You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: utf8.rs
    path of file: ./repos/regex/regex-lite/src
    
    the code of the file until where you have to start completion: /// Returns true if and only if the given byte is considered a word character.
/// This only applies to ASCII.
pub(crate) fn is_word_byte(b: u8) -> bool {
    const fn mkwordset() -> [bool; 256] {
        // FIXME: Use as_usize() once const functions in traits are stable.
        let mut set = [false; 256];
        set[b'_' as us
    
pub(crate) fn is_word_byte(b: u8) -> bool {
    const fn mkwordset() -> [bool; 256] {
        // FIXME: Use as_usize() once const functions in traits are stable.
        let mut set = [false; 256];
        set[b'_' as usize] = true;

        let mut byte = b'0';
        while byte <= b'9' {
            set[byte as usize] = true;
            byte += 1;
        }
        byte = b'A';
        while byte <= b'Z' {
            set[byte as usize] = true;
            byte += 1;
        }
        byte = b'a';
        while byte <= b'z' {
            set[byte as usize] = true;
            byte += 1;
        }
        set
    }
    const WORD: [bool; 256] = mkwordset();
    WORD[b as usize]
}