What’s interesting about this announcement is that they not only announced a type checking tool, they are also open sourcing a tool that will apply a patch and annotate your code with types for you. I tried a demo of this at the Instagram booth at pycon yesterday. They basically had a package that would run your tests for you, and using the coverage that you created, it could infer the types while executing your code. Now if the point of type annotations is purely to check for bugs that are avoided in statically typed languages it seems like you should be able to just combine the two tools and catch type based bugs without ever applying the annotation.

I think the type checking community also has quite a ways to go when it comes to asynchronous code. It becomes quite worthless to check that a future is being returned by a function, but it could be more helpful to know what that future will eventually yield.