anchor.diff:      return super.handleUnrecoverableError(token, message);
     }
   
  -  void handleUnaryPrefixExpression(Token token) {
  +  void handleUnaryPrefixExpression(Token operator) {
  +    // TODO(brianwilkerson): Enable this assert.
  +    // TokenType.isUnaryPrefixOperator currently return `false` for `-`.
  +//    assert(operator.type.isUnaryPrefixOperator);
       debugEvent("UnaryPrefixExpression");
  -    push(ast.prefixExpression(token, pop()));
  -  }
  -
  -  void handleUnaryPrefixAssignmentExpression(Token token) {
  +
  +    push(ast.prefixExpression(operator, pop()));
  +  }
  +
  +  void handleUnaryPrefixAssignmentExpression(Token operator) {
  +    assert(operator.type.isUnaryPrefixOperator);
       debugEvent("UnaryPrefixAssignmentExpression");
  -    push(ast.prefixExpression(token, pop()));
  -  }
  -
  -  void handleUnaryPostfixAssignmentExpression(Token token) {
  +
  +    push(ast.prefixExpression(operator, pop()));
  +  }
  +
  +  void handleUnaryPostfixAssignmentExpression(Token operator) {
  +    assert(operator.type.isUnaryPostfixOperator);
       debugEvent("UnaryPostfixAssignmentExpression");
  -    push(ast.postfixExpression(pop(), token));
  +
  +    push(ast.postfixExpression(pop(), operator));
     }
   
     void handleModifier(Token token) {
  +    assert(token.isModifier);
       debugEvent("Modifier");
  +
       push(token);
     }
   
     void handleModifiers(int count) {
       debugEvent("Modifiers");
  +
       if (count == 0) {
         push(NullValue.Modifiers);
       } else {
  
positive.code:   @override
    void endFactoryMethod(
        Token beginToken, Token factoryKeyword, Token semicolon) {
      debugEvent("FactoryMethod");
  
      FunctionBody body;
  
negative.code:   @override
    void handleInvalidTopLevelDeclaration(Token endToken) {
      debugEvent("InvalidTopLevelDeclaration");
  
      pop(); // metadata star
      // TODO(danrubel): consider creating a AST node
      // representing the invalid declaration to better support code completion,
  