Changing the way `unsafeNull` works

The Dotty project is doing fewer big user-visible changes these days, and focusing more on fixing bugs and making everything consistent. But once in a while, a significant change still pops up.

So for those following along at home, I call your attention to this PR that just got opened. It’s still a draft, so it’s way, way early, but worth paying attention to. It’s a major change to the long-standing project of making Scala more null-safe, by making nulls more explicit.

The complication there is, how do you work with external APIs that might produce nulls? How much ceremony is involved in that?

The previous design was a concept of UncheckedNull, an odd little type that allowed you to live dangerously with those values. Apparently that’s proven problematic, so this PR switches to a new model: using a new language import that declares this scope as an “unsafe null” zone, where you can do dangerous things.

It seems like a sensible approach; hopefully it will work well. In general, I consider null-safety one of the lovelier features in the Dotty project, so I’d like it to get nice and solid soon…