From aea86d154ec5adde6adb05088a50f01380ffb8bf Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Mon, 30 Jul 2018 23:45:10 +0300
Subject: stackless traversal

---
 src/yellow/red.rs    |  3 +++
 src/yellow/syntax.rs | 28 +++++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

(limited to 'src/yellow')

diff --git a/src/yellow/red.rs b/src/yellow/red.rs
index bffb72510..8329ec5b2 100644
--- a/src/yellow/red.rs
+++ b/src/yellow/red.rs
@@ -84,4 +84,7 @@ impl RedNode {
     pub(crate) fn parent(&self) -> Option<ptr::NonNull<RedNode>> {
         Some(self.parent.as_ref()?.parent)
     }
+    pub(crate) fn index_in_parent(&self) -> Option<usize> {
+        Some(self.parent.as_ref()?.index_in_parent)
+    }
 }
diff --git a/src/yellow/syntax.rs b/src/yellow/syntax.rs
index 5c31a3f35..65ce647c7 100644
--- a/src/yellow/syntax.rs
+++ b/src/yellow/syntax.rs
@@ -18,6 +18,15 @@ pub struct SyntaxNode<R: TreeRoot = Arc<SyntaxRoot>> {
     red: ptr::NonNull<RedNode>,
 }
 
+impl <R1: TreeRoot, R2: TreeRoot> PartialEq<SyntaxNode<R1>> for SyntaxNode<R2> {
+    fn eq(&self, other: &SyntaxNode<R1>) -> bool {
+        self.red == other.red
+    }
+}
+
+impl <R: TreeRoot> Eq for SyntaxNode<R> {
+}
+
 pub type SyntaxNodeRef<'a> = SyntaxNode<&'a SyntaxRoot>;
 
 #[derive(Debug)]
@@ -53,7 +62,7 @@ impl SyntaxNode<Arc<SyntaxRoot>> {
 }
 
 impl<R: TreeRoot> SyntaxNode<R> {
-    pub fn borrow<'a>(&'a self) -> SyntaxNode<&'a SyntaxRoot> {
+    pub fn as_ref<'a>(&'a self) -> SyntaxNode<&'a SyntaxRoot> {
         SyntaxNode {
             root: &*self.root,
             red: ptr::NonNull::clone(&self.red),
@@ -92,6 +101,23 @@ impl<R: TreeRoot> SyntaxNode<R> {
         })
     }
 
+    pub fn first_child(&self) -> Option<SyntaxNode<R>> {
+        self.children().next()
+    }
+
+    pub fn next_sibling(&self) -> Option<SyntaxNode<R>> {
+        let red = self.red();
+        let parent = self.parent()?;
+        let next_sibling_idx = red.index_in_parent()? + 1;
+        if next_sibling_idx == red.n_children() {
+            return None;
+        }
+        Some(SyntaxNode {
+            root: self.root.clone(),
+            red: parent.red().nth_child(next_sibling_idx),
+        })
+    }
+
     fn red(&self) -> &RedNode {
         unsafe { self.red.as_ref() }
     }
-- 
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