Compile Time Constants cycle check

compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java

 // Copyright (c) 2011, 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.
 package com.google.dart.compiler.resolver;
 
 import com.google.dart.compiler.ErrorCode;
 import com.google.dart.compiler.ErrorSeverity;
 import com.google.dart.compiler.SubSystem;
 
 /**
@@ skipping 13 matching lines @@
   CANNOT_INIT_STATIC_FIELD_IN_INITIALIZER("Cannot initialize a static field in an initializer list"),
   CANNOT_OVERRIDE_INSTANCE_MEMBER("static member cannot override instance member %s of %s"),
   CANNOT_OVERRIDE_STATIC_MEMBER("cannot override static member %s of %s"),
   CANNOT_RESOLVE_CONSTRUCTOR("cannot resolve constructor %s"),
   CANNOT_RESOLVE_FIELD("cannot resolve field %s"),
   CANNOT_RESOLVE_LABEL("cannot resolve label %s"),
   CANNOT_RESOLVE_METHOD("cannot resolve method %s"),
   CANNOT_RESOLVE_SUPER_CONSTRUCTOR("cannot resolve method %s"),
   CANNOT_RESOLVE_IMPLICIT_CALL_TO_SUPER_CONSTRUCTOR(
       "super type %s does not have a default constructor"),
+  CIRCULAR_REFERENCE("Circular reference"),

[mmendez, 2011/11/17 15:32:10]

Nit: Maybe reword to explain that this is due to the restrictions on consts? 
"Compile time constants cannot depend on themselves" or something that clues
them to the compile-time const restrictions.

[zundel, 2011/11/17 16:26:42]

Done.

   CONSTRUCTOR_CANNOT_BE_ABSTRACT("A constructor cannot be asbstract"),
   CONSTRUCTOR_CANNOT_BE_STATIC("A constructor cannot be static"),
   CONSTRUCTOR_CANNOT_HAVE_RETURN_TYPE("Generative constructors cannot have return type"),
   CONST_CONSTRUCTOR_CANNOT_HAVE_BODY("A const constructor cannot have a body"),
   CONST_CONSTRUCTOR_MUST_CALL_CONST_SUPER("const constructor must call const super constructor"),
   CONSTANTS_MUST_BE_INITIALIZED("constants must be initialized"),
   CYCLIC_CLASS("%s causes a cycle in the supertype graph"),
   DID_YOU_MEAN_NEW("%1$s is a %2$s. Did you mean (new %1$s)?"),
   DUPLICATE_DEFINITION("duplicate definition of %s"),
   DUPLICATED_INTERFACE("%s and %s are duplicated in the supertype graph"),
@@ skipping 70 matching lines @@
   }
 
   /**
    * Initialize a newly created error code to have the given severity and message.
    */
   private ResolverErrorCode(ErrorSeverity severity, String message) {
     this.severity = severity;
     this.message = message;
   }
 
+  @Override
   public String getMessage() {
     return message;
   }
 
+  @Override
   public ErrorSeverity getErrorSeverity() {
     return severity;
   }
 
+  @Override
   public SubSystem getSubSystem() {
     return SubSystem.RESOLVER;
   }
 }