In a similar fashion I was extremely impressed with how Dart approaches this as well and was able to move the entire ecosystem along in about 18 months. https://dart.dev/null-safety
It was a lot of work to get there and we're still not totally there yet. Dart still supports running legacy code that isn't null safe. But I'm really glad we did this and very grateful that Leaf and others on the team were able to design a null safety type system that:
* Defaults to non-nullable.
* Is fully sound.
The latter in particular is very nice because it means the compiler can take advantage of null safety to generate more efficient code, which isn't true in languages like Java, C#, and TypeScript where their null safety type rules deliberately have holes.
Yeah, I did a bit of Dart null safety migration work at Google and I thought they did a good job. (The auto migration tool sometimes made things nullable unnecessarily, and so you had to carefully review its output, but you could always just not use the tool.)
