Typescript: Inference of generic type

[Roam-Cooper]

Currently a generic class such as

class A<B extends C<D>, D>

Must have both B and D passed when instantiated, but it would be nice if the type system could infer the type D from type B. Because if I pass in type B which extends type C, then type D is known from C. Why do I have to pass type D separately as well?

Or am I approaching this the wrong way? I'm just trying to avoid us having to unnecessarily import interfaces all over the place!

[Roam-Cooper]

Say that I define a generic class as such

class A<B<C>>

Is it therefore possible in any form or fashion to be able to extract type C from generic type B? Or is this impossible?

It would be incredibly, immensely useful to be able to extract the type of a generic type, especially when type mapping (another issue that I have opened).

[aluanhaddad]

In the nightly build there is some nice new syntactic sugar around default type arguments that allows you to omit type them from consumption sites in a number of places as well as pass down defaults which can, optionally, be themselves derived from other type arguments.

That said, I think you are after higher-kinded types, or perhaps existential types.