Abstract class type argument inference

[tinganho]

It would be good if TypeScript can infer the type of an extended class of an generic abstract class:

abstract class A<T> {
    abstract a: T;
    get(): T {
        return '' as any;
    }
}

class B extends A {
    a: 'helloworld';
}

const b = new B():
b.get(); // string

In a similar fashion, it does inference elsewhere.

[aluanhaddad]

This is a really interesting idea. Seems like it would improve life for React users for sure.
Is there any particular reason it would be limited to abstract classes? It seems applicable to interfaces as well as concrete classes.

[tinganho]

@aluanhaddad I suggested it applied to abstract, mostly because abstract implies there will be at least another declaration. But after thinking about it, I cannot see why it's not applicable to normal classes as well.

[RyanCavanaugh]

See notes at #13368

[tinganho]

I hope this covers statics as well, example taken from #10603:

abstract class BaseClass<T> {
    abstract static defaultValue: T;
    // ...
}

class ClassA extends BaseClass {
    static defaultValue = {
         name: 1;
    }
}

[infeng]

I hope it apply to normal class also. see ant-design/ant-design#4324