Fix for invalid 'extends/implements/with SomeEnum'.

pkg/analyzer/lib/src/dart/element/builder.dart

Index: pkg/analyzer/lib/src/dart/element/builder.dart
diff --git a/pkg/analyzer/lib/src/dart/element/builder.dart b/pkg/analyzer/lib/src/dart/element/builder.dart
index 17f98e9db72f0de10a1941fe077b7067868af7ef..cfda5c033c7920812df67f5f114b72c3eab0d8fe 100644
--- a/pkg/analyzer/lib/src/dart/element/builder.dart
+++ b/pkg/analyzer/lib/src/dart/element/builder.dart
@@ -156,6 +156,7 @@ class ApiElementBuilder extends _BaseElementBuilder {
     element.localVariables = holder.localVariables;
     element.parameters = holder.parameters;
     element.isConst = node.constKeyword != null;
+    element.isCycleFree = element.isConst;
     if (body.isAsynchronous) {
       element.asynchronous = true;
     }