[Yoric]

Is Dart sound these days? When I tried it, it was pretty easy to trigger type errors at runtime.

[igouy]

These days Dart — considers all variables non-nullable — enforces sound null safety."

https://dart.dev/null-safety

[Yoric]

Well, null safety is a good start.

But I seem to remember that the type-checker got confused rather easily with nested closures, for instance, or co/contra-variance.