Cover PredTy case in Type.tyFamInsts

[ghc-hetmet.git] / compiler / types / Type.lhs

diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs
index 79a561a..cf38146 100644 (file)
--- a/compiler/types/Type.lhs
+++ b/compiler/types/Type.lhs
@@ -44,7 +44,7 @@ module Type (
        newTyConInstRhs,
        
        -- (Type families)
-        tyFamInsts,
+        tyFamInsts, predFamInsts,
 
         -- (Source types)
         mkPredTy, mkPredTys, mkFamilyTyConApp,
@@ -887,6 +887,14 @@ tyFamInsts (TyConApp tc tys)
 tyFamInsts (FunTy ty1 ty2)      = tyFamInsts ty1 ++ tyFamInsts ty2
 tyFamInsts (AppTy ty1 ty2)      = tyFamInsts ty1 ++ tyFamInsts ty2
 tyFamInsts (ForAllTy _ ty)      = tyFamInsts ty
+tyFamInsts (PredTy pty)         = predFamInsts pty
+
+-- | Finds type family instances occuring in a predicate type after expanding 
+-- synonyms.
+predFamInsts :: PredType -> [(TyCon, [Type])]
+predFamInsts (ClassP _cla tys) = concat (map tyFamInsts tys)
+predFamInsts (IParam _ ty)     = tyFamInsts ty
+predFamInsts (EqPred ty1 ty2)  = tyFamInsts ty1 ++ tyFamInsts ty2
 \end{code}
 
 
@@ -1147,14 +1155,16 @@ coreEqType t1 t2
 
 \begin{code}
 tcEqType :: Type -> Type -> Bool
--- ^ Type equality on source types. Does not look through @newtypes@ or 'PredType's
+-- ^ Type equality on source types. Does not look through @newtypes@ or 
+-- 'PredType's, but it does look through type synonyms.
 tcEqType t1 t2 = isEqual $ cmpType t1 t2
 
 tcEqTypes :: [Type] -> [Type] -> Bool
 tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
 
 tcCmpType :: Type -> Type -> Ordering
--- ^ Type ordering on source types. Does not look through @newtypes@ or 'PredType's
+-- ^ Type ordering on source types. Does not look through @newtypes@ or 
+-- 'PredType's, but it does look through type synonyms.
 tcCmpType t1 t2 = cmpType t1 t2
 
 tcCmpTypes :: [Type] -> [Type] -> Ordering