Range outside for and patterns

Built from the repository at commit a8614dc.

A range such as 0..n or 0..=n can only be the source of a for loop, or a pattern in a match arm.

Why

A range is not a value in Sisu. It describes what a for loop counts through, or which values a pattern matches, so it cannot be stored, passed or returned.

Broken

fn main() {
    let r = 0..3
    print(1)
}

What sisu says

error[E0023]: ranges are only allowed in `for` and in patterns
 --> E0023.sisu:2:14
  |
2 |     let r = 0..3
  |              ^^

sisu: 1 error
sisu: for more on a code, run `sisu explain <code>`: E0023

Fixed

fn main() {
    for i in 0..3 {
        print(i)
    }
}