1 files changed, 87 insertions, 0 deletions
diff --git a/third_party/rust/indexmap/src/map/mutable.rs b/third_party/rust/indexmap/src/map/mutable.rs
new file mode 100644
index 0000000000..7df325948f
--- /dev/null
+++ b/third_party/rust/indexmap/src/map/mutable.rs
@@ -0,0 +1,87 @@
+use core::hash::{BuildHasher, Hash};
+
+use super::{Bucket, Entries, Equivalent, IndexMap};
+
+/// Opt-in mutable access to [`IndexMap`] keys.
+///
+/// These methods expose `&mut K`, mutable references to the key as it is stored
+/// in the map.
+/// You are allowed to modify the keys in the map **if the modification
+/// does not change the key’s hash and equality**.
+///
+/// If keys are modified erroneously, you can no longer look them up.
+/// This is sound (memory safe) but a logical error hazard (just like
+/// implementing `PartialEq`, `Eq`, or `Hash` incorrectly would be).
+///
+/// `use` this trait to enable its methods for `IndexMap`.
+///
+/// This trait is sealed and cannot be implemented for types outside this crate.
+pub trait MutableKeys: private::Sealed {
+    type Key;
+    type Value;
+
+    /// Return item index, mutable reference to key and value
+    ///
+    /// Computes in **O(1)** time (average).
+    fn get_full_mut2<Q>(&mut self, key: &Q) -> Option<(usize, &mut Self::Key, &mut Self::Value)>
+    where
+        Q: ?Sized + Hash + Equivalent<Self::Key>;
+
+    /// Return mutable reference to key and value at an index.
+    ///
+    /// Valid indices are *0 <= index < self.len()*
+    ///
+    /// Computes in **O(1)** time.
+    fn get_index_mut2(&mut self, index: usize) -> Option<(&mut Self::Key, &mut Self::Value)>;
+
+    /// Scan through each key-value pair in the map and keep those where the
+    /// closure `keep` returns `true`.
+    ///
+    /// The elements are visited in order, and remaining elements keep their
+    /// order.
+    ///
+    /// Computes in **O(n)** time (average).
+    fn retain2<F>(&mut self, keep: F)
+    where
+        F: FnMut(&mut Self::Key, &mut Self::Value) -> bool;
+}
+
+/// Opt-in mutable access to [`IndexMap`] keys.
+///
+/// See [`MutableKeys`] for more information.
+impl<K, V, S> MutableKeys for IndexMap<K, V, S>
+where
+    S: BuildHasher,
+{
+    type Key = K;
+    type Value = V;
+
+    fn get_full_mut2<Q>(&mut self, key: &Q) -> Option<(usize, &mut K, &mut V)>
+    where
+        Q: ?Sized + Hash + Equivalent<K>,
+    {
+        if let Some(i) = self.get_index_of(key) {
+            let entry = &mut self.as_entries_mut()[i];
+            Some((i, &mut entry.key, &mut entry.value))
+        } else {
+            None
+        }
+    }
+
+    fn get_index_mut2(&mut self, index: usize) -> Option<(&mut K, &mut V)> {
+        self.as_entries_mut().get_mut(index).map(Bucket::muts)
+    }
+
+    fn retain2<F>(&mut self, keep: F)
+    where
+        F: FnMut(&mut K, &mut V) -> bool,
+    {
+        self.core.retain_in_order(keep);
+    }
+}
+
+mod private {
+    pub trait Sealed {}
+
+    impl<K, V, S> Sealed for super::IndexMap<K, V, S> {}
+}