rust/src/doc/unstable-book/src/language-features/const-indexing.md

const_indexing

The tracking issue for this feature is: #29947

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

Examples

#![feature(const_indexing)]

const ARR: [usize; 5] = [1, 2, 3, 4, 5];
const ARR2: [usize; ARR[1]] = [42, 99];