Adding new enumerators to an Enum specifier using CDT ASTRewrite

Question

I have a header file with an Enum with a set of enumerators, e.g.,

typedef enum MyEnum{
  A = 0,
  B = 1
}

I want to add a new enumerator like C = 2 to the end of it.

So I tried to do it using the ASTRewrite like below:

public void addEnumerator(IASTTranslationUnit ast, String enumName, String name, String value){
  INodeFactory nodeFactory = ast.getASTNodeFactory();
  ASTRewrite astRewrite =  ASTRewrite.create(ast);
  ast.accept(new ASTVisitor(true) {
     @Override
     public int visit(IASTDeclSpecifier declSpec) {
       if (declSpec instanceof IASTEnumerationSpecifier 
&& ((IASTEnumerationSpecifier) declSpec).getName().getRawSignature().equals(enumName)) {
         IASTName nameNode = nodeFactory.newName(name);
         IASTExpression valueNode = nodeFactory.newLiteralExpression  
             (IASTLiteralExpression.lk_integer_constant, value);
         IASTEnumerator newEnumerator = nodeFactory.newEnumerator(nameNode, valueNode);
         astRewrite.insertBefore(declSpec, null, newEnumerator, null);
             return ASTVisitor.PROCESS_SKIP;
         }
      return super.visit(declSpec);
    }
  });
  Change change = rewrite.rewriteAST();
  try {
      change.perform(new NullProgressMonitor());
  } catch (CoreException exp) {
       LOGGER.log(Level.SEVERE, ExceptionUtils.getStackTrace(exp));
  }
}

However, the change object does not reflect the changes!

Based on my checks on CDT src code, apprently, only IASTDeclaration and IASTStatement are allowed for APPEND_CHILD modification operation but I don't understand why and how I can do the modification that I need (which is of type IASTEnumerator)!