better error message from checkPLam

diff --git a/TypeChecker.hs b/TypeChecker.hs
index 7a038de00252bbdfe9c807839be36dc788646691..12135e7633debac3b24c826085d6d41aae5f515c 100644 (file)
--- a/TypeChecker.hs
+++ b/TypeChecker.hs
@@ -403,7 +403,8 @@ checkPLam v t = do
   vt <- infer t\r
   case vt of\r
     VPathP a a0 a1 -> do\r
-      unlessM (a === v) $ throwError "checkPLam"\r
+      unlessM (a === v) $ throwError (\r
+        "checkPLam\n" ++ show v ++ "\n/=\n" ++ show a)\r
       return (a0,a1)\r
     _ -> throwError $ show vt ++ " is not a path"\r
 \r