X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fiface%2FBuildTyCl.lhs;h=de1c1915a67e37c4fd9ff0845ffc5c11dfc30393;hb=81e41fe31fb27b6330762d93ce90eb98899beb24;hp=9213afd4ce3a699b61c871bb4bba1dbeb8a2152e;hpb=9ffadf219cbc4f8ec57264786df936a3cee88aec;p=ghc-hetmet.git

diff --git a/compiler/iface/BuildTyCl.lhs b/compiler/iface/BuildTyCl.lhs
index 9213afd..de1c191 100644
--- a/compiler/iface/BuildTyCl.lhs
+++ b/compiler/iface/BuildTyCl.lhs
@@ -20,7 +20,6 @@ import Var
 import VarSet
 import BasicTypes
 import Name
-import OccName
 import MkId
 import Class
 import TyCon
@@ -30,8 +29,6 @@ import Coercion
 import TcRnMonad
 import Util		( count )
 import Outputable
-
-import Data.List
 \end{code}
 	
 
@@ -121,7 +118,18 @@ 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,  Otherwise we
+                  -- end up generating an empty table for
+                  --   <mod>_<type>_closure_tbl
+                  -- which is used by tagToEnum# to map Int# to constructors
+                  -- in an enumeration. The empty table apparently upset
+                  -- the linker.
+                  not (null cons) &&
+                  all isNullarySrcDataCon cons
+    }
 
 mkNewTyConRhs :: Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
 -- Monadic because it makes a Name for the coercion TyCon