fix more bugs

[fp.git] / src / HM.hs

diff --git a/src/HM.hs b/src/HM.hs
index 9591706..3cbf5c9 100644 (file)
--- a/src/HM.hs
+++ b/src/HM.hs
@@ -67,7 +67,7 @@ composeSub s1 s2 = Map.map (substituteT s1) s2 `Map.union` s1
 
 varBind :: TypeVarName -> Type -> TI Substitution
 varBind v t | t == TypeVar v = return idSub
-            | v `Set.member` freeVarsT t = fail $ "occur check failed: " ++ v ++ " in " ++ show t
+            | v `Set.member` freeVarsT t = fail $ "occur check failed: " ++ v ++ " ~ " ++ show t
             | otherwise = return $ Map.singleton v t
 
 instantiate :: TypeScheme -> TI Type