anchor.diff:    DartType getType(CoreTypes types) => types.stringType;
   
     bool operator ==(var other) {
  +    if (identical(this, other)) return true;
       if (other is !StringConstantValue) return false;
       StringConstantValue otherString = other;
       return hashCode == otherString.hashCode &&
  
positive.code:   bool get isConstructedObject => true;
  
    bool operator ==(var otherVar) {
      if (otherVar is !ConstructedConstantValue) return false;
      ConstructedConstantValue other = otherVar;
      if (hashCode != other.hashCode) return false;
  
negative.code:   bool get isMap => true;
  
    bool operator ==(var other) {
      if (identical(this, other)) return true;
      if (other is !MapConstantValue) return false;
      MapConstantValue otherMap = other;
      if (hashCode != otherMap.hashCode) return false;
  