--- a/langtools/src/share/classes/com/sun/tools/javac/comp/Attr.java	Thu Apr 28 08:46:06 2011 -0700
+++ b/langtools/src/share/classes/com/sun/tools/javac/comp/Attr.java	Thu Apr 28 15:05:36 2011 -0700
@@ -2910,6 +2910,7 @@
 
     public void visitTypeUnion(JCTypeUnion tree) {
         ListBuffer<Type> multicatchTypes = ListBuffer.lb();
+        ListBuffer<Type> all_multicatchTypes = null; // lazy, only if needed
         for (JCExpression typeTree : tree.alternatives) {
             Type ctype = attribType(typeTree, env);
             ctype = chk.checkType(typeTree.pos(),
@@ -2931,9 +2932,23 @@
                     }
                 }
                 multicatchTypes.append(ctype);
+                if (all_multicatchTypes != null)
+                    all_multicatchTypes.append(ctype);
+            } else {
+                if (all_multicatchTypes == null) {
+                    all_multicatchTypes = ListBuffer.lb();
+                    all_multicatchTypes.appendList(multicatchTypes);
+                }
+                all_multicatchTypes.append(ctype);
             }
         }
-        tree.type = result = check(tree, types.lub(multicatchTypes.toList()), TYP, pkind, pt);
+        Type t = check(tree, types.lub(multicatchTypes.toList()), TYP, pkind, pt);
+        if (t.tag == CLASS) {
+            List<Type> alternatives =
+                ((all_multicatchTypes == null) ? multicatchTypes : all_multicatchTypes).toList();
+            t = new UnionClassType((ClassType) t, alternatives);
+        }
+        tree.type = result = t;
     }
 
     public void visitTypeParameter(JCTypeParameter tree) {