Progress on #16185

15 files changed, 79 insertions, 64 deletions

diff --git a/compiler/basicTypes/Var.hs-boot b/compiler/basicTypes/Var.hs-boot
new file mode 100644
index 0000000000..0f013beef7
--- /dev/null
+++ b/compiler/basicTypes/Var.hs-boot
@@ -0,0 +1,7 @@
+module Var where
+
+-- Var.hs-boot is Imported (only) by TyCoRep.hs-boot
+
+data ArgFlag
+data AnonArgFlag
+data Var
diff --git a/compiler/iface/IfaceType.hs b/compiler/iface/IfaceType.hs
index f8994d6b9b..a862197866 100644
--- a/compiler/iface/IfaceType.hs
+++ b/compiler/iface/IfaceType.hs
@@ -717,7 +717,9 @@ pprIfaceTyConBinders = sep . map go
     go (Bndr (IfaceTvBndr bndr) vis) =
       -- See Note [Pretty-printing invisible arguments]
       case vis of
-        AnonTCB            -> ppr_bndr True
+        AnonTCB  VisArg    -> ppr_bndr True
+        AnonTCB  InvisArg  -> ppr_bndr True  -- Rare; just promoted GADT data constructors
+                                             -- Should we print them differently?
         NamedTCB Required  -> ppr_bndr True
         NamedTCB Specified -> char '@' <> ppr_bndr True
         NamedTCB Inferred  -> char '@' <> braces (ppr_bndr False)
@@ -765,7 +767,14 @@ pprPrecIfaceType :: PprPrec -> IfaceType -> SDoc
 -- called from other places, besides `:type` and `:info`.
 pprPrecIfaceType prec ty = eliminateRuntimeRep (ppr_ty prec) ty
 
+ppr_sigma :: PprPrec -> IfaceType -> SDoc
+ppr_sigma ctxt_prec ty
+  = maybeParen ctxt_prec funPrec (pprIfaceSigmaType ShowForAllMust ty)
+
 ppr_ty :: PprPrec -> IfaceType -> SDoc
+ppr_ty ctxt_prec ty@(IfaceForAllTy {})        = ppr_sigma ctxt_prec ty
+ppr_ty ctxt_prec ty@(IfaceFunTy InvisArg _ _) = ppr_sigma ctxt_prec ty
+
 ppr_ty _         (IfaceFreeTyVar tyvar) = ppr tyvar  -- This is the main reason for IfaceFreeTyVar!
 ppr_ty _         (IfaceTyVar tyvar)     = ppr tyvar  -- See Note [TcTyVars in IfaceType]
 ppr_ty ctxt_prec (IfaceTyConApp tc tys) = pprTyTcApp ctxt_prec tc tys
@@ -777,7 +786,7 @@ ppr_ty ctxt_prec (IfaceFunTy _ ty1 ty2)  -- Should be VisArg
     maybeParen ctxt_prec funPrec $
     sep [ppr_ty funPrec ty1, sep (ppr_fun_tail ty2)]
   where
-    ppr_fun_tail (IfaceFunTy _ ty1 ty2)
+    ppr_fun_tail (IfaceFunTy VisArg ty1 ty2)
       = (arrow <+> ppr_ty funPrec ty1) : ppr_fun_tail ty2
     ppr_fun_tail other_ty
       = [arrow <+> pprIfaceType other_ty]
@@ -816,9 +825,6 @@ ppr_ty ctxt_prec (IfaceCoercionTy co)
       (ppr_co ctxt_prec co)
       (text "<>")
 
-ppr_ty ctxt_prec ty -- IfaceForAllTy
-  = maybeParen ctxt_prec funPrec (pprIfaceSigmaType ShowForAllMust ty)
-
 {- Note [Defaulting RuntimeRep variables]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 RuntimeRep variables are considered by many (most?) users to be little
diff --git a/compiler/prelude/TysWiredIn.hs b/compiler/prelude/TysWiredIn.hs
index ff958131b8..59283983ee 100644
--- a/compiler/prelude/TysWiredIn.hs
+++ b/compiler/prelude/TysWiredIn.hs
@@ -16,8 +16,6 @@ module TysWiredIn (
 
         mkWiredInIdName,    -- used in MkId
 
-        mkFunKind, mkForAllKind,
-
         -- * All wired in things
         wiredInTyCons, isBuiltInOcc_maybe,
 
@@ -595,14 +593,6 @@ liftedTypeKind, constraintKind :: Kind
 liftedTypeKind   = tYPE liftedRepTy
 constraintKind   = mkTyConApp constraintKindTyCon []
 
--- mkFunKind and mkForAllKind are defined here
--- solely so that TyCon can use them via a SOURCE import
-mkFunKind :: Kind -> Kind -> Kind
-mkFunKind = mkVisFunTy
-
-mkForAllKind :: TyCoVar -> ArgFlag -> Kind -> Kind
-mkForAllKind = mkForAllTy
-
 {-
 ************************************************************************
 *                                                                      *
diff --git a/compiler/prelude/TysWiredIn.hs-boot b/compiler/prelude/TysWiredIn.hs-boot
index 1481a758b1..4e8ebba223 100644
--- a/compiler/prelude/TysWiredIn.hs-boot
+++ b/compiler/prelude/TysWiredIn.hs-boot
@@ -1,13 +1,8 @@
 module TysWiredIn where
 
-import Var( TyVar, ArgFlag )
 import {-# SOURCE #-} TyCon      ( TyCon )
 import {-# SOURCE #-} TyCoRep    (Type, Kind)
 
-
-mkFunKind :: Kind -> Kind -> Kind
-mkForAllKind :: TyVar -> ArgFlag -> Kind -> Kind
-
 listTyCon :: TyCon
 typeNatKind, typeSymbolKind :: Type
 mkBoxedTupleTy :: [Type] -> Type
diff --git a/compiler/typecheck/TcFlatten.hs b/compiler/typecheck/TcFlatten.hs
index d4850aea16..8b5d8a4c06 100644
--- a/compiler/typecheck/TcFlatten.hs
+++ b/compiler/typecheck/TcFlatten.hs
@@ -2183,7 +2183,7 @@ ty_con_binders_ty_binders' = foldr go ([], False)
   where
     go (Bndr tv (NamedTCB vis)) (bndrs, _)
       = (Named (Bndr tv vis) : bndrs, True)
-    go (Bndr tv AnonTCB)        (bndrs, n)
-      = (Anon VisArg (tyVarKind tv)   : bndrs, n)
+    go (Bndr tv (AnonTCB af))   (bndrs, n)
+      = (Anon af (tyVarKind tv)   : bndrs, n)
     {-# INLINE go #-}
 {-# INLINE ty_con_binders_ty_binders' #-}
diff --git a/compiler/typecheck/TcHsType.hs b/compiler/typecheck/TcHsType.hs
index fea0eabe64..a0ebe712ae 100644
--- a/compiler/typecheck/TcHsType.hs
+++ b/compiler/typecheck/TcHsType.hs
@@ -2206,7 +2206,7 @@ etaExpandAlgTyCon tc_bndrs kind
               arg'   = substTy subst arg
               tv     = mkTyVar (mkInternalName uniq occ loc) arg'
               subst' = extendTCvInScope subst tv
-              tcb    = Bndr tv AnonTCB
+              tcb    = Bndr tv (AnonTCB VisArg)
               (uniq:uniqs') = uniqs
               (occ:occs')   = occs
 
@@ -2235,7 +2235,7 @@ tcbVisibilities tc orig_args
     go fun_kind subst all_args@(arg : args)
       | Just (tcb, inner_kind) <- splitPiTy_maybe fun_kind
       = case tcb of
-          Anon {}             -> AnonTCB      : go inner_kind subst  args
+          Anon af _           -> AnonTCB af   : go inner_kind subst  args
           Named (Bndr tv vis) -> NamedTCB vis : go inner_kind subst' args
                  where
                     subst' = extendTCvSubst subst tv arg
diff --git a/compiler/typecheck/TcMatches.hs b/compiler/typecheck/TcMatches.hs
index 5a3a270c88..4286a5463a 100644
--- a/compiler/typecheck/TcMatches.hs
+++ b/compiler/typecheck/TcMatches.hs
@@ -619,7 +619,7 @@ tcMcStmt ctxt (TransStmt { trS_stmts = stmts, trS_bndrs = bindersMap
                          , trS_by = by, trS_using = using, trS_form = form
                          , trS_ret = return_op, trS_bind = bind_op
                          , trS_fmap = fmap_op }) res_ty thing_inside
-  = do { let star_star_kind = liftedTypeKind `mkFunKind` liftedTypeKind
+  = do { let star_star_kind = liftedTypeKind `mkVisFunTy` liftedTypeKind
        ; m1_ty   <- newFlexiTyVarTy star_star_kind
        ; m2_ty   <- newFlexiTyVarTy star_star_kind
        ; tup_ty  <- newFlexiTyVarTy liftedTypeKind
@@ -744,7 +744,7 @@ tcMcStmt ctxt (TransStmt { trS_stmts = stmts, trS_bndrs = bindersMap
 --        -> m (st1, (st2, st3))
 --
 tcMcStmt ctxt (ParStmt _ bndr_stmts_s mzip_op bind_op) res_ty thing_inside
-  = do { let star_star_kind = liftedTypeKind `mkFunKind` liftedTypeKind
+  = do { let star_star_kind = liftedTypeKind `mkVisFunTy` liftedTypeKind
        ; m_ty   <- newFlexiTyVarTy star_star_kind
 
        ; let mzip_ty  = mkInvForAllTys [alphaTyVar, betaTyVar] $
diff --git a/compiler/typecheck/TcSigs.hs b/compiler/typecheck/TcSigs.hs
index ec50bf2791..359d48202d 100644
--- a/compiler/typecheck/TcSigs.hs
+++ b/compiler/typecheck/TcSigs.hs
@@ -217,6 +217,7 @@ tcUserTypeSig :: SrcSpan -> LHsSigWcType GhcRn -> Maybe Name
 tcUserTypeSig loc hs_sig_ty mb_name
   | isCompleteHsSig hs_sig_ty
   = do { sigma_ty <- tcHsSigWcType ctxt_F hs_sig_ty
+       ; traceTc "tcuser" (ppr sigma_ty)
        ; return $
          CompleteSig { sig_bndr  = mkLocalId name sigma_ty
                      , sig_ctxt  = ctxt_T
diff --git a/compiler/typecheck/TcUnify.hs b/compiler/typecheck/TcUnify.hs
index 1416e6b41e..aaf459bde9 100644
--- a/compiler/typecheck/TcUnify.hs
+++ b/compiler/typecheck/TcUnify.hs
@@ -444,7 +444,7 @@ matchExpectedAppTy orig_ty
            ; return (co, (ty1, ty2)) }
 
     orig_kind = tcTypeKind orig_ty
-    kind1 = mkFunKind liftedTypeKind orig_kind
+    kind1 = mkVisFunTy liftedTypeKind orig_kind
     kind2 = liftedTypeKind    -- m :: * -> k
                               -- arg type :: *
 
@@ -2043,7 +2043,7 @@ matchExpectedFunKind hs_ty = go
     defer k
       = do { arg_kind <- newMetaKindVar
            ; res_kind <- newMetaKindVar
-           ; let new_fun = mkFunKind arg_kind res_kind
+           ; let new_fun = mkVisFunTy arg_kind res_kind
                  origin  = TypeEqOrigin { uo_actual   = k
                                         , uo_expected = new_fun
                                         , uo_thing    = Just (ppr hs_ty)
diff --git a/compiler/types/OptCoercion.hs b/compiler/types/OptCoercion.hs
index 1d48ed05b5..385a4b3740 100644
--- a/compiler/types/OptCoercion.hs
+++ b/compiler/types/OptCoercion.hs
@@ -2,9 +2,13 @@
 
 {-# LANGUAGE CPP #-}
 
--- The default iteration limit is a bit too low for the definitions
--- in this module.
-{-# OPTIONS_GHC -fmax-pmcheck-iterations=10000000 #-}
+{-# OPTIONS_GHC -Wno-overlapping-patterns -Wno-incomplete-patterns #-}
+    -- Yuk!  Suppresses bogus warnings
+    -- The -Wno-incomplete-patterns suppresses
+    --     a pattern-checker iteration limit error
+    -- I have not idea why the iteration limit had suddenly blown up
+    -- This happened when I added FFunTy, and a COMPLETE pragma for
+    -- Type; but there is no pattern matching on Type here!
 
 module OptCoercion ( optCoercion, checkAxInstCo ) where
 
diff --git a/compiler/types/TyCoRep.hs b/compiler/types/TyCoRep.hs
index 2fbf6b1933..d8eac95812 100644
--- a/compiler/types/TyCoRep.hs
+++ b/compiler/types/TyCoRep.hs
@@ -17,7 +17,7 @@ Note [The Type-related module hierarchy]
 
 -- We expose the relevant stuff from this module via the Type module
 {-# OPTIONS_HADDOCK not-home #-}
-{-# LANGUAGE CPP, DeriveDataTypeable, MultiWayIf, PatternSynonyms #-}
+{-# LANGUAGE CPP, DeriveDataTypeable, MultiWayIf, PatternSynonyms, BangPatterns #-}
 
 module TyCoRep (
         TyThing(..), tyThingCategory, pprTyThingCategory, pprShortTyThing,
@@ -45,7 +45,7 @@ module TyCoRep (
         -- * Functions over types
         mkTyConTy, mkTyVarTy, mkTyVarTys,
         mkTyCoVarTy, mkTyCoVarTys,
-        mkVisFunTy, mkInvisFunTy, mkVisFunTys, mkInvisFunTys,
+        mkFFunTy, mkVisFunTy, mkInvisFunTy, mkVisFunTys, mkInvisFunTys,
         mkTyCoForAllTy, mkForAllTys,
         mkForAllTy,
         mkTyCoPiTy, mkTyCoPiTys,
@@ -337,7 +337,8 @@ data Type
 
   deriving Data.Data
 
-{-# COMPLETE FunTy, TyVarTy, AppTy, TyConApp, ForAllTy, LitTy, CastTy, CoercionTy #-}
+{-# COMPLETE FunTy, TyVarTy, AppTy, TyConApp
+           , ForAllTy, LitTy, CastTy, CoercionTy :: Type #-}
 
 -- | 'FunTy' is a (uni-directional) pattern synonym for the common
 -- case where we want to match on the argument/result type, but
@@ -829,10 +830,14 @@ mkTyCoVarTy v
 mkTyCoVarTys :: [TyCoVar] -> [Type]
 mkTyCoVarTys = map mkTyCoVarTy
 
-infixr 3 `mkVisFunTy`, `mkInvisFunTy`      -- Associates to the right
+infixr 3 `mkFFunTy`, `mkVisFunTy`, `mkInvisFunTy`      -- Associates to the right
+
+mkFFunTy :: AnonArgFlag -> Type -> Type -> Type
+mkFFunTy af arg res = FFunTy { ft_af = af, ft_arg = arg, ft_res = res }
+
 mkVisFunTy, mkInvisFunTy :: Type -> Type -> Type
-mkVisFunTy   arg res = FFunTy { ft_af = VisArg,   ft_arg = arg, ft_res = res }
-mkInvisFunTy arg res = FFunTy { ft_af = InvisArg, ft_arg = arg, ft_res = res }
+mkVisFunTy   = mkFFunTy VisArg
+mkInvisFunTy = mkFFunTy InvisArg
 
 -- | Make nested arrow types
 mkVisFunTys, mkInvisFunTys :: [Type] -> Type -> Type
@@ -2124,10 +2129,10 @@ almost_devoid_co_var_of_types (ty:tys) cv
 injectiveVarsOfBinder :: TyConBinder -> FV
 injectiveVarsOfBinder (Bndr tv vis) =
   case vis of
-    AnonTCB           -> injectiveVarsOfType (varType tv)
+    AnonTCB VisArg    -> injectiveVarsOfType (varType tv)
     NamedTCB Required -> unitFV tv `unionFV`
                          injectiveVarsOfType (varType tv)
-    NamedTCB _        -> emptyFV
+    _                 -> emptyFV
 
 -- | Returns the free variables of a 'Type' that are in injective positions.
 -- (See @Note [Kind annotations on TyConApps]@ in "TcSplice" for an explanation
diff --git a/compiler/types/TyCoRep.hs-boot b/compiler/types/TyCoRep.hs-boot
index 5af8c1d57f..85ef782553 100644
--- a/compiler/types/TyCoRep.hs-boot
+++ b/compiler/types/TyCoRep.hs-boot
@@ -4,6 +4,7 @@ import GhcPrelude
 
 import Outputable ( SDoc )
 import Data.Data  ( Data )
+import {-# SOURCE #-} Var( Var, ArgFlag, AnonArgFlag )
 
 data Type
 data TyThing
@@ -22,8 +23,9 @@ type MCoercionN = MCoercion
 
 pprKind :: Kind -> SDoc
 pprType :: Type -> SDoc
+mkFFunTy   :: AnonArgFlag -> Type -> Type -> Type
+mkForAllTy :: Var -> ArgFlag -> Type -> Type
 
 isRuntimeRepTy :: Type -> Bool
 
-instance Data Type
-  -- To support Data instances in CoAxiom
+instance Data Type  -- To support Data instances in CoAxiom
diff --git a/compiler/types/TyCon.hs b/compiler/types/TyCon.hs
index eb0b84d47e..e19f980aca 100644
--- a/compiler/types/TyCon.hs
+++ b/compiler/types/TyCon.hs
@@ -132,10 +132,9 @@ module TyCon(
 
 import GhcPrelude
 
-import {-# SOURCE #-} TyCoRep    ( Kind, Type, PredType, pprType )
+import {-# SOURCE #-} TyCoRep    ( Kind, Type, PredType, pprType, mkForAllTy, mkFFunTy )
 import {-# SOURCE #-} TysWiredIn ( runtimeRepTyCon, constraintKind
-                                 , vecCountTyCon, vecElemTyCon, liftedTypeKind
-                                 , mkFunKind, mkForAllKind )
+                                 , vecCountTyCon, vecElemTyCon, liftedTypeKind )
 import {-# SOURCE #-} DataCon    ( DataCon, dataConExTyCoVars, dataConFieldLabels
                                  , dataConTyCon, dataConFullSig
                                  , isUnboxedSumCon )
@@ -402,15 +401,15 @@ type TyConTyCoBinder = VarBndr TyCoVar TyConBndrVis
 
 data TyConBndrVis
   = NamedTCB ArgFlag
-  | AnonTCB
+  | AnonTCB  AnonArgFlag
 
 instance Outputable TyConBndrVis where
-  ppr (NamedTCB flag) = text "NamedTCB" <+> ppr flag
-  ppr AnonTCB         = text "AnonTCB"
+  ppr (NamedTCB flag) = text "NamedTCB" <> ppr flag
+  ppr (AnonTCB af)    = text "AnonTCB"  <> ppr af
 
 mkAnonTyConBinder :: TyVar -> TyConBinder
 mkAnonTyConBinder tv = ASSERT( isTyVar tv)
-                       Bndr tv AnonTCB
+                       Bndr tv (AnonTCB VisArg)
 
 mkAnonTyConBinders :: [TyVar] -> [TyConBinder]
 mkAnonTyConBinders tvs = map mkAnonTyConBinder tvs
@@ -437,8 +436,9 @@ tyConBinderArgFlag :: TyConBinder -> ArgFlag
 tyConBinderArgFlag (Bndr _ vis) = tyConBndrVisArgFlag vis
 
 tyConBndrVisArgFlag :: TyConBndrVis -> ArgFlag
-tyConBndrVisArgFlag (NamedTCB vis) = vis
-tyConBndrVisArgFlag AnonTCB        = Required
+tyConBndrVisArgFlag (NamedTCB vis)     = vis
+tyConBndrVisArgFlag (AnonTCB VisArg)   = Required
+tyConBndrVisArgFlag (AnonTCB InvisArg) = Inferred
 
 isNamedTyConBinder :: TyConBinder -> Bool
 -- Identifies kind variables
@@ -452,8 +452,9 @@ isVisibleTyConBinder :: VarBndr tv TyConBndrVis -> Bool
 isVisibleTyConBinder (Bndr _ tcb_vis) = isVisibleTcbVis tcb_vis
 
 isVisibleTcbVis :: TyConBndrVis -> Bool
-isVisibleTcbVis (NamedTCB vis) = isVisibleArgFlag vis
-isVisibleTcbVis AnonTCB        = True
+isVisibleTcbVis (NamedTCB vis)     = isVisibleArgFlag vis
+isVisibleTcbVis (AnonTCB VisArg)   = True
+isVisibleTcbVis (AnonTCB InvisArg) = False
 
 isInvisibleTyConBinder :: VarBndr tv TyConBndrVis -> Bool
 -- Works for IfaceTyConBinder too
@@ -463,8 +464,8 @@ mkTyConKind :: [TyConBinder] -> Kind -> Kind
 mkTyConKind bndrs res_kind = foldr mk res_kind bndrs
   where
     mk :: TyConBinder -> Kind -> Kind
-    mk (Bndr tv AnonTCB)        k = mkFunKind (varType tv) k
-    mk (Bndr tv (NamedTCB vis)) k = mkForAllKind tv vis k
+    mk (Bndr tv (AnonTCB af))   k = mkFFunTy af (varType tv) k
+    mk (Bndr tv (NamedTCB vis)) k = mkForAllTy tv vis k
 
 tyConTyVarBinders :: [TyConBinder]   -- From the TyCon
                   -> [TyVarBinder]   -- Suitable for the foralls of a term function
@@ -475,7 +476,8 @@ tyConTyVarBinders tc_bndrs
    mk_binder (Bndr tv tc_vis) = mkTyVarBinder vis tv
       where
         vis = case tc_vis of
-                AnonTCB           -> Specified
+                AnonTCB VisArg    -> Specified
+                AnonTCB InvisArg  -> Inferred
                 NamedTCB Required -> Specified
                 NamedTCB vis      -> vis
 
@@ -596,18 +598,21 @@ They fit together like so:
 -}
 
 instance Outputable tv => Outputable (VarBndr tv TyConBndrVis) where
-  ppr (Bndr v AnonTCB)              = text "anon" <+> parens (ppr v)
-  ppr (Bndr v (NamedTCB Required))  = text "req"  <+> parens (ppr v)
-  ppr (Bndr v (NamedTCB Specified)) = text "spec" <+> parens (ppr v)
-  ppr (Bndr v (NamedTCB Inferred))  = text "inf"  <+> parens (ppr v)
+  ppr (Bndr v bi) = ppr_bi bi <+> parens (ppr v)
+    where
+      ppr_bi (AnonTCB VisArg)     = text "anon-vis"
+      ppr_bi (AnonTCB InvisArg)   = text "anon-invis"
+      ppr_bi (NamedTCB Required)  = text "req"
+      ppr_bi (NamedTCB Specified) = text "spec"
+      ppr_bi (NamedTCB Inferred)  = text "inf"
 
 instance Binary TyConBndrVis where
-  put_ bh AnonTCB        = putByte bh 0
+  put_ bh (AnonTCB af)   = do { putByte bh 0; put_ bh af }
   put_ bh (NamedTCB vis) = do { putByte bh 1; put_ bh vis }
 
   get bh = do { h <- getByte bh
               ; case h of
-                  0 -> return AnonTCB
+                  0 -> do { af  <- get bh; return (AnonTCB af) }
                   _ -> do { vis <- get bh; return (NamedTCB vis) } }
 
 
diff --git a/compiler/types/Type.hs b/compiler/types/Type.hs
index d8d0c516dd..2042451ae5 100644
--- a/compiler/types/Type.hs
+++ b/compiler/types/Type.hs
@@ -1287,7 +1287,7 @@ tyConBindersTyCoBinders :: [TyConBinder] -> [TyCoBinder]
 tyConBindersTyCoBinders = map to_tyb
   where
     to_tyb (Bndr tv (NamedTCB vis)) = Named (Bndr tv vis)
-    to_tyb (Bndr tv AnonTCB)        = Anon VisArg (varType tv)
+    to_tyb (Bndr tv (AnonTCB af))   = Anon af (varType tv)
 
 {-
 --------------------------------------------------------------------
@@ -1411,7 +1411,7 @@ mkTyConBindersPreferAnon vars inner_tkvs = ASSERT( all isTyVar vars)
               = ( Bndr v (NamedTCB Required) : binders
                 , fvs `delVarSet` v `unionVarSet` kind_vars )
               | otherwise
-              = ( Bndr v AnonTCB : binders
+              = ( Bndr v (AnonTCB VisArg) : binders
                 , fvs `unionVarSet` kind_vars )
       where
         (binders, fvs) = go vs
diff --git a/testsuite/tests/typecheck/should_fail/tcfail057.stderr b/testsuite/tests/typecheck/should_fail/tcfail057.stderr
index 9ddffeb28b..cb6bb97f92 100644
--- a/testsuite/tests/typecheck/should_fail/tcfail057.stderr
+++ b/testsuite/tests/typecheck/should_fail/tcfail057.stderr
@@ -10,4 +10,4 @@ tcfail057.hs:6:7: error:
       In an equation for ‘f’: f x = x
     • Relevant bindings include
         x :: RealFrac a (bound at tcfail057.hs:6:3)
-        f :: RealFrac a => a -> a (bound at tcfail057.hs:6:1)
+        f :: RealFrac a -> a -> a (bound at tcfail057.hs:6:1)