The tracking issue for this feature is: #29947

The const_indexing feature allows the constant evaluation of index operations on constant arrays and repeat expressions.

#![allow(unused_variables)]
#![feature(const_indexing)]

fn main() {
const ARR: [usize; 5] = [1, 2, 3, 4, 5];
const ARR2: [usize; ARR[1]] = [42, 99];
}