DDC: mixing in a concrete getter/setter clobbers inherited corresponding setter/getter

[greglittlefield-wf]

Classes that declare a concrete getter or setter without a corresponding setter or getter, when mixed in, clobber the corresponding setter or getter inherited by a given class.

class Setter {
  set foo(value) {
    print('Setting foo to `$value`');
  }
}

class Getter {
  get foo => 'foo';
}

class GetterFail1 extends Getter with Setter {}
class GetterFail2 extends Object with Getter, Setter {}

class SetterFail1 extends Setter with Getter {}
class SetterFail2 extends Object with Setter, Getter {}

class Pass1 extends Getter {
  set foo(value) {
    print('Setting foo to `$value`');
  }
}

class Pass2 extends Setter {
  get foo => 'foo';
}

main() {
  print(new Pass1().foo); // 'foo'
  print(new Pass2().foo); // 'foo'
  new Pass1().foo = 'bar'; // Setting foo to `bar`
  new Pass2().foo = 'bar'; // Setting foo to `bar`

  print(new GetterFail1().foo); // undefined
  print(new GetterFail2().foo); // undefined

  // TypeError: Cannot set property foo of [object Object] which has only a getter
  new SetterFail1().foo = 'bar';

  // TypeError: Cannot set property foo of [object Object] which has only a getter
  new SetterFail2().foo = 'bar';
}

Related: #29914

[robbecker-wf]

FYI @kevmoo # 1 DDC issue for Workiva

[greglittlefield-wf]

This no longer reproduces in the latest stable Dart version; closing as fixed.