Type families: fix decomposition problem

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

diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs
index 1a3fad7..fe5ea39 100644 (file)
--- a/compiler/typecheck/TcType.lhs
+++ b/compiler/typecheck/TcType.lhs
@@ -1007,8 +1007,9 @@ 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}