The number of elements in an array or slice pattern differed from the number of
elements in the array being matched.
Example of erroneous code:
```compile_fail,E0527
let r = &[1, 2, 3, 4];
match r {
&[a, b] => { // error: pattern requires 2 elements but array
// has 4
println!("a={}, b={}", a, b);
}
}
```
Ensure that the pattern is consistent with the size of the matched
array. Additional elements can be matched with `..`:
```
#![feature(slice_patterns)]
let r = &[1, 2, 3, 4];
match r {
&[a, b, ..] => { // ok!
println!("a={}, b={}", a, b);
}
}
```