X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplUtils.lhs;h=84506d85cdeade446579af1b0ccd5f6b6cced86a;hb=2fb8e343ac2b9dcb5c2476648cf3e30ec6637afd;hp=45ef88a454698f643af166f03eba408b276606be;hpb=7b144d53463590a536a8ffed36acb093f9dde523;p=ghc-hetmet.git

diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs
index 45ef88a..84506d8 100644
--- a/compiler/simplCore/SimplUtils.lhs
+++ b/compiler/simplCore/SimplUtils.lhs
@@ -1425,6 +1425,11 @@ prepareDefault _ _ case_bndr (Just (tycon, inst_tys)) imposs_cons (Just deflt_rh
 
 	_ -> return [(DEFAULT, [], deflt_rhs)]
 
+  | debugIsOn, isAlgTyCon tycon, [] <- tyConDataCons tycon
+  = pprTrace "prepareDefault" (ppr case_bndr <+> ppr tycon)
+	-- This can legitimately happen for type families
+        $ return [(DEFAULT, [], deflt_rhs)]
+
 --------- Catch-all cases -----------
 prepareDefault _dflags _env _case_bndr _bndr_ty _imposs_cons (Just deflt_rhs)
   = return [(DEFAULT, [], deflt_rhs)]