I think people remembering to test all the typing-related corner cases is never going to come close to being as effective as something enforced by static checki

I think people remembering to test all the typing-related corner cases is never going to come close to being as effective as something enforced by static checking -- and even if it did, it seems like I've lost all the time I saved and then some, if that's the price of not having to write the declarations.