I don't really know what it means, but I've seen it used to work around depth issues in Typescript, but can this use a "trampoline"?

I don't think there's any way to do iteration in the type system (other than recursion), so there's no way around it.

I considered forking the compiler to set a deeper limit, but at some point Typescript itself is going to stack overflow. Also that probably goes a bit beyond what Criss is expecting in an interview...

I don't know about the typescript compiler, but the way around template recursion limits in "classic" C++ template metaprogramming is to figure out a way to make it O(log N) depth instead of O(N) (for some value of N). Like instead of linearly iterating through a range of types through recursion, you divide and conquer. Easier said than done, but possible in some cases.