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

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

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

    -}

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

    #include "HsVersions.h"

    import GHC.Prelude

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

                         ; forall (m :: * -> *) a. Monad m => a -> m a
    return (out
    p'forall a. a -> [a] -> [a]
    :[out]
    ps', r
    res) }

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

    --------------------
    tc_lpat :: Scaled ExpSigmaType
            -> Checker (LPat GhcRn) (LPat GhcTc)
    tc_lpat :: Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
    tc_lpat Scaled ExpSigmaType
    pat_ty PatEnv
    penv (L SrcSpanAnn' (EpAnn AnnListItem)
    span Pat GhcRn
    pat) TcM r
    thing_inside
      = forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
    setSrcSpanA SrcSpanAnn' (EpAnn AnnListItem)
    span forall a b. (a -> b) -> a -> b
    $
        do  { (Pat GhcTc
    pat', r
    res) <- forall a b. Pat GhcRn -> (TcM a -> TcM b) -> TcM a -> TcM b
    maybeWrapPatCtxt Pat GhcRn
    pat (Scaled ExpSigmaType -> Checker (Pat GhcRn) (Pat GhcTc)
    tc_pat Scaled ExpSigmaType
    pat_ty PatEnv
    penv Pat GhcRn
    pat)
                                              TcM r
    thing_inside
            ; forall (m :: * -> *) a. Monad m => a -> m a
    return (forall l e. l -> e -> GenLocated l e
    L SrcSpanAnn' (EpAnn AnnListItem)
    span Pat GhcTc
    pat', r
    res) }

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

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

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

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

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

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

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

      LazyPat XLazyPat GhcRn
    x LPat GhcRn
    pat -> do
            { HsWrapper
    mult_wrap <- forall a. Scaled a -> TcM HsWrapper
    checkManyPattern Scaled ExpSigmaType
    pat_ty
                -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
            ; (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)
    pat', (r
    res, WantedConstraints
    pat_ct))
                    <- Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
    tc_lpat Scaled ExpSigmaType
    pat_ty (PatEnv -> PatEnv
    makeLazy PatEnv
    penv) LPat GhcRn
    pat forall a b. (a -> b) -> a -> b
    $
                       forall a. TcM a -> TcM (a, WantedConstraints)
    captureConstraints TcM r
    thing_inside
                    -- Ignore refined penv', revert to penv

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

            -- Check that the expected pattern type is itself lifted
            ; TcType
    pat_ty <- ExpSigmaType -> TcM TcType
    readExpType (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; TcCoercionN
    _ <- Maybe SDoc -> TcType -> TcType -> TcM TcCoercionN
    unifyType forall a. Maybe a
    Nothing (HasDebugCallStack => TcType -> TcType
    tcTypeKind TcType
    pat_ty) TcType
    liftedTypeKind

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

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

      AsPat XAsPat GhcRn
    x (L SrcSpanAnnN
    nm_loc Name
    name) LPat GhcRn
    pat -> do
            { HsWrapper
    mult_wrap <- forall a. Scaled a -> TcM HsWrapper
    checkManyPattern Scaled ExpSigmaType
    pat_ty
                -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
            ; (HsWrapper
    wrap, TyVar
    bndr_id) <- forall ann a. SrcSpanAnn' ann -> TcRn a -> TcRn a
    setSrcSpanA SrcSpanAnnN
    nm_loc (PatEnv -> Name -> Scaled ExpSigmaType -> TcM (HsWrapper, TyVar)
    tcPatBndr PatEnv
    penv Name
    name Scaled ExpSigmaType
    pat_ty)
            ; (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)
    pat', r
    res) <- forall a. Name -> TyVar -> TcM a -> TcM a
    tcExtendIdEnv1 Name
    name TyVar
    bndr_id forall a b. (a -> b) -> a -> b
    $
                             Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
    tc_lpat (Scaled ExpSigmaType
    pat_ty forall a b. Scaled a -> b -> Scaled b
    `scaledSet`(TcType -> ExpSigmaType
    mkCheckExpType forall a b. (a -> b) -> a -> b
    $ TyVar -> TcType
    idType TyVar
    bndr_id))
                                     PatEnv
    penv LPat GhcRn
    pat TcM r
    thing_inside
                -- NB: if we do inference on:
                --          \ (y@(x::forall a. a->a)) = e
                -- we'll fail.  The as-pattern infers a monotype for 'y', which then
                -- fails to unify with the polymorphic type for 'x'.  This could
                -- perhaps be fixed, but only with a bit more work.
                --
                -- If you fix it, don't forget the bindInstsOfPatIds!
            ; TcType
    pat_ty <- ExpSigmaType -> TcM TcType
    readExpType (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; forall (m :: * -> *) a. Monad m => a -> m a
    return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
    mkHsWrapPat (HsWrapper
    wrap HsWrapper -> HsWrapper -> HsWrapper
    <.> HsWrapper
    mult_wrap) (forall p. XAsPat p -> LIdP p -> LPat p -> Pat p
    AsPat XAsPat GhcRn
    x (forall l e. l -> e -> GenLocated l e
    L SrcSpanAnnN
    nm_loc TyVar
    bndr_id) GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)
    pat') TcType
    pat_ty, r
    res) }

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

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

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

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

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

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

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

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

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

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

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

    ------------------------
    -- Lists, tuples, arrays
      ListPat Maybe SyntaxExprRn
    XListPat GhcRn
    Nothing [LPat GhcRn]
    pats -> do
            { (HsWrapper
    coi, TcType
    elt_ty) <- forall a.
    (TcType -> TcM (TcCoercionN, a))
    -> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
    matchExpectedPatTy TcType -> IOEnv (Env TcGblEnv TcLclEnv) (TcCoercionN, TcType)
    matchExpectedListTy PatEnv
    penv (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; ([GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)]
    pats', r
    res) <- forall inp out. Checker inp out -> Checker [inp] [out]
    tcMultiple (Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
    tc_lpat (Scaled ExpSigmaType
    pat_ty forall a b. Scaled a -> b -> Scaled b
    `scaledSet` TcType -> ExpSigmaType
    mkCheckExpType TcType
    elt_ty))
                                         PatEnv
    penv [LPat GhcRn]
    pats TcM r
    thing_inside
            ; TcType
    pat_ty <- ExpSigmaType -> TcM TcType
    readExpType (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; forall (m :: * -> *) a. Monad m => a -> m a
    return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
    mkHsWrapPat HsWrapper
    coi
                             (forall p. XListPat p -> [LPat p] -> Pat p
    ListPat (TcType -> Maybe (TcType, SyntaxExpr GhcTc) -> ListPatTc
    ListPatTc TcType
    elt_ty forall a. Maybe a
    Nothing) [GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)]
    pats') TcType
    pat_ty, r
    res)
    }

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

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

            ; DynFlags
    dflags <- forall (m :: * -> *). HasDynFlags m => m DynFlags
    getDynFlags

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

            ; TcType
    pat_ty <- ExpSigmaType -> TcM TcType
    readExpType (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; ASSERT( con_arg_tys `equalLength` pats ) -- Syntactically enforced
              forall (m :: * -> *) a. Monad m => a -> m a
    return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
    mkHsWrapPat HsWrapper
    coi Pat GhcTc
    possibly_mangled_result TcType
    pat_ty, r
    res)
            }

      SumPat XSumPat GhcRn
    _ LPat GhcRn
    pat Int
    alt Int
    arity  -> do
            { let tc :: TyCon
    tc = Int -> TyCon
    sumTyCon Int
    arity
            ; (HsWrapper
    coi, [TcType]
    arg_tys) <- forall a.
    (TcType -> TcM (TcCoercionN, a))
    -> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
    matchExpectedPatTy (TyCon -> TcType -> TcM (TcCoercionN, [TcType])
    matchExpectedTyConApp TyCon
    tc)
                                                   PatEnv
    penv (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; -- Drop levity vars, we don't care about them here
              let con_arg_tys :: [TcType]
    con_arg_tys = forall a. Int -> [a] -> [a]
    drop Int
    arity [TcType]
    arg_tys
            ; (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)
    pat', r
    res) <- Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
    tc_lpat (Scaled ExpSigmaType
    pat_ty forall a b. Scaled a -> b -> Scaled b
    `scaledSet` TcType -> ExpSigmaType
    mkCheckExpType ([TcType]
    con_arg_tys forall a. Outputable a => [a] -> Int -> a
    `getNth` (Int
    alt forall a. Num a => a -> a -> a
    - Int
    1)))
                                     PatEnv
    penv LPat GhcRn
    pat TcM r
    thing_inside
            ; TcType
    pat_ty <- ExpSigmaType -> TcM TcType
    readExpType (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; forall (m :: * -> *) a. Monad m => a -> m a
    return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
    mkHsWrapPat HsWrapper
    coi (forall p. XSumPat p -> LPat p -> Int -> Int -> Pat p
    SumPat [TcType]
    con_arg_tys GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)
    pat' Int
    alt Int
    arity) TcType
    pat_ty
                     , r
    res)
            }

    ------------------------
    -- Data constructors
      ConPat XConPat GhcRn
    _ XRec GhcRn (ConLikeP GhcRn)
    con HsConPatDetails GhcRn
    arg_pats ->
        forall a.
    PatEnv
    -> GenLocated SrcSpanAnnN Name
    -> Scaled ExpSigmaType
    -> HsConPatDetails GhcRn
    -> TcM a
    -> TcM (Pat GhcTc, a)
    tcConPat PatEnv
    penv XRec GhcRn (ConLikeP GhcRn)
    con Scaled ExpSigmaType
    pat_ty HsConPatDetails GhcRn
    arg_pats TcM r
    thing_inside

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

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

    -- In the case of a negative literal (the more complicated case),
    -- we get
    --
    --   case v of (-5) -> blah
    --
    -- becoming
    --
    --   if v == (negate (fromInteger 5)) then blah else ...
    --
    -- There are two bits of rebindable syntax:
    --   (==)   :: pat_ty -> neg_lit_ty -> Bool
    --   negate :: lit_ty -> neg_lit_ty
    -- where lit_ty is the type of the overloaded literal 5.
    --
    -- When there is no negation, neg_lit_ty and lit_ty are the same
      NPat XNPat GhcRn
    _ (L SrcSpan
    l HsOverLit GhcRn
    over_lit) Maybe (SyntaxExpr GhcRn)
    mb_neg SyntaxExpr GhcRn
    eq -> do
            { HsWrapper
    mult_wrap <- forall a. Scaled a -> TcM HsWrapper
    checkManyPattern Scaled ExpSigmaType
    pat_ty
              -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
              --
              -- It may be possible to refine linear pattern so that they work in
              -- linear environments. But it is not clear how useful this is.
            ; let orig :: CtOrigin
    orig = HsOverLit GhcRn -> CtOrigin
    LiteralOrigin HsOverLit GhcRn
    over_lit
            ; ((HsOverLit GhcTc
    lit', Maybe SyntaxExprTc
    mb_neg'), SyntaxExprTc
    eq')
                <- forall a.
    CtOrigin
    -> SyntaxExprRn
    -> [SyntaxOpType]
    -> ExpSigmaType
    -> ([TcType] -> [TcType] -> TcM a)
    -> TcM (a, SyntaxExprTc)
    tcSyntaxOp CtOrigin
    orig SyntaxExpr GhcRn
    eq [ExpSigmaType -> SyntaxOpType
    SynType (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty), SyntaxOpType
    SynAny]
                              (TcType -> ExpSigmaType
    mkCheckExpType TcType
    boolTy) forall a b. (a -> b) -> a -> b
    $
                   \ [TcType
    neg_lit_ty] [TcType]
    _ ->
                   let new_over_lit :: TcType -> TcM (HsOverLit GhcTc)
    new_over_lit TcType
    lit_ty = HsOverLit GhcRn -> ExpSigmaType -> TcM (HsOverLit GhcTc)
    newOverloadedLit HsOverLit GhcRn
    over_lit
                                               (TcType -> ExpSigmaType
    mkCheckExpType TcType
    lit_ty)
                   in case Maybe (SyntaxExpr GhcRn)
    mb_neg of
                     Maybe (SyntaxExpr GhcRn)
    Nothing  -> (, forall a. Maybe a
    Nothing) forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> TcType -> TcM (HsOverLit GhcTc)
    new_over_lit TcType
    neg_lit_ty
                     Just SyntaxExpr GhcRn
    neg -> -- Negative literal
                                 -- The 'negate' is re-mappable syntax
                       forall (a :: * -> * -> *) b c d.
    Arrow a =>
    a b c -> a (d, b) (d, c)
    second forall a. a -> Maybe a
    Just forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$>
                       (forall a.
    CtOrigin
    -> SyntaxExprRn
    -> [SyntaxOpType]
    -> ExpSigmaType
    -> ([TcType] -> [TcType] -> TcM a)
    -> TcM (a, SyntaxExprTc)
    tcSyntaxOp CtOrigin
    orig SyntaxExpr GhcRn
    neg [SyntaxOpType
    SynRho] (TcType -> ExpSigmaType
    mkCheckExpType TcType
    neg_lit_ty) forall a b. (a -> b) -> a -> b
    $
                        \ [TcType
    lit_ty] [TcType]
    _ -> TcType -> TcM (HsOverLit GhcTc)
    new_over_lit TcType
    lit_ty)
                         -- applied to a closed literal: linearity doesn't matter as
                         -- literals are typed in an empty environment, hence have
                         -- all multiplicities.

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

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

      case v of x + 5 -> blah

    we get

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    and a case expression

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

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

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

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

    In other words, boxySplitTyConAppWithFamily implicitly takes the coercion

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

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

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

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

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

    -}

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

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

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

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

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

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

            ; TCvSubst
    tenv1 <- CtOrigin -> [TyVar] -> [TcType] -> TcM TCvSubst
    instTyVarsWith CtOrigin
    PatOrigin [TyVar]
    univ_tvs [TcType]
    ctxt_res_tys
                      -- NB: Do not use zipTvSubst!  See #14154
                      -- We want to create a well-kinded substitution, so
                      -- that the instantiated type is well-kinded

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

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

            ; String -> SDoc -> TcRn ()
    traceTc String
    "tcConPat" ([SDoc] -> SDoc
    vcat [ forall a. Outputable a => a -> SDoc
    ppr Name
    con_name
                                       , [TyVar] -> SDoc
    pprTyVars [TyVar]
    univ_tvs
                                       , [TyVar] -> SDoc
    pprTyVars [TyVar]
    ex_tvs
                                       , forall a. Outputable a => a -> SDoc
    ppr [EqSpec]
    eq_spec
                                       , forall a. Outputable a => a -> SDoc
    ppr [TcType]
    theta
                                       , [TyVar] -> SDoc
    pprTyVars [TyVar]
    ex_tvs'
                                       , forall a. Outputable a => a -> SDoc
    ppr [TcType]
    ctxt_res_tys
                                       , forall a. Outputable a => a -> SDoc
    ppr [Scaled TcType]
    arg_tys'
                                       , forall a. Outputable a => a -> SDoc
    ppr HsConPatDetails GhcRn
    arg_pats ])
            ; if forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [TyVar]
    ex_tvs Bool -> Bool -> Bool
    && forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [EqSpec]
    eq_spec Bool -> Bool -> Bool
    && forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [TcType]
    theta
              then do { -- The common case; no class bindings etc
                        -- (see Note [Arrows and patterns])
                        (HsConDetails
      (HsPatSigType GhcRn)
      (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc))
      (HsRecFields
         GhcTc (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)))
    arg_pats', a
    res) <- ConLike
    -> [Scaled TcType]
    -> TCvSubst
    -> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)
    tcConArgs (DataCon -> ConLike
    RealDataCon DataCon
    data_con) [Scaled TcType]
    arg_tys_scaled
                                                      TCvSubst
    tenv PatEnv
    penv HsConPatDetails GhcRn
    arg_pats TcM a
    thing_inside
                      ; let res_pat :: Pat GhcTc
    res_pat = ConPat { pat_con :: XRec GhcTc (ConLikeP GhcTc)
    pat_con = GenLocated SrcSpanAnnN ConLike
    header
                                             , pat_args :: HsConPatDetails GhcTc
    pat_args = HsConDetails
      (HsPatSigType GhcRn)
      (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc))
      (HsRecFields
         GhcTc (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)))
    arg_pats'
                                             , pat_con_ext :: XConPat GhcTc
    pat_con_ext = ConPatTc
                                               { cpt_tvs :: [TyVar]
    cpt_tvs = [], cpt_dicts :: [TyVar]
    cpt_dicts = []
                                               , cpt_binds :: TcEvBinds
    cpt_binds = TcEvBinds
    emptyTcEvBinds
                                               , cpt_arg_tys :: [TcType]
    cpt_arg_tys = [TcType]
    ctxt_res_tys
                                               , cpt_wrap :: HsWrapper
    cpt_wrap = HsWrapper
    idHsWrapper
                                               }
                                             }

                      ; forall (m :: * -> *) a. Monad m => a -> m a
    return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
    mkHsWrapPat HsWrapper
    wrap Pat GhcTc
    res_pat TcType
    pat_ty, a
    res) }

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

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

            ; [TyVar]
    given <- [TcType] -> TcM [TyVar]
    newEvVars [TcType]
    theta'
            ; (TcEvBinds
    ev_binds, (HsConDetails
      (HsPatSigType GhcRn)
      (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc))
      (HsRecFields
         GhcTc (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)))
    arg_pats', a
    res))
                 <- forall result.
    SkolemInfo
    -> [TyVar] -> [TyVar] -> TcM result -> TcM (TcEvBinds, result)
    checkConstraints SkolemInfo
    skol_info [TyVar]
    ex_tvs' [TyVar]
    given forall a b. (a -> b) -> a -> b
    $
                    ConLike
    -> [Scaled TcType]
    -> TCvSubst
    -> Checker (HsConPatDetails GhcRn) (HsConPatDetails GhcTc)
    tcConArgs (DataCon -> ConLike
    RealDataCon DataCon
    data_con) [Scaled TcType]
    arg_tys_scaled TCvSubst
    tenv PatEnv
    penv HsConPatDetails GhcRn
    arg_pats TcM a
    thing_inside

            ; let res_pat :: Pat GhcTc
    res_pat = ConPat
                    { pat_con :: XRec GhcTc (ConLikeP GhcTc)
    pat_con   = GenLocated SrcSpanAnnN ConLike
    header
                    , pat_args :: HsConPatDetails GhcTc
    pat_args  = HsConDetails
      (HsPatSigType GhcRn)
      (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc))
      (HsRecFields
         GhcTc (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)))
    arg_pats'
                    , pat_con_ext :: XConPat GhcTc
    pat_con_ext = ConPatTc
                      { cpt_tvs :: [TyVar]
    cpt_tvs   = [TyVar]
    ex_tvs'
                      , cpt_dicts :: [TyVar]
    cpt_dicts = [TyVar]
    given
                      , cpt_binds :: TcEvBinds
    cpt_binds = TcEvBinds
    ev_binds
                      , cpt_arg_tys :: [TcType]
    cpt_arg_tys = [TcType]
    ctxt_res_tys
                      , cpt_wrap :: HsWrapper
    cpt_wrap  = HsWrapper
    idHsWrapper
                      }
                    }
            ; forall (m :: * -> *) a. Monad m => a -> m a
    return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
    mkHsWrapPat HsWrapper
    wrap Pat GhcTc
    res_pat TcType
    pat_ty, a
    res)
            } }

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

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

            -- Check that we aren't matching on a GADT-like pattern synonym
            -- in situations in which that isn't allowed.
            ; let all_arg_tys :: [TcType]
    all_arg_tys = TcType
    ty forall a. a -> [a] -> [a]
    : [TcType]
    prov_theta forall a. [a] -> [a] -> [a]
    ++ (forall a b. (a -> b) -> [a] -> [b]
    map forall a. Scaled a -> a
    scaledThing [Scaled TcType]
    arg_tys)
            ; ConLike -> [TyVar] -> [TcType] -> PatEnv -> TcRn ()
    checkGADT (PatSyn -> ConLike
    PatSynCon PatSyn
    pat_syn) [TyVar]
    ex_tvs [TcType]
    all_arg_tys PatEnv
    penv

            ; (TCvSubst
    tenv, [TyVar]
    ex_tvs') <- TCvSubst -> [TyVar] -> TcM (TCvSubst, [TyVar])
    tcInstSuperSkolTyVarsX TCvSubst
    subst [TyVar]
    ex_tvs
               -- This freshens: Note [Freshen existentials]

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

            ; HsWrapper
    mult_wrap <- forall a. Scaled a -> TcM HsWrapper
    checkManyPattern Scaled ExpSigmaType
    pat_ty
                -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.

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

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

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

            ; HsWrapper
    req_wrap <- CtOrigin -> [TcType] -> [TcType] -> TcM HsWrapper
    instCall (Name -> CtOrigin
    OccurrenceOf Name
    con_name) ([TyVar] -> [TcType]
    mkTyVarTys [TyVar]
    univ_tvs') [TcType]
    req_theta'
                          -- Origin (OccurrenceOf con_name):
                          -- see Note [Call-stack tracing of pattern synonyms]
            ; String -> SDoc -> TcRn ()
    traceTc String
    "instCall" (forall a. Outputable a => a -> SDoc
    ppr HsWrapper
    req_wrap)

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

            ; String -> SDoc -> TcRn ()
    traceTc String
    "checkConstraints }" (forall a. Outputable a => a -> SDoc
    ppr TcEvBinds
    ev_binds)
            ; let res_pat :: Pat GhcTc
    res_pat = ConPat { pat_con :: XRec GhcTc (ConLikeP GhcTc)
    pat_con   = forall l e. l -> e -> GenLocated l e
    L SrcSpanAnnN
    con_span forall a b. (a -> b) -> a -> b
    $ PatSyn -> ConLike
    PatSynCon PatSyn
    pat_syn
                                   , pat_args :: HsConPatDetails GhcTc
    pat_args  = HsConDetails
      (HsPatSigType GhcRn)
      (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc))
      (HsRecFields
         GhcTc (GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)))
    arg_pats'
                                   , pat_con_ext :: XConPat GhcTc
    pat_con_ext = ConPatTc
                                     { cpt_tvs :: [TyVar]
    cpt_tvs   = [TyVar]
    ex_tvs'
                                     , cpt_dicts :: [TyVar]
    cpt_dicts = [TyVar]
    prov_dicts'
                                     , cpt_binds :: TcEvBinds
    cpt_binds = TcEvBinds
    ev_binds
                                     , cpt_arg_tys :: [TcType]
    cpt_arg_tys = [TyVar] -> [TcType]
    mkTyVarTys [TyVar]
    univ_tvs'
                                     , cpt_wrap :: HsWrapper
    cpt_wrap  = HsWrapper
    req_wrap
                                     }
                                   }
            ; TcType
    pat_ty <- ExpSigmaType -> TcM TcType
    readExpType (forall a. Scaled a -> a
    scaledThing Scaled ExpSigmaType
    pat_ty)
            ; forall (m :: * -> *) a. Monad m => a -> m a
    return (HsWrapper -> Pat GhcTc -> TcType -> Pat GhcTc
    mkHsWrapPat (HsWrapper
    wrap HsWrapper -> HsWrapper -> HsWrapper
    <.> HsWrapper
    mult_wrap) Pat GhcTc
    res_pat TcType
    pat_ty, a
    res) }

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

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

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

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

    See also Note [Overview of implicit CallStacks] in GHC.Tc.Types.Evidence
    and Note [Solving CallStack constraints] in GHC.Tc.Solver.Monad
    -}
    ----------------------------
    -- | Convenient wrapper for calling a matchExpectedXXX function
    matchExpectedPatTy :: (TcRhoType -> TcM (TcCoercionN, a))
                        -> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
    -- See Note [Matching polytyped patterns]
    -- Returns a wrapper : pat_ty ~R inner_ty
    matchExpectedPatTy :: forall a.
    (TcType -> TcM (TcCoercionN, a))
    -> PatEnv -> ExpSigmaType -> TcM (HsWrapper, a)
    matchExpectedPatTy TcType -> TcM (TcCoercionN, a)
    inner_match (PE { pe_orig :: PatEnv -> CtOrigin
    pe_orig = CtOrigin
    orig }) ExpSigmaType
    pat_ty
      = do { TcType
    pat_ty <- ExpSigmaType -> TcM TcType
    expTypeToType ExpSigmaType
    pat_ty
           ; (HsWrapper
    wrap, TcType
    pat_rho) <- CtOrigin -> TcType -> TcM (HsWrapper, TcType)
    topInstantiate CtOrigin
    orig TcType
    pat_ty
           ; (TcCoercionN
    co, a
    res) <- TcType -> TcM (TcCoercionN, a)
    inner_match TcType
    pat_rho
           ; String -> SDoc -> TcRn ()
    traceTc String
    "matchExpectedPatTy" (forall a. Outputable a => a -> SDoc
    ppr TcType
    pat_ty SDoc -> SDoc -> SDoc
    $$ forall a. Outputable a => a -> SDoc
    ppr HsWrapper
    wrap)
           ; forall (m :: * -> *) a. Monad m => a -> m a
    return (TcCoercionN -> HsWrapper
    mkWpCastN (TcCoercionN -> TcCoercionN
    mkTcSymCo TcCoercionN
    co) HsWrapper -> HsWrapper -> HsWrapper
    <.> HsWrapper
    wrap, a
    res) }

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

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

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

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

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

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

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

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

     * In the simple case, pat_ty = tc tys

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

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

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

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

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

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

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

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

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

    Wrinkles:

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

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

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

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

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

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

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

            ; forall (m :: * -> *) a. Monad m => a -> m a
    return (forall tyarg arg rec.
    [tyarg] -> [arg] -> HsConDetails tyarg arg rec
    PrefixCon [HsPatSigType (NoGhcTc GhcRn)]
    type_args [GenLocated (SrcSpanAnn' (EpAnn AnnListItem)) (Pat GhcTc)]
    arg_pats', r
    res) }
        where
          con_arity :: Int
    con_arity  = ConLike -> Int
    conLikeArity ConLike
    con_like
          no_of_args :: Int
    no_of_args = forall (t :: * -> *) a. Foldable t => t a -> Int
    length [LPat GhcRn]
    arg_pats

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

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

          find_field_ty :: Name -> FieldLabelString -> TcM (Scaled TcType)
          find_field_ty :: Name -> FieldLabelString -> TcRn (Scaled TcType)
    find_field_ty Name
    sel FieldLabelString
    lbl
            = case [Scaled TcType
    ty | (FieldLabel
    fl, Scaled TcType
    ty) <- [(FieldLabel, Scaled TcType)]
    field_tys, FieldLabel -> Name
    flSelector FieldLabel
    fl 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".
               [] -> forall a. SDoc -> TcRn a
    failWith (ConLike -> FieldLabelString -> SDoc
    badFieldCon ConLike
    con_like FieldLabelString
    lbl)

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

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

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

    tcConArg :: Checker (LPat GhcRn, Scaled TcSigmaType) (LPat GhcTc)
    tcConArg :: Checker (LPat GhcRn, Scaled TcType) (LPat GhcTc)
    tcConArg PatEnv
    penv (LPat GhcRn
    arg_pat, Scaled TcType
    arg_mult TcType
    arg_ty)
      = Scaled ExpSigmaType -> Checker (LPat GhcRn) (LPat GhcTc)
    tc_lpat (forall a. TcType -> a -> Scaled a
    Scaled TcType
    arg_mult (TcType -> ExpSigmaType
    mkCheckExpType TcType
    arg_ty)) PatEnv
    penv LPat GhcRn
    arg_pat

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

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

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

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

    The Right Thing is not to confuse these constraints together. But for
    now the Easy Thing is to ensure that we do not have existential or
    GADT constraints in a 'proc', which we do by disallowing any
    non-vanilla pattern match (i.e. one that introduces existential
    variables or provided constraints), in tcDataConPat and tcPatSynPat.

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

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

    In principle, these program would be reasonable:

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

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

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

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

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

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

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

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

    We desugar this as follows:

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

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

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

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

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

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

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

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

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

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

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

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

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