Compile Time Constants cycle check

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

Index: compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java b/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
index 1a6b82cca5ea8b00a09bac5e50c1199f7dff118b..fced8884aaf284fe6f8dc2979450e4a6c5320592 100644
--- a/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
+++ b/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
@@ -31,6 +31,7 @@ public enum ResolverErrorCode implements ErrorCode {
   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"),
@@ -121,14 +122,17 @@ public enum ResolverErrorCode implements ErrorCode {
     this.message = message;
   }
 
+  @Override
   public String getMessage() {
     return message;
   }
 
+  @Override
   public ErrorSeverity getErrorSeverity() {
     return severity;
   }
 
+  @Override
   public SubSystem getSubSystem() {
     return SubSystem.RESOLVER;
   }