Move util::vec::ForgetfulSink to style::sink and simplify it

components/style/dom.rs

@@ -15,7 +15,7 @@ use restyle_hints::{ElementSnapshot, RESTYLE_DESCENDANTS, RESTYLE_LATER_SIBLINGS
 use selector_impl::{ElementExt, SelectorImplExt};
 use selectors::Element;
 use selectors::matching::DeclarationBlock;
-use smallvec::VecLike;
+use sink::Push;
 use std::ops::BitOr;
 use std::sync::Arc;
 use string_cache::{Atom, Namespace};
@@ -194,7 +194,7 @@ pub trait TDocument : Sized + Copy + Clone {
 
 pub trait PresentationalHintsSynthetizer {
     fn synthesize_presentational_hints_for_legacy_attributes<V>(&self, hints: &mut V)
-        where V: VecLike<DeclarationBlock<Vec<PropertyDeclaration>>>;
+        where V: Push<DeclarationBlock<Vec<PropertyDeclaration>>>;
 }
 
 pub trait TElement : Sized + Copy + Clone + ElementExt + PresentationalHintsSynthetizer {

components/style/lib.rs

@@ -88,6 +88,7 @@ pub mod selector_impl;
 pub mod selector_matching;
 pub mod sequential;
 pub mod servo;
+pub mod sink;
 pub mod stylesheets;
 pub mod traversal;
 #[macro_use]

components/style/matching.rs

@@ -17,6 +17,7 @@ use selectors::Element;
 use selectors::bloom::BloomFilter;
 use selectors::matching::{CommonStyleAffectingAttributeMode, CommonStyleAffectingAttributes};
 use selectors::matching::{common_style_affecting_attributes, rare_style_affecting_attributes};
+use sink::ForgetfulSink;
 use smallvec::SmallVec;
 use std::collections::HashMap;
 use std::hash::{BuildHasherDefault, Hash, Hasher};
@@ -26,7 +27,6 @@ use string_cache::{Atom, Namespace};
 use util::arc_ptr_eq;
 use util::cache::{LRUCache, SimpleHashCache};
 use util::opts;
-use util::vec::ForgetfulSink;
 
 fn create_common_style_affecting_attributes_from_element<E: TElement>(element: &E)
                                                          -> CommonStyleAffectingAttributes {

components/style/selector_matching.rs

@@ -18,6 +18,7 @@ use selectors::bloom::BloomFilter;
 use selectors::matching::DeclarationBlock as GenericDeclarationBlock;
 use selectors::matching::{Rule, SelectorMap};
 use selectors::parser::SelectorImpl;
+use sink::Push;
 use smallvec::VecLike;
 use std::collections::HashMap;
 use std::hash::BuildHasherDefault;
@@ -389,7 +390,7 @@ impl<Impl: SelectorImplExt> Stylist<Impl> {
                                         applicable_declarations: &mut V)
                                         -> bool
                                         where E: Element<Impl=Impl> + PresentationalHintsSynthetizer,
-                                              V: VecLike<DeclarationBlock> {
+                                              V: Push<DeclarationBlock> + VecLike<DeclarationBlock> {
         assert!(!self.is_device_dirty);
         assert!(style_attribute.is_none() || pseudo_element.is_none(),
                 "Style attributes do not apply to pseudo-elements");
@@ -430,7 +431,8 @@ impl<Impl: SelectorImplExt> Stylist<Impl> {
         // Step 4: Normal style attributes.
         style_attribute.map(|sa| {
             shareable = false;
-            applicable_declarations.push(
+            Push::push(
+                applicable_declarations,
                 GenericDeclarationBlock::from_declarations(sa.normal.clone()))
         });
 
@@ -443,7 +445,8 @@ impl<Impl: SelectorImplExt> Stylist<Impl> {
         // Step 6: `!important` style attributes.
         style_attribute.map(|sa| {
             shareable = false;
-            applicable_declarations.push(
+            Push::push(
+                applicable_declarations,
                 GenericDeclarationBlock::from_declarations(sa.important.clone()))
         });
 

components/style/sink.rs

@@ -0,0 +1,40 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use smallvec::{Array, SmallVec};
+use std::marker::PhantomData;
+
+pub trait Push<T> {
+    fn push(&mut self, value: T);
+}
+
+impl<T> Push<T> for Vec<T> {
+    fn push(&mut self, value: T) {
+        Vec::push(self, value);
+    }
+}
+
+impl<A: Array> Push<A::Item> for SmallVec<A> {
+    fn push(&mut self, value: A::Item) {
+        SmallVec::push(self, value);
+    }
+}
+
+pub struct ForgetfulSink<T>(bool, PhantomData<T>);
+
+impl<T> ForgetfulSink<T> {
+    pub fn new() -> Self {
+        ForgetfulSink(true, PhantomData)
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0
+    }
+}
+
+impl<T> Push<T> for ForgetfulSink<T> {
+    fn push(&mut self, _value: T) {
+        self.0 = false;
+    }
+}