Function rustc_lexer::unescape::unescape_str_common

fn unescape_str_common<F, T: From<u8> + From<char>>(
    src: &str,
    mode: Mode,
    callback: &mut F
)where
    F: FnMut(Range<usize>, Result<T, EscapeError>),

Takes a contents of a string literal (without quotes) and produces a sequence of escaped characters or errors.