Method output_layout_with_checker

crates/literal/src/escape.rs:150–198

(
        source: &Wtf8,
        preferred_quote: Quote,
        length_add: impl Fn(usize, usize) -> Option<usize>,
    )

    }

    fn output_layout_with_checker(
        source: &Wtf8,
        preferred_quote: Quote,
        length_add: impl Fn(usize, usize) -> Option<usize>,
    ) -> EscapeLayout {
        let mut out_len = Self::REPR_RESERVED_LEN;
        let mut single_count = 0;
        let mut double_count = 0;

        for ch in source.code_points() {
            let incr = match ch.to_char() {
                Some('\'') => {
                    single_count += 1;
                    1
                }
                Some('"') => {
                    double_count += 1;
                    1
                }
                _ => Self::escaped_char_len(ch),
            };
            let Some(new_len) = length_add(out_len, incr) else {
                #[cold]
                const fn stop(
                    single_count: usize,
                    double_count: usize,
                    preferred_quote: Quote,
                ) -> EscapeLayout {
                    EscapeLayout {
                        quote: choose_quote(single_count, double_count, preferred_quote).0,
                        len: None,
                    }
                }
                return stop(single_count, double_count, preferred_quote);
            };
            out_len = new_len;
        }

        let (quote, num_escaped_quotes) = choose_quote(single_count, double_count, preferred_quote);
        // we'll be adding backslashes in front of the existing inner quotes
        let Some(out_len) = length_add(out_len, num_escaped_quotes) else {
            return EscapeLayout { quote, len: None };
        };

        EscapeLayout {
            quote,
            len: Some(out_len - Self::REPR_RESERVED_LEN),
        }
    }

    fn escaped_char_len(ch: CodePoint) -> usize {
        // surrogates are \uHHHH