[munificent]

> There is no mainstream typed language which can write a fully general type for the vararg compose function.

True. A more interesting question might be what level of static safety and performance benefits you'd be willing to sacrifice to be able to write functions like this.

Personally, I don't find the kind of code I can't fit into static types particularly appealing, but I find the code navigation, error checking, and optimizations of static types to be priceless.