super and this in compile-time constants.

frog/leg/compiler.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class WorkItem {
   final Element element;
   TreeElements resolutionTree;
   Function run;
   bool allowSpeculativeOptimization = true;
   List<HTypeGuard> guards = const <HTypeGuard>[];
@@ skipping 383 matching lines @@
 
   Type resolveType(ClassElement element) {
     return withCurrentElement(element, () => resolver.resolveType(element));
   }
 
   FunctionParameters resolveSignature(FunctionElement element) {
     return withCurrentElement(element,
                               () => resolver.resolveSignature(element));
   }
 
-  Object compileVariable(VariableElement element) {
+  Constant compileVariable(VariableElement element) {
     return withCurrentElement(element, () {
       return constantHandler.compileVariable(element);
     });
   }
 
   reportWarning(Node node, var message) {
     if (message is ResolutionWarning) {
       // TODO(ahe): Don't supress this warning when we support type variables.
       if (message.message.kind === MessageKind.CANNOT_RESOLVE_TYPE) return;
     } else if (message is TypeWarning) {
@@ skipping 128 matching lines @@
   }
 }
 
 class SourceSpan {
   final Uri uri;
   final int begin;
   final int end;
 
   const SourceSpan(this.uri, this.begin, this.end);
 }