Use a newtype within EagerPseudoValues.

MozReview-Commit-ID: IIDxBJ8mqvJ

components/style/context.rs

@@ -332,7 +332,7 @@ impl Clone for EagerPseudoCascadeInputs {
 impl EagerPseudoCascadeInputs {
     /// Construct inputs from previous cascade results, if any.
     fn new_from_style(styles: &EagerPseudoStyles) -> Self {
-        EagerPseudoCascadeInputs(styles.0.as_ref().map(|styles| {
+        EagerPseudoCascadeInputs(styles.as_array().map(|styles| {
             let mut inputs: [Option<CascadeInputs>; EAGER_PSEUDO_COUNT] = Default::default();
             for i in 0..EAGER_PSEUDO_COUNT {
                 inputs[i] = styles[i].as_ref().map(|s| CascadeInputs::new_from_style(s));

components/style/data.rs

@@ -13,6 +13,7 @@ use properties::longhands::display::computed_value as display;
 use rule_tree::StrongRuleNode;
 use selector_parser::{EAGER_PSEUDO_COUNT, PseudoElement, RestyleDamage};
 use shared_lock::{Locked, StylesheetGuards};
+use std::ops::{Deref, DerefMut};
 use stylearc::Arc;
 
 bitflags! {
@@ -100,22 +101,35 @@ impl RestyleData {
 
 /// A list of styles for eagerly-cascaded pseudo-elements.
 /// Lazily-allocated.
-#[derive(Debug)]
-pub struct EagerPseudoStyles(pub Option<Box<[Option<Arc<ComputedValues>>; EAGER_PSEUDO_COUNT]>>);
+#[derive(Clone, Debug)]
+pub struct EagerPseudoStyles(Option<Box<EagerPseudoArray>>);
+
+#[derive(Debug, Default)]
+struct EagerPseudoArray(EagerPseudoArrayInner);
+type EagerPseudoArrayInner = [Option<Arc<ComputedValues>>; EAGER_PSEUDO_COUNT];
+
+impl Deref for EagerPseudoArray {
+    type Target = EagerPseudoArrayInner;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for EagerPseudoArray {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
 
 // Manually implement `Clone` here because the derived impl of `Clone` for
 // array types assumes the value inside is `Copy`.
-impl Clone for EagerPseudoStyles {
+impl Clone for EagerPseudoArray {
     fn clone(&self) -> Self {
-        if self.0.is_none() {
-            return EagerPseudoStyles(None)
-        }
-        let self_values = self.0.as_ref().unwrap();
-        let mut values: [Option<Arc<ComputedValues>>; EAGER_PSEUDO_COUNT] = Default::default();
+        let mut clone = Self::default();
         for i in 0..EAGER_PSEUDO_COUNT {
-            values[i] = self_values[i].clone();
+            clone[i] = self.0[i].clone();
         }
-        EagerPseudoStyles(Some(Box::new(values)))
+        clone
     }
 }
 
@@ -125,6 +139,14 @@ impl EagerPseudoStyles {
         self.0.is_none()
     }
 
+    /// Grabs a reference to the list of styles, if they exist.
+    pub fn as_array(&self) -> Option<&EagerPseudoArrayInner> {
+        match self.0 {
+            None => None,
+            Some(ref x) => Some(&x.0),
+        }
+    }
+
     /// Returns a reference to the style for a given eager pseudo, if it exists.
     pub fn get(&self, pseudo: &PseudoElement) -> Option<&Arc<ComputedValues>> {
         debug_assert!(pseudo.is_eager());