I believe this is the way that

List

and

MutableList

and the like are written in stdlib

No, it's not. A bit of advise: You may want to look up and verify such assumptions before you use them to make decisions.

You don’t happen to be basing this off of the

List() {}

and

MutableList() {}

functions, do you?

kind of

List and MutableList are just interfaces though

yeah, and i was considering making my class just an interface

also, I mean, composition makes sense in a lot of cases

composition just gets messy when you're trying to generalize functions. Afaik, you have to create interfaces that describe the composition of every class, and the naming can get messy. it feels really bad to have to write something like:

fun <F: HasFoo> fooer(foo: F)

than

fun <F: Foo> fooer(foo: F)