Removing recursion from ComplexSelector

components/selectors/Cargo.toml

@@ -21,3 +21,4 @@ matches = "0.1"
 cssparser = "0.12.1"
 fnv = "1.0"
 precomputed-hash = "0.1"
+smallvec = "0.3"

components/selectors/lib.rs

@@ -7,6 +7,7 @@
 #[macro_use] extern crate matches;
 extern crate fnv;
 extern crate precomputed_hash;
+extern crate smallvec;
 
 pub mod bloom;
 pub mod matching;

components/selectors/parser.rs

@@ -360,12 +360,29 @@ impl<Impl: SelectorImpl> ToCss for Selector<Impl> {
 
 impl<Impl: SelectorImpl> ToCss for ComplexSelector<Impl> {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-        if let Some((ref next, ref combinator)) = self.next {
-            next.to_css(dest)?;
-            combinator.to_css(dest)?;
-        }
-        for simple in &self.compound_selector {
-            simple.to_css(dest)?;
+       use smallvec::SmallVec;
+       let mut current = self;
+       let mut nodes = SmallVec::<[&Self;8]>::new();
+       nodes.push(current);
+
+       loop {
+           match current.next {
+               None => break,
+               Some((ref next, _)) => {
+                   current = &**next;
+                   nodes.push(next);
+               }
+           }
+       }
+
+       for selector in nodes.iter().rev() {
+           if let Some((_, ref combinator)) = selector.next {
+               combinator.to_css(dest)?;
+           }
+
+           for simple in &selector.compound_selector {
+               simple.to_css(dest)?;
+           }
         }
         Ok(())
     }