Match on fixed-length vec gives wrong error message

[jruderman]

let f = &[99]; println!("{:?}", match [1,2,3,4] { [x, ..xs] => (x, xs), [] => (9, f) });

Says

vectors of length 4 not covered

Should say

pattern [] is unreachable

Duplicate of #13482.

[alexcrichton]

Looks like it, thanks!