{"ast_node_type":"other","tokens":[{"end":99,"kind":"keyword","start":0,"text":"const"}]}
    const DIGITS: [char; 10] = ['⁰', '¹', '²', '³', '⁴', '⁵', '⁶', '⁷', '⁸', '⁹'];
fn pwr2_to_exponent(num: u128) -> String {
    assert_eq!(num.count_ones(), 1);