> d2c (strip u) `thenUs` \u ->
> d2c (strip u') `thenUs` \u' ->
> trace ("failed consistency check:\n" ++
-> ppShow 80 (ppr PprDebug u) ++ "\n" ++
-> ppShow 80 (ppr PprDebug u'))
+> show (ppr PprDebug u) ++ "\n" ++
+> show (ppr PprDebug u'))
> (returnUs (InconsistentRenaming r))
> else
> trace "Renaming!" (returnUs (IsRenaming r))