Float without digits on both sides of .

Built from the repository at commit a8614dc.

A float literal has at least one digit before its . and at least one after it: 1.0 and 0.5. 1. and .5 are errors.

Why

A . belongs to a number only when a digit follows it, so that 0..n is a range and 1.max(2) is a method call on 1. That leaves 1. with nothing to tell it from a call that lost its method name, and .5 with nothing to tell it from a field read that lost its object. Writing the 0 says which one you mean. The fix writes the missing 0, after the . in 1. and before it in .5, and nothing else, so it is safe.

Broken

fn main() {
    let x = 1.
    print(x)
}

What sisu says

error[E0101]: a float needs digits on both sides of `.`
 --> E0101.sisu:2:14
  |
2 |     let x = 1.
  |              ^
  |
help: write a `0` after the `.`
  |
2 |     let x = 1.0
  |               +

sisu: 1 error
sisu: for more on a code, run `sisu explain <code>`: E0101

Fixed

fn main() {
    let x = 1.0
    print(x)
}