Constants, slice patterns, and exhaustiveness interact in suboptimal ways

[arielb1]

For example,

#![feature(slice_patterns)]

const C0: &'static [u8] = b"\x00";

fn main() {
   let x: &[u8] = &[0];
   match x { // this code compiles
       &[] => {},
       &[1..=255] => {},
       C0 => {}, //~ unreachable pattern (no it's not)
       &[_, _, ..] => {}
   }
}

cc @oli-obk

[varkor]

Probably related to #53708: consts are mishandled at the moment.

[Centril]

Reduced:

#![feature(slice_patterns)]

fn main() {
   let x: &[u8] = &[0];
   match x { // this code compiles
       &[] => {},
       &[1..=255] => {},
       b"\x00" => {}, //~ unreachable pattern (no it's not)
       &[_, _, ..] => {}
   }
}

[Nadrieril]

I found a fix, I'll make a PR once #66497 gets merged