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BTree: no longer define impossible casts #82440

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Mar 1, 2021
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BTree: no longer define impossible casts #82440

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18 changes: 10 additions & 8 deletions library/alloc/src/collections/btree/node.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -461,7 +461,7 @@ impl<K, V> NodeRef<marker::Dying, K, V, marker::LeafOrInternal> {
}
}

impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
/// Unsafely asserts to the compiler the static information that this node is a `Leaf`.
unsafe fn cast_to_leaf_unchecked(self) -> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
debug_assert!(self.height == 0);
Expand All @@ -473,7 +473,9 @@ impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
debug_assert!(self.height > 0);
NodeRef { height: self.height, node: self.node, _marker: PhantomData }
}
}

impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
/// Temporarily takes out another, mutable reference to the same node. Beware, as
/// this method is very dangerous, doubly so since it may not immediately appear
/// dangerous.
Expand Down Expand Up @@ -761,15 +763,17 @@ impl<BorrowType, K, V, NodeType, HandleType>
}
}

impl<'a, K, V, NodeType, HandleType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, HandleType> {
impl<'a, K, V, Type> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, Type> {
/// Unsafely asserts to the compiler the static information that the handle's node is a `Leaf`.
pub unsafe fn cast_to_leaf_unchecked(
self,
) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, HandleType> {
) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, Type> {
let node = unsafe { self.node.cast_to_leaf_unchecked() };
Handle { node, idx: self.idx, _marker: PhantomData }
}
}

impl<'a, K, V, NodeType, HandleType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, HandleType> {
/// Temporarily takes out another, mutable handle on the same location. Beware, as
/// this method is very dangerous, doubly so since it may not immediately appear
/// dangerous.
Expand Down Expand Up @@ -1519,15 +1523,13 @@ impl<BorrowType, K, V> Handle<NodeRef<BorrowType, K, V, marker::Internal>, marke
}
}

impl<BorrowType, K, V, HandleType>
Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, HandleType>
{
impl<BorrowType, K, V, Type> Handle<NodeRef<BorrowType, K, V, marker::LeafOrInternal>, Type> {
/// Checks whether the underlying node is an `Internal` node or a `Leaf` node.
pub fn force(
self,
) -> ForceResult<
Handle<NodeRef<BorrowType, K, V, marker::Leaf>, HandleType>,
Handle<NodeRef<BorrowType, K, V, marker::Internal>, HandleType>,
Handle<NodeRef<BorrowType, K, V, marker::Leaf>, Type>,
Handle<NodeRef<BorrowType, K, V, marker::Internal>, Type>,
> {
match self.node.force() {
ForceResult::Leaf(node) => {
Expand Down