Switching to `?` for wildcard types

This one isn’t precisely news — we’ve been talking about it for quite a while — but Martin has just submitted a PR to change the wildcard type from _ to ?.

I think most folks who have looked at this seriously are in favor of this change, and I suspect it’ll go through, but it’s one of those changes that will touch a lot of day-to-day code, and it’s going to take some getting used to, so it’s worth paying attention to. If you have thoughts, check out the PR.

As always: this is just a PR; it’s not a formal Scala 3 proposal yet…