`mut` is accepted before constants in patterns

[petrochenkov]

This compiles on stable/beta/nightly and C is resolved as a constant and not a new binding.

const C: u8 = 0;

fn main() {
    match 1u8 {
        mut C => {}
        _ => {}
    }
}

[durka]

It doesn't match though: https://is.gd/ylHuUv

[hanna-kruppe]

@durka The example matches on 1, while C is 0, so of course it doesn't match. Conversely, match 0u8 correctly takes the C arm, and the generated code looks good too. It seems the mut is simply ignored.