box selector field of pseudo selectors

gives a ~3% improvement to bootstrap by decreasing size of
`SimpleSelector` to 88 bytes

src/selector/compound.rs

@@ -134,8 +134,9 @@ impl CompoundSelector {
                             if !sel.contains_parent_selector() {
                                 return Ok(SimpleSelector::Pseudo(pseudo));
                             }
-                            pseudo.selector =
+                            pseudo.selector = Some(Box::new(
-                                Some(sel.resolve_parent_selectors(Some(parent.clone()), false)?);
+                                sel.resolve_parent_selectors(Some(parent.clone()), false)?,
+                            ));
                             Ok(SimpleSelector::Pseudo(pseudo))
                         } else {
                             Ok(SimpleSelector::Pseudo(pseudo))

src/selector/extend/mod.rs

@@ -582,13 +582,14 @@ impl Extender {
         let extended = self.extend_list(
             pseudo
                 .selector
-                .clone()
+                .as_deref()
+                .cloned()
                 .unwrap_or_else(|| SelectorList::new(self.span)),
             extensions,
             media_query_context,
         );
         /*todo: identical(extended, pseudo.selector)*/
-        if Some(&extended) == pseudo.selector.as_ref() {
+        if Some(&extended) == pseudo.selector.as_deref() {
             return None;
         }
 
@@ -689,10 +690,10 @@ impl Extender {
             let result = complexes
                 .into_iter()
                 .map(|complex| {
-                    pseudo.clone().with_selector(Some(SelectorList {
+                    pseudo.clone().with_selector(Some(Box::new(SelectorList {
                         components: vec![complex],
                         span: self.span,
-                    }))
+                    })))
                 })
                 .collect::<Vec<Pseudo>>();
             if result.is_empty() {
@@ -701,10 +702,10 @@ impl Extender {
                 Some(result)
             }
         } else {
-            Some(vec![pseudo.with_selector(Some(SelectorList {
+            Some(vec![pseudo.with_selector(Some(Box::new(SelectorList {
                 components: complexes,
                 span: self.span,
-            }))])
+            })))])
         }
     }
 
@@ -925,7 +926,7 @@ impl Extender {
                             ..
                         }) = simple
                         {
-                            self.register_selector(simple_selector, selector);
+                            self.register_selector(*simple_selector, selector);
                         }
                     }
                 }

src/selector/parse.rs

@@ -312,19 +312,19 @@ impl<'a, 'b> SelectorParser<'a, 'b> {
         let unvendored = unvendor(&name);
 
         let mut argument: Option<Box<str>> = None;
-        let mut selector: Option<SelectorList> = None;
+        let mut selector: Option<Box<SelectorList>> = None;
 
         if element {
             // todo: lowercase?
             if SELECTOR_PSEUDO_ELEMENTS.contains(&unvendored) {
-                selector = Some(self.parse_selector_list()?);
+                selector = Some(Box::new(self.parse_selector_list()?));
                 self.parser.whitespace();
                 self.expect_closing_paren()?;
             } else {
                 argument = Some(self.declaration_value()?.into_boxed_str());
             }
         } else if SELECTOR_PSEUDO_CLASSES.contains(&unvendored) {
-            selector = Some(self.parse_selector_list()?);
+            selector = Some(Box::new(self.parse_selector_list()?));
             self.parser.whitespace();
             self.expect_closing_paren()?;
         } else if unvendored == "nth-child" || unvendored == "nth-last-child" {
@@ -337,7 +337,7 @@ impl<'a, 'b> SelectorParser<'a, 'b> {
                     self.expect_identifier("of")?;
                     this_arg.push_str(" of");
                     self.parser.whitespace();
-                    selector = Some(self.parse_selector_list()?);
+                    selector = Some(Box::new(self.parse_selector_list()?));
                 }
                 _ => {}
             }

src/selector/simple.rs

@@ -119,7 +119,7 @@ impl SimpleSelector {
             | Self::Class(..)
             | Self::Attribute(..) => false,
             Self::Pseudo(Pseudo { name, selector, .. }) => {
-                name != "not" && selector.as_ref().map_or(false, SelectorList::is_invisible)
+                name != "not" && selector.as_ref().map_or(false, |sel| sel.is_invisible())
             }
             Self::Placeholder(..) => true,
             Self::Parent(..) => todo!(),
@@ -411,7 +411,7 @@ pub(crate) struct Pseudo {
     ///
     /// This is `None` if there's no selector. If `argument` and `selector` are
     /// both non-`None`, the selector follows the argument.
-    pub selector: Option<SelectorList>,
+    pub selector: Option<Box<SelectorList>>,
 
     pub span: Span,
 }
@@ -601,7 +601,7 @@ impl Pseudo {
     }
 
     #[allow(clippy::missing_const_for_fn)]
-    pub fn with_selector(self, selector: Option<SelectorList>) -> Self {
+    pub fn with_selector(self, selector: Option<Box<SelectorList>>) -> Self {
         Self { selector, ..self }
     }