From: Manuel M T Chakravarty <chak@cse.unsw.edu.au>
Date: Mon, 3 Sep 2007 07:45:28 +0000 (+0000)
Subject: Better error message for unsolvable equalities
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=e913ed4d009dac1be837b79e99f352ca1d3fc965

Better error message for unsolvable equalities
---

diff --git a/compiler/typecheck/TcTyFuns.lhs b/compiler/typecheck/TcTyFuns.lhs
index 141afb1..39cee90 100644
--- a/compiler/typecheck/TcTyFuns.lhs
+++ b/compiler/typecheck/TcTyFuns.lhs
@@ -591,10 +591,11 @@ decompInst i@(EqInst {})
       | con1 /= con2 && not (isOpenSynTyCon con1 || isOpenSynTyCon con2)
         -- not matching data constructors (of any flavour) are bad news
       = do { env0 <- tcInitTidyEnv
-           ; let (env1, tidy_ty1)  =  tidyOpenType env0 ty1
-                 (env2, tidy_ty2)  =  tidyOpenType env1 ty2
-                 extra 	         = sep [ppr tidy_ty1, char '~', ppr tidy_ty2]
-                 msg 		 = ptext SLIT("Couldn't match expected type against inferred type")
+           ; let (env1, tidy_ty1) = tidyOpenType env0 ty1
+                 (env2, tidy_ty2) = tidyOpenType env1 ty2
+                 extra 	          = sep [ppr tidy_ty1, char '~', ppr tidy_ty2]
+                 msg 		  = 
+                   ptext SLIT("Unsolvable equality constraint:")
            ; failWithTcM (env2, hang msg 2 extra)
            }
       where