X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fiface%2FBuildTyCl.lhs;h=54adfdf84c761649f39b7cb3ef799622f4c65fa1;hb=09d2b3b2e1f9d0a4c4b938dc6ff6a0b068138445;hp=ba383d8d1d0fb9f1c0b122b8e54eb9ab9545a946;hpb=703ca1542c8e0983cc9d8eebce6e9f3dd3fd71e2;p=ghc-hetmet.git

diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs
index ba383d8..54adfdf 100644
--- a/compiler/iface/BuildTyCl.lhs
+++ b/compiler/iface/BuildTyCl.lhs
@@ -118,7 +118,13 @@ mkOpenDataTyConRhs = OpenTyCon Nothing
 
 mkDataTyConRhs :: [DataCon] -> AlgTyConRhs
 mkDataTyConRhs cons
-  = DataTyCon { data_cons = cons, is_enum = all isNullarySrcDataCon cons }
+  = DataTyCon {
+        data_cons = cons,
+        is_enum = -- We define datatypes with no constructors to not be
+                  -- enumerations; this fixes trac #2578
+                  not (null cons) &&
+                  all isNullarySrcDataCon cons
+    }
 
 mkNewTyConRhs :: Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
 -- Monadic because it makes a Name for the coercion TyCon