[Jtsummers]

Not that you should ever write this in any language, but as an illustration:

  fn main() {
    let x: i32 = if true {1} else {"3"};
    println!("{}", x);
  }

This will not compile even though if it were allowed to execute it would, correctly, assign an integer to x. Python will happily interpret its equivalent:

  x = 1 if True else "3"
  print(x)

Even giving the if-expression an explicit `true` constant for the condition, Rust won't accept that as a valid program even though we can prove that the result of the expression is always 1.