Support compilation of Hello World

pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart

 // Copyright (c) 2014, 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.
 
 part of js_backend;
 
 /// [ConstantCompilerTask] for compilation of constants for the JavaScript
 /// backend.
 ///
 /// Since this task needs to distinguish between frontend and backend constants
@@ skipping 227 matching lines @@
   }
 
   void forgetElement(Element element) {
     super.forgetElement(element);
     const ForgetConstantElementVisitor().visit(element, this);
     if (element is AstElement && element.hasNode) {
       element.node.accept(new ForgetConstantNodeVisitor(this));
     }
   }
 
+  @override
   ConstantValue getConstantValue(ConstantExpression expression) {
+    assert(invariant(CURRENT_ELEMENT_SPANNABLE, expression != null,
+        message: "ConstantExpression is null in getConstantValue."));
+    evaluate(expression);
     ConstantValue value = super.getConstantValue(expression);
     if (value == null &&
         expression != null &&
         expression.kind == ConstantExpressionKind.ERRONEOUS) {
       // TODO(johnniwinther): When the Dart constant system sees a constant
       // expression as erroneous but the JavaScript constant system finds it ok
       // we have store a constant value for the erroneous constant expression.
       // Ensure the computed constant expressions are always the same; that only
       // the constant values may be different.
       value = new NullConstantValue();
@@ skipping 36 matching lines @@
     // TODO(ahe): This doesn't belong here. Rename this class and generalize.
     var closureClassMap = constants
         .compiler.closureToClassMapper.closureMappingCache
         .remove(node);
     if (closureClassMap != null) {
       closureClassMap
           .removeMyselfFrom(constants.compiler.enqueuer.codegen.universe);
     }
   }
 }