Rollup merge of rust-lang#146820 - cammeresi:alloc-20250919, r=tgross35

Add unstable attribute to BTreeMap-related allocator generics

Although these types aren't directly constructable externally, since they're pub, I think this omission was an oversight.

r? libs-api

Author: Zalathar

library/alloc/src/collections/btree/map.rs

@@ -546,7 +546,11 @@ impl<K, V: fmt::Debug> fmt::Debug for ValuesMut<'_, K, V> {
 /// [`into_keys`]: BTreeMap::into_keys
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 #[stable(feature = "map_into_keys_values", since = "1.54.0")]
-pub struct IntoKeys<K, V, A: Allocator + Clone = Global> {
+pub struct IntoKeys<
+    K,
+    V,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + Clone = Global,
+> {
     inner: IntoIter<K, V, A>,
 }
 

library/alloc/src/collections/btree/map/entry.rs

@@ -99,7 +99,12 @@ impl<K: Debug + Ord, V: Debug, A: Allocator + Clone> Debug for OccupiedEntry<'_,
 ///
 /// Contains the occupied entry, and the value that was not inserted.
 #[unstable(feature = "map_try_insert", issue = "82766")]
-pub struct OccupiedError<'a, K: 'a, V: 'a, A: Allocator + Clone = Global> {
+pub struct OccupiedError<
+    'a,
+    K: 'a,
+    V: 'a,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + Clone = Global,
+> {
     /// The entry in the map that was already occupied.
     pub entry: OccupiedEntry<'a, K, V, A>,
     /// The value which was not inserted, because the entry was already occupied.