Variables should probably not shadow parent methods

[qznc via Digitalmars-d]

Just seen on Reddit [0] and there are a few more examples.
  class Test
  {
    string function() toString = function() { return "one"; };
  }

  void main()
  {
    auto test = new Test;
    writeln(test);
    test.toString = function() { return "two"; };
    writeln(cast(Object)test);
  }

Test has a delegate field `toString` which shadows the method 
`toString` inherited from Object. Could we make this an error?


[0] 
https://www.reddit.com/r/d_language/comments/4sfcv8/overriding_parents_member_function_with_anonymous/