Improve scanner

src/scanner.rs

@@ -27,7 +27,7 @@ static KEYWORDS: phf::Map<&'static str, TokenType> = phf_map! {
 };
 
 pub struct Scanner {
-	source: String,
+	chars: Vec<char>,
 	tokens: Vec<Token>,
 	start: usize,
 	current: usize,
@@ -36,8 +36,9 @@ pub struct Scanner {
 
 impl Scanner {
 	pub fn new(source: String) -> Self {
+		let chars = source.chars().collect();
 		Self {
-			source,
+			chars,
 			tokens: Vec::new(),
 			start: 0,
 			current: 0,
@@ -142,21 +143,19 @@ impl Scanner {
 	}
 
 	fn is_at_end(&self) -> bool {
-		self.current >= self.source.chars().count()
+		self.current >= self.chars.len()
 	}
 
 	fn advance(&mut self) -> char {
 		self.current += 1;
-		self.source.chars().collect::<Vec<char>>()[self.current - 1]
+		self.chars[self.current - 1]
 	}
 
 	fn add_token(&mut self, token_type: TokenType) {
 		if token_type == NoToken {
 			return;
 		}
-		let text: String = self.source.chars().collect::<Vec<char>>()[self.start..self.current]
-			.iter()
-			.collect();
+		let text: String = self.chars[self.start..self.current].iter().collect();
 		self.tokens.push(Token::new(token_type, text, self.line));
 	}
 
@@ -164,7 +163,7 @@ impl Scanner {
 		if self.is_at_end() {
 			return false;
 		}
-		if self.source.chars().collect::<Vec<char>>()[self.current] != expected {
+		if self.chars[self.current] != expected {
 			return false;
 		}
 
@@ -176,15 +175,15 @@ impl Scanner {
 		if self.is_at_end() {
 			return '\0';
 		}
-		self.chars()[self.current]
+		self.chars[self.current]
 	}
 
 	fn peek_next(&self) -> char {
-		if self.current + 1 >= self.source.chars().count() {
+		if self.current + 1 >= self.chars.len() {
 			return '\0';
 		}
 
-		self.chars()[self.current + 1]
+		self.chars[self.current + 1]
 	}
 
 	fn string(&mut self) -> Result<(), (usize, String)> {
@@ -202,7 +201,7 @@ impl Scanner {
 
 		self.advance(); // Closing "
 
-		let value: String = self.chars()[(self.start + 1)..(self.current - 1)]
+		let value: String = self.chars[(self.start + 1)..(self.current - 1)]
 			.iter()
 			.collect();
 		self.add_token(TokenType::String(value));
@@ -210,10 +209,6 @@ impl Scanner {
 		Ok(())
 	}
 
-	fn chars(&self) -> Vec<char> {
-		self.source.chars().collect()
-	}
-
 	fn number(&mut self) {
 		while Scanner::is_digit(self.peek()) {
 			self.advance();
@@ -227,7 +222,7 @@ impl Scanner {
 			} // Keep consuming digits
 		}
 
-		let s: String = self.chars()[self.start..self.current].iter().collect();
+		let s: String = self.chars[self.start..self.current].iter().collect();
 		self.add_token(Number(f64::from_str(&s).unwrap()))
 	}
 
@@ -236,7 +231,7 @@ impl Scanner {
 			self.advance();
 		}
 
-		let text: String = self.chars()[self.start..self.current].iter().collect();
+		let text: String = self.chars[self.start..self.current].iter().collect();
 		let token: TokenType = match KEYWORDS.get(text.as_str()) {
 			Some(x) => x.clone(),
 			None => Identifier,