The headline isn't very explicit, but I think this is pretty exciting. What this means is that we are taking the previous unsound optional type system and replacing it with a sound static type system.
Even though strong mode is sound and mandatory, the language still has much of the flexible feel it had before. The folks who designed the type system did a fantastic job on the inference engine. Having a few million lines of existing optionally-typed code that needed to gracefully migrate into strong mode certainly helped too.
I'm on the Dart team.
The headline isn't very explicit, but I think this is pretty exciting. What this means is that we are taking the previous unsound optional type system and replacing it with a sound static type system.
Even though strong mode is sound and mandatory, the language still has much of the flexible feel it had before. The folks who designed the type system did a fantastic job on the inference engine. Having a few million lines of existing optionally-typed code that needed to gracefully migrate into strong mode certainly helped too.