Allow extending multiple interfaces with different, but compatible types

interface Change {
  uid: string;
  type: string;
}

interface SomeChangeExtension {
  type: 'some';
  foo: number;
}

interface SomeChange extends Change, SomeChangeExtension { }

In this example, I was expecting SomeChange to have a type equivalent to:

interface SomeChange {
  uid: string;
  type: 'some';
  foo: number;
}

But it would result in error:

Interface 'SomeChange' cannot simultaneously extend types 'Change' and 'SomeChangeExtension'.
  Named property 'type' of types 'Change' and 'SomeChangeExtension' are not identical.

In this case, 'some' is compatible with string if the order of interfaces being extended is respected.

The reason why I want this to be allowed is that, I need to maintain multiple interfaces of the same kind of change during different stages: raw change, change, broadcast change. And having to duplicate part of the "extension" on every of them doesn't look good.

Beginne damit, das Interface-Beispiel im TypeScript compiler zu reproduzieren, und untersuche, wie mehrere Interface-Erweiterungen Member mit demselben Namen prüfen. Als erledigt gilt die Aufgabe, wenn kompatible, enger gefasste Eigenschaften wie 'some' und string akzeptiert werden, während inkompatible Deklarationen weiterhin Fehler bleiben; im Issue werden keine bestimmten Dateien oder Tests genannt.