However, if you set the symbol locking depth larger (-Yrecursion n) you'll also get a stack overflow as well. So it isn't necessarily that Scala has an algorit

However, if you set the symbol locking depth larger (-Yrecursion n) you'll also get a stack overflow as well. So it isn't necessarily that Scala has an algorithmically better approach to subtyping. The symbol locking algorithm is more of a catchall...