Improved documentation for HashMap/BTreeMap Entry's .or_insert_with_key method

1 files changed, 6 insertions, 3 deletions

diff --git a/library/alloc/src/collections/btree/map/entry.rs b/library/alloc/src/collections/btree/map/entry.rs
index 77c285ef595..9dd68e27914 100644
--- a/library/alloc/src/collections/btree/map/entry.rs
+++ b/library/alloc/src/collections/btree/map/entry.rs
@@ -116,9 +116,12 @@ impl<'a, K: Ord, V> Entry<'a, K, V> {
         }
     }
 
-    /// Ensures a value is in the entry by inserting, if empty, the result of the default function,
-    /// which takes the key as its argument, and returns a mutable reference to the value in the
-    /// entry.
+    /// Ensures a value is in the entry by inserting, if empty, the result of the default function.
+    /// This method allows for generating key-derived values for insertion by providing the default
+    /// function a reference to the key that was moved during the `.entry(key)` method call.<br />
+    ///
+    /// The reference to the moved key is provided so that cloning or copying the key is
+    /// unnecessary, unlike with `.or_insert_with(|| ... )`.
     ///
     /// # Examples
     ///