Comment by skywhopper

Based on the relative smoothness of Ruby version transitions versus Python, I trust Matz’s preference on this implicitly. One good thing about it being external is that you can optionally and experimentally annotate existing code without munging up your source files. At least so long as this is a bleeding edge feature, that separation makes a lot of sense to me. It’ll be a while before anyone can be confident in a particular model for how this should work, until it’s been in use for a good long while.