Pat GhcRn)]
arg_pats

  InfixCon LPat GhcRn
p1 LPat GhcRn
p2 -> do
        { Bool -> TcRnMessage -> TcM ()
checkTc (Int
con_arity Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
2)      -- Check correct arity
                  (TyThing -> Int -> Int -> TcRnMessage
TcRnArityMismatch (ConLike -> TyThing
AConLike ConLike
con_like) Int
con_arity Int
2)
        ; let [Scaled Type
arg_ty1,Scaled Type
arg_ty2] = [Scaled Type]
arg_tys       -- This can't fail after the arity check
        ; ([p1',p2'], res) <- Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
-> Checker
     [(GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)]
     [GenLocated SrcSpanAnnA (Pat GhcTc)]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple PatEnv -> (LPat GhcRn, Scaled Type) -> TcM r -> TcM (LPat GhcTc, r)
PatEnv
-> (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)
-> TcM r
-> IOEnv
     (Env TcGblEnv TcLclEnv) (GenLocated SrcSpanAnnA (Pat GhcTc), r)
Checker (LPat GhcRn, Scaled Type) (LPat GhcTc)
Checker
  (GenLocated SrcSpanAnnA (Pat GhcRn), Scaled Type)
  (GenLocated SrcSpanAnnA (Pat GhcTc))
tcConArg PatEnv
penv [(LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
p1,Scaled Type
arg_ty1),(LPat GhcRn
GenLocated SrcSpanAnnA (Pat GhcRn)
p2,Scaled Type
arg_ty2)]
                                                  TcM r
thing_inside
        ; return (InfixCon p1' p2', res) }
    where
      con_arity :: Int
con_arity  = ConLike -> Int
conLikeArity ConLike
con_like

  RecCon (HsRecFields XHsRecFields GhcRn
x [LHsRecField GhcRn (LPat GhcRn)]
rpats Maybe (XRec GhcRn RecFieldsDotDot)
dd) -> do
        { TcM ()
check_omitted_fields_multiplicity
        ; (rpats', res) <- Checker
  (GenLocated
     SrcSpanAnnA
     (HsFieldBind
        (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
        (GenLocated SrcSpanAnnA (Pat GhcRn))))
  (GenLocated
     SrcSpanAnnA
     (HsFieldBind
        (GenLocated SrcSpanAnnA (FieldOcc GhcTc))
        (GenLocated SrcSpanAnnA (Pat GhcTc))))
-> Checker
     [GenLocated
        SrcSpanAnnA
        (HsFieldBind
           (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
           (GenLocated SrcSpanAnnA (Pat GhcRn)))]
     [GenLocated
        SrcSpanAnnA
        (HsFieldBind
           (GenLocated SrcSpanAnnA (FieldOcc GhcTc))
           (GenLocated SrcSpanAnnA (Pat GhcTc)))]
forall inp out. Checker inp out -> Checker [inp] [out]
tcMultiple PatEnv
-> LHsRecField GhcRn (LPat GhcRn)
-> TcM r
-> TcM (LHsRecField GhcTc (LPat GhcTc), r)
PatEnv
-> GenLocated
     SrcSpanAnnA
     (HsFieldBind
        (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
        (GenLocated SrcSpanAnnA (Pat GhcRn)))
-> TcM r
-> IOEnv
     (Env TcGblEnv TcLclEnv)
     (GenLocated
        SrcSpanAnnA
        (HsFieldBind
           (GenLocated SrcSpanAnnA (FieldOcc GhcTc))
           (GenLocated SrcSpanAnnA (Pat GhcTc))),
      r)
Checker
  (LHsRecField GhcRn (LPat GhcRn)) (LHsRecField GhcTc (LPat GhcTc))
Checker
  (GenLocated
     SrcSpanAnnA
     (HsFieldBind
        (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
        (GenLocated SrcSpanAnnA (Pat GhcRn))))
  (GenLocated
     SrcSpanAnnA
     (HsFieldBind
        (GenLocated SrcSpanAnnA (FieldOcc GhcTc))
        (GenLocated SrcSpanAnnA (Pat GhcTc))))
tc_field PatEnv
penv [LHsRecField GhcRn (LPat GhcRn)]
[GenLocated
   SrcSpanAnnA
   (HsFieldBind
      (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
      (GenLocated SrcSpanAnnA (Pat GhcRn)))]
rpats TcM r
thing_inside
        ; return ((RecCon (HsRecFields x rpats' dd)), 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 (HsFieldBind XHsFieldBind (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
ann (L SrcSpanAnnA
loc (FieldOcc XCFieldOcc GhcRn
rdr (L SrcSpanAnnN
lr Name
sel))) GenLocated SrcSpanAnnA (Pat GhcRn)
pat Bool
pun))
                TcM r
thing_inside
        = do { sel'   <- Name -> TcM TyCoVar
tcLookupId Name
sel
             ; pat_ty <- setSrcSpanA loc $ find_field_ty sel
                                            (occNameFS $ rdrNameOcc rdr)
             ; (pat', res) <- tcConArg penv (pat, pat_ty) thing_inside
             ; return (L l (HsFieldBind ann (L loc (FieldOcc rdr (L lr sel'))) pat'
                                                                        pun), res) }
      -- See Note [Omitted record fields and linearity]
      check_omitted_fields_multiplicity :: TcM ()
      check_omitted_fields_multiplicity :: TcM ()
check_omitted_fields_multiplicity = do
        [(Maybe FieldLabel, Scaled Type)]
-> ((Maybe FieldLabel, Scaled Type) -> TcM ()) -> TcM ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
t a -> (a -> m b) -> m ()
forM_ [(Maybe FieldLabel, Scaled Type)]
omitted_field_tys (((Maybe FieldLabel, Scaled Type) -> TcM ()) -> TcM ())
-> ((Maybe FieldLabel, Scaled Type) -> TcM ()) -> TcM ()
forall a b. (a -> b) -> a -> b
$ \(Maybe FieldLabel
fl, Scaled Type
pat_ty) ->
          CtOrigin -> Type -> Type -> TcM ()
tcSubMult (Maybe FieldLabel -> CtOrigin
OmittedFieldOrigin Maybe FieldLabel
fl) Type
ManyTy (Scaled Type -> Type
forall a. Scaled a -> Type
scaledMult Scaled Type
pat_ty)

      find_field_ty :: Name -> FastString -> TcM (Scaled TcType)
      find_field_ty :: Name -> FastString -> TcRn (Scaled Type)
find_field_ty Name
sel FastString
lbl
        = case [Scaled Type
ty | (Just FieldLabel
fl, Scaled Type
ty) <- [(Maybe FieldLabel, Scaled Type)]
bound_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".
           [] -> TcRnMessage -> TcRn (Scaled Type)
forall a. TcRnMessage -> TcRn a
failWith (Name -> FieldLabelString -> TcRnMessage
badFieldConErr (ConLike -> Name
forall a. NamedThing a => a -> Name
getName ConLike
con_like) (FastString -> FieldLabelString
FieldLabelString FastString
lbl))

                -- The normal case, when the field comes from the right constructor
           (Scaled Type
pat_ty : [Scaled Type]
extras) -> do
                String -> SDoc -> TcM ()
traceTc String
"find_field" (Scaled Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Scaled Type
pat_ty SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> [Scaled Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Scaled Type]
extras)
                Bool -> TcRn (Scaled Type) -> TcRn (Scaled Type)
forall a. HasCallStack => Bool -> a -> a
assert ([Scaled Type] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Scaled Type]
extras) (Scaled Type -> TcRn (Scaled Type)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Scaled Type
pat_ty)

      bound_field_tys, omitted_field_tys :: [(Maybe FieldLabel, Scaled TcType)]
      ([(Maybe FieldLabel, Scaled Type)]
bound_field_tys, [(Maybe FieldLabel, Scaled Type)]
omitted_field_tys) = ((Maybe FieldLabel, Scaled Type) -> Bool)
-> [(Maybe FieldLabel, Scaled Type)]
-> ([(Maybe FieldLabel, Scaled Type)],
    [(Maybe FieldLabel, Scaled Type)])
forall a. (a -> Bool) -> [a] -> ([a], [a])
partition (Maybe FieldLabel, Scaled Type) -> Bool
is_bound [(Maybe FieldLabel, Scaled Type)]
all_field_tys

      is_bound :: (Maybe FieldLabel, Scaled TcType) -> Bool
      is_bound :: (Maybe FieldLabel, Scaled Type) -> Bool
is_bound (Just FieldLabel
fl, Scaled Type
_) = Name -> [Name] -> Bool
forall a. Eq a => a -> [a] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
elem (FieldLabel -> Name
flSelector FieldLabel
fl) ((GenLocated
   SrcSpanAnnA
   (HsFieldBind
      (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
      (GenLocated SrcSpanAnnA (Pat GhcRn)))
 -> Name)
-> [GenLocated
      SrcSpanAnnA
      (HsFieldBind
         (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
         (GenLocated SrcSpanAnnA (Pat GhcRn)))]
-> [Name]
forall a b. (a -> b) -> [a] -> [b]
map (\(L SrcSpanAnnA
_ (HsFieldBind XHsFieldBind (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
_ (L SrcSpanAnnA
_ (FieldOcc XCFieldOcc GhcRn
_ LIdP GhcRn
sel )) GenLocated SrcSpanAnnA (Pat GhcRn)
_ Bool
_)) -> GenLocated SrcSpanAnnN Name -> Name
forall l e. GenLocated l e -> e
unLoc LIdP GhcRn
GenLocated SrcSpanAnnN Name
sel) [LHsRecField GhcRn (LPat GhcRn)]
[GenLocated
   SrcSpanAnnA
   (HsFieldBind
      (GenLocated SrcSpanAnnA (FieldOcc GhcRn))
      (GenLocated SrcSpanAnnA (Pat GhcRn)))]
rpats)
      is_bound (Maybe FieldLabel, Scaled Type)
_ = Bool
False

      all_field_tys :: [(Maybe FieldLabel, Scaled TcType)]
      all_field_tys :: [(Maybe FieldLabel, Scaled Type)]
all_field_tys = [Maybe FieldLabel]
-> [Scaled Type] -> [(Maybe FieldLabel, Scaled Type)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Maybe FieldLabel]
con_field_labels [Scaled Type]
arg_tys
          -- If the constructor isn't really a record, then dataConFieldLabels
          -- will be empty (and each field in the pattern will generate an error
          -- below). We still need those unnamed fields for
          -- linearity-checking. Hence we zip the anonymous fields with Nothing.

      con_field_labels :: [Maybe FieldLabel]
      con_field_labels :: [Maybe FieldLabel]
con_field_labels = ((FieldLabel -> Maybe FieldLabel)
-> [FieldLabel] -> [Maybe FieldLabel]
forall a b. (a -> b) -> [a] -> [b]
map FieldLabel -> Maybe FieldLabel
forall a. a -> Maybe a
Just (ConLike -> [FieldLabel]
conLikeFieldLabels ConLike
con_like)) [Maybe FieldLabel] -> [Maybe FieldLabel] -> [Maybe FieldLabel]
forall a. [a] -> [a] -> [a]
++ Maybe FieldLabel -> [Maybe FieldLabel]
forall a. a -> [a]
repeat Maybe FieldLabel
forall a. Maybe a
Nothing


splitConTyArgs :: ConLike -> HsConPatDetails GhcRn
               -> TcM ( [(HsConPatTyArg GhcRn, TyVar)]    -- Universals
                      , [(HsConPatTyArg GhcRn, TyVar)] )  -- Existentials
-- See Note [Type applications in patterns] (W4)
-- This function is monadic only because of the error check
-- for too many type arguments
splitConTyArgs :: ConLike
-> HsConDetails
     (HsConPatTyArg (NoGhcTc GhcRn))
     (LPat GhcRn)
     (HsRecFields GhcRn (LPat GhcRn))
-> TcM
     ([(HsConPatTyArg GhcRn, TyCoVar)],
      [(HsConPatTyArg GhcRn, TyCoVar)])
splitConTyArgs ConLike
con_like (PrefixCon [HsConPatTyArg (NoGhcTc GhcRn)]
type_args [LPat GhcRn]
_)
  = do { Bool -> TcRnMessage -> TcM ()
checkTc ([HsConPatTyArg (NoGhcTc GhcRn)]
[HsConPatTyArg GhcRn]
type_args [HsConPatTyArg GhcRn] -> [TyCoVar] -> Bool
forall a b. [a] -> [b] -> Bool
`leLength` [TyCoVar]
con_spec_bndrs)
                 (ConLike -> Int -> Int -> TcRnMessage
TcRnTooManyTyArgsInConPattern ConLike
con_like
                          ([TyCoVar] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [TyCoVar]
con_spec_bndrs) ([HsConPatTyArg GhcRn] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [HsConPatTyArg (NoGhcTc GhcRn)]
[HsConPatTyArg GhcRn]
type_args))
       ; if [TyCoVar] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TyCoVar]
ex_tvs  -- Short cut common case
         then ([(HsConPatTyArg GhcRn, TyCoVar)],
 [(HsConPatTyArg GhcRn, TyCoVar)])
-> TcM
     ([(HsConPatTyArg GhcRn, TyCoVar)],
      [(HsConPatTyArg GhcRn, TyCoVar)])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ([(HsConPatTyArg GhcRn, TyCoVar)]
bndr_ty_arg_prs, [])
         else ([(HsConPatTyArg GhcRn, TyCoVar)],
 [(HsConPatTyArg GhcRn, TyCoVar)])
-> TcM
     ([(HsConPatTyArg GhcRn, TyCoVar)],
      [(HsConPatTyArg GhcRn, TyCoVar)])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (((HsConPatTyArg GhcRn, TyCoVar) -> Bool)
-> [(HsConPatTyArg GhcRn, TyCoVar)]
-> ([(HsConPatTyArg GhcRn, TyCoVar)],
    [(HsConPatTyArg GhcRn, TyCoVar)])
forall a. (a -> Bool) -> [a] -> ([a], [a])
partition (HsConPatTyArg GhcRn, TyCoVar) -> Bool
is_universal [(HsConPatTyArg GhcRn, TyCoVar)]
bndr_ty_arg_prs) }
  where
    ex_tvs :: [TyCoVar]
ex_tvs = ConLike -> [TyCoVar]
conLikeExTyCoVars ConLike
con_like
    con_spec_bndrs :: [TyCoVar]
con_spec_bndrs = [ TyCoVar
tv | Bndr TyCoVar
tv Specificity
SpecifiedSpec <- ConLike -> [VarBndr TyCoVar Specificity]
conLikeUserTyVarBinders ConLike
con_like ]
        -- conLikeUserTyVarBinders: see (W3) in
        --    Note [Type applications in patterns]
        -- SpecifiedSpec: forgetting to filter out inferred binders led to #20443

    bndr_ty_arg_prs :: [(HsConPatTyArg GhcRn, TyCoVar)]
bndr_ty_arg_prs = [HsConPatTyArg (NoGhcTc GhcRn)]
[HsConPatTyArg GhcRn]
type_args [HsConPatTyArg GhcRn]
-> [TyCoVar] -> [(HsConPatTyArg GhcRn, TyCoVar)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [TyCoVar]
con_spec_bndrs
                      -- The zip truncates to length(type_args)

    is_universal :: (HsConPatTyArg GhcRn, TyCoVar) -> Bool
is_universal (HsConPatTyArg GhcRn
_, TyCoVar
tv) = Bool -> Bool
not (TyCoVar
tv TyCoVar -> [TyCoVar] -> Bool
forall a. Eq a => a -> [a] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`elem` [TyCoVar]
ex_tvs)
         -- See Note [DataCon user type variable binders] in GHC.Core.DataCon
         -- especially INVARIANT(dataConTyVars).

splitConTyArgs ConLike
_ (RecCon {})   = ([(HsConPatTyArg GhcRn, TyCoVar)],
 [(HsConPatTyArg GhcRn, TyCoVar)])
-> TcM
     ([(HsConPatTyArg GhcRn, TyCoVar)],
      [(HsConPatTyArg GhcRn, TyCoVar)])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ([], []) -- No type args in RecCon
splitConTyArgs ConLike
_ (InfixCon {}) = ([(HsConPatTyArg GhcRn, TyCoVar)],
 [(HsConPatTyArg GhcRn, TyCoVar)])
-> TcM
     ([(HsConPatTyArg GhcRn, TyCoVar)],
      [(HsConPatTyArg GhcRn, TyCoVar)])
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ([], []) -- No type args in InfixCon

tcConTyArgs :: Subst -> PatEnv -> [(HsConPatTyArg GhcRn, TyVar)]
            -> TcM a -> TcM a
tcConTyArgs :: forall a.
Subst
-> PatEnv -> [(HsConPatTyArg GhcRn, TyCoVar)] -> TcM a -> TcM a
tcConTyArgs Subst
tenv PatEnv
penv [(HsConPatTyArg GhcRn, TyCoVar)]
prs TcM a
thing_inside
  = Checker (HsConPatTyArg GhcRn, TyCoVar) ()
-> PatEnv -> [(HsConPatTyArg GhcRn, TyCoVar)] -> TcM a -> TcM a
forall inp r. Checker inp () -> PatEnv -> [inp] -> TcM r -> TcM r
tcMultiple_ (Subst -> Checker (HsConPatTyArg GhcRn, TyCoVar) ()
tcConTyArg Subst
tenv) PatEnv
penv [(HsConPatTyArg GhcRn, TyCoVar)]
prs TcM a
thing_inside

tcConTyArg :: Subst -> Checker (HsConPatTyArg GhcRn, TyVar) ()
tcConTyArg :: Subst -> Checker (HsConPatTyArg GhcRn, TyCoVar) ()
tcConTyArg Subst
tenv PatEnv
penv (HsConPatTyArg XConPatTyArg GhcRn
_ HsTyPat GhcRn
rn_ty, TyCoVar
con_tv) TcM r
thing_inside
  = do { (sig_wcs, sig_ibs, arg_ty) <- HsTyPat GhcRn
-> Type -> TcM ([(Name, TyCoVar)], [(Name, TyCoVar)], Type)
tcHsTyPat HsTyPat GhcRn
rn_ty (HasDebugCallStack => Subst -> Type -> Type
Subst -> Type -> Type
substTy Subst
tenv (TyCoVar -> Type
varType TyCoVar
con_tv))

       ; case NE.nonEmpty sig_ibs of
           Just NonEmpty (Name, TyCoVar)
sig_ibs_ne | PatEnv -> Bool
inPatBind PatEnv
penv ->
             TcRnMessage -> TcM ()
addErr (NonEmpty (Name, TyCoVar) -> TcRnMessage
TcRnCannotBindTyVarsInPatBind NonEmpty (Name, TyCoVar)
sig_ibs_ne)
           Maybe (NonEmpty (Name, TyCoVar))
_ -> () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (f :: * -> *) a. Applicative f => a -> f a
pure ()

          -- This unification is straight from Figure 7 of
          -- "Type Variables in Patterns", Haskell'18
          -- OK to drop coercions here. These unifications are all about
          -- guiding inference based on a user-written type annotation
          -- See Note [Type applications in patterns] (W1)
       ; _ <- unifyType Nothing arg_ty (substTyVar tenv con_tv)

       ; result <- tcExtendNameTyVarEnv sig_wcs $
                   tcExtendNameTyVarEnv sig_ibs $
                   thing_inside
             -- NB: Because we call tConTyArgs twice, once for universals and
             --     once for existentials; so this brings things into scope
             --     "out of left-right order". But it doesn't matter; the renamer
             --     has dealt with all that.

       ; return ((), result) }

tcConArg :: Checker (LPat GhcRn, Scaled TcSigmaType) (LPat GhcTc)
tcConArg :: Checker (LPat GhcRn, Scaled Type) (LPat GhcTc)
tcConArg PatEnv
penv (LPat GhcRn
arg_pat, Scaled Type
arg_mult Type
arg_ty)
  = Scaled ExpSigmaTypeFRR -> Checker (LPat GhcRn) (LPat GhcTc)
tc_lpat (Type -> ExpSigmaTypeFRR -> Scaled ExpSigmaTypeFRR
forall a. Type -> a -> Scaled a
Scaled Type
arg_mult (Type -> ExpSigmaTypeFRR
mkCheckExpType Type
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.
-- See Note [The stupid context] in GHC.Core.DataCon.
addDataConStupidTheta :: DataCon -> [Type] -> TcM ()
addDataConStupidTheta DataCon
data_con [Type]
inst_tys
  | [Type] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Type]
stupid_theta = () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  | Bool
otherwise         = CtOrigin -> [Type] -> TcM ()
instStupidTheta CtOrigin
origin [Type]
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 :: [Type]
stupid_theta = DataCon -> [Type]
dataConStupidTheta DataCon
data_con
    univ_tvs :: [TyCoVar]
univ_tvs     = DataCon -> [TyCoVar]
dataConUnivTyVars DataCon
data_con
    tenv :: Subst
tenv = [TyCoVar] -> [Type] -> Subst
HasDebugCallStack => [TyCoVar] -> [Type] -> Subst
zipTvSubst [TyCoVar]
univ_tvs ([TyCoVar] -> [Type] -> [Type]
forall b a. [b] -> [a] -> [a]
takeList [TyCoVar]
univ_tvs [Type]
inst_tys)
         -- NB: inst_tys can be longer than the univ tyvars
         --     because the constructor might have existentials
    inst_theta :: [Type]
inst_theta = HasDebugCallStack => Subst -> [Type] -> [Type]
Subst -> [Type] -> [Type]
substTheta Subst
tenv [Type]
stupid_theta

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

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

The Right Thing is not to confuse these constraints together. But for
now the Easy Thing is to ensure that we do not have existential or
GADT constraints in a 'proc', 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
forall doc. IsLine doc => String -> doc
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 -> [TyCoVar] -> [Type] -> PatEnv -> TcM ()
checkGADT ConLike
conlike [TyCoVar]
ex_tvs [Type]
arg_tys = \case
  PE { pe_ctxt :: PatEnv -> PatCtxt
pe_ctxt = LetPat {} }
    -> () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
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]
    -> TcRnMessage -> TcM ()
forall a. TcRnMessage -> TcRn a
failWithTc TcRnMessage
TcRnArrowProcGADTPattern
  PE { pe_lazy :: PatEnv -> Bool
pe_lazy = Bool
True }
    | Bool
has_existentials
    -- See Note [Existential check]
    -> TcRnMessage -> TcM ()
forall a. TcRnMessage -> TcRn a
failWithTc TcRnMessage
TcRnLazyGADTPattern
  PatEnv
_ -> () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  where
    has_existentials :: Bool
    has_existentials :: Bool
has_existentials = (TyCoVar -> Bool) -> [TyCoVar] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (TyCoVar -> VarSet -> Bool
`elemVarSet` [Type] -> VarSet
tyCoVarsOfTypes [Type]
arg_tys) [TyCoVar]
ex_tvs