optimize string escaping by writing chunks instead of individual chars

The previous implementation wrote each character individually using write! macro,
which is inefficient for string formatting. The new implementation uses write_str
to write larger chunks of the string at once, significantly reducing the number
of write operations and formatting overhead.

This change maintains the same escaping behavior but improves performance by
avoiding character-by-character writes.

Author: lovasoa

src/ast/value.rs

@@ -456,30 +456,34 @@ impl fmt::Display for EscapeQuotedString<'_> {
         // | `"A\"B\"A"`    | default   | `DoubleQuotedString(String::from("A\"B\"A"))`      | `"A""B""A"`  |
         let quote = self.quote;
         let mut previous_char = char::default();
-        let mut peekable_chars = self.string.chars().peekable();
-        while let Some(&ch) = peekable_chars.peek() {
+        let mut start_idx = 0;
+        let mut peekable_chars = self.string.char_indices().peekable();
+        while let Some(&(idx, ch)) = peekable_chars.peek() {
             match ch {
                 char if char == quote => {
                     if previous_char == '\\' {
-                        write!(f, "{char}")?;
                         peekable_chars.next();
                         continue;
                     }
                     peekable_chars.next();
-                    if peekable_chars.peek().map(|c| *c == quote).unwrap_or(false) {
-                        write!(f, "{char}{char}")?;
-                        peekable_chars.next();
-                    } else {
-                        write!(f, "{char}{char}")?;
+                    match peekable_chars.peek() {
+                        Some((_, c)) if *c == quote => {
+                            peekable_chars.next();
+                        }
+                        _ => {
+                            // not calling .next(), so the quote at idx will be printed twice
+                            f.write_str(&self.string[start_idx..=idx])?;
+                            start_idx = idx;
+                        }
                     }
                 }
                 _ => {
-                    write!(f, "{ch}")?;
                     peekable_chars.next();
                 }
             }
             previous_char = ch;
         }
+        f.write_str(&self.string[start_idx..])?;
         Ok(())
     }
 }