Don’t cache skipped tokens

Author: SimonSapin

src/parser.rs

@@ -80,11 +80,6 @@ impl<'i> ParserInput<'i> {
             cached_token: None,
         }
     }
-
-    #[inline]
-    fn cached_token_ref(&self) -> &Token<'i> {
-        &self.cached_token.as_ref().unwrap().token
-    }
 }
 
 /// A CSS parser that borrows its `&str` input,
@@ -332,27 +327,15 @@ impl<'i: 't, 't> Parser<'i, 't> {
     /// See the `Parser::parse_nested_block` method to parse the content of functions or blocks.
     ///
     /// This only returns a closing token when it is unmatched (and therefore an error).
+    #[inline]
     pub fn next(&mut self) -> Result<&Token<'i>, BasicParseError<'i>> {
-        loop {
-            match self.next_including_whitespace_and_comments() {
-                Err(e) => return Err(e),
-                Ok(&Token::WhiteSpace(_)) | Ok(&Token::Comment(_)) => {},
-                _ => break
-            }
-        }
-        Ok(self.input.cached_token_ref())
+        self.next_common(true, true)
     }
 
     /// Same as `Parser::next`, but does not skip whitespace tokens.
+    #[inline]
     pub fn next_including_whitespace(&mut self) -> Result<&Token<'i>, BasicParseError<'i>> {
-        loop {
-            match self.next_including_whitespace_and_comments() {
-                Err(e) => return Err(e),
-                Ok(&Token::Comment(_)) => {},
-                _ => break
-            }
-        }
-        Ok(self.input.cached_token_ref())
+        self.next_common(false, true)
     }
 
     /// Same as `Parser::next`, but does not skip whitespace or comment tokens.
@@ -361,37 +344,59 @@ impl<'i: 't, 't> Parser<'i, 't> {
     /// where comments are preserved.
     /// When parsing higher-level values, per the CSS Syntax specification,
     /// comments should always be ignored between tokens.
+    #[inline]
     pub fn next_including_whitespace_and_comments(&mut self) -> Result<&Token<'i>, BasicParseError<'i>> {
+        self.next_common(false, false)
+    }
+
+    fn next_common(&mut self, skip_whitespace: bool, skip_comments: bool)
+                    -> Result<&Token<'i>, BasicParseError<'i>> {
+        let return_this_token = |token: &Token| {
+            match *token {
+                Token::WhiteSpace(_) if skip_whitespace => false,
+                Token::Comment(_) if skip_comments => false,
+                _ => true
+            }
+        };
+
         if let Some(block_type) = self.at_start_of.take() {
             consume_until_end_of_block(block_type, &mut self.input.tokenizer);
         }
 
-        let byte = self.input.tokenizer.next_byte();
-        if self.stop_before.contains(Delimiters::from_byte(byte)) {
-            return Err(BasicParseError::EndOfInput)
-        }
-
-        let token_start_position = self.input.tokenizer.position();
-        let token;
-        match self.input.cached_token {
-            Some(ref cached_token) if cached_token.start_position == token_start_position => {
-                self.input.tokenizer.reset(cached_token.end_position);
-                token = &cached_token.token
+        loop {
+            let byte = self.input.tokenizer.next_byte();
+            if self.stop_before.contains(Delimiters::from_byte(byte)) {
+                return Err(BasicParseError::EndOfInput)
             }
-            _ => {
-                let new_token = self.input.tokenizer.next().map_err(|()| BasicParseError::EndOfInput)?;
-                self.input.cached_token = Some(CachedToken {
-                    token: new_token,
-                    start_position: token_start_position,
-                    end_position: self.input.tokenizer.position(),
-                });
-                token = self.input.cached_token_ref()
+
+            let token_start_position = self.input.tokenizer.position();
+            match self.input.cached_token {
+                Some(ref cached_token) if cached_token.start_position == token_start_position => {
+                    self.input.tokenizer.reset(cached_token.end_position);
+                    if return_this_token(&cached_token.token) {
+                        break
+                    }
+                }
+                _ => {
+                    let new_token = self.input.tokenizer.next().map_err(|()| BasicParseError::EndOfInput)?;
+                    if return_this_token(&new_token) {
+                        self.input.cached_token = Some(CachedToken {
+                            token: new_token,
+                            start_position: token_start_position,
+                            end_position: self.input.tokenizer.position(),
+                        });
+                        break
+                    }
+                }
             }
         }
 
+        let token = &self.input.cached_token.as_ref().unwrap().token;
+
         if let Some(block_type) = BlockType::opening(token) {
             self.at_start_of = Some(block_type);
         }
+
         Ok(token)
     }