Auto merge of #17515 - frewsxcv:frewsxcv-simple-node-iterator, r=KiChjang

Merge explicit node iterator structures into single generic structure.

<!-- Reviewable:start -->
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/17515)
<!-- Reviewable:end -->

1 files changed, 40 insertions, 80 deletions

diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 2e0152195dd..bf24682ede7 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -504,15 +504,17 @@ impl Node {
         TreeIterator::new(self)
     }
 
-    pub fn inclusively_following_siblings(&self) -> NodeSiblingIterator {
-        NodeSiblingIterator {
+    pub fn inclusively_following_siblings(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
             current: Some(Root::from_ref(self)),
+            next_node: |n| n.GetNextSibling(),
         }
     }
 
-    pub fn inclusively_preceding_siblings(&self) -> ReverseSiblingIterator {
-        ReverseSiblingIterator {
+    pub fn inclusively_preceding_siblings(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
             current: Some(Root::from_ref(self)),
+            next_node: |n| n.GetPreviousSibling(),
         }
     }
 
@@ -524,15 +526,17 @@ impl Node {
         parent.ancestors().any(|ancestor| &*ancestor == self)
     }
 
-    pub fn following_siblings(&self) -> NodeSiblingIterator {
-        NodeSiblingIterator {
+    pub fn following_siblings(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
             current: self.GetNextSibling(),
+            next_node: |n| n.GetNextSibling(),
         }
     }
 
-    pub fn preceding_siblings(&self) -> ReverseSiblingIterator {
-        ReverseSiblingIterator {
+    pub fn preceding_siblings(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
             current: self.GetPreviousSibling(),
+            next_node: |n| n.GetPreviousSibling(),
         }
     }
 
@@ -550,9 +554,10 @@ impl Node {
         }
     }
 
-    pub fn descending_last_children(&self) -> LastChildIterator {
-        LastChildIterator {
+    pub fn descending_last_children(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
             current: self.GetLastChild(),
+            next_node: |n| n.GetLastChild(),
         }
     }
 
@@ -760,15 +765,17 @@ impl Node {
         Ok(NodeList::new_simple_list(&window, iter))
     }
 
-    pub fn ancestors(&self) -> AncestorIterator {
-        AncestorIterator {
-            current: self.GetParentNode()
+    pub fn ancestors(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
+            current: self.GetParentNode(),
+            next_node: |n| n.GetParentNode(),
         }
     }
 
-    pub fn inclusive_ancestors(&self) -> AncestorIterator {
-        AncestorIterator {
-            current: Some(Root::from_ref(self))
+    pub fn inclusive_ancestors(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
+            current: Some(Root::from_ref(self)),
+            next_node: |n| n.GetParentNode(),
         }
     }
 
@@ -788,15 +795,17 @@ impl Node {
         self.is_in_doc() && self.owner_doc().browsing_context().is_some()
     }
 
-    pub fn children(&self) -> NodeSiblingIterator {
-        NodeSiblingIterator {
+    pub fn children(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
             current: self.GetFirstChild(),
+            next_node: |n| n.GetNextSibling(),
         }
     }
 
-    pub fn rev_children(&self) -> ReverseSiblingIterator {
-        ReverseSiblingIterator {
+    pub fn rev_children(&self) -> impl Iterator<Item=Root<Node>> {
+        SimpleNodeIterator {
             current: self.GetLastChild(),
+            next_node: |n| n.GetPreviousSibling(),
         }
     }
 
@@ -1162,40 +1171,6 @@ impl LayoutNodeHelpers for LayoutJS<Node> {
 // Iteration and traversal
 //
 
-pub struct NodeSiblingIterator {
-    current: Option<Root<Node>>,
-}
-
-impl Iterator for NodeSiblingIterator {
-    type Item = Root<Node>;
-
-    fn next(&mut self) -> Option<Root<Node>> {
-        let current = match self.current.take() {
-            None => return None,
-            Some(current) => current,
-        };
-        self.current = current.GetNextSibling();
-        Some(current)
-    }
-}
-
-pub struct ReverseSiblingIterator {
-    current: Option<Root<Node>>,
-}
-
-impl Iterator for ReverseSiblingIterator {
-    type Item = Root<Node>;
-
-    fn next(&mut self) -> Option<Root<Node>> {
-        let current = match self.current.take() {
-            None => return None,
-            Some(current) => current,
-        };
-        self.current = current.GetPreviousSibling();
-        Some(current)
-    }
-}
-
 pub struct FollowingNodeIterator {
     current: Option<Root<Node>>,
     root: Root<Node>,
@@ -1288,37 +1263,22 @@ impl Iterator for PrecedingNodeIterator {
     }
 }
 
-pub struct LastChildIterator {
-    current: Option<Root<Node>>,
-}
-
-impl Iterator for LastChildIterator {
-    type Item = Root<Node>;
-
-    fn next(&mut self) -> Option<Root<Node>> {
-        let current = match self.current.take() {
-            None => return None,
-            Some(current) => current,
-        };
-        self.current = current.GetLastChild();
-        Some(current)
-    }
-}
-
-pub struct AncestorIterator {
+struct SimpleNodeIterator<I>
+    where I: Fn(&Node) -> Option<Root<Node>>
+{
     current: Option<Root<Node>>,
+    next_node: I,
 }
 
-impl Iterator for AncestorIterator {
+impl<I> Iterator for SimpleNodeIterator<I>
+    where I: Fn(&Node) -> Option<Root<Node>>
+{
     type Item = Root<Node>;
 
-    fn next(&mut self) -> Option<Root<Node>> {
-        let current = match self.current.take() {
-            None => return None,
-            Some(current) => current,
-        };
-        self.current = current.GetParentNode();
-        Some(current)
+    fn next(&mut self) -> Option<Self::Item> {
+        let current = self.current.take();
+        self.current = current.as_ref().and_then(|c| (self.next_node)(c));
+        current
     }
 }