pub fn walk_flat_map_item<K: WalkItemKind<Ctxt = ()>>(
visitor: &mut impl MutVisitor,
item: P<Item<K>>,
) -> SmallVec<[P<Item<K>>; 1]>
pub fn walk_flat_map_item<K: WalkItemKind<Ctxt = ()>>(
visitor: &mut impl MutVisitor,
item: P<Item<K>>,
) -> SmallVec<[P<Item<K>>; 1]>