From: Ian Lynagh <igloo@earth.li>
Date: Sun, 8 Aug 2010 15:57:32 +0000 (+0000)
Subject: Make a parse error say what it is failing to parse; part of #3811
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=4186a2d5ae04d985fe141a8701fd75d05760f7f7

Make a parse error say what it is failing to parse; part of #3811
---

diff --git a/compiler/parser/RdrHsSyn.lhs b/compiler/parser/RdrHsSyn.lhs
index ac1a028..4c1da58 100644
--- a/compiler/parser/RdrHsSyn.lhs
+++ b/compiler/parser/RdrHsSyn.lhs
@@ -799,12 +799,14 @@ checkValSig
 checkValSig (L l (HsVar v)) ty 
   | isUnqual v && not (isDataOcc (rdrNameOcc v))
   = return (TypeSig (L l v) ty)
-checkValSig lhs@(L l _)         _
-  | looks_like_foreign lhs
-  = parseError l "Invalid type signature; perhaps you meant to use -XForeignFunctionInterface?"
-  | otherwise
-  = parseError l "Invalid type signature: should be of form <variable> :: <type>"
+checkValSig lhs@(L l _) ty
+  = parseErrorSDoc l ((text "Invalid type signature:" <+>
+                       ppr lhs <+> text "::" <+> ppr ty)
+                   $$ text hint)
   where
+    hint = if looks_like_foreign lhs
+           then "Perhaps you meant to use -XForeignFunctionInterface?"
+           else "Should be of form <variable> :: <type>"
     -- A common error is to forget the ForeignFunctionInterface flag
     -- so check for that, and suggest.  cf Trac #3805
     -- Sadly 'foreign import' still barfs 'parse error' because 'import' is a keyword