Comment by refried_

It produces a name conflict, but (unlike git merge conflicts) these don't prevent any previously written code from running normally. A name conflict only needs to be resolved as a convenience to the next person to try calling the function by that name, and even that next person might not have trouble if the two new functions with the same name have different types. The person just calls the one they mean, and the type-checker uses the one with the type that fits.