anchor.diff:  class D = C with M;
   D f(int/*2*/ i) => D(i);
   ''');
  -    var syntheticConstructor = findElement.class_('D').unnamedConstructor;
  +    var syntheticConstructor = findElement.unnamedConstructor('D');
       var constructorType = variables.decoratedElementType(syntheticConstructor);
       var constructorParameterType = constructorType.positionalParameters[0];
       assertEdge(
  
positive.code: class D = C with M;
  D f(int/*2*/ i) => D(i: i);
  ''');
      var syntheticConstructor = findElement.class_('D').unnamedConstructor;
      var constructorType = variables.decoratedElementType(syntheticConstructor);
      var constructorParameterType = constructorType.namedParameters['i'];
      assertEdge(
  
negative.code: class D = C with M;
  D f(int/*2*/ i) => D(i);
  ''');
      var syntheticConstructor = findElement.unnamedConstructor('D');
      var constructorType = variables.decoratedElementType(syntheticConstructor);
      var constructorParameterType = constructorType.positionalParameters[0];
      assertEdge(
  