char::try_to_ascii ?

[leonardo-m]

A simple method that could be useful:

char::try_to_ascii() -> Option<u8>;

related to char::is_ascii and char::to_ascii_lowercase/uppercase. Its purpose is to avoid some 'as' casts in user code:

if let Some(c) = c.try_to_ascii() {
    let order = c.to_ascii_uppercase() - b'A';

A simple implementation could be:

#[inline]
pub const fn try_to_ascii(&self) -> Option<u8> {
    if *self as u32 <= 0x7F {
        Some(*self as u8)
    } else {
        None
    }
}

[fmease]

Closing in favor of #110998 which currently includes char::as_ascii (fn(self: &str) -> Option<AsciiChar>).