perf(token): return static str from DelimTokenType avoiding alloc

Changed `DelimTokenType::string()` to `DelimTokenType::as_str()`, returning `&'static str` instead of allocating a new `String` object. Updated dependent calls across the crate.

Co-authored-by: ashyanSpada <22587148+ashyanSpada@users.noreply.github.com>

Author: google-labs-jules[bot]

src/token.rs

@@ -52,16 +52,16 @@ impl From<&str> for DelimTokenType {
 }
 
 impl DelimTokenType {
-    pub fn string(&self) -> String {
+    pub fn as_str(&self) -> &'static str {
         use DelimTokenType::*;
         match self {
-            OpenParen => "(".to_string(),
-            CloseParen => ")".to_string(),
-            OpenBracket => "[".to_string(),
-            CloseBracket => "]".to_string(),
-            OpenBrace => "{".to_string(),
-            CloseBrace => "}".to_string(),
-            Unknown => "??".to_string(),
+            OpenParen => "(",
+            CloseParen => ")",
+            OpenBracket => "[",
+            CloseBracket => "]",
+            OpenBrace => "{",
+            CloseBrace => "}",
+            Unknown => "??",
         }
     }
 }
@@ -86,7 +86,7 @@ pub enum Token<'input> {
 pub fn check_op(token: Token, expected: &str) -> bool {
     match token {
         Token::Delim(op, _) => {
-            if op.string() == expected {
+            if op.as_str() == expected {
                 return true;
             }
         }
@@ -187,7 +187,7 @@ impl<'input> Token<'input> {
             Reference(val, _) => val.to_string(),
             Function(val, _) => val.to_string(),
             Semicolon(val, _) => val.to_string(),
-            Delim(ty, _) => ty.string(),
+            Delim(ty, _) => ty.as_str().to_string(),
             EOF => "EOF".to_string(),
         }
     }
@@ -213,7 +213,7 @@ impl<'input> fmt::Display for Token<'input> {
             Function(val, span) => write!(f, "Function Token: {}, {}", val, span),
             String(val, span) => write!(f, "String Token: {}, {}", val, span),
             Semicolon(val, span) => write!(f, "Semicolon Token: {}, {}", val, span),
-            Delim(ty, span) => write!(f, "Delim Token: {}, {}", ty.string(), span),
+            Delim(ty, span) => write!(f, "Delim Token: {}, {}", ty.as_str(), span),
             EOF => write!(f, "EOF"),
         }
     }

src/tokenizer.rs

@@ -145,7 +145,7 @@ impl<'a> Tokenizer<'a> {
         self.next()?;
         match token {
             Token::Delim(bracket, _) => {
-                if bracket.string() == op {
+                if bracket.as_str() == op {
                     return Ok(());
                 }
             }