Your replacing what 'f' is bound to; this would include replacing any type annotations, and triggering any system that relies on type annotations to drop/reset

Your replacing what 'f' is bound to; this would include replacing any type annotations, and triggering any system that relies on type annotations to drop/reset its optimizations for 'f'. You're not actually rewriting the original function to return something different; this would probably also be possible, but would be considered as even more of a dirty trick. It is unfortunate that such dynamicity is the default in Python, when in reality it is rarely needed. So it would be advantageous to be able to tell the optimization system: this function is not going to change dynamically (on an opt-in basis).