[commit: ghc] wip/nested-cpr: Elaborate "non-algebraic or open body type" message (92da8cd)

[git at git.haskell.org]

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

On branch  : wip/nested-cpr
Link       : http://ghc.haskell.org/trac/ghc/changeset/92da8cd29e6872d1fb7228cf1f548808d0320940/ghc

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

commit 92da8cd29e6872d1fb7228cf1f548808d0320940
Author: Joachim Breitner <mail at joachim-breitner.de>
Date:   Wed Dec 4 09:36:04 2013 +0000

    Elaborate "non-algebraic or open body type" message


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

92da8cd29e6872d1fb7228cf1f548808d0320940
 compiler/stranal/WwLib.lhs |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/compiler/stranal/WwLib.lhs b/compiler/stranal/WwLib.lhs
index 861a03b..4f2e68b 100644
--- a/compiler/stranal/WwLib.lhs
+++ b/compiler/stranal/WwLib.lhs
@@ -584,7 +584,8 @@ mkWWcpr_help inner ty res
                     , \e body -> mkUnpackCase e co work_uniq data_con arg_vars (nested_decon body)
                     )
             |  otherwise
-            -> pprPanic "mkWWcpr: non-algebraic or open body type" (ppr ty)
+            -> pprPanic "mkWWcpr:" $ ptext (sLit "non-algebraic or open body type") <+>
+                                     (ppr ty) <+> ptext (sLit "but CPR type") <+> ppr (res)
         Nothing -> do
            uniq <- getUniqueM
            let var = mk_ww_local uniq ty