[commit: ghc] master: Turn manual Typeable instances into errors; fixes #8132 (5335e56)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/5335e56953c4bbe18166039c06256e725f074b64/ghc

>---------------------------------------------------------------

commit 5335e56953c4bbe18166039c06256e725f074b64
Author: Jose Pedro Magalhaes <jpm at cs.uu.nl>
Date:   Wed Sep 4 10:09:17 2013 +0200

    Turn manual Typeable instances into errors; fixes #8132


>---------------------------------------------------------------

5335e56953c4bbe18166039c06256e725f074b64
 compiler/typecheck/TcInstDcls.lhs |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/typecheck/TcInstDcls.lhs b/compiler/typecheck/TcInstDcls.lhs
index 1481b25..9f89afe 100644
--- a/compiler/typecheck/TcInstDcls.lhs
+++ b/compiler/typecheck/TcInstDcls.lhs
@@ -409,7 +409,7 @@ tcInstDecls1 tycl_decls inst_decls deriv_decls
        -- Remove any handwritten instance of poly-kinded Typeable and warn
        ; dflags <- getDynFlags
        ; when (wopt Opt_WarnTypeableInstances dflags) $
-              mapM_ (addWarnTc . instMsg) typeable_instances
+              mapM_ (failWithTc . instMsg) typeable_instances
 
        -- Check that if the module is compiled with -XSafe, there are no
        -- hand written instances of old Typeable as then unsafe casts could be
@@ -444,7 +444,7 @@ tcInstDecls1 tycl_decls inst_decls deriv_decls
     typInstErr = ptext $ sLit $ "Can't create hand written instances of Typeable in Safe"
                               ++ " Haskell! Can only derive them"
 
-    instMsg i = hang (ptext (sLit $ "Typeable instances can only be derived; ignoring "
+    instMsg i = hang (ptext (sLit $ "Typeable instances can only be derived; replace "
                                  ++ "the following instance:"))
                      2 (pprInstance (iSpec i))