> “ If you type code "xs: List[Int]" and try to change xs[4], the compiler (phase) would have to reject your code.” This just can’t work - because lists are mu

> “ If you type code "xs: List[Int]" and try to change xs[4], the compiler (phase) would have to reject your code.” This just can’t work - because lists are mutable, so code that mutates them must be valid and permitted by any such compiler. Similarly, values are dynamically typed, so the value of the assignment might be an int or might not, and it cannot be decided until runtime (and this inability to prove at compile time can’t cause the program to fail to compile, it’s Python). Additionally, Python only has infinite precision ints, so it would be quite hard to get anything useful out of this, unless you wholesale switch to using ctypes or something, but then just use Cython and it will be way easier. I’m not convinced this could ever be anything more than a super limited toy.