It seems like the author is looking for the ability to specify types as `typeof <function>:arguments` and `typeof <function>:return`. I can see how this could make prototyping easier. It is also helpful for cases (not uncommon in Python) where you're just proxying another function.
TypeScript has the equivalent of what you're describing via the `Parameters` and `ReturnType` utility types [1][2], and I've found these types indispensable. So you can do the following:
type R = ReturnType<typeof someFunction>
type P = Parameters<typeof someFunction>
[2] https://www.typescriptlang.org/docs/handbook/utility-types.h...