poor error message when colon is used instead of semicolon

[tshepang]

I get this error:

error: expected type, found keyword `let`
 --> src/main.rs:3:5
  |
3 |     let two_squared = two * two;
  |     ^^^

That's with this code:

fn main() {
    let two = 2:
    let two_squared = two * two;
}

[brson]

Is this because of the type ascription parser? I recall there was another issue about making the stable parser not parse unstable things.

[Mark-Simulacrum]

Closing in favor of #34255.