"Transitive type conversion" in typescript

Question

in a typescript project which I'm currently working on, I have a class A, a class B extends A, a class C extends B and a class D extends C. I also have a method getFoo(): A.

The following type conversion doesn't work:

const foo = this.getFoo() as D;

The error I get is that the conversion may be a mistake, because neither type sufficiently overlaps the other (although D is a subclass of A).

What, funnily enough, works, is:

const foo = this.getFoo() as C as D

Why? Is the inheritance chain somehow too long for TS? Is there any way to write this without the double cast?

Thanks in advance!