Adding it later is not impossible, but unfortunately is not that easy either. Ignoring the very high bar for changing Go in general, doing it this way has imple

Adding it later is not impossible, but unfortunately is not that easy either. Ignoring the very high bar for changing Go in general, doing it this way has implementation consequences that would have to be undone. Also the spec change is not just a matter of adding more stuff, but it requires reformalization of the existing semantics because interfaces are already rank-2 types, you just can't see it yet. This feature interacts with interfaces. It's very unfortunate thay didn't do this from the start. The original paper that introduced Go generics had this and used to to solve the Expression Problem.