Fix #810 and #814: don't infer polymorphic types for data constructors.

paf31 · paf31 · commit f89b14f7dd64 · 2015-02-02T20:18:45.000-08:00
diff --git a/examples/passing/810.purs b/examples/passing/810.purs
@@ -0,0 +1,11 @@
+module Main where
+
+data Maybe a = Nothing | Just a
+
+test :: forall a. Maybe a -> Maybe a
+test m = o.x
+  where
+    o = case m of Nothing -> { x : Nothing }
+                  Just a  -> { x : Just a }
+
+main = Debug.Trace.trace "Done"
diff --git a/src/Language/PureScript/TypeChecker/Types.hs b/src/Language/PureScript/TypeChecker/Types.hs
@@ -52,6 +52,7 @@ import Language.PureScript.Errors
 import Language.PureScript.Kinds
 import Language.PureScript.Names
 import Language.PureScript.Pretty
+import Language.PureScript.Traversals
 import Language.PureScript.TypeChecker.Entailment
 import Language.PureScript.TypeChecker.Kinds
 import Language.PureScript.TypeChecker.Monad
@@ -271,8 +272,8 @@ infer' v@(Constructor c) = do
   env <- getEnv
   case M.lookup c (dataConstructors env) of
     Nothing -> throwError . strMsg $ "Constructor " ++ show c ++ " is undefined"
-    Just (_, _, ty) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
-                          return $ TypedValue True v ty'
+    Just (_, _, ty) -> do (v', ty') <- sndM (introduceSkolemScope <=< replaceAllTypeSynonyms) <=< instantiatePolyTypeWithUnknowns v $ ty
+                          return $ TypedValue True v' ty'
 infer' (Case vals binders) = do
   ts <- mapM infer vals
   ret <- fresh
