anchor.diff:    bool visitBooleanLiteral(BooleanLiteral node) {
       BooleanLiteral other = _other as BooleanLiteral;
       return isEqualTokens(node.literal, other.literal) &&
  -        node.value == other.value;
  +        failIfNotEqual(node, node.value, other, other.value);
     }
   
     @override
  
positive.code:   bool visitSimpleStringLiteral(SimpleStringLiteral node) {
      SimpleStringLiteral other = _other as SimpleStringLiteral;
      return isEqualTokens(node.literal, other.literal) &&
          (node.value == other.value);
    }
  
    @override
  
negative.code:   bool visitIntegerLiteral(IntegerLiteral node) {
      IntegerLiteral other = _other as IntegerLiteral;
      return isEqualTokens(node.literal, other.literal) &&
          failIfNotEqual(node, node.value, other, other.value);
    }
  
    @override
  