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use SyntaxNodeRef;
pub fn preorder<'a>(root: SyntaxNodeRef<'a>) -> impl Iterator<Item = SyntaxNodeRef<'a>> {
walk(root).filter_map(|event| match event {
WalkEvent::Enter(node) => Some(node),
WalkEvent::Exit(_) => None,
})
}
#[derive(Debug, Copy, Clone)]
enum WalkEvent<'a> {
Enter(SyntaxNodeRef<'a>),
Exit(SyntaxNodeRef<'a>),
}
fn walk<'a>(root: SyntaxNodeRef<'a>) -> impl Iterator<Item = WalkEvent<'a>> {
let mut done = false;
::itertools::unfold(WalkEvent::Enter(root), move |pos| {
if done {
return None;
}
let res = *pos;
*pos = match *pos {
WalkEvent::Enter(node) => match node.first_child() {
Some(child) => WalkEvent::Enter(child),
None => WalkEvent::Exit(node),
},
WalkEvent::Exit(node) => {
if node == root {
done = true;
WalkEvent::Exit(node)
} else {
match node.next_sibling() {
Some(sibling) => WalkEvent::Enter(sibling),
None => match node.parent() {
Some(node) => WalkEvent::Exit(node),
None => WalkEvent::Exit(node),
},
}
}
}
};
Some(res)
})
}
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