I don't think Python's type system is capable enough (yet) for something like this. However tail recursion optimization to me is a non issue - for something exp

I don't think Python's type system is capable enough (yet) for something like this. However tail recursion optimization to me is a non issue - for something expensive and deeply nested I use an iterative approach, and for everything else python's recursion is good enough. There are not that many usecases like this per code base anyways, in my experience. In my current one there is one central facility to do object loading based on yaml definitions, that's the one place I need it there for example.