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.

Inizia riproducendo l'esempio di interfaccia nel TypeScript compiler e analizza come più estensioni di interfaccia controllano i membri con lo stesso nome. Il lavoro è completato quando vengono accettate proprietà compatibili e più specifiche come 'some' e string, mentre le dichiarazioni incompatibili continuano a produrre errori; nell'issue non sono indicati file o test specifici.