fn raw_string_prefix(chars: &[char], i: usize) -> Option<(char, usize)>Expand description
Check if position i starts an R 4.0+ raw string like r"(...)", R"[...]",
r'(...)', R'{...}', etc. Returns the closing delimiter char and the number
of chars consumed for the prefix (e.g. r"( = 3 chars) if it matches.