It would be really useful if I could set default values for my generic type variables. In many cases, the users of my class don't want to use a different value and so it's cumbersome to having to type it in.

If I could do this:

class MyClass<T = String>
{
public userData: T;
constructor() {}
}

then the people who don't care about the type of userData (because they don't use it) and the people who are fine with it being a String don't have to set a generic type but others can if they want.

Also, these type variables could default to any or the type they extend (if they do) without explicitly defaulting them.
For example:
<T extends MyClass> would default to MyClass (without explicitly writing it)
and
<T> could default to any

What do you think?