Yeah, that is definitely a big "just" - it's basically whole program type inference, which I expect to be very messy in Python, if not intractable. > unless th

Yeah, that is definitely a big "just" - it's basically whole program type inference, which I expect to be very messy in Python, if not intractable. > unless there was a way to specify functions that don't modify their parameter this way (readonly parameters?). Right, so in a language with typed mutability (ie: Rust) or total immutability flow typing would be a lot easier to implement without these footguns. Python is such an insane language, I'm not surprised to see that you can subvert the type checker like this.