Fix Trac #2985: generating superclasses and recursive dictionaries

[ghc-hetmet.git] / compiler / typecheck / TcType.lhs

diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs
index 6ff9732..e0e7649 100644 (file)
--- a/compiler/typecheck/TcType.lhs
+++ b/compiler/typecheck/TcType.lhs
@@ -421,7 +421,7 @@ pprUserTypeCtxt SpecInstCtxt    = ptext (sLit "a SPECIALISE instance pragma")
 tidySkolemTyVar :: TidyEnv -> TcTyVar -> (TidyEnv, TcTyVar)
 -- Tidy the type inside a GenSkol, preparatory to printing it
 tidySkolemTyVar env tv
-  = ASSERT( isSkolemTyVar tv || isSigTyVar tv )
+  = ASSERT( isTcTyVar tv && (isSkolemTyVar tv || isSigTyVar tv ) )
     (env1, mkTcTyVar (tyVarName tv) (tyVarKind tv) info1)
   where
     (env1, info1) = case tcTyVarDetails tv of
@@ -508,7 +508,7 @@ isTyConableTyVar tv
        SkolemTv {}         -> False
        
 isSkolemTyVar tv 
-  = ASSERT( isTcTyVar tv )
+  = ASSERT2( isTcTyVar tv, ppr tv )
     case tcTyVarDetails tv of
        SkolemTv _         -> True
        MetaTv _ _         -> False
@@ -965,10 +965,13 @@ isSigmaTy (FunTy a _)    = isPredTy a
 isSigmaTy _              = False
 
 isOverloadedTy :: Type -> Bool
+-- Yes for a type of a function that might require evidence-passing
+-- Used only by bindInstsOfLocalFuns/Pats
+-- NB: be sure to check for type with an equality predicate; hence isCoVar
 isOverloadedTy ty | Just ty' <- tcView ty = isOverloadedTy ty'
-isOverloadedTy (ForAllTy _ ty) = isOverloadedTy ty
-isOverloadedTy (FunTy a _)     = isPredTy a
-isOverloadedTy _               = False
+isOverloadedTy (ForAllTy tv ty) = isCoVar tv || isOverloadedTy ty
+isOverloadedTy (FunTy a _)      = isPredTy a
+isOverloadedTy _                = False
 
 isPredTy :: Type -> Bool       -- Belongs in TcType because it does 
                                -- not look through newtypes, or predtypes (of course)
@@ -1007,8 +1010,9 @@ is_tc uniq ty = case tcSplitTyConApp_maybe ty of
 --     hence no 'coreView'.  This could, however, be changed without breaking
 --     any code.
 isOpenSynTyConApp :: TcTauType -> Bool
-isOpenSynTyConApp (TyConApp tc _) = isOpenSynTyCon tc
-isOpenSynTyConApp _other          = False
+isOpenSynTyConApp (TyConApp tc tys) = isOpenSynTyCon tc && 
+                                      length tys == tyConArity tc 
+isOpenSynTyConApp _other            = False
 \end{code}