Alow Mutating Entry keys and iterator keys

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "indexmap"
 edition = "2021"
-version = "2.2.6"
+version = "2.3.0"
 documentation = "https://docs.rs/indexmap/"
 repository = "https://github.com/indexmap-rs/indexmap"
 license = "Apache-2.0 OR MIT"

RELEASES.md

@@ -1,5 +1,11 @@
 # Releases
 
+## 2.3.0
+
+- Added trait `MutableEntryKey` for opt-in mutable access to map entry keys.
+- Added method `MutableKeys::iter_mut2` for opt-in mutable iteration of map
+  keys and values.
+
 ## 2.2.6
 
 - Added trait `MutableValues` for opt-in mutable access to set values.

src/map.rs

@@ -16,8 +16,9 @@ mod tests;
 pub use self::core::raw_entry_v1::{self, RawEntryApiV1};
 pub use self::core::{Entry, IndexedEntry, OccupiedEntry, VacantEntry};
 pub use self::iter::{
-    Drain, IntoIter, IntoKeys, IntoValues, Iter, IterMut, Keys, Splice, Values, ValuesMut,
+    Drain, IntoIter, IntoKeys, IntoValues, Iter, IterMut, IterMut2, Keys, Splice, Values, ValuesMut,
 };
+pub use self::mutable::MutableEntryKey;
 pub use self::mutable::MutableKeys;
 pub use self::slice::Slice;
 

src/map/core/entry.rs

@@ -144,6 +144,10 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
         &self.raw.bucket().key
     }
 
+    pub(crate) fn key_mut(&mut self) -> &mut K {
+        &mut self.raw.bucket_mut().key
+    }
+
     /// Gets a reference to the entry's value in the map.
     pub fn get(&self) -> &V {
         &self.raw.bucket().value
@@ -297,6 +301,10 @@ impl<'a, K, V> VacantEntry<'a, K, V> {
         &self.key
     }
 
+    pub(crate) fn key_mut(&mut self) -> &mut K {
+        &mut self.key
+    }
+
     /// Takes ownership of the key, leaving the entry vacant.
     pub fn into_key(self) -> K {
         self.key
@@ -373,6 +381,10 @@ impl<'a, K, V> IndexedEntry<'a, K, V> {
         &self.map.entries[self.index].key
     }
 
+    pub(crate) fn key_mut(&mut self) -> &mut K {
+        &mut self.map.entries[self.index].key
+    }
+
     /// Gets a reference to the entry's value in the map.
     pub fn get(&self) -> &V {
         &self.map.entries[self.index].value

src/map/iter.rs

@@ -156,6 +156,67 @@ impl<K, V> Default for IterMut<'_, K, V> {
     }
 }
 
+/// A mutable iterator over the entries of an [`IndexMap`].
+///
+/// This `struct` is created by the [`MutableKeys::iter_mut2`][super::MutableKeys::iter_mut2] method.
+/// See its documentation for more.
+pub struct IterMut2<'a, K, V> {
+    iter: slice::IterMut<'a, Bucket<K, V>>,
+}
+
+impl<'a, K, V> IterMut2<'a, K, V> {
+    pub(super) fn new(entries: &'a mut [Bucket<K, V>]) -> Self {
+        Self {
+            iter: entries.iter_mut(),
+        }
+    }
+
+    /// Returns a slice of the remaining entries in the iterator.
+    pub fn as_slice(&self) -> &Slice<K, V> {
+        Slice::from_slice(self.iter.as_slice())
+    }
+
+    /// Returns a mutable slice of the remaining entries in the iterator.
+    ///
+    /// To avoid creating `&mut` references that alias, this is forced to consume the iterator.
+    pub fn into_slice(self) -> &'a mut Slice<K, V> {
+        Slice::from_mut_slice(self.iter.into_slice())
+    }
+}
+
+impl<'a, K, V> Iterator for IterMut2<'a, K, V> {
+    type Item = (&'a mut K, &'a mut V);
+
+    iterator_methods!(Bucket::muts);
+}
+
+impl<K, V> DoubleEndedIterator for IterMut2<'_, K, V> {
+    double_ended_iterator_methods!(Bucket::muts);
+}
+
+impl<K, V> ExactSizeIterator for IterMut2<'_, K, V> {
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<K, V> FusedIterator for IterMut2<'_, K, V> {}
+
+impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IterMut2<'_, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let iter = self.iter.as_slice().iter().map(Bucket::refs);
+        f.debug_list().entries(iter).finish()
+    }
+}
+
+impl<K, V> Default for IterMut2<'_, K, V> {
+    fn default() -> Self {
+        Self {
+            iter: [].iter_mut(),
+        }
+    }
+}
+
 /// An owning iterator over the entries of an [`IndexMap`].
 ///
 /// This `struct` is created by the [`IndexMap::into_iter`] method

src/map/mutable.rs

@@ -1,6 +1,9 @@
 use core::hash::{BuildHasher, Hash};
 
-use super::{Bucket, Entries, Equivalent, IndexMap};
+use super::{
+    Bucket, Entries, Entry, Equivalent, IndexMap, IndexedEntry, IterMut2, OccupiedEntry,
+    VacantEntry,
+};
 
 /// Opt-in mutable access to [`IndexMap`] keys.
 ///
@@ -34,6 +37,9 @@ pub trait MutableKeys: private::Sealed {
     /// Computes in **O(1)** time.
     fn get_index_mut2(&mut self, index: usize) -> Option<(&mut Self::Key, &mut Self::Value)>;
 
+    /// Return an iterator over the key-value pairs of the map, in their order
+    fn iter_mut2(&mut self) -> IterMut2<'_, Self::Key, Self::Value>;
+
     /// Scan through each key-value pair in the map and keep those where the
     /// closure `keep` returns `true`.
     ///
@@ -72,6 +78,10 @@ where
         self.as_entries_mut().get_mut(index).map(Bucket::muts)
     }
 
+    fn iter_mut2(&mut self) -> IterMut2<'_, Self::Key, Self::Value> {
+        IterMut2::new(self.as_entries_mut())
+    }
+
     fn retain2<F>(&mut self, keep: F)
     where
         F: FnMut(&mut K, &mut V) -> bool,
@@ -80,8 +90,77 @@ where
     }
 }
 
+/// Opt-in mutable access to [`Entry`] 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 `Entry`.
+///
+/// This trait is sealed and cannot be implemented for types outside this crate.
+pub trait MutableEntryKey: private::Sealed {
+    type Key;
+    fn key_mut(&mut self) -> &mut Self::Key;
+}
+
+/// Opt-in mutable access to [`Entry`] keys.
+///
+/// See [`MutableEntryKey`] for more information.
+impl<K, V> MutableEntryKey for Entry<'_, K, V> {
+    type Key = K;
+
+    /// Gets a mutable reference to the entry's key, either within the map if occupied,
+    /// or else the new key that was used to find the entry.
+    fn key_mut(&mut self) -> &mut Self::Key {
+        match self {
+            Entry::Occupied(e) => e.key_mut(),
+            Entry::Vacant(e) => e.key_mut(),
+        }
+    }
+}
+
+/// Opt-in mutable access to [`OccupiedEntry`] keys.
+///
+/// See [`MutableEntryKey`] for more information.
+impl<K, V> MutableEntryKey for OccupiedEntry<'_, K, V> {
+    type Key = K;
+    fn key_mut(&mut self) -> &mut Self::Key {
+        self.key_mut()
+    }
+}
+
+/// Opt-in mutable access to [`VacantEntry`] keys.
+///
+/// See [`MutableEntryKey`] for more information.
+impl<K, V> MutableEntryKey for VacantEntry<'_, K, V> {
+    type Key = K;
+    fn key_mut(&mut self) -> &mut Self::Key {
+        self.key_mut()
+    }
+}
+
+/// Opt-in mutable access to [`IndexedEntry`] keys.
+///
+/// See [`MutableEntryKey`] for more information.
+impl<K, V> MutableEntryKey for IndexedEntry<'_, K, V> {
+    type Key = K;
+    fn key_mut(&mut self) -> &mut Self::Key {
+        self.key_mut()
+    }
+}
+
 mod private {
     pub trait Sealed {}
 
     impl<K, V, S> Sealed for super::IndexMap<K, V, S> {}
+    impl<K, V> Sealed for super::Entry<'_, K, V> {}
+    impl<K, V> Sealed for super::OccupiedEntry<'_, K, V> {}
+    impl<K, V> Sealed for super::VacantEntry<'_, K, V> {}
+    impl<K, V> Sealed for super::IndexedEntry<'_, K, V> {}
 }

src/map/tests.rs

@@ -497,6 +497,7 @@ fn iter_default() {
     }
     assert_default::<Iter<'static, K, V>>();
     assert_default::<IterMut<'static, K, V>>();
+    assert_default::<IterMut2<'static, K, V>>();
     assert_default::<IntoIter<K, V>>();
     assert_default::<Keys<'static, K, V>>();
     assert_default::<IntoKeys<K, V>>();