map.rs source code [crates/hashbrown/src/map.rs]

1	use crate::raw::{
2	Allocator, Bucket, Global, RawDrain, RawExtractIf, RawIntoIter, RawIter, RawTable,
3	};
4	use crate::{DefaultHashBuilder, Equivalent, TryReserveError};
5	use core::borrow::Borrow;
6	use core::fmt::{self, Debug};
7	use core::hash::{BuildHasher, Hash};
8	use core::iter::FusedIterator;
9	use core::marker::PhantomData;
10	use core::mem;
11	use core::ops::Index;
12
13	#[cfg(feature = "raw-entry")]
14	pub use crate::raw_entry::*;
15
16	/// A hash map implemented with quadratic probing and SIMD lookup.
17	///
18	/// The default hashing algorithm is currently [`foldhash`], though this is
19	/// subject to change at any point in the future. This hash function is very
20	/// fast for all types of keys, but this algorithm will typically not* protect*
21	/// against attacks such as HashDoS.
22	///
23	/// The hashing algorithm can be replaced on a per-`HashMap` basis using the
24	/// [`default`], [`with_hasher`], and [`with_capacity_and_hasher`] methods. Many
25	/// alternative algorithms are available on crates.io, such as the [`fnv`] crate.
26	///
27	/// It is required that the keys implement the [`Eq`] and [`Hash`] traits, although
28	/// this can frequently be achieved by using `#[derive(PartialEq, Eq, Hash)]`.
29	/// If you implement these yourself, it is important that the following
30	/// property holds:
31	///
32	/// ```text
33	/// k1 == k2 -> hash(k1) == hash(k2)
34	/// ```
35	///
36	/// In other words, if two keys are equal, their hashes must be equal.
37	///
38	/// It is a logic error for a key to be modified in such a way that the key's
39	/// hash, as determined by the [`Hash`] trait, or its equality, as determined by
40	/// the [`Eq`] trait, changes while it is in the map. This is normally only
41	/// possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
42	///
43	/// It is also a logic error for the [`Hash`] implementation of a key to panic.
44	/// This is generally only possible if the trait is implemented manually. If a
45	/// panic does occur then the contents of the `HashMap` may become corrupted and
46	/// some items may be dropped from the table.
47	///
48	/// # Examples
49	///
50	/// ```
51	/// use hashbrown::HashMap;
52	///
53	/// // Type inference lets us omit an explicit type signature (which
54	/// // would be `HashMap<String, String>` in this example).
55	/// let mut book_reviews = HashMap::new();
56	///
57	/// // Review some books.
58	/// book_reviews.insert(
59	/// "Adventures of Huckleberry Finn".to_string(),
60	/// "My favorite book.".to_string(),
61	/// );
62	/// book_reviews.insert(
63	/// "Grimms' Fairy Tales".to_string(),
64	/// "Masterpiece.".to_string(),
65	/// );
66	/// book_reviews.insert(
67	/// "Pride and Prejudice".to_string(),
68	/// "Very enjoyable.".to_string(),
69	/// );
70	/// book_reviews.insert(
71	/// "The Adventures of Sherlock Holmes".to_string(),
72	/// "Eye lyked it alot.".to_string(),
73	/// );
74	///
75	/// // Check for a specific one.
76	/// // When collections store owned values (String), they can still be
77	/// // queried using references (&str).
78	/// if !book_reviews.contains_key("Les Misérables") {
79	/// println!("We've got {} reviews, but Les Misérables ain't one.",
80	/// book_reviews.len());
81	/// }
82	///
83	/// // oops, this review has a lot of spelling mistakes, let's delete it.
84	/// book_reviews.remove("The Adventures of Sherlock Holmes");
85	///
86	/// // Look up the values associated with some keys.
87	/// let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
88	/// for &book in &to_find {
89	/// match book_reviews.get(book) {
90	/// Some(review) => println!("{}: {}", book, review),
91	/// None => println!("{} is unreviewed.", book)
92	/// }
93	/// }
94	///
95	/// // Look up the value for a key (will panic if the key is not found).
96	/// println!("Review for Jane: {}", book_reviews["Pride and Prejudice"]);
97	///
98	/// // Iterate over everything.
99	/// for (book, review) in &book_reviews {
100	/// println!("{}: `\"`{}`\"`", book, review);
101	/// }
102	/// ```
103	///
104	/// `HashMap` also implements an [`Entry API`](#method.entry), which allows
105	/// for more complex methods of getting, setting, updating and removing keys and
106	/// their values:
107	///
108	/// ```
109	/// use hashbrown::HashMap;
110	///
111	/// // type inference lets us omit an explicit type signature (which
112	/// // would be `HashMap<&str, u8>` in this example).
113	/// let mut player_stats = HashMap::new();
114	///
115	/// fn random_stat_buff() -> u8 {
116	/// // could actually return some random value here - let's just return
117	/// // some fixed value for now
118	/// `42`
119	/// }
120	///
121	/// // insert a key only if it doesn't already exist
122	/// player_stats.entry("health").or_insert(`100`);
123	///
124	/// // insert a key using a function that provides a new value only if it
125	/// // doesn't already exist
126	/// player_stats.entry("defence").or_insert_with(random_stat_buff);
127	///
128	/// // update a key, guarding against the key possibly not being set
129	/// let stat = player_stats.entry("attack").or_insert(`100`);
130	/// *stat += random_stat_buff();
131	/// ```
132	///
133	/// The easiest way to use `HashMap` with a custom key type is to derive [`Eq`] and [`Hash`].
134	/// We must also derive [`PartialEq`].
135	///
136	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
137	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
138	/// [`PartialEq`]: https://doc.rust-lang.org/std/cmp/trait.PartialEq.html
139	/// [`RefCell`]: https://doc.rust-lang.org/std/cell/struct.RefCell.html
140	/// [`Cell`]: https://doc.rust-lang.org/std/cell/struct.Cell.html
141	/// [`default`]: #method.default
142	/// [`with_hasher`]: #method.with_hasher
143	/// [`with_capacity_and_hasher`]: #method.with_capacity_and_hasher
144	/// [`fnv`]: https://crates.io/crates/fnv
145	/// [`foldhash`]: https://crates.io/crates/foldhash
146	///
147	/// ```
148	/// use hashbrown::HashMap;
149	///
150	/// #[derive(Hash, Eq, PartialEq, Debug)]
151	/// struct Viking {
152	/// name: String,
153	/// country: String,
154	/// }
155	///
156	/// impl Viking {
157	/// /// Creates a new Viking.
158	/// fn new(name: &str, country: &str) -> Viking {
159	/// Viking { name: name.to_string(), country: country.to_string() }
160	/// }
161	/// }
162	///
163	/// // Use a HashMap to store the vikings' health points.
164	/// let mut vikings = HashMap::new();
165	///
166	/// vikings.insert(Viking::new("Einar", "Norway"), `25`);
167	/// vikings.insert(Viking::new("Olaf", "Denmark"), `24`);
168	/// vikings.insert(Viking::new("Harald", "Iceland"), `12`);
169	///
170	/// // Use derived implementation to print the status of the vikings.
171	/// for (viking, health) in &vikings {
172	/// println!("{:?} has {} hp", viking, health);
173	/// }
174	/// ```
175	///
176	/// A `HashMap` with fixed list of elements can be initialized from an array:
177	///
178	/// ```
179	/// use hashbrown::HashMap;
180	///
181	/// let timber_resources: HashMap<&str, i32> = [("Norway", `100`), ("Denmark", `50`), ("Iceland", `10`)]
182	/// .into_iter().collect();
183	/// // use the values stored in map
184	/// ```
185	pub struct HashMap<K, V, S = DefaultHashBuilder, A: Allocator = Global> {
186	pub(crate) hash_builder: S,
187	pub(crate) table: RawTable<(K, V), A>,
188	}
189
190	impl<K: Clone, V: Clone, S: Clone, A: Allocator + Clone> Clone for HashMap<K, V, S, A> {
191	fn clone(&self) -> Self {
192	HashMap {
193	hash_builder: self.hash_builder.clone(),
194	table: self.table.clone(),
195	}
196	}
197
198	fn clone_from(&mut self, source: &Self) {
199	self.table.clone_from(&source.table);
200
201	// Update hash_builder only if we successfully cloned all elements.
202	self.hash_builder.clone_from(&source.hash_builder);
203	}
204	}
205
206	/// Ensures that a single closure type across uses of this which, in turn prevents multiple
207	/// instances of any functions like `RawTable::reserve` from being generated
208	#[cfg_attr(feature = "inline-more", inline)]
209	pub(crate) fn make_hasher<Q, V, S>(hash_builder: &S) -> impl Fn(&(Q, V)) -> u64 + '_
210	where
211	Q: Hash,
212	S: BuildHasher,
213	{
214	move \|val: &(Q, V)\| make_hash::<Q, S>(hash_builder, &val.0)
215	}
216
217	/// Ensures that a single closure type across uses of this which, in turn prevents multiple
218	/// instances of any functions like `RawTable::reserve` from being generated
219	#[cfg_attr(feature = "inline-more", inline)]
220	pub(crate) fn equivalent_key<Q, K, V>(k: &Q) -> impl Fn(&(K, V)) -> bool + '_
221	where
222	Q: Equivalent<K> + ?Sized,
223	{
224	move \|x: &(K, V)\| k.equivalent(&x.0)
225	}
226
227	/// Ensures that a single closure type across uses of this which, in turn prevents multiple
228	/// instances of any functions like `RawTable::reserve` from being generated
229	#[cfg_attr(feature = "inline-more", inline)]
230	#[allow(dead_code)]
231	pub(crate) fn equivalent<Q, K>(k: &Q) -> impl Fn(&K) -> bool + '_
232	where
233	Q: Equivalent<K> + ?Sized,
234	{
235	move \|x: &K\| k.equivalent(key:x)
236	}
237
238	#[cfg(not(feature = "nightly"))]
239	#[cfg_attr(feature = "inline-more", inline)]
240	pub(crate) fn make_hash<Q, S>(hash_builder: &S, val: &Q) -> u64
241	where
242	Q: Hash + ?Sized,
243	S: BuildHasher,
244	{
245	use core::hash::Hasher;
246	let mut state = hash_builder.build_hasher();
247	val.hash(&mut state);
248	state.finish()
249	}
250
251	#[cfg(feature = "nightly")]
252	#[cfg_attr(feature = "inline-more", inline)]
253	pub(crate) fn make_hash<Q, S>(hash_builder: &S, val: &Q) -> u64
254	where
255	Q: Hash + ?Sized,
256	S: BuildHasher,
257	{
258	hash_builder.hash_one(val)
259	}
260
261	#[cfg(feature = "default-hasher")]
262	impl<K, V> HashMap<K, V, DefaultHashBuilder> {
263	/// Creates an empty `HashMap`.
264	///
265	/// The hash map is initially created with a capacity of 0, so it will not allocate until it
266	/// is first inserted into.
267	///
268	/// # HashDoS resistance
269	///
270	/// The `hash_builder` normally use a fixed key by default and that does
271	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
272	/// Users who require HashDoS resistance should explicitly use
273	/// [`std::collections::hash_map::RandomState`]
274	/// as the hasher when creating a [`HashMap`], for example with
275	/// [`with_hasher`](HashMap::with_hasher) method.
276	///
277	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
278	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
279	///
280	/// # Examples
281	///
282	/// ```
283	/// use hashbrown::HashMap;
284	/// let mut map: HashMap<&str, i32> = HashMap::new();
285	/// assert_eq!(map.len(), 0);
286	/// assert_eq!(map.capacity(), 0);
287	/// ```
288	#[cfg_attr(feature = "inline-more", inline)]
289	pub fn new() -> Self {
290	Self::default()
291	}
292
293	/// Creates an empty `HashMap` with the specified capacity.
294	///
295	/// The hash map will be able to hold at least `capacity` elements without
296	/// reallocating. If `capacity` is 0, the hash map will not allocate.
297	///
298	/// # HashDoS resistance
299	///
300	/// The `hash_builder` normally use a fixed key by default and that does
301	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
302	/// Users who require HashDoS resistance should explicitly use
303	/// [`std::collections::hash_map::RandomState`]
304	/// as the hasher when creating a [`HashMap`], for example with
305	/// [`with_capacity_and_hasher`](HashMap::with_capacity_and_hasher) method.
306	///
307	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
308	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
309	///
310	/// # Examples
311	///
312	/// ```
313	/// use hashbrown::HashMap;
314	/// let mut map: HashMap<&str, i32> = HashMap::with_capacity(10);
315	/// assert_eq!(map.len(), 0);
316	/// assert!(map.capacity() >= 10);
317	/// ```
318	#[cfg_attr(feature = "inline-more", inline)]
319	pub fn with_capacity(capacity: usize) -> Self {
320	Self::with_capacity_and_hasher(capacity, DefaultHashBuilder::default())
321	}
322	}
323
324	#[cfg(feature = "default-hasher")]
325	impl<K, V, A: Allocator> HashMap<K, V, DefaultHashBuilder, A> {
326	/// Creates an empty `HashMap` using the given allocator.
327	///
328	/// The hash map is initially created with a capacity of 0, so it will not allocate until it
329	/// is first inserted into.
330	///
331	/// # HashDoS resistance
332	///
333	/// The `hash_builder` normally use a fixed key by default and that does
334	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
335	/// Users who require HashDoS resistance should explicitly use
336	/// [`std::collections::hash_map::RandomState`]
337	/// as the hasher when creating a [`HashMap`], for example with
338	/// [`with_hasher_in`](HashMap::with_hasher_in) method.
339	///
340	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
341	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
342	///
343	/// # Examples
344	///
345	/// ```
346	/// use hashbrown::HashMap;
347	/// use bumpalo::Bump;
348	///
349	/// let bump = Bump::new();
350	/// let mut map = HashMap::new_in(&bump);
351	///
352	/// // The created HashMap holds none elements
353	/// assert_eq!(map.len(), 0);
354	///
355	/// // The created HashMap also doesn't allocate memory
356	/// assert_eq!(map.capacity(), 0);
357	///
358	/// // Now we insert element inside created HashMap
359	/// map.insert("One", 1);
360	/// // We can see that the HashMap holds 1 element
361	/// assert_eq!(map.len(), 1);
362	/// // And it also allocates some capacity
363	/// assert!(map.capacity() > 1);
364	/// ```
365	#[cfg_attr(feature = "inline-more", inline)]
366	pub fn new_in(alloc: A) -> Self {
367	Self::with_hasher_in(DefaultHashBuilder::default(), alloc)
368	}
369
370	/// Creates an empty `HashMap` with the specified capacity using the given allocator.
371	///
372	/// The hash map will be able to hold at least `capacity` elements without
373	/// reallocating. If `capacity` is 0, the hash map will not allocate.
374	///
375	/// # HashDoS resistance
376	///
377	/// The `hash_builder` normally use a fixed key by default and that does
378	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
379	/// Users who require HashDoS resistance should explicitly use
380	/// [`std::collections::hash_map::RandomState`]
381	/// as the hasher when creating a [`HashMap`], for example with
382	/// [`with_capacity_and_hasher_in`](HashMap::with_capacity_and_hasher_in) method.
383	///
384	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
385	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
386	///
387	/// # Examples
388	///
389	/// ```
390	/// use hashbrown::HashMap;
391	/// use bumpalo::Bump;
392	///
393	/// let bump = Bump::new();
394	/// let mut map = HashMap::with_capacity_in(5, &bump);
395	///
396	/// // The created HashMap holds none elements
397	/// assert_eq!(map.len(), 0);
398	/// // But it can hold at least 5 elements without reallocating
399	/// let empty_map_capacity = map.capacity();
400	/// assert!(empty_map_capacity >= 5);
401	///
402	/// // Now we insert some 5 elements inside created HashMap
403	/// map.insert("One", 1);
404	/// map.insert("Two", 2);
405	/// map.insert("Three", 3);
406	/// map.insert("Four", 4);
407	/// map.insert("Five", 5);
408	///
409	/// // We can see that the HashMap holds 5 elements
410	/// assert_eq!(map.len(), 5);
411	/// // But its capacity isn't changed
412	/// assert_eq!(map.capacity(), empty_map_capacity)
413	/// ```
414	#[cfg_attr(feature = "inline-more", inline)]
415	pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
416	Self::with_capacity_and_hasher_in(capacity, DefaultHashBuilder::default(), alloc)
417	}
418	}
419
420	impl<K, V, S> HashMap<K, V, S> {
421	/// Creates an empty `HashMap` which will use the given hash builder to hash
422	/// keys.
423	///
424	/// The hash map is initially created with a capacity of 0, so it will not
425	/// allocate until it is first inserted into.
426	///
427	/// # HashDoS resistance
428	///
429	/// The `hash_builder` normally use a fixed key by default and that does
430	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
431	/// Users who require HashDoS resistance should explicitly use
432	/// [`std::collections::hash_map::RandomState`]
433	/// as the hasher when creating a [`HashMap`].
434	///
435	/// The `hash_builder` passed should implement the [`BuildHasher`] trait for
436	/// the `HashMap` to be useful, see its documentation for details.
437	///
438	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
439	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
440	/// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
441	///
442	/// # Examples
443	///
444	/// ```
445	/// use hashbrown::HashMap;
446	/// use hashbrown::DefaultHashBuilder;
447	///
448	/// let s = DefaultHashBuilder::default();
449	/// let mut map = HashMap::with_hasher(s);
450	/// assert_eq!(map.len(), `0`);
451	/// assert_eq!(map.capacity(), `0`);
452	///
453	/// map.insert(`1`, `2`);
454	/// ```
455	#[cfg_attr(feature = "inline-more", inline)]
456	#[cfg_attr(feature = "rustc-dep-of-std", rustc_const_stable_indirect)]
457	pub const fn with_hasher(hash_builder: S) -> Self {
458	Self {
459	hash_builder,
460	table: RawTable::new(),
461	}
462	}
463
464	/// Creates an empty `HashMap` with the specified capacity, using `hash_builder`
465	/// to hash the keys.
466	///
467	/// The hash map will be able to hold at least `capacity` elements without
468	/// reallocating. If `capacity` is 0, the hash map will not allocate.
469	///
470	/// # HashDoS resistance
471	///
472	/// The `hash_builder` normally use a fixed key by default and that does
473	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
474	/// Users who require HashDoS resistance should explicitly use
475	/// [`std::collections::hash_map::RandomState`]
476	/// as the hasher when creating a [`HashMap`].
477	///
478	/// The `hash_builder` passed should implement the [`BuildHasher`] trait for
479	/// the `HashMap` to be useful, see its documentation for details.
480	///
481	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
482	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
483	/// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
484	///
485	/// # Examples
486	///
487	/// ```
488	/// use hashbrown::HashMap;
489	/// use hashbrown::DefaultHashBuilder;
490	///
491	/// let s = DefaultHashBuilder::default();
492	/// let mut map = HashMap::with_capacity_and_hasher(`10`, s);
493	/// assert_eq!(map.len(), `0`);
494	/// assert!(map.capacity() >= `10`);
495	///
496	/// map.insert(`1`, `2`);
497	/// ```
498	#[cfg_attr(feature = "inline-more", inline)]
499	pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> Self {
500	Self {
501	hash_builder,
502	table: RawTable::with_capacity(capacity),
503	}
504	}
505	}
506
507	impl<K, V, S, A: Allocator> HashMap<K, V, S, A> {
508	/// Returns a reference to the underlying allocator.
509	#[inline]
510	pub fn allocator(&self) -> &A {
511	self.table.allocator()
512	}
513
514	/// Creates an empty `HashMap` which will use the given hash builder to hash
515	/// keys. It will be allocated with the given allocator.
516	///
517	/// The hash map is initially created with a capacity of 0, so it will not allocate until it
518	/// is first inserted into.
519	///
520	/// # HashDoS resistance
521	///
522	/// The `hash_builder` normally use a fixed key by default and that does
523	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
524	/// Users who require HashDoS resistance should explicitly use
525	/// [`std::collections::hash_map::RandomState`]
526	/// as the hasher when creating a [`HashMap`].
527	///
528	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
529	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
530	///
531	/// # Examples
532	///
533	/// ```
534	/// use hashbrown::HashMap;
535	/// use hashbrown::DefaultHashBuilder;
536	///
537	/// let s = DefaultHashBuilder::default();
538	/// let mut map = HashMap::with_hasher(s);
539	/// map.insert(`1`, `2`);
540	/// ```
541	#[cfg_attr(feature = "inline-more", inline)]
542	#[cfg_attr(feature = "rustc-dep-of-std", rustc_const_stable_indirect)]
543	pub const fn with_hasher_in(hash_builder: S, alloc: A) -> Self {
544	Self {
545	hash_builder,
546	table: RawTable::new_in(alloc),
547	}
548	}
549
550	/// Creates an empty `HashMap` with the specified capacity, using `hash_builder`
551	/// to hash the keys. It will be allocated with the given allocator.
552	///
553	/// The hash map will be able to hold at least `capacity` elements without
554	/// reallocating. If `capacity` is 0, the hash map will not allocate.
555	///
556	/// # HashDoS resistance
557	///
558	/// The `hash_builder` normally use a fixed key by default and that does
559	/// not allow the `HashMap` to be protected against attacks such as [`HashDoS`].
560	/// Users who require HashDoS resistance should explicitly use
561	/// [`std::collections::hash_map::RandomState`]
562	/// as the hasher when creating a [`HashMap`].
563	///
564	/// [`HashDoS`]: https://en.wikipedia.org/wiki/Collision_attack
565	/// [`std::collections::hash_map::RandomState`]: https://doc.rust-lang.org/std/collections/hash_map/struct.RandomState.html
566	///
567	/// # Examples
568	///
569	/// ```
570	/// use hashbrown::HashMap;
571	/// use hashbrown::DefaultHashBuilder;
572	///
573	/// let s = DefaultHashBuilder::default();
574	/// let mut map = HashMap::with_capacity_and_hasher(`10`, s);
575	/// map.insert(`1`, `2`);
576	/// ```
577	#[cfg_attr(feature = "inline-more", inline)]
578	pub fn with_capacity_and_hasher_in(capacity: usize, hash_builder: S, alloc: A) -> Self {
579	Self {
580	hash_builder,
581	table: RawTable::with_capacity_in(capacity, alloc),
582	}
583	}
584
585	/// Returns a reference to the map's [`BuildHasher`].
586	///
587	/// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
588	///
589	/// # Examples
590	///
591	/// ```
592	/// use hashbrown::HashMap;
593	/// use hashbrown::DefaultHashBuilder;
594	///
595	/// let hasher = DefaultHashBuilder::default();
596	/// let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
597	/// let hasher: &DefaultHashBuilder = map.hasher();
598	/// ```
599	#[cfg_attr(feature = "inline-more", inline)]
600	pub fn hasher(&self) -> &S {
601	&self.hash_builder
602	}
603
604	/// Returns the number of elements the map can hold without reallocating.
605	///
606	/// This number is a lower bound; the `HashMap<K, V>` might be able to hold
607	/// more, but is guaranteed to be able to hold at least this many.
608	///
609	/// # Examples
610	///
611	/// ```
612	/// use hashbrown::HashMap;
613	/// let map: HashMap<i32, i32> = HashMap::with_capacity(`100`);
614	/// assert_eq!(map.len(), `0`);
615	/// assert!(map.capacity() >= `100`);
616	/// ```
617	#[cfg_attr(feature = "inline-more", inline)]
618	pub fn capacity(&self) -> usize {
619	self.table.capacity()
620	}
621
622	/// An iterator visiting all keys in arbitrary order.
623	/// The iterator element type is `&'a K`.
624	///
625	/// # Examples
626	///
627	/// ```
628	/// use hashbrown::HashMap;
629	///
630	/// let mut map = HashMap::new();
631	/// map.insert("a", `1`);
632	/// map.insert("b", `2`);
633	/// map.insert("c", `3`);
634	/// assert_eq!(map.len(), `3`);
635	/// let mut vec: Vec<&str> = Vec::new();
636	///
637	/// for key in map.keys() {
638	/// println!("{}", key);
639	/// vec.push(*key);
640	/// }
641	///
642	/// // The `Keys` iterator produces keys in arbitrary order, so the
643	/// // keys must be sorted to test them against a sorted array.
644	/// vec.sort_unstable();
645	/// assert_eq!(vec, ["a", "b", "c"]);
646	///
647	/// assert_eq!(map.len(), `3`);
648	/// ```
649	#[cfg_attr(feature = "inline-more", inline)]
650	pub fn keys(&self) -> Keys<'_, K, V> {
651	Keys { inner: self.iter() }
652	}
653
654	/// An iterator visiting all values in arbitrary order.
655	/// The iterator element type is `&'a V`.
656	///
657	/// # Examples
658	///
659	/// ```
660	/// use hashbrown::HashMap;
661	///
662	/// let mut map = HashMap::new();
663	/// map.insert("a", `1`);
664	/// map.insert("b", `2`);
665	/// map.insert("c", `3`);
666	/// assert_eq!(map.len(), `3`);
667	/// let mut vec: Vec<i32> = Vec::new();
668	///
669	/// for val in map.values() {
670	/// println!("{}", val);
671	/// vec.push(*val);
672	/// }
673	///
674	/// // The `Values` iterator produces values in arbitrary order, so the
675	/// // values must be sorted to test them against a sorted array.
676	/// vec.sort_unstable();
677	/// assert_eq!(vec, [`1`, `2`, `3`]);
678	///
679	/// assert_eq!(map.len(), `3`);
680	/// ```
681	#[cfg_attr(feature = "inline-more", inline)]
682	pub fn values(&self) -> Values<'_, K, V> {
683	Values { inner: self.iter() }
684	}
685
686	/// An iterator visiting all values mutably in arbitrary order.
687	/// The iterator element type is `&'a mut V`.
688	///
689	/// # Examples
690	///
691	/// ```
692	/// use hashbrown::HashMap;
693	///
694	/// let mut map = HashMap::new();
695	///
696	/// map.insert("a", `1`);
697	/// map.insert("b", `2`);
698	/// map.insert("c", `3`);
699	///
700	/// for val in map.values_mut() {
701	/// val = val + `10`;
702	/// }
703	///
704	/// assert_eq!(map.len(), `3`);
705	/// let mut vec: Vec<i32> = Vec::new();
706	///
707	/// for val in map.values() {
708	/// println!("{}", val);
709	/// vec.push(*val);
710	/// }
711	///
712	/// // The `Values` iterator produces values in arbitrary order, so the
713	/// // values must be sorted to test them against a sorted array.
714	/// vec.sort_unstable();
715	/// assert_eq!(vec, [`11`, `12`, `13`]);
716	///
717	/// assert_eq!(map.len(), `3`);
718	/// ```
719	#[cfg_attr(feature = "inline-more", inline)]
720	pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
721	ValuesMut {
722	inner: self.iter_mut(),
723	}
724	}
725
726	/// An iterator visiting all key-value pairs in arbitrary order.
727	/// The iterator element type is `(&'a K, &'a V)`.
728	///
729	/// # Examples
730	///
731	/// ```
732	/// use hashbrown::HashMap;
733	///
734	/// let mut map = HashMap::new();
735	/// map.insert("a", `1`);
736	/// map.insert("b", `2`);
737	/// map.insert("c", `3`);
738	/// assert_eq!(map.len(), `3`);
739	/// let mut vec: Vec<(&str, i32)> = Vec::new();
740	///
741	/// for (key, val) in map.iter() {
742	/// println!("key: {} val: {}", key, val);
743	/// vec.push((key, val));
744	/// }
745	///
746	/// // The `Iter` iterator produces items in arbitrary order, so the
747	/// // items must be sorted to test them against a sorted array.
748	/// vec.sort_unstable();
749	/// assert_eq!(vec, [("a", `1`), ("b", `2`), ("c", `3`)]);
750	///
751	/// assert_eq!(map.len(), `3`);
752	/// ```
753	#[cfg_attr(feature = "inline-more", inline)]
754	pub fn iter(&self) -> Iter<'_, K, V> {
755	// Here we tie the lifetime of self to the iter.
756	unsafe {
757	Iter {
758	inner: self.table.iter(),
759	marker: PhantomData,
760	}
761	}
762	}
763
764	/// An iterator visiting all key-value pairs in arbitrary order,
765	/// with mutable references to the values.
766	/// The iterator element type is `(&'a K, &'a mut V)`.
767	///
768	/// # Examples
769	///
770	/// ```
771	/// use hashbrown::HashMap;
772	///
773	/// let mut map = HashMap::new();
774	/// map.insert("a", `1`);
775	/// map.insert("b", `2`);
776	/// map.insert("c", `3`);
777	///
778	/// // Update all values
779	/// for (_, val) in map.iter_mut() {
780	/// val = `2`;
781	/// }
782	///
783	/// assert_eq!(map.len(), `3`);
784	/// let mut vec: Vec<(&str, i32)> = Vec::new();
785	///
786	/// for (key, val) in &map {
787	/// println!("key: {} val: {}", key, val);
788	/// vec.push((key, val));
789	/// }
790	///
791	/// // The `Iter` iterator produces items in arbitrary order, so the
792	/// // items must be sorted to test them against a sorted array.
793	/// vec.sort_unstable();
794	/// assert_eq!(vec, [("a", `2`), ("b", `4`), ("c", `6`)]);
795	///
796	/// assert_eq!(map.len(), `3`);
797	/// ```
798	#[cfg_attr(feature = "inline-more", inline)]
799	pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
800	// Here we tie the lifetime of self to the iter.
801	unsafe {
802	IterMut {
803	inner: self.table.iter(),
804	marker: PhantomData,
805	}
806	}
807	}
808
809	#[cfg(test)]
810	#[cfg_attr(feature = "inline-more", inline)]
811	fn raw_capacity(&self) -> usize {
812	self.table.buckets()
813	}
814
815	/// Returns the number of elements in the map.
816	///
817	/// # Examples
818	///
819	/// ```
820	/// use hashbrown::HashMap;
821	///
822	/// let mut a = HashMap::new();
823	/// assert_eq!(a.len(), `0`);
824	/// a.insert(`1`, "a");
825	/// assert_eq!(a.len(), `1`);
826	/// ```
827	#[cfg_attr(feature = "inline-more", inline)]
828	pub fn len(&self) -> usize {
829	self.table.len()
830	}
831
832	/// Returns `true` if the map contains no elements.
833	///
834	/// # Examples
835	///
836	/// ```
837	/// use hashbrown::HashMap;
838	///
839	/// let mut a = HashMap::new();
840	/// assert!(a.is_empty());
841	/// a.insert(`1`, "a");
842	/// assert!(!a.is_empty());
843	/// ```
844	#[cfg_attr(feature = "inline-more", inline)]
845	pub fn is_empty(&self) -> bool {
846	self.len() == `0`
847	}
848
849	/// Clears the map, returning all key-value pairs as an iterator. Keeps the
850	/// allocated memory for reuse.
851	///
852	/// If the returned iterator is dropped before being fully consumed, it
853	/// drops the remaining key-value pairs. The returned iterator keeps a
854	/// mutable borrow on the vector to optimize its implementation.
855	///
856	/// # Examples
857	///
858	/// ```
859	/// use hashbrown::HashMap;
860	///
861	/// let mut a = HashMap::new();
862	/// a.insert(`1`, "a");
863	/// a.insert(`2`, "b");
864	/// let capacity_before_drain = a.capacity();
865	///
866	/// for (k, v) in a.drain().take(`1`) {
867	/// assert!(k == `1` \|\| k == `2`);
868	/// assert!(v == "a" \|\| v == "b");
869	/// }
870	///
871	/// // As we can see, the map is empty and contains no element.
872	/// assert!(a.is_empty() && a.len() == `0`);
873	/// // But map capacity is equal to old one.
874	/// assert_eq!(a.capacity(), capacity_before_drain);
875	///
876	/// let mut a = HashMap::new();
877	/// a.insert(`1`, "a");
878	/// a.insert(`2`, "b");
879	///
880	/// { // Iterator is dropped without being consumed.
881	/// let d = a.drain();
882	/// }
883	///
884	/// // But the map is empty even if we do not use Drain iterator.
885	/// assert!(a.is_empty());
886	/// ```
887	#[cfg_attr(feature = "inline-more", inline)]
888	pub fn drain(&mut self) -> Drain<'_, K, V, A> {
889	Drain {
890	inner: self.table.drain(),
891	}
892	}
893
894	/// Retains only the elements specified by the predicate. Keeps the
895	/// allocated memory for reuse.
896	///
897	/// In other words, remove all pairs `(k, v)` such that `f(&k, &mut v)` returns `false`.
898	/// The elements are visited in unsorted (and unspecified) order.
899	///
900	/// # Examples
901	///
902	/// ```
903	/// use hashbrown::HashMap;
904	///
905	/// let mut map: HashMap<i32, i32> = (`0`..`8`).map(\|x\|(x, x*`10`)).collect();
906	/// assert_eq!(map.len(), `8`);
907	///
908	/// map.retain(\|&k, _\| k % `2` == `0`);
909	///
910	/// // We can see, that the number of elements inside map is changed.
911	/// assert_eq!(map.len(), `4`);
912	///
913	/// let mut vec: Vec<(i32, i32)> = map.iter().map(\|(&k, &v)\| (k, v)).collect();
914	/// vec.sort_unstable();
915	/// assert_eq!(vec, [(`0`, `0`), (`2`, `20`), (`4`, `40`), (`6`, `60`)]);
916	/// ```
917	pub fn retain<F>(&mut self, mut f: F)
918	where
919	F: FnMut(&K, &mut V) -> bool,
920	{
921	// Here we only use `iter` as a temporary, preventing use-after-free
922	unsafe {
923	for item in self.table.iter() {
924	let &mut (ref key, ref mut value) = item.as_mut();
925	if !f(key, value) {
926	self.table.erase(item);
927	}
928	}
929	}
930	}
931
932	/// Drains elements which are true under the given predicate,
933	/// and returns an iterator over the removed items.
934	///
935	/// In other words, move all pairs `(k, v)` such that `f(&k, &mut v)` returns `true` out
936	/// into another iterator.
937	///
938	/// Note that `extract_if` lets you mutate every value in the filter closure, regardless of
939	/// whether you choose to keep or remove it.
940	///
941	/// If the returned `ExtractIf` is not exhausted, e.g. because it is dropped without iterating
942	/// or the iteration short-circuits, then the remaining elements will be retained.
943	/// Use [`retain()`] with a negated predicate if you do not need the returned iterator.
944	///
945	/// Keeps the allocated memory for reuse.
946	///
947	/// [`retain()`]: HashMap::retain
948	///
949	/// # Examples
950	///
951	/// ```
952	/// use hashbrown::HashMap;
953	///
954	/// let mut map: HashMap<i32, i32> = (`0`..`8`).map(\|x\| (x, x)).collect();
955	///
956	/// let drained: HashMap<i32, i32> = map.extract_if(\|k, _v\| k % `2` == `0`).collect();
957	///
958	/// let mut evens = drained.keys().cloned().collect::<Vec<_>>();
959	/// let mut odds = map.keys().cloned().collect::<Vec<_>>();
960	/// evens.sort();
961	/// odds.sort();
962	///
963	/// assert_eq!(evens, vec![`0`, `2`, `4`, `6`]);
964	/// assert_eq!(odds, vec![`1`, `3`, `5`, `7`]);
965	///
966	/// let mut map: HashMap<i32, i32> = (`0`..`8`).map(\|x\| (x, x)).collect();
967	///
968	/// { // Iterator is dropped without being consumed.
969	/// let d = map.extract_if(\|k, _v\| k % `2` != `0`);
970	/// }
971	///
972	/// // ExtractIf was not exhausted, therefore no elements were drained.
973	/// assert_eq!(map.len(), `8`);
974	/// ```
975	#[cfg_attr(feature = "inline-more", inline)]
976	pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, K, V, F, A>
977	where
978	F: FnMut(&K, &mut V) -> bool,
979	{
980	ExtractIf {
981	f,
982	inner: RawExtractIf {
983	iter: unsafe { self.table.iter() },
984	table: &mut self.table,
985	},
986	}
987	}
988
989	/// Clears the map, removing all key-value pairs. Keeps the allocated memory
990	/// for reuse.
991	///
992	/// # Examples
993	///
994	/// ```
995	/// use hashbrown::HashMap;
996	///
997	/// let mut a = HashMap::new();
998	/// a.insert(`1`, "a");
999	/// let capacity_before_clear = a.capacity();
1000	///
1001	/// a.clear();
1002	///
1003	/// // Map is empty.
1004	/// assert!(a.is_empty());
1005	/// // But map capacity is equal to old one.
1006	/// assert_eq!(a.capacity(), capacity_before_clear);
1007	/// ```
1008	#[cfg_attr(feature = "inline-more", inline)]
1009	pub fn clear(&mut self) {
1010	self.table.clear();
1011	}
1012
1013	/// Creates a consuming iterator visiting all the keys in arbitrary order.
1014	/// The map cannot be used after calling this.
1015	/// The iterator element type is `K`.
1016	///
1017	/// # Examples
1018	///
1019	/// ```
1020	/// use hashbrown::HashMap;
1021	///
1022	/// let mut map = HashMap::new();
1023	/// map.insert("a", `1`);
1024	/// map.insert("b", `2`);
1025	/// map.insert("c", `3`);
1026	///
1027	/// let mut vec: Vec<&str> = map.into_keys().collect();
1028	///
1029	/// // The `IntoKeys` iterator produces keys in arbitrary order, so the
1030	/// // keys must be sorted to test them against a sorted array.
1031	/// vec.sort_unstable();
1032	/// assert_eq!(vec, ["a", "b", "c"]);
1033	/// ```
1034	#[inline]
1035	pub fn into_keys(self) -> IntoKeys<K, V, A> {
1036	IntoKeys {
1037	inner: self.into_iter(),
1038	}
1039	}
1040
1041	/// Creates a consuming iterator visiting all the values in arbitrary order.
1042	/// The map cannot be used after calling this.
1043	/// The iterator element type is `V`.
1044	///
1045	/// # Examples
1046	///
1047	/// ```
1048	/// use hashbrown::HashMap;
1049	///
1050	/// let mut map = HashMap::new();
1051	/// map.insert("a", `1`);
1052	/// map.insert("b", `2`);
1053	/// map.insert("c", `3`);
1054	///
1055	/// let mut vec: Vec<i32> = map.into_values().collect();
1056	///
1057	/// // The `IntoValues` iterator produces values in arbitrary order, so
1058	/// // the values must be sorted to test them against a sorted array.
1059	/// vec.sort_unstable();
1060	/// assert_eq!(vec, [`1`, `2`, `3`]);
1061	/// ```
1062	#[inline]
1063	pub fn into_values(self) -> IntoValues<K, V, A> {
1064	IntoValues {
1065	inner: self.into_iter(),
1066	}
1067	}
1068	}
1069
1070	impl<K, V, S, A> HashMap<K, V, S, A>
1071	where
1072	K: Eq + Hash,
1073	S: BuildHasher,
1074	A: Allocator,
1075	{
1076	/// Reserves capacity for at least `additional` more elements to be inserted
1077	/// in the `HashMap`. The collection may reserve more space to avoid
1078	/// frequent reallocations.
1079	///
1080	/// # Panics
1081	///
1082	/// Panics if the new capacity exceeds [`isize::MAX`] bytes and [`abort`] the program
1083	/// in case of allocation error. Use [`try_reserve`](HashMap::try_reserve) instead
1084	/// if you want to handle memory allocation failure.
1085	///
1086	/// [`isize::MAX`]: https://doc.rust-lang.org/std/primitive.isize.html
1087	/// [`abort`]: https://doc.rust-lang.org/alloc/alloc/fn.handle_alloc_error.html
1088	///
1089	/// # Examples
1090	///
1091	/// ```
1092	/// use hashbrown::HashMap;
1093	/// let mut map: HashMap<&str, i32> = HashMap::new();
1094	/// // Map is empty and doesn't allocate memory
1095	/// assert_eq!(map.capacity(), `0`);
1096	///
1097	/// map.reserve(`10`);
1098	///
1099	/// // And now map can hold at least 10 elements
1100	/// assert!(map.capacity() >= `10`);
1101	/// ```
1102	#[cfg_attr(feature = "inline-more", inline)]
1103	pub fn reserve(&mut self, additional: usize) {
1104	self.table
1105	.reserve(additional, make_hasher::<_, V, S>(&self.hash_builder));
1106	}
1107
1108	/// Tries to reserve capacity for at least `additional` more elements to be inserted
1109	/// in the given `HashMap<K,V>`. The collection may reserve more space to avoid
1110	/// frequent reallocations.
1111	///
1112	/// # Errors
1113	///
1114	/// If the capacity overflows, or the allocator reports a failure, then an error
1115	/// is returned.
1116	///
1117	/// # Examples
1118	///
1119	/// ```
1120	/// use hashbrown::HashMap;
1121	///
1122	/// let mut map: HashMap<&str, isize> = HashMap::new();
1123	/// // Map is empty and doesn't allocate memory
1124	/// assert_eq!(map.capacity(), `0`);
1125	///
1126	/// map.try_reserve(`10`).expect("why is the test harness OOMing on 10 bytes?");
1127	///
1128	/// // And now map can hold at least 10 elements
1129	/// assert!(map.capacity() >= `10`);
1130	/// ```
1131	/// If the capacity overflows, or the allocator reports a failure, then an error
1132	/// is returned:
1133	/// ```
1134	/// # fn test() {
1135	/// use hashbrown::HashMap;
1136	/// use hashbrown::TryReserveError;
1137	/// let mut map: HashMap<i32, i32> = HashMap::new();
1138	///
1139	/// match map.try_reserve(usize::MAX) {
1140	/// Err(error) => match error {
1141	/// TryReserveError::CapacityOverflow => {}
1142	/// _ => panic!("TryReserveError::AllocError ?"),
1143	/// },
1144	/// _ => panic!(),
1145	/// }
1146	/// # }
1147	/// # fn main() {
1148	/// # #[cfg(not(miri))]
1149	/// # test()
1150	/// # }
1151	/// ```
1152	#[cfg_attr(feature = "inline-more", inline)]
1153	pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
1154	self.table
1155	.try_reserve(additional, make_hasher::<_, V, S>(&self.hash_builder))
1156	}
1157
1158	/// Shrinks the capacity of the map as much as possible. It will drop
1159	/// down as much as possible while maintaining the internal rules
1160	/// and possibly leaving some space in accordance with the resize policy.
1161	///
1162	/// # Examples
1163	///
1164	/// ```
1165	/// use hashbrown::HashMap;
1166	///
1167	/// let mut map: HashMap<i32, i32> = HashMap::with_capacity(`100`);
1168	/// map.insert(`1`, `2`);
1169	/// map.insert(`3`, `4`);
1170	/// assert!(map.capacity() >= `100`);
1171	/// map.shrink_to_fit();
1172	/// assert!(map.capacity() >= `2`);
1173	/// ```
1174	#[cfg_attr(feature = "inline-more", inline)]
1175	pub fn shrink_to_fit(&mut self) {
1176	self.table
1177	.shrink_to(`0`, make_hasher::<_, V, S>(&self.hash_builder));
1178	}
1179
1180	/// Shrinks the capacity of the map with a lower limit. It will drop
1181	/// down no lower than the supplied limit while maintaining the internal rules
1182	/// and possibly leaving some space in accordance with the resize policy.
1183	///
1184	/// This function does nothing if the current capacity is smaller than the
1185	/// supplied minimum capacity.
1186	///
1187	/// # Examples
1188	///
1189	/// ```
1190	/// use hashbrown::HashMap;
1191	///
1192	/// let mut map: HashMap<i32, i32> = HashMap::with_capacity(`100`);
1193	/// map.insert(`1`, `2`);
1194	/// map.insert(`3`, `4`);
1195	/// assert!(map.capacity() >= `100`);
1196	/// map.shrink_to(`10`);
1197	/// assert!(map.capacity() >= `10`);
1198	/// map.shrink_to(`0`);
1199	/// assert!(map.capacity() >= `2`);
1200	/// map.shrink_to(`10`);
1201	/// assert!(map.capacity() >= `2`);
1202	/// ```
1203	#[cfg_attr(feature = "inline-more", inline)]
1204	pub fn shrink_to(&mut self, min_capacity: usize) {
1205	self.table
1206	.shrink_to(min_capacity, make_hasher::<_, V, S>(&self.hash_builder));
1207	}
1208
1209	/// Gets the given key's corresponding entry in the map for in-place manipulation.
1210	///
1211	/// # Examples
1212	///
1213	/// ```
1214	/// use hashbrown::HashMap;
1215	///
1216	/// let mut letters = HashMap::new();
1217	///
1218	/// for ch in "a short treatise on fungi".chars() {
1219	/// let counter = letters.entry(ch).or_insert(`0`);
1220	/// *counter += `1`;
1221	/// }
1222	///
1223	/// assert_eq!(letters[&'s'], `2`);
1224	/// assert_eq!(letters[&'t'], `3`);
1225	/// assert_eq!(letters[&'u'], `1`);
1226	/// assert_eq!(letters.get(&'y'), None);
1227	/// ```
1228	#[cfg_attr(feature = "inline-more", inline)]
1229	pub fn entry(&mut self, key: K) -> Entry<'_, K, V, S, A> {
1230	let hash = make_hash::<K, S>(&self.hash_builder, &key);
1231	if let Some(elem) = self.table.find(hash, equivalent_key(&key)) {
1232	Entry::Occupied(OccupiedEntry {
1233	hash,
1234	elem,
1235	table: self,
1236	})
1237	} else {
1238	Entry::Vacant(VacantEntry {
1239	hash,
1240	key,
1241	table: self,
1242	})
1243	}
1244	}
1245
1246	/// Gets the given key's corresponding entry by reference in the map for in-place manipulation.
1247	///
1248	/// # Examples
1249	///
1250	/// ```
1251	/// use hashbrown::HashMap;
1252	///
1253	/// let mut words: HashMap<String, usize> = HashMap::new();
1254	/// let source = ["poneyland", "horseyland", "poneyland", "poneyland"];
1255	/// for (i, &s) in source.iter().enumerate() {
1256	/// let counter = words.entry_ref(s).or_insert(`0`);
1257	/// *counter += `1`;
1258	/// }
1259	///
1260	/// assert_eq!(words["poneyland"], `3`);
1261	/// assert_eq!(words["horseyland"], `1`);
1262	/// ```
1263	#[cfg_attr(feature = "inline-more", inline)]
1264	pub fn entry_ref<'a, 'b, Q>(&'a mut self, key: &'b Q) -> EntryRef<'a, 'b, K, Q, V, S, A>
1265	where
1266	Q: Hash + Equivalent<K> + ?Sized,
1267	{
1268	let hash = make_hash::<Q, S>(&self.hash_builder, key);
1269	if let Some(elem) = self.table.find(hash, equivalent_key(key)) {
1270	EntryRef::Occupied(OccupiedEntry {
1271	hash,
1272	elem,
1273	table: self,
1274	})
1275	} else {
1276	EntryRef::Vacant(VacantEntryRef {
1277	hash,
1278	key,
1279	table: self,
1280	})
1281	}
1282	}
1283
1284	/// Returns a reference to the value corresponding to the key.
1285	///
1286	/// The key may be any borrowed form of the map's key type, but
1287	/// [`Hash`] and [`Eq`] on the borrowed form must* match those for*
1288	/// the key type.
1289	///
1290	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
1291	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
1292	///
1293	/// # Examples
1294	///
1295	/// ```
1296	/// use hashbrown::HashMap;
1297	///
1298	/// let mut map = HashMap::new();
1299	/// map.insert(`1`, "a");
1300	/// assert_eq!(map.get(&`1`), Some(&"a"));
1301	/// assert_eq!(map.get(&`2`), None);
1302	/// ```
1303	#[inline]
1304	pub fn get<Q>(&self, k: &Q) -> Option<&V>
1305	where
1306	Q: Hash + Equivalent<K> + ?Sized,
1307	{
1308	// Avoid `Option::map` because it bloats LLVM IR.
1309	match self.get_inner(k) {
1310	Some((_, v)) => Some(v),
1311	None => None,
1312	}
1313	}
1314
1315	/// Returns the key-value pair corresponding to the supplied key.
1316	///
1317	/// The supplied key may be any borrowed form of the map's key type, but
1318	/// [`Hash`] and [`Eq`] on the borrowed form must* match those for*
1319	/// the key type.
1320	///
1321	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
1322	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
1323	///
1324	/// # Examples
1325	///
1326	/// ```
1327	/// use hashbrown::HashMap;
1328	///
1329	/// let mut map = HashMap::new();
1330	/// map.insert(`1`, "a");
1331	/// assert_eq!(map.get_key_value(&`1`), Some((&`1`, &"a")));
1332	/// assert_eq!(map.get_key_value(&`2`), None);
1333	/// ```
1334	#[inline]
1335	pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>
1336	where
1337	Q: Hash + Equivalent<K> + ?Sized,
1338	{
1339	// Avoid `Option::map` because it bloats LLVM IR.
1340	match self.get_inner(k) {
1341	Some((key, value)) => Some((key, value)),
1342	None => None,
1343	}
1344	}
1345
1346	#[inline]
1347	fn get_inner<Q>(&self, k: &Q) -> Option<&(K, V)>
1348	where
1349	Q: Hash + Equivalent<K> + ?Sized,
1350	{
1351	if self.table.is_empty() {
1352	None
1353	} else {
1354	let hash = make_hash::<Q, S>(&self.hash_builder, k);
1355	self.table.get(hash, equivalent_key(k))
1356	}
1357	}
1358
1359	/// Returns the key-value pair corresponding to the supplied key, with a mutable reference to value.
1360	///
1361	/// The supplied key may be any borrowed form of the map's key type, but
1362	/// [`Hash`] and [`Eq`] on the borrowed form must* match those for*
1363	/// the key type.
1364	///
1365	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
1366	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
1367	///
1368	/// # Examples
1369	///
1370	/// ```
1371	/// use hashbrown::HashMap;
1372	///
1373	/// let mut map = HashMap::new();
1374	/// map.insert(`1`, "a");
1375	/// let (k, v) = map.get_key_value_mut(&`1`).unwrap();
1376	/// assert_eq!(k, &`1`);
1377	/// assert_eq!(v, &mut "a");
1378	/// *v = "b";
1379	/// assert_eq!(map.get_key_value_mut(&`1`), Some((&`1`, &mut "b")));
1380	/// assert_eq!(map.get_key_value_mut(&`2`), None);
1381	/// ```
1382	#[inline]
1383	pub fn get_key_value_mut<Q>(&mut self, k: &Q) -> Option<(&K, &mut V)>
1384	where
1385	Q: Hash + Equivalent<K> + ?Sized,
1386	{
1387	// Avoid `Option::map` because it bloats LLVM IR.
1388	match self.get_inner_mut(k) {
1389	Some(&mut (ref key, ref mut value)) => Some((key, value)),
1390	None => None,
1391	}
1392	}
1393
1394	/// Returns `true` if the map contains a value for the specified key.
1395	///
1396	/// The key may be any borrowed form of the map's key type, but
1397	/// [`Hash`] and [`Eq`] on the borrowed form must* match those for*
1398	/// the key type.
1399	///
1400	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
1401	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
1402	///
1403	/// # Examples
1404	///
1405	/// ```
1406	/// use hashbrown::HashMap;
1407	///
1408	/// let mut map = HashMap::new();
1409	/// map.insert(`1`, "a");
1410	/// assert_eq!(map.contains_key(&`1`), `true`);
1411	/// assert_eq!(map.contains_key(&`2`), `false`);
1412	/// ```
1413	#[cfg_attr(feature = "inline-more", inline)]
1414	pub fn contains_key<Q>(&self, k: &Q) -> bool
1415	where
1416	Q: Hash + Equivalent<K> + ?Sized,
1417	{
1418	self.get_inner(k).is_some()
1419	}
1420
1421	/// Returns a mutable reference to the value corresponding to the key.
1422	///
1423	/// The key may be any borrowed form of the map's key type, but
1424	/// [`Hash`] and [`Eq`] on the borrowed form must* match those for*
1425	/// the key type.
1426	///
1427	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
1428	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
1429	///
1430	/// # Examples
1431	///
1432	/// ```
1433	/// use hashbrown::HashMap;
1434	///
1435	/// let mut map = HashMap::new();
1436	/// map.insert(`1`, "a");
1437	/// if let Some(x) = map.get_mut(&`1`) {
1438	/// *x = "b";
1439	/// }
1440	/// assert_eq!(map[&`1`], "b");
1441	///
1442	/// assert_eq!(map.get_mut(&`2`), None);
1443	/// ```
1444	#[cfg_attr(feature = "inline-more", inline)]
1445	pub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
1446	where
1447	Q: Hash + Equivalent<K> + ?Sized,
1448	{
1449	// Avoid `Option::map` because it bloats LLVM IR.
1450	match self.get_inner_mut(k) {
1451	Some(&mut (_, ref mut v)) => Some(v),
1452	None => None,
1453	}
1454	}
1455
1456	#[inline]
1457	fn get_inner_mut<Q>(&mut self, k: &Q) -> Option<&mut (K, V)>
1458	where
1459	Q: Hash + Equivalent<K> + ?Sized,
1460	{
1461	if self.table.is_empty() {
1462	None
1463	} else {
1464	let hash = make_hash::<Q, S>(&self.hash_builder, k);
1465	self.table.get_mut(hash, equivalent_key(k))
1466	}
1467	}
1468
1469	/// Attempts to get mutable references to `N` values in the map at once.
1470	///
1471	/// Returns an array of length `N` with the results of each query. For soundness, at most one
1472	/// mutable reference will be returned to any value. `None` will be used if the key is missing.
1473	///
1474	/// # Panics
1475	///
1476	/// Panics if any keys are overlapping.
1477	///
1478	/// # Examples
1479	///
1480	/// ```
1481	/// use hashbrown::HashMap;
1482	///
1483	/// let mut libraries = HashMap::new();
1484	/// libraries.insert("Bodleian Library".to_string(), `1602`);
1485	/// libraries.insert("Athenæum".to_string(), `1807`);
1486	/// libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), `1691`);
1487	/// libraries.insert("Library of Congress".to_string(), `1800`);
1488	///
1489	/// // Get Athenæum and Bodleian Library
1490	/// let [Some(a), Some(b)] = libraries.get_many_mut([
1491	/// "Athenæum",
1492	/// "Bodleian Library",
1493	/// ]) else { panic!() };
1494	///
1495	/// // Assert values of Athenæum and Library of Congress
1496	/// let got = libraries.get_many_mut([
1497	/// "Athenæum",
1498	/// "Library of Congress",
1499	/// ]);
1500	/// assert_eq!(
1501	/// got,
1502	/// [
1503	/// Some(&mut `1807`),
1504	/// Some(&mut `1800`),
1505	/// ],
1506	/// );
1507	///
1508	/// // Missing keys result in None
1509	/// let got = libraries.get_many_mut([
1510	/// "Athenæum",
1511	/// "New York Public Library",
1512	/// ]);
1513	/// assert_eq!(
1514	/// got,
1515	/// [
1516	/// Some(&mut `1807`),
1517	/// None
1518	/// ]
1519	/// );
1520	/// ```
1521	///
1522	/// ```should_panic
1523	/// use hashbrown::HashMap;
1524	///
1525	/// let mut libraries = HashMap::new();
1526	/// libraries.insert("Athenæum".to_string(), `1807`);
1527	///
1528	/// // Duplicate keys panic!
1529	/// let got = libraries.get_many_mut([
1530	/// "Athenæum",
1531	/// "Athenæum",
1532	/// ]);
1533	/// ```
1534	pub fn get_many_mut<Q, const N: usize>(&mut self, ks: [&Q; N]) -> [Option<&'_ mut V>; N]
1535	where
1536	Q: Hash + Equivalent<K> + ?Sized,
1537	{
1538	self.get_many_mut_inner(ks).map(\|res\| res.map(\|(_, v)\| v))
1539	}
1540
1541	/// Attempts to get mutable references to `N` values in the map at once, without validating that
1542	/// the values are unique.
1543	///
1544	/// Returns an array of length `N` with the results of each query. `None` will be used if
1545	/// the key is missing.
1546	///
1547	/// For a safe alternative see [`get_many_mut`](`HashMap::get_many_mut`).
1548	///
1549	/// # Safety
1550	///
1551	/// Calling this method with overlapping keys is [undefined behavior]* even if the resulting*
1552	/// references are not used.
1553	///
1554	/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1555	///
1556	/// # Examples
1557	///
1558	/// ```
1559	/// use hashbrown::HashMap;
1560	///
1561	/// let mut libraries = HashMap::new();
1562	/// libraries.insert("Bodleian Library".to_string(), `1602`);
1563	/// libraries.insert("Athenæum".to_string(), `1807`);
1564	/// libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), `1691`);
1565	/// libraries.insert("Library of Congress".to_string(), `1800`);
1566	///
1567	/// // SAFETY: The keys do not overlap.
1568	/// let [Some(a), Some(b)] = (unsafe { libraries.get_many_unchecked_mut([
1569	/// "Athenæum",
1570	/// "Bodleian Library",
1571	/// ]) }) else { panic!() };
1572	///
1573	/// // SAFETY: The keys do not overlap.
1574	/// let got = unsafe { libraries.get_many_unchecked_mut([
1575	/// "Athenæum",
1576	/// "Library of Congress",
1577	/// ]) };
1578	/// assert_eq!(
1579	/// got,
1580	/// [
1581	/// Some(&mut `1807`),
1582	/// Some(&mut `1800`),
1583	/// ],
1584	/// );
1585	///
1586	/// // SAFETY: The keys do not overlap.
1587	/// let got = unsafe { libraries.get_many_unchecked_mut([
1588	/// "Athenæum",
1589	/// "New York Public Library",
1590	/// ]) };
1591	/// // Missing keys result in None
1592	/// assert_eq!(got, [Some(&mut `1807`), None]);
1593	/// ```
1594	pub unsafe fn get_many_unchecked_mut<Q, const N: usize>(
1595	&mut self,
1596	ks: [&Q; N],
1597	) -> [Option<&'_ mut V>; N]
1598	where
1599	Q: Hash + Equivalent<K> + ?Sized,
1600	{
1601	self.get_many_unchecked_mut_inner(ks)
1602	.map(\|res\| res.map(\|(_, v)\| v))
1603	}
1604
1605	/// Attempts to get mutable references to `N` values in the map at once, with immutable
1606	/// references to the corresponding keys.
1607	///
1608	/// Returns an array of length `N` with the results of each query. For soundness, at most one
1609	/// mutable reference will be returned to any value. `None` will be used if the key is missing.
1610	///
1611	/// # Panics
1612	///
1613	/// Panics if any keys are overlapping.
1614	///
1615	/// # Examples
1616	///
1617	/// ```
1618	/// use hashbrown::HashMap;
1619	///
1620	/// let mut libraries = HashMap::new();
1621	/// libraries.insert("Bodleian Library".to_string(), `1602`);
1622	/// libraries.insert("Athenæum".to_string(), `1807`);
1623	/// libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), `1691`);
1624	/// libraries.insert("Library of Congress".to_string(), `1800`);
1625	///
1626	/// let got = libraries.get_many_key_value_mut([
1627	/// "Bodleian Library",
1628	/// "Herzogin-Anna-Amalia-Bibliothek",
1629	/// ]);
1630	/// assert_eq!(
1631	/// got,
1632	/// [
1633	/// Some((&"Bodleian Library".to_string(), &mut `1602`)),
1634	/// Some((&"Herzogin-Anna-Amalia-Bibliothek".to_string(), &mut `1691`)),
1635	/// ],
1636	/// );
1637	/// // Missing keys result in None
1638	/// let got = libraries.get_many_key_value_mut([
1639	/// "Bodleian Library",
1640	/// "Gewandhaus",
1641	/// ]);
1642	/// assert_eq!(got, [Some((&"Bodleian Library".to_string(), &mut `1602`)), None]);
1643	/// ```
1644	///
1645	/// ```should_panic
1646	/// use hashbrown::HashMap;
1647	///
1648	/// let mut libraries = HashMap::new();
1649	/// libraries.insert("Bodleian Library".to_string(), `1602`);
1650	/// libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), `1691`);
1651	///
1652	/// // Duplicate keys result in panic!
1653	/// let got = libraries.get_many_key_value_mut([
1654	/// "Bodleian Library",
1655	/// "Herzogin-Anna-Amalia-Bibliothek",
1656	/// "Herzogin-Anna-Amalia-Bibliothek",
1657	/// ]);
1658	/// ```
1659	pub fn get_many_key_value_mut<Q, const N: usize>(
1660	&mut self,
1661	ks: [&Q; N],
1662	) -> [Option<(&'_ K, &'_ mut V)>; N]
1663	where
1664	Q: Hash + Equivalent<K> + ?Sized,
1665	{
1666	self.get_many_mut_inner(ks)
1667	.map(\|res\| res.map(\|(k, v)\| (&*k, v)))
1668	}
1669
1670	/// Attempts to get mutable references to `N` values in the map at once, with immutable
1671	/// references to the corresponding keys, without validating that the values are unique.
1672	///
1673	/// Returns an array of length `N` with the results of each query. `None` will be returned if
1674	/// any of the keys are missing.
1675	///
1676	/// For a safe alternative see [`get_many_key_value_mut`](`HashMap::get_many_key_value_mut`).
1677	///
1678	/// # Safety
1679	///
1680	/// Calling this method with overlapping keys is [undefined behavior]* even if the resulting*
1681	/// references are not used.
1682	///
1683	/// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
1684	///
1685	/// # Examples
1686	///
1687	/// ```
1688	/// use hashbrown::HashMap;
1689	///
1690	/// let mut libraries = HashMap::new();
1691	/// libraries.insert("Bodleian Library".to_string(), `1602`);
1692	/// libraries.insert("Athenæum".to_string(), `1807`);
1693	/// libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), `1691`);
1694	/// libraries.insert("Library of Congress".to_string(), `1800`);
1695	///
1696	/// let got = libraries.get_many_key_value_mut([
1697	/// "Bodleian Library",
1698	/// "Herzogin-Anna-Amalia-Bibliothek",
1699	/// ]);
1700	/// assert_eq!(
1701	/// got,
1702	/// [
1703	/// Some((&"Bodleian Library".to_string(), &mut `1602`)),
1704	/// Some((&"Herzogin-Anna-Amalia-Bibliothek".to_string(), &mut `1691`)),
1705	/// ],
1706	/// );
1707	/// // Missing keys result in None
1708	/// let got = libraries.get_many_key_value_mut([
1709	/// "Bodleian Library",
1710	/// "Gewandhaus",
1711	/// ]);
1712	/// assert_eq!(
1713	/// got,
1714	/// [
1715	/// Some((&"Bodleian Library".to_string(), &mut `1602`)),
1716	/// None,
1717	/// ],
1718	/// );
1719	/// ```
1720	pub unsafe fn get_many_key_value_unchecked_mut<Q, const N: usize>(
1721	&mut self,
1722	ks: [&Q; N],
1723	) -> [Option<(&'_ K, &'_ mut V)>; N]
1724	where
1725	Q: Hash + Equivalent<K> + ?Sized,
1726	{
1727	self.get_many_unchecked_mut_inner(ks)
1728	.map(\|res\| res.map(\|(k, v)\| (&*k, v)))
1729	}
1730
1731	fn get_many_mut_inner<Q, const N: usize>(&mut self, ks: [&Q; N]) -> [Option<&'_ mut (K, V)>; N]
1732	where
1733	Q: Hash + Equivalent<K> + ?Sized,
1734	{
1735	let hashes = self.build_hashes_inner(ks);
1736	self.table
1737	.get_many_mut(hashes, \|i, (k, _)\| ks[i].equivalent(k))
1738	}
1739
1740	unsafe fn get_many_unchecked_mut_inner<Q, const N: usize>(
1741	&mut self,
1742	ks: [&Q; N],
1743	) -> [Option<&'_ mut (K, V)>; N]
1744	where
1745	Q: Hash + Equivalent<K> + ?Sized,
1746	{
1747	let hashes = self.build_hashes_inner(ks);
1748	self.table
1749	.get_many_unchecked_mut(hashes, \|i, (k, _)\| ks[i].equivalent(k))
1750	}
1751
1752	fn build_hashes_inner<Q, const N: usize>(&self, ks: [&Q; N]) -> [u64; N]
1753	where
1754	Q: Hash + Equivalent<K> + ?Sized,
1755	{
1756	let mut hashes = [`0_u64`; N];
1757	for i in `0`..N {
1758	hashes[i] = make_hash::<Q, S>(&self.hash_builder, ks[i]);
1759	}
1760	hashes
1761	}
1762
1763	/// Inserts a key-value pair into the map.
1764	///
1765	/// If the map did not have this key present, [`None`] is returned.
1766	///
1767	/// If the map did have this key present, the value is updated, and the old
1768	/// value is returned. The key is not updated, though; this matters for
1769	/// types that can be `==` without being identical. See the [`std::collections`]
1770	/// [module-level documentation] for more.
1771	///
1772	/// [`None`]: https://doc.rust-lang.org/std/option/enum.Option.html#variant.None
1773	/// [`std::collections`]: https://doc.rust-lang.org/std/collections/index.html
1774	/// [module-level documentation]: https://doc.rust-lang.org/std/collections/index.html#insert-and-complex-keys
1775	///
1776	/// # Examples
1777	///
1778	/// ```
1779	/// use hashbrown::HashMap;
1780	///
1781	/// let mut map = HashMap::new();
1782	/// assert_eq!(map.insert(`37`, "a"), None);
1783	/// assert_eq!(map.is_empty(), `false`);
1784	///
1785	/// map.insert(`37`, "b");
1786	/// assert_eq!(map.insert(`37`, "c"), Some("b"));
1787	/// assert_eq!(map[&`37`], "c");
1788	/// ```
1789	#[cfg_attr(feature = "inline-more", inline)]
1790	pub fn insert(&mut self, k: K, v: V) -> Option<V> {
1791	let hash = make_hash::<K, S>(&self.hash_builder, &k);
1792	match self.find_or_find_insert_slot(hash, &k) {
1793	Ok(bucket) => Some(mem::replace(unsafe { &mut bucket.as_mut().1 }, v)),
1794	Err(slot) => {
1795	unsafe {
1796	self.table.insert_in_slot(hash, slot, (k, v));
1797	}
1798	None
1799	}
1800	}
1801	}
1802
1803	#[cfg_attr(feature = "inline-more", inline)]
1804	pub(crate) fn find_or_find_insert_slot<Q>(
1805	&mut self,
1806	hash: u64,
1807	key: &Q,
1808	) -> Result<Bucket<(K, V)>, crate::raw::InsertSlot>
1809	where
1810	Q: Equivalent<K> + ?Sized,
1811	{
1812	self.table.find_or_find_insert_slot(
1813	hash,
1814	equivalent_key(key),
1815	make_hasher(&self.hash_builder),
1816	)
1817	}
1818
1819	/// Insert a key-value pair into the map without checking
1820	/// if the key already exists in the map.
1821	///
1822	/// This operation is faster than regular insert, because it does not perform
1823	/// lookup before insertion.
1824	///
1825	/// This operation is useful during initial population of the map.
1826	/// For example, when constructing a map from another map, we know
1827	/// that keys are unique.
1828	///
1829	/// Returns a reference to the key and value just inserted.
1830	///
1831	/// # Safety
1832	///
1833	/// This operation is safe if a key does not exist in the map.
1834	///
1835	/// However, if a key exists in the map already, the behavior is unspecified:
1836	/// this operation may panic, loop forever, or any following operation with the map
1837	/// may panic, loop forever or return arbitrary result.
1838	///
1839	/// That said, this operation (and following operations) are guaranteed to
1840	/// not violate memory safety.
1841	///
1842	/// However this operation is still unsafe because the resulting `HashMap`
1843	/// may be passed to unsafe code which does expect the map to behave
1844	/// correctly, and would cause unsoundness as a result.
1845	///
1846	/// # Examples
1847	///
1848	/// ```
1849	/// use hashbrown::HashMap;
1850	///
1851	/// let mut map1 = HashMap::new();
1852	/// assert_eq!(map1.insert(`1`, "a"), None);
1853	/// assert_eq!(map1.insert(`2`, "b"), None);
1854	/// assert_eq!(map1.insert(`3`, "c"), None);
1855	/// assert_eq!(map1.len(), `3`);
1856	///
1857	/// let mut map2 = HashMap::new();
1858	///
1859	/// for (key, value) in map1.into_iter() {
1860	/// unsafe {
1861	/// map2.insert_unique_unchecked(key, value);
1862	/// }
1863	/// }
1864	///
1865	/// let (key, value) = unsafe { map2.insert_unique_unchecked(`4`, "d") };
1866	/// assert_eq!(key, &`4`);
1867	/// assert_eq!(value, &mut "d");
1868	/// *value = "e";
1869	///
1870	/// assert_eq!(map2[&`1`], "a");
1871	/// assert_eq!(map2[&`2`], "b");
1872	/// assert_eq!(map2[&`3`], "c");
1873	/// assert_eq!(map2[&`4`], "e");
1874	/// assert_eq!(map2.len(), `4`);
1875	/// ```
1876	#[cfg_attr(feature = "inline-more", inline)]
1877	pub unsafe fn insert_unique_unchecked(&mut self, k: K, v: V) -> (&K, &mut V) {
1878	let hash = make_hash::<K, S>(&self.hash_builder, &k);
1879	let bucket = self
1880	.table
1881	.insert(hash, (k, v), make_hasher::<_, V, S>(&self.hash_builder));
1882	let (k_ref, v_ref) = unsafe { bucket.as_mut() };
1883	(k_ref, v_ref)
1884	}
1885
1886	/// Tries to insert a key-value pair into the map, and returns
1887	/// a mutable reference to the value in the entry.
1888	///
1889	/// # Errors
1890	///
1891	/// If the map already had this key present, nothing is updated, and
1892	/// an error containing the occupied entry and the value is returned.
1893	///
1894	/// # Examples
1895	///
1896	/// Basic usage:
1897	///
1898	/// ```
1899	/// use hashbrown::HashMap;
1900	/// use hashbrown::hash_map::OccupiedError;
1901	///
1902	/// let mut map = HashMap::new();
1903	/// assert_eq!(map.try_insert(`37`, "a").unwrap(), &"a");
1904	///
1905	/// match map.try_insert(`37`, "b") {
1906	/// Err(OccupiedError { entry, value }) => {
1907	/// assert_eq!(entry.key(), &`37`);
1908	/// assert_eq!(entry.get(), &"a");
1909	/// assert_eq!(value, "b");
1910	/// }
1911	/// _ => panic!()
1912	/// }
1913	/// ```
1914	#[cfg_attr(feature = "inline-more", inline)]
1915	pub fn try_insert(
1916	&mut self,
1917	key: K,
1918	value: V,
1919	) -> Result<&mut V, OccupiedError<'_, K, V, S, A>> {
1920	match self.entry(key) {
1921	Entry::Occupied(entry) => Err(OccupiedError { entry, value }),
1922	Entry::Vacant(entry) => Ok(entry.insert(value)),
1923	}
1924	}
1925
1926	/// Removes a key from the map, returning the value at the key if the key
1927	/// was previously in the map. Keeps the allocated memory for reuse.
1928	///
1929	/// The key may be any borrowed form of the map's key type, but
1930	/// [`Hash`] and [`Eq`] on the borrowed form must* match those for*
1931	/// the key type.
1932	///
1933	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
1934	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
1935	///
1936	/// # Examples
1937	///
1938	/// ```
1939	/// use hashbrown::HashMap;
1940	///
1941	/// let mut map = HashMap::new();
1942	/// // The map is empty
1943	/// assert!(map.is_empty() && map.capacity() == `0`);
1944	///
1945	/// map.insert(`1`, "a");
1946	///
1947	/// assert_eq!(map.remove(&`1`), Some("a"));
1948	/// assert_eq!(map.remove(&`1`), None);
1949	///
1950	/// // Now map holds none elements
1951	/// assert!(map.is_empty());
1952	/// ```
1953	#[cfg_attr(feature = "inline-more", inline)]
1954	pub fn remove<Q>(&mut self, k: &Q) -> Option<V>
1955	where
1956	Q: Hash + Equivalent<K> + ?Sized,
1957	{
1958	// Avoid `Option::map` because it bloats LLVM IR.
1959	match self.remove_entry(k) {
1960	Some((_, v)) => Some(v),
1961	None => None,
1962	}
1963	}
1964
1965	/// Removes a key from the map, returning the stored key and value if the
1966	/// key was previously in the map. Keeps the allocated memory for reuse.
1967	///
1968	/// The key may be any borrowed form of the map's key type, but
1969	/// [`Hash`] and [`Eq`] on the borrowed form must* match those for*
1970	/// the key type.
1971	///
1972	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
1973	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
1974	///
1975	/// # Examples
1976	///
1977	/// ```
1978	/// use hashbrown::HashMap;
1979	///
1980	/// let mut map = HashMap::new();
1981	/// // The map is empty
1982	/// assert!(map.is_empty() && map.capacity() == `0`);
1983	///
1984	/// map.insert(`1`, "a");
1985	///
1986	/// assert_eq!(map.remove_entry(&`1`), Some((`1`, "a")));
1987	/// assert_eq!(map.remove(&`1`), None);
1988	///
1989	/// // Now map hold none elements
1990	/// assert!(map.is_empty());
1991	/// ```
1992	#[cfg_attr(feature = "inline-more", inline)]
1993	pub fn remove_entry<Q>(&mut self, k: &Q) -> Option<(K, V)>
1994	where
1995	Q: Hash + Equivalent<K> + ?Sized,
1996	{
1997	let hash = make_hash::<Q, S>(&self.hash_builder, k);
1998	self.table.remove_entry(hash, equivalent_key(k))
1999	}
2000
2001	/// Returns the total amount of memory allocated internally by the hash
2002	/// set, in bytes.
2003	///
2004	/// The returned number is informational only. It is intended to be
2005	/// primarily used for memory profiling.
2006	#[inline]
2007	pub fn allocation_size(&self) -> usize {
2008	self.table.allocation_size()
2009	}
2010	}
2011
2012	impl<K, V, S, A> PartialEq for HashMap<K, V, S, A>
2013	where
2014	K: Eq + Hash,
2015	V: PartialEq,
2016	S: BuildHasher,
2017	A: Allocator,
2018	{
2019	fn eq(&self, other: &Self) -> bool {
2020	if self.len() != other.len() {
2021	return `false`;
2022	}
2023
2024	self.iter()
2025	.all(\|(key: &K, value: &V)\| other.get(key).map_or(default:`false`, \|v: &V\| value == v))
2026	}
2027	}
2028
2029	impl<K, V, S, A> Eq for HashMap<K, V, S, A>
2030	where
2031	K: Eq + Hash,
2032	V: Eq,
2033	S: BuildHasher,
2034	A: Allocator,
2035	{
2036	}
2037
2038	impl<K, V, S, A> Debug for HashMap<K, V, S, A>
2039	where
2040	K: Debug,
2041	V: Debug,
2042	A: Allocator,
2043	{
2044	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2045	f.debug_map().entries(self.iter()).finish()
2046	}
2047	}
2048
2049	impl<K, V, S, A> Default for HashMap<K, V, S, A>
2050	where
2051	S: Default,
2052	A: Default + Allocator,
2053	{
2054	/// Creates an empty `HashMap<K, V, S, A>`, with the `Default` value for the hasher and allocator.
2055	///
2056	/// # Examples
2057	///
2058	/// ```
2059	/// use hashbrown::HashMap;
2060	/// use std::collections::hash_map::RandomState;
2061	///
2062	/// // You can specify all types of HashMap, including hasher and allocator.
2063	/// // Created map is empty and don't allocate memory
2064	/// let map: HashMap<u32, String> = Default::default();
2065	/// assert_eq!(map.capacity(), `0`);
2066	/// let map: HashMap<u32, String, RandomState> = HashMap::default();
2067	/// assert_eq!(map.capacity(), `0`);
2068	/// ```
2069	#[cfg_attr(feature = "inline-more", inline)]
2070	fn default() -> Self {
2071	Self::with_hasher_in(hash_builder:Default::default(), alloc:Default::default())
2072	}
2073	}
2074
2075	impl<K, Q, V, S, A> Index<&Q> for HashMap<K, V, S, A>
2076	where
2077	K: Eq + Hash,
2078	Q: Hash + Equivalent<K> + ?Sized,
2079	S: BuildHasher,
2080	A: Allocator,
2081	{
2082	type Output = V;
2083
2084	/// Returns a reference to the value corresponding to the supplied key.
2085	///
2086	/// # Panics
2087	///
2088	/// Panics if the key is not present in the `HashMap`.
2089	///
2090	/// # Examples
2091	///
2092	/// ```
2093	/// use hashbrown::HashMap;
2094	///
2095	/// let map: HashMap<_, _> = [("a", "One"), ("b", "Two")].into();
2096	///
2097	/// assert_eq!(map[&"a"], "One");
2098	/// assert_eq!(map[&"b"], "Two");
2099	/// ```
2100	#[cfg_attr(feature = "inline-more", inline)]
2101	fn index(&self, key: &Q) -> &V {
2102	self.get(key).expect(msg:"no entry found for key")
2103	}
2104	}
2105
2106	// The default hasher is used to match the std implementation signature
2107	#[cfg(feature = "default-hasher")]
2108	impl<K, V, A, const N: usize> From<[(K, V); N]> for HashMap<K, V, DefaultHashBuilder, A>
2109	where
2110	K: Eq + Hash,
2111	A: Default + Allocator,
2112	{
2113	/// # Examples
2114	///
2115	/// ```
2116	/// use hashbrown::HashMap;
2117	///
2118	/// let map1 = HashMap::from([(1, 2), (3, 4)]);
2119	/// let map2: HashMap<_, _> = [(1, 2), (3, 4)].into();
2120	/// assert_eq!(map1, map2);
2121	/// ```
2122	fn from(arr: [(K, V); N]) -> Self {
2123	arr.into_iter().collect()
2124	}
2125	}
2126
2127	/// An iterator over the entries of a `HashMap` in arbitrary order.
2128	/// The iterator element type is `(&'a K, &'a V)`.
2129	///
2130	/// This `struct` is created by the [`iter`] method on [`HashMap`]. See its
2131	/// documentation for more.
2132	///
2133	/// [`iter`]: struct.HashMap.html#method.iter
2134	/// [`HashMap`]: struct.HashMap.html
2135	///
2136	/// # Examples
2137	///
2138	/// ```
2139	/// use hashbrown::HashMap;
2140	///
2141	/// let map: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2142	///
2143	/// let mut iter = map.iter();
2144	/// let mut vec = vec![iter.next(), iter.next(), iter.next()];
2145	///
2146	/// // The `Iter` iterator produces items in arbitrary order, so the
2147	/// // items must be sorted to test them against a sorted array.
2148	/// vec.sort_unstable();
2149	/// assert_eq!(vec, [Some((&`1`, &"a")), Some((&`2`, &"b")), Some((&`3`, &"c"))]);
2150	///
2151	/// // It is fused iterator
2152	/// assert_eq!(iter.next(), None);
2153	/// assert_eq!(iter.next(), None);
2154	/// ```
2155	pub struct Iter<'a, K, V> {
2156	inner: RawIter<(K, V)>,
2157	marker: PhantomData<(&'a K, &'a V)>,
2158	}
2159
2160	// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2161	impl<K, V> Clone for Iter<'_, K, V> {
2162	#[cfg_attr(feature = "inline-more", inline)]
2163	fn clone(&self) -> Self {
2164	Iter {
2165	inner: self.inner.clone(),
2166	marker: PhantomData,
2167	}
2168	}
2169	}
2170
2171	impl<K: Debug, V: Debug> fmt::Debug for Iter<'_, K, V> {
2172	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2173	f.debug_list().entries(self.clone()).finish()
2174	}
2175	}
2176
2177	/// A mutable iterator over the entries of a `HashMap` in arbitrary order.
2178	/// The iterator element type is `(&'a K, &'a mut V)`.
2179	///
2180	/// This `struct` is created by the [`iter_mut`] method on [`HashMap`]. See its
2181	/// documentation for more.
2182	///
2183	/// [`iter_mut`]: struct.HashMap.html#method.iter_mut
2184	/// [`HashMap`]: struct.HashMap.html
2185	///
2186	/// # Examples
2187	///
2188	/// ```
2189	/// use hashbrown::HashMap;
2190	///
2191	/// let mut map: HashMap<_, _> = [(`1`, "One".to_owned()), (`2`, "Two".into())].into();
2192	///
2193	/// let mut iter = map.iter_mut();
2194	/// iter.next().map(\|(_, v)\| v.push_str(" Mississippi"));
2195	/// iter.next().map(\|(_, v)\| v.push_str(" Mississippi"));
2196	///
2197	/// // It is fused iterator
2198	/// assert_eq!(iter.next(), None);
2199	/// assert_eq!(iter.next(), None);
2200	///
2201	/// assert_eq!(map.get(&`1`).unwrap(), &"One Mississippi".to_owned());
2202	/// assert_eq!(map.get(&`2`).unwrap(), &"Two Mississippi".to_owned());
2203	/// ```
2204	pub struct IterMut<'a, K, V> {
2205	inner: RawIter<(K, V)>,
2206	// To ensure invariance with respect to V
2207	marker: PhantomData<(&'a K, &'a mut V)>,
2208	}
2209
2210	// We override the default Send impl which has K: Sync instead of K: Send. Both
2211	// are correct, but this one is more general since it allows keys which
2212	// implement Send but not Sync.
2213	unsafe impl<K: Send, V: Send> Send for IterMut<'_, K, V> {}
2214
2215	impl<K, V> IterMut<'_, K, V> {
2216	/// Returns a iterator of references over the remaining items.
2217	#[cfg_attr(feature = "inline-more", inline)]
2218	pub(super) fn iter(&self) -> Iter<'_, K, V> {
2219	Iter {
2220	inner: self.inner.clone(),
2221	marker: PhantomData,
2222	}
2223	}
2224	}
2225
2226	/// An owning iterator over the entries of a `HashMap` in arbitrary order.
2227	/// The iterator element type is `(K, V)`.
2228	///
2229	/// This `struct` is created by the [`into_iter`] method on [`HashMap`]
2230	/// (provided by the [`IntoIterator`] trait). See its documentation for more.
2231	/// The map cannot be used after calling that method.
2232	///
2233	/// [`into_iter`]: struct.HashMap.html#method.into_iter
2234	/// [`HashMap`]: struct.HashMap.html
2235	/// [`IntoIterator`]: https://doc.rust-lang.org/core/iter/trait.IntoIterator.html
2236	///
2237	/// # Examples
2238	///
2239	/// ```
2240	/// use hashbrown::HashMap;
2241	///
2242	/// let map: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2243	///
2244	/// let mut iter = map.into_iter();
2245	/// let mut vec = vec![iter.next(), iter.next(), iter.next()];
2246	///
2247	/// // The `IntoIter` iterator produces items in arbitrary order, so the
2248	/// // items must be sorted to test them against a sorted array.
2249	/// vec.sort_unstable();
2250	/// assert_eq!(vec, [Some((`1`, "a")), Some((`2`, "b")), Some((`3`, "c"))]);
2251	///
2252	/// // It is fused iterator
2253	/// assert_eq!(iter.next(), None);
2254	/// assert_eq!(iter.next(), None);
2255	/// ```
2256	pub struct IntoIter<K, V, A: Allocator = Global> {
2257	inner: RawIntoIter<(K, V), A>,
2258	}
2259
2260	impl<K, V, A: Allocator> IntoIter<K, V, A> {
2261	/// Returns a iterator of references over the remaining items.
2262	#[cfg_attr(feature = "inline-more", inline)]
2263	pub(super) fn iter(&self) -> Iter<'_, K, V> {
2264	Iter {
2265	inner: self.inner.iter(),
2266	marker: PhantomData,
2267	}
2268	}
2269	}
2270
2271	/// An owning iterator over the keys of a `HashMap` in arbitrary order.
2272	/// The iterator element type is `K`.
2273	///
2274	/// This `struct` is created by the [`into_keys`] method on [`HashMap`].
2275	/// See its documentation for more.
2276	/// The map cannot be used after calling that method.
2277	///
2278	/// [`into_keys`]: struct.HashMap.html#method.into_keys
2279	/// [`HashMap`]: struct.HashMap.html
2280	///
2281	/// # Examples
2282	///
2283	/// ```
2284	/// use hashbrown::HashMap;
2285	///
2286	/// let map: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2287	///
2288	/// let mut keys = map.into_keys();
2289	/// let mut vec = vec![keys.next(), keys.next(), keys.next()];
2290	///
2291	/// // The `IntoKeys` iterator produces keys in arbitrary order, so the
2292	/// // keys must be sorted to test them against a sorted array.
2293	/// vec.sort_unstable();
2294	/// assert_eq!(vec, [Some(`1`), Some(`2`), Some(`3`)]);
2295	///
2296	/// // It is fused iterator
2297	/// assert_eq!(keys.next(), None);
2298	/// assert_eq!(keys.next(), None);
2299	/// ```
2300	pub struct IntoKeys<K, V, A: Allocator = Global> {
2301	inner: IntoIter<K, V, A>,
2302	}
2303
2304	impl<K, V, A: Allocator> Default for IntoKeys<K, V, A> {
2305	#[cfg_attr(feature = "inline-more", inline)]
2306	fn default() -> Self {
2307	Self {
2308	inner: Default::default(),
2309	}
2310	}
2311	}
2312	impl<K, V, A: Allocator> Iterator for IntoKeys<K, V, A> {
2313	type Item = K;
2314
2315	#[inline]
2316	fn next(&mut self) -> Option<K> {
2317	self.inner.next().map(\|(k: K, _)\| k)
2318	}
2319	#[inline]
2320	fn size_hint(&self) -> (usize, Option<usize>) {
2321	self.inner.size_hint()
2322	}
2323	#[inline]
2324	fn fold<B, F>(self, init: B, mut f: F) -> B
2325	where
2326	Self: Sized,
2327	F: FnMut(B, Self::Item) -> B,
2328	{
2329	self.inner.fold(init, \|acc: B, (k: K, _)\| f(acc, k))
2330	}
2331	}
2332
2333	impl<K, V, A: Allocator> ExactSizeIterator for IntoKeys<K, V, A> {
2334	#[inline]
2335	fn len(&self) -> usize {
2336	self.inner.len()
2337	}
2338	}
2339
2340	impl<K, V, A: Allocator> FusedIterator for IntoKeys<K, V, A> {}
2341
2342	impl<K: Debug, V: Debug, A: Allocator> fmt::Debug for IntoKeys<K, V, A> {
2343	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2344	f&mut DebugList<'_, '_>.debug_list()
2345	.entries(self.inner.iter().map(\|(k: &K, _)\| k))
2346	.finish()
2347	}
2348	}
2349
2350	/// An owning iterator over the values of a `HashMap` in arbitrary order.
2351	/// The iterator element type is `V`.
2352	///
2353	/// This `struct` is created by the [`into_values`] method on [`HashMap`].
2354	/// See its documentation for more. The map cannot be used after calling that method.
2355	///
2356	/// [`into_values`]: struct.HashMap.html#method.into_values
2357	/// [`HashMap`]: struct.HashMap.html
2358	///
2359	/// # Examples
2360	///
2361	/// ```
2362	/// use hashbrown::HashMap;
2363	///
2364	/// let map: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2365	///
2366	/// let mut values = map.into_values();
2367	/// let mut vec = vec![values.next(), values.next(), values.next()];
2368	///
2369	/// // The `IntoValues` iterator produces values in arbitrary order, so
2370	/// // the values must be sorted to test them against a sorted array.
2371	/// vec.sort_unstable();
2372	/// assert_eq!(vec, [Some("a"), Some("b"), Some("c")]);
2373	///
2374	/// // It is fused iterator
2375	/// assert_eq!(values.next(), None);
2376	/// assert_eq!(values.next(), None);
2377	/// ```
2378	pub struct IntoValues<K, V, A: Allocator = Global> {
2379	inner: IntoIter<K, V, A>,
2380	}
2381
2382	impl<K, V, A: Allocator> Default for IntoValues<K, V, A> {
2383	#[cfg_attr(feature = "inline-more", inline)]
2384	fn default() -> Self {
2385	Self {
2386	inner: Default::default(),
2387	}
2388	}
2389	}
2390	impl<K, V, A: Allocator> Iterator for IntoValues<K, V, A> {
2391	type Item = V;
2392
2393	#[inline]
2394	fn next(&mut self) -> Option<V> {
2395	self.inner.next().map(\|(_, v: V)\| v)
2396	}
2397	#[inline]
2398	fn size_hint(&self) -> (usize, Option<usize>) {
2399	self.inner.size_hint()
2400	}
2401	#[inline]
2402	fn fold<B, F>(self, init: B, mut f: F) -> B
2403	where
2404	Self: Sized,
2405	F: FnMut(B, Self::Item) -> B,
2406	{
2407	self.inner.fold(init, \|acc: B, (_, v: V)\| f(acc, v))
2408	}
2409	}
2410
2411	impl<K, V, A: Allocator> ExactSizeIterator for IntoValues<K, V, A> {
2412	#[inline]
2413	fn len(&self) -> usize {
2414	self.inner.len()
2415	}
2416	}
2417
2418	impl<K, V, A: Allocator> FusedIterator for IntoValues<K, V, A> {}
2419
2420	impl<K, V: Debug, A: Allocator> fmt::Debug for IntoValues<K, V, A> {
2421	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2422	f&mut DebugList<'_, '_>.debug_list()
2423	.entries(self.inner.iter().map(\|(_, v: &V)\| v))
2424	.finish()
2425	}
2426	}
2427
2428	/// An iterator over the keys of a `HashMap` in arbitrary order.
2429	/// The iterator element type is `&'a K`.
2430	///
2431	/// This `struct` is created by the [`keys`] method on [`HashMap`]. See its
2432	/// documentation for more.
2433	///
2434	/// [`keys`]: struct.HashMap.html#method.keys
2435	/// [`HashMap`]: struct.HashMap.html
2436	///
2437	/// # Examples
2438	///
2439	/// ```
2440	/// use hashbrown::HashMap;
2441	///
2442	/// let map: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2443	///
2444	/// let mut keys = map.keys();
2445	/// let mut vec = vec![keys.next(), keys.next(), keys.next()];
2446	///
2447	/// // The `Keys` iterator produces keys in arbitrary order, so the
2448	/// // keys must be sorted to test them against a sorted array.
2449	/// vec.sort_unstable();
2450	/// assert_eq!(vec, [Some(&`1`), Some(&`2`), Some(&`3`)]);
2451	///
2452	/// // It is fused iterator
2453	/// assert_eq!(keys.next(), None);
2454	/// assert_eq!(keys.next(), None);
2455	/// ```
2456	pub struct Keys<'a, K, V> {
2457	inner: Iter<'a, K, V>,
2458	}
2459
2460	// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2461	impl<K, V> Clone for Keys<'_, K, V> {
2462	#[cfg_attr(feature = "inline-more", inline)]
2463	fn clone(&self) -> Self {
2464	Keys {
2465	inner: self.inner.clone(),
2466	}
2467	}
2468	}
2469
2470	impl<K: Debug, V> fmt::Debug for Keys<'_, K, V> {
2471	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2472	f.debug_list().entries(self.clone()).finish()
2473	}
2474	}
2475
2476	/// An iterator over the values of a `HashMap` in arbitrary order.
2477	/// The iterator element type is `&'a V`.
2478	///
2479	/// This `struct` is created by the [`values`] method on [`HashMap`]. See its
2480	/// documentation for more.
2481	///
2482	/// [`values`]: struct.HashMap.html#method.values
2483	/// [`HashMap`]: struct.HashMap.html
2484	///
2485	/// # Examples
2486	///
2487	/// ```
2488	/// use hashbrown::HashMap;
2489	///
2490	/// let map: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2491	///
2492	/// let mut values = map.values();
2493	/// let mut vec = vec![values.next(), values.next(), values.next()];
2494	///
2495	/// // The `Values` iterator produces values in arbitrary order, so the
2496	/// // values must be sorted to test them against a sorted array.
2497	/// vec.sort_unstable();
2498	/// assert_eq!(vec, [Some(&"a"), Some(&"b"), Some(&"c")]);
2499	///
2500	/// // It is fused iterator
2501	/// assert_eq!(values.next(), None);
2502	/// assert_eq!(values.next(), None);
2503	/// ```
2504	pub struct Values<'a, K, V> {
2505	inner: Iter<'a, K, V>,
2506	}
2507
2508	// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
2509	impl<K, V> Clone for Values<'_, K, V> {
2510	#[cfg_attr(feature = "inline-more", inline)]
2511	fn clone(&self) -> Self {
2512	Values {
2513	inner: self.inner.clone(),
2514	}
2515	}
2516	}
2517
2518	impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
2519	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2520	f.debug_list().entries(self.clone()).finish()
2521	}
2522	}
2523
2524	/// A draining iterator over the entries of a `HashMap` in arbitrary
2525	/// order. The iterator element type is `(K, V)`.
2526	///
2527	/// This `struct` is created by the [`drain`] method on [`HashMap`]. See its
2528	/// documentation for more.
2529	///
2530	/// [`drain`]: struct.HashMap.html#method.drain
2531	/// [`HashMap`]: struct.HashMap.html
2532	///
2533	/// # Examples
2534	///
2535	/// ```
2536	/// use hashbrown::HashMap;
2537	///
2538	/// let mut map: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2539	///
2540	/// let mut drain_iter = map.drain();
2541	/// let mut vec = vec![drain_iter.next(), drain_iter.next(), drain_iter.next()];
2542	///
2543	/// // The `Drain` iterator produces items in arbitrary order, so the
2544	/// // items must be sorted to test them against a sorted array.
2545	/// vec.sort_unstable();
2546	/// assert_eq!(vec, [Some((`1`, "a")), Some((`2`, "b")), Some((`3`, "c"))]);
2547	///
2548	/// // It is fused iterator
2549	/// assert_eq!(drain_iter.next(), None);
2550	/// assert_eq!(drain_iter.next(), None);
2551	/// ```
2552	pub struct Drain<'a, K, V, A: Allocator = Global> {
2553	inner: RawDrain<'a, (K, V), A>,
2554	}
2555
2556	impl<K, V, A: Allocator> Drain<'_, K, V, A> {
2557	/// Returns a iterator of references over the remaining items.
2558	#[cfg_attr(feature = "inline-more", inline)]
2559	pub(super) fn iter(&self) -> Iter<'_, K, V> {
2560	Iter {
2561	inner: self.inner.iter(),
2562	marker: PhantomData,
2563	}
2564	}
2565	}
2566
2567	/// A draining iterator over entries of a `HashMap` which don't satisfy the predicate
2568	/// `f(&k, &mut v)` in arbitrary order. The iterator element type is `(K, V)`.
2569	///
2570	/// This `struct` is created by the [`extract_if`] method on [`HashMap`]. See its
2571	/// documentation for more.
2572	///
2573	/// [`extract_if`]: struct.HashMap.html#method.extract_if
2574	/// [`HashMap`]: struct.HashMap.html
2575	///
2576	/// # Examples
2577	///
2578	/// ```
2579	/// use hashbrown::HashMap;
2580	///
2581	/// let mut map: HashMap<i32, &str> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
2582	///
2583	/// let mut extract_if = map.extract_if(\|k, _v\| k % `2` != `0`);
2584	/// let mut vec = vec![extract_if.next(), extract_if.next()];
2585	///
2586	/// // The `ExtractIf` iterator produces items in arbitrary order, so the
2587	/// // items must be sorted to test them against a sorted array.
2588	/// vec.sort_unstable();
2589	/// assert_eq!(vec, [Some((`1`, "a")),Some((`3`, "c"))]);
2590	///
2591	/// // It is fused iterator
2592	/// assert_eq!(extract_if.next(), None);
2593	/// assert_eq!(extract_if.next(), None);
2594	/// drop(extract_if);
2595	///
2596	/// assert_eq!(map.len(), `1`);
2597	/// ```
2598	#[must_use = "Iterators are lazy unless consumed"]
2599	pub struct ExtractIf<'a, K, V, F, A: Allocator = Global>
2600	where
2601	F: FnMut(&K, &mut V) -> bool,
2602	{
2603	f: F,
2604	inner: RawExtractIf<'a, (K, V), A>,
2605	}
2606
2607	impl<K, V, F, A> Iterator for ExtractIf<'_, K, V, F, A>
2608	where
2609	F: FnMut(&K, &mut V) -> bool,
2610	A: Allocator,
2611	{
2612	type Item = (K, V);
2613
2614	#[cfg_attr(feature = "inline-more", inline)]
2615	fn next(&mut self) -> Option<Self::Item> {
2616	self.inner.next(\|&mut (ref k: &K, ref mut v: &mut V)\| (self.f)(k, v))
2617	}
2618
2619	#[inline]
2620	fn size_hint(&self) -> (usize, Option<usize>) {
2621	(`0`, self.inner.iter.size_hint().1)
2622	}
2623	}
2624
2625	impl<K, V, F> FusedIterator for ExtractIf<'_, K, V, F> where F: FnMut(&K, &mut V) -> bool {}
2626
2627	/// A mutable iterator over the values of a `HashMap` in arbitrary order.
2628	/// The iterator element type is `&'a mut V`.
2629	///
2630	/// This `struct` is created by the [`values_mut`] method on [`HashMap`]. See its
2631	/// documentation for more.
2632	///
2633	/// [`values_mut`]: struct.HashMap.html#method.values_mut
2634	/// [`HashMap`]: struct.HashMap.html
2635	///
2636	/// # Examples
2637	///
2638	/// ```
2639	/// use hashbrown::HashMap;
2640	///
2641	/// let mut map: HashMap<_, _> = [(`1`, "One".to_owned()), (`2`, "Two".into())].into();
2642	///
2643	/// let mut values = map.values_mut();
2644	/// values.next().map(\|v\| v.push_str(" Mississippi"));
2645	/// values.next().map(\|v\| v.push_str(" Mississippi"));
2646	///
2647	/// // It is fused iterator
2648	/// assert_eq!(values.next(), None);
2649	/// assert_eq!(values.next(), None);
2650	///
2651	/// assert_eq!(map.get(&`1`).unwrap(), &"One Mississippi".to_owned());
2652	/// assert_eq!(map.get(&`2`).unwrap(), &"Two Mississippi".to_owned());
2653	/// ```
2654	pub struct ValuesMut<'a, K, V> {
2655	inner: IterMut<'a, K, V>,
2656	}
2657
2658	/// A view into a single entry in a map, which may either be vacant or occupied.
2659	///
2660	/// This `enum` is constructed from the [`entry`] method on [`HashMap`].
2661	///
2662	/// [`HashMap`]: struct.HashMap.html
2663	/// [`entry`]: struct.HashMap.html#method.entry
2664	///
2665	/// # Examples
2666	///
2667	/// ```
2668	/// use hashbrown::hash_map::{Entry, HashMap, OccupiedEntry};
2669	///
2670	/// let mut map = HashMap::new();
2671	/// map.extend([("a", `10`), ("b", `20`), ("c", `30`)]);
2672	/// assert_eq!(map.len(), `3`);
2673	///
2674	/// // Existing key (insert)
2675	/// let entry: Entry<_, _, _> = map.entry("a");
2676	/// let _raw_o: OccupiedEntry<_, _, _> = entry.insert(`1`);
2677	/// assert_eq!(map.len(), `3`);
2678	/// // Nonexistent key (insert)
2679	/// map.entry("d").insert(`4`);
2680	///
2681	/// // Existing key (or_insert)
2682	/// let v = map.entry("b").or_insert(`2`);
2683	/// assert_eq!(std::mem::replace(v, `2`), `20`);
2684	/// // Nonexistent key (or_insert)
2685	/// map.entry("e").or_insert(`5`);
2686	///
2687	/// // Existing key (or_insert_with)
2688	/// let v = map.entry("c").or_insert_with(\|\| `3`);
2689	/// assert_eq!(std::mem::replace(v, `3`), `30`);
2690	/// // Nonexistent key (or_insert_with)
2691	/// map.entry("f").or_insert_with(\|\| `6`);
2692	///
2693	/// println!("Our HashMap: {:?}", map);
2694	///
2695	/// let mut vec: Vec<_> = map.iter().map(\|(&k, &v)\| (k, v)).collect();
2696	/// // The `Iter` iterator produces items in arbitrary order, so the
2697	/// // items must be sorted to test them against a sorted array.
2698	/// vec.sort_unstable();
2699	/// assert_eq!(vec, [("a", `1`), ("b", `2`), ("c", `3`), ("d", `4`), ("e", `5`), ("f", `6`)]);
2700	/// ```
2701	pub enum Entry<'a, K, V, S, A = Global>
2702	where
2703	A: Allocator,
2704	{
2705	/// An occupied entry.
2706	///
2707	/// # Examples
2708	///
2709	/// ```
2710	/// use hashbrown::hash_map::{Entry, HashMap};
2711	/// let mut map: HashMap<_, _> = [("a", `100`), ("b", `200`)].into();
2712	///
2713	/// match map.entry("a") {
2714	/// Entry::Vacant(_) => unreachable!(),
2715	/// Entry::Occupied(_) => { }
2716	/// }
2717	/// ```
2718	Occupied(OccupiedEntry<'a, K, V, S, A>),
2719
2720	/// A vacant entry.
2721	///
2722	/// # Examples
2723	///
2724	/// ```
2725	/// use hashbrown::hash_map::{Entry, HashMap};
2726	/// let mut map: HashMap<&str, i32> = HashMap::new();
2727	///
2728	/// match map.entry("a") {
2729	/// Entry::Occupied(_) => unreachable!(),
2730	/// Entry::Vacant(_) => { }
2731	/// }
2732	/// ```
2733	Vacant(VacantEntry<'a, K, V, S, A>),
2734	}
2735
2736	impl<K: Debug, V: Debug, S, A: Allocator> Debug for Entry<'_, K, V, S, A> {
2737	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2738	match *self {
2739	Entry::Vacant(ref v: &VacantEntry<'_, K, V, S, …>) => f.debug_tuple(name:"Entry").field(v).finish(),
2740	Entry::Occupied(ref o: &OccupiedEntry<'_, K, V, S, …>) => f.debug_tuple(name:"Entry").field(o).finish(),
2741	}
2742	}
2743	}
2744
2745	/// A view into an occupied entry in a [`HashMap`].
2746	/// It is part of the [`Entry`] and [`EntryRef`] enums.
2747	///
2748	/// # Examples
2749	///
2750	/// ```
2751	/// use hashbrown::hash_map::{Entry, HashMap, OccupiedEntry};
2752	///
2753	/// let mut map = HashMap::new();
2754	/// map.extend([("a", `10`), ("b", `20`), ("c", `30`)]);
2755	///
2756	/// let _entry_o: OccupiedEntry<_, _, _> = map.entry("a").insert(`100`);
2757	/// assert_eq!(map.len(), `3`);
2758	///
2759	/// // Existing key (insert and update)
2760	/// match map.entry("a") {
2761	/// Entry::Vacant(_) => unreachable!(),
2762	/// Entry::Occupied(mut view) => {
2763	/// assert_eq!(view.get(), &`100`);
2764	/// let v = view.get_mut();
2765	/// v = `10`;
2766	/// assert_eq!(view.insert(`1111`), `1000`);
2767	/// }
2768	/// }
2769	///
2770	/// assert_eq!(map[&"a"], `1111`);
2771	/// assert_eq!(map.len(), `3`);
2772	///
2773	/// // Existing key (take)
2774	/// match map.entry("c") {
2775	/// Entry::Vacant(_) => unreachable!(),
2776	/// Entry::Occupied(view) => {
2777	/// assert_eq!(view.remove_entry(), ("c", `30`));
2778	/// }
2779	/// }
2780	/// assert_eq!(map.get(&"c"), None);
2781	/// assert_eq!(map.len(), `2`);
2782	/// ```
2783	pub struct OccupiedEntry<'a, K, V, S = DefaultHashBuilder, A: Allocator = Global> {
2784	hash: u64,
2785	elem: Bucket<(K, V)>,
2786	table: &'a mut HashMap<K, V, S, A>,
2787	}
2788
2789	unsafe impl<K, V, S, A> Send for OccupiedEntry<'_, K, V, S, A>
2790	where
2791	K: Send,
2792	V: Send,
2793	S: Send,
2794	A: Send + Allocator,
2795	{
2796	}
2797	unsafe impl<K, V, S, A> Sync for OccupiedEntry<'_, K, V, S, A>
2798	where
2799	K: Sync,
2800	V: Sync,
2801	S: Sync,
2802	A: Sync + Allocator,
2803	{
2804	}
2805
2806	impl<K: Debug, V: Debug, S, A: Allocator> Debug for OccupiedEntry<'_, K, V, S, A> {
2807	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2808	f&mut DebugStruct<'_, '_>.debug_struct("OccupiedEntry")
2809	.field("key", self.key())
2810	.field(name:"value", self.get())
2811	.finish()
2812	}
2813	}
2814
2815	/// A view into a vacant entry in a `HashMap`.
2816	/// It is part of the [`Entry`] enum.
2817	///
2818	/// [`Entry`]: enum.Entry.html
2819	///
2820	/// # Examples
2821	///
2822	/// ```
2823	/// use hashbrown::hash_map::{Entry, HashMap, VacantEntry};
2824	///
2825	/// let mut map = HashMap::<&str, i32>::new();
2826	///
2827	/// let entry_v: VacantEntry<_, _, _> = match map.entry("a") {
2828	/// Entry::Vacant(view) => view,
2829	/// Entry::Occupied(_) => unreachable!(),
2830	/// };
2831	/// entry_v.insert(`10`);
2832	/// assert!(map[&"a"] == `10` && map.len() == `1`);
2833	///
2834	/// // Nonexistent key (insert and update)
2835	/// match map.entry("b") {
2836	/// Entry::Occupied(_) => unreachable!(),
2837	/// Entry::Vacant(view) => {
2838	/// let value = view.insert(`2`);
2839	/// assert_eq!(*value, `2`);
2840	/// *value = `20`;
2841	/// }
2842	/// }
2843	/// assert!(map[&"b"] == `20` && map.len() == `2`);
2844	/// ```
2845	pub struct VacantEntry<'a, K, V, S = DefaultHashBuilder, A: Allocator = Global> {
2846	hash: u64,
2847	key: K,
2848	table: &'a mut HashMap<K, V, S, A>,
2849	}
2850
2851	impl<K: Debug, V, S, A: Allocator> Debug for VacantEntry<'_, K, V, S, A> {
2852	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2853	f.debug_tuple(name:"VacantEntry").field(self.key()).finish()
2854	}
2855	}
2856
2857	/// A view into a single entry in a map, which may either be vacant or occupied,
2858	/// with any borrowed form of the map's key type.
2859	///
2860	///
2861	/// This `enum` is constructed from the [`entry_ref`] method on [`HashMap`].
2862	///
2863	/// [`Hash`] and [`Eq`] on the borrowed form of the map's key type must* match those*
2864	/// for the key type. It also require that key may be constructed from the borrowed
2865	/// form through the [`From`] trait.
2866	///
2867	/// [`HashMap`]: struct.HashMap.html
2868	/// [`entry_ref`]: struct.HashMap.html#method.entry_ref
2869	/// [`Eq`]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
2870	/// [`Hash`]: https://doc.rust-lang.org/std/hash/trait.Hash.html
2871	/// [`From`]: https://doc.rust-lang.org/std/convert/trait.From.html
2872	///
2873	/// # Examples
2874	///
2875	/// ```
2876	/// use hashbrown::hash_map::{EntryRef, HashMap, OccupiedEntry};
2877	///
2878	/// let mut map = HashMap::new();
2879	/// map.extend([("a".to_owned(), `10`), ("b".into(), `20`), ("c".into(), `30`)]);
2880	/// assert_eq!(map.len(), `3`);
2881	///
2882	/// // Existing key (insert)
2883	/// let key = String::from("a");
2884	/// let entry: EntryRef<_, _, _, _> = map.entry_ref(&key);
2885	/// let _raw_o: OccupiedEntry<_, _, _, _> = entry.insert(`1`);
2886	/// assert_eq!(map.len(), `3`);
2887	/// // Nonexistent key (insert)
2888	/// map.entry_ref("d").insert(`4`);
2889	///
2890	/// // Existing key (or_insert)
2891	/// let v = map.entry_ref("b").or_insert(`2`);
2892	/// assert_eq!(std::mem::replace(v, `2`), `20`);
2893	/// // Nonexistent key (or_insert)
2894	/// map.entry_ref("e").or_insert(`5`);
2895	///
2896	/// // Existing key (or_insert_with)
2897	/// let v = map.entry_ref("c").or_insert_with(\|\| `3`);
2898	/// assert_eq!(std::mem::replace(v, `3`), `30`);
2899	/// // Nonexistent key (or_insert_with)
2900	/// map.entry_ref("f").or_insert_with(\|\| `6`);
2901	///
2902	/// println!("Our HashMap: {:?}", map);
2903	///
2904	/// for (key, value) in ["a", "b", "c", "d", "e", "f"].into_iter().zip(`1`..=`6`) {
2905	/// assert_eq!(map[key], value)
2906	/// }
2907	/// assert_eq!(map.len(), `6`);
2908	/// ```
2909	pub enum EntryRef<'a, 'b, K, Q: ?Sized, V, S, A = Global>
2910	where
2911	A: Allocator,
2912	{
2913	/// An occupied entry.
2914	///
2915	/// # Examples
2916	///
2917	/// ```
2918	/// use hashbrown::hash_map::{EntryRef, HashMap};
2919	/// let mut map: HashMap<_, _> = [("a".to_owned(), `100`), ("b".into(), `200`)].into();
2920	///
2921	/// match map.entry_ref("a") {
2922	/// EntryRef::Vacant(_) => unreachable!(),
2923	/// EntryRef::Occupied(_) => { }
2924	/// }
2925	/// ```
2926	Occupied(OccupiedEntry<'a, K, V, S, A>),
2927
2928	/// A vacant entry.
2929	///
2930	/// # Examples
2931	///
2932	/// ```
2933	/// use hashbrown::hash_map::{EntryRef, HashMap};
2934	/// let mut map: HashMap<String, i32> = HashMap::new();
2935	///
2936	/// match map.entry_ref("a") {
2937	/// EntryRef::Occupied(_) => unreachable!(),
2938	/// EntryRef::Vacant(_) => { }
2939	/// }
2940	/// ```
2941	Vacant(VacantEntryRef<'a, 'b, K, Q, V, S, A>),
2942	}
2943
2944	impl<K, Q, V, S, A> Debug for EntryRef<'_, '_, K, Q, V, S, A>
2945	where
2946	K: Debug + Borrow<Q>,
2947	Q: Debug + ?Sized,
2948	V: Debug,
2949	A: Allocator,
2950	{
2951	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2952	match *self {
2953	EntryRef::Vacant(ref v: &VacantEntryRef<'_, '_, K, …, …, …, …>) => f.debug_tuple(name:"EntryRef").field(v).finish(),
2954	EntryRef::Occupied(ref o: &OccupiedEntry<'_, K, V, S, …>) => f.debug_tuple(name:"EntryRef").field(o).finish(),
2955	}
2956	}
2957	}
2958
2959	/// A view into a vacant entry in a `HashMap`.
2960	/// It is part of the [`EntryRef`] enum.
2961	///
2962	/// [`EntryRef`]: enum.EntryRef.html
2963	///
2964	/// # Examples
2965	///
2966	/// ```
2967	/// use hashbrown::hash_map::{EntryRef, HashMap, VacantEntryRef};
2968	///
2969	/// let mut map = HashMap::<String, i32>::new();
2970	///
2971	/// let entry_v: VacantEntryRef<_, _, _, _> = match map.entry_ref("a") {
2972	/// EntryRef::Vacant(view) => view,
2973	/// EntryRef::Occupied(_) => unreachable!(),
2974	/// };
2975	/// entry_v.insert(`10`);
2976	/// assert!(map["a"] == `10` && map.len() == `1`);
2977	///
2978	/// // Nonexistent key (insert and update)
2979	/// match map.entry_ref("b") {
2980	/// EntryRef::Occupied(_) => unreachable!(),
2981	/// EntryRef::Vacant(view) => {
2982	/// let value = view.insert(`2`);
2983	/// assert_eq!(*value, `2`);
2984	/// *value = `20`;
2985	/// }
2986	/// }
2987	/// assert!(map["b"] == `20` && map.len() == `2`);
2988	/// ```
2989	pub struct VacantEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator = Global> {
2990	hash: u64,
2991	key: &'b Q,
2992	table: &'a mut HashMap<K, V, S, A>,
2993	}
2994
2995	impl<K, Q, V, S, A> Debug for VacantEntryRef<'_, '_, K, Q, V, S, A>
2996	where
2997	K: Borrow<Q>,
2998	Q: Debug + ?Sized,
2999	A: Allocator,
3000	{
3001	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3002	f.debug_tuple(name:"VacantEntryRef").field(&self.key()).finish()
3003	}
3004	}
3005
3006	/// The error returned by [`try_insert`](HashMap::try_insert) when the key already exists.
3007	///
3008	/// Contains the occupied entry, and the value that was not inserted.
3009	///
3010	/// # Examples
3011	///
3012	/// ```
3013	/// use hashbrown::hash_map::{HashMap, OccupiedError};
3014	///
3015	/// let mut map: HashMap<_, _> = [("a", `10`), ("b", `20`)].into();
3016	///
3017	/// // try_insert method returns mutable reference to the value if keys are vacant,
3018	/// // but if the map did have key present, nothing is updated, and the provided
3019	/// // value is returned inside `Err(_)` variant
3020	/// match map.try_insert("a", `100`) {
3021	/// Err(OccupiedError { mut entry, value }) => {
3022	/// assert_eq!(entry.key(), &"a");
3023	/// assert_eq!(value, `100`);
3024	/// assert_eq!(entry.insert(`100`), `10`)
3025	/// }
3026	/// _ => unreachable!(),
3027	/// }
3028	/// assert_eq!(map[&"a"], `100`);
3029	/// ```
3030	pub struct OccupiedError<'a, K, V, S, A: Allocator = Global> {
3031	/// The entry in the map that was already occupied.
3032	pub entry: OccupiedEntry<'a, K, V, S, A>,
3033	/// The value which was not inserted, because the entry was already occupied.
3034	pub value: V,
3035	}
3036
3037	impl<K: Debug, V: Debug, S, A: Allocator> Debug for OccupiedError<'_, K, V, S, A> {
3038	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3039	f&mut DebugStruct<'_, '_>.debug_struct("OccupiedError")
3040	.field("key", self.entry.key())
3041	.field("old_value", self.entry.get())
3042	.field(name:"new_value", &self.value)
3043	.finish()
3044	}
3045	}
3046
3047	impl<K: Debug, V: Debug, S, A: Allocator> fmt::Display for OccupiedError<'_, K, V, S, A> {
3048	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3049	write!(
3050	f,
3051	"failed to insert {:?}, key {:?} already exists with value {:?}",
3052	self.value,
3053	self.entry.key(),
3054	self.entry.get(),
3055	)
3056	}
3057	}
3058
3059	impl<'a, K, V, S, A: Allocator> IntoIterator for &'a HashMap<K, V, S, A> {
3060	type Item = (&'a K, &'a V);
3061	type IntoIter = Iter<'a, K, V>;
3062
3063	/// Creates an iterator over the entries of a `HashMap` in arbitrary order.
3064	/// The iterator element type is `(&'a K, &'a V)`.
3065	///
3066	/// Return the same `Iter` struct as by the [`iter`] method on [`HashMap`].
3067	///
3068	/// [`iter`]: struct.HashMap.html#method.iter
3069	/// [`HashMap`]: struct.HashMap.html
3070	///
3071	/// # Examples
3072	///
3073	/// ```
3074	/// use hashbrown::HashMap;
3075	/// let map_one: HashMap<_, _> = [(`1`, "a"), (`2`, "b"), (`3`, "c")].into();
3076	/// let mut map_two = HashMap::new();
3077	///
3078	/// for (key, value) in &map_one {
3079	/// println!("Key: {}, Value: {}", key, value);
3080	/// map_two.insert(key, value);
3081	/// }
3082	///
3083	/// assert_eq!(map_one, map_two);
3084	/// ```
3085	#[cfg_attr(feature = "inline-more", inline)]
3086	fn into_iter(self) -> Iter<'a, K, V> {
3087	self.iter()
3088	}
3089	}
3090
3091	impl<'a, K, V, S, A: Allocator> IntoIterator for &'a mut HashMap<K, V, S, A> {
3092	type Item = (&'a K, &'a mut V);
3093	type IntoIter = IterMut<'a, K, V>;
3094
3095	/// Creates an iterator over the entries of a `HashMap` in arbitrary order
3096	/// with mutable references to the values. The iterator element type is
3097	/// `(&'a K, &'a mut V)`.
3098	///
3099	/// Return the same `IterMut` struct as by the [`iter_mut`] method on
3100	/// [`HashMap`].
3101	///
3102	/// [`iter_mut`]: struct.HashMap.html#method.iter_mut
3103	/// [`HashMap`]: struct.HashMap.html
3104	///
3105	/// # Examples
3106	///
3107	/// ```
3108	/// use hashbrown::HashMap;
3109	/// let mut map: HashMap<_, _> = [("a", `1`), ("b", `2`), ("c", `3`)].into();
3110	///
3111	/// for (key, value) in &mut map {
3112	/// println!("Key: {}, Value: {}", key, value);
3113	/// value = `2`;
3114	/// }
3115	///
3116	/// let mut vec = map.iter().collect::<Vec<_>>();
3117	/// // The `Iter` iterator produces items in arbitrary order, so the
3118	/// // items must be sorted to test them against a sorted array.
3119	/// vec.sort_unstable();
3120	/// assert_eq!(vec, [(&"a", &`2`), (&"b", &`4`), (&"c", &`6`)]);
3121	/// ```
3122	#[cfg_attr(feature = "inline-more", inline)]
3123	fn into_iter(self) -> IterMut<'a, K, V> {
3124	self.iter_mut()
3125	}
3126	}
3127
3128	impl<K, V, S, A: Allocator> IntoIterator for HashMap<K, V, S, A> {
3129	type Item = (K, V);
3130	type IntoIter = IntoIter<K, V, A>;
3131
3132	/// Creates a consuming iterator, that is, one that moves each key-value
3133	/// pair out of the map in arbitrary order. The map cannot be used after
3134	/// calling this.
3135	///
3136	/// # Examples
3137	///
3138	/// ```
3139	/// use hashbrown::HashMap;
3140	///
3141	/// let map: HashMap<_, _> = [("a", `1`), ("b", `2`), ("c", `3`)].into();
3142	///
3143	/// // Not possible with .iter()
3144	/// let mut vec: Vec<(&str, i32)> = map.into_iter().collect();
3145	/// // The `IntoIter` iterator produces items in arbitrary order, so
3146	/// // the items must be sorted to test them against a sorted array.
3147	/// vec.sort_unstable();
3148	/// assert_eq!(vec, [("a", `1`), ("b", `2`), ("c", `3`)]);
3149	/// ```
3150	#[cfg_attr(feature = "inline-more", inline)]
3151	fn into_iter(self) -> IntoIter<K, V, A> {
3152	IntoIter {
3153	inner: self.table.into_iter(),
3154	}
3155	}
3156	}
3157
3158	impl<K, V> Default for Iter<'_, K, V> {
3159	#[cfg_attr(feature = "inline-more", inline)]
3160	fn default() -> Self {
3161	Self {
3162	inner: Default::default(),
3163	marker: PhantomData,
3164	}
3165	}
3166	}
3167	impl<'a, K, V> Iterator for Iter<'a, K, V> {
3168	type Item = (&'a K, &'a V);
3169
3170	#[cfg_attr(feature = "inline-more", inline)]
3171	fn next(&mut self) -> Option<(&'a K, &'a V)> {
3172	// Avoid `Option::map` because it bloats LLVM IR.
3173	match self.inner.next() {
3174	Some(x) => unsafe {
3175	let r = x.as_ref();
3176	Some((&r.0, &r.1))
3177	},
3178	None => None,
3179	}
3180	}
3181	#[cfg_attr(feature = "inline-more", inline)]
3182	fn size_hint(&self) -> (usize, Option<usize>) {
3183	self.inner.size_hint()
3184	}
3185	#[cfg_attr(feature = "inline-more", inline)]
3186	fn fold<B, F>(self, init: B, mut f: F) -> B
3187	where
3188	Self: Sized,
3189	F: FnMut(B, Self::Item) -> B,
3190	{
3191	self.inner.fold(init, \|acc, x\| unsafe {
3192	let (k, v) = x.as_ref();
3193	f(acc, (k, v))
3194	})
3195	}
3196	}
3197	impl<K, V> ExactSizeIterator for Iter<'_, K, V> {
3198	#[cfg_attr(feature = "inline-more", inline)]
3199	fn len(&self) -> usize {
3200	self.inner.len()
3201	}
3202	}
3203
3204	impl<K, V> FusedIterator for Iter<'_, K, V> {}
3205
3206	impl<K, V> Default for IterMut<'_, K, V> {
3207	#[cfg_attr(feature = "inline-more", inline)]
3208	fn default() -> Self {
3209	Self {
3210	inner: Default::default(),
3211	marker: PhantomData,
3212	}
3213	}
3214	}
3215	impl<'a, K, V> Iterator for IterMut<'a, K, V> {
3216	type Item = (&'a K, &'a mut V);
3217
3218	#[cfg_attr(feature = "inline-more", inline)]
3219	fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
3220	// Avoid `Option::map` because it bloats LLVM IR.
3221	match self.inner.next() {
3222	Some(x) => unsafe {
3223	let r = x.as_mut();
3224	Some((&r.0, &mut r.1))
3225	},
3226	None => None,
3227	}
3228	}
3229	#[cfg_attr(feature = "inline-more", inline)]
3230	fn size_hint(&self) -> (usize, Option<usize>) {
3231	self.inner.size_hint()
3232	}
3233	#[cfg_attr(feature = "inline-more", inline)]
3234	fn fold<B, F>(self, init: B, mut f: F) -> B
3235	where
3236	Self: Sized,
3237	F: FnMut(B, Self::Item) -> B,
3238	{
3239	self.inner.fold(init, \|acc, x\| unsafe {
3240	let (k, v) = x.as_mut();
3241	f(acc, (k, v))
3242	})
3243	}
3244	}
3245	impl<K, V> ExactSizeIterator for IterMut<'_, K, V> {
3246	#[cfg_attr(feature = "inline-more", inline)]
3247	fn len(&self) -> usize {
3248	self.inner.len()
3249	}
3250	}
3251	impl<K, V> FusedIterator for IterMut<'_, K, V> {}
3252
3253	impl<K, V> fmt::Debug for IterMut<'_, K, V>
3254	where
3255	K: fmt::Debug,
3256	V: fmt::Debug,
3257	{
3258	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3259	f.debug_list().entries(self.iter()).finish()
3260	}
3261	}
3262
3263	impl<K, V, A: Allocator> Default for IntoIter<K, V, A> {
3264	#[cfg_attr(feature = "inline-more", inline)]
3265	fn default() -> Self {
3266	Self {
3267	inner: Default::default(),
3268	}
3269	}
3270	}
3271	impl<K, V, A: Allocator> Iterator for IntoIter<K, V, A> {
3272	type Item = (K, V);
3273
3274	#[cfg_attr(feature = "inline-more", inline)]
3275	fn next(&mut self) -> Option<(K, V)> {
3276	self.inner.next()
3277	}
3278	#[cfg_attr(feature = "inline-more", inline)]
3279	fn size_hint(&self) -> (usize, Option<usize>) {
3280	self.inner.size_hint()
3281	}
3282	#[cfg_attr(feature = "inline-more", inline)]
3283	fn fold<B, F>(self, init: B, f: F) -> B
3284	where
3285	Self: Sized,
3286	F: FnMut(B, Self::Item) -> B,
3287	{
3288	self.inner.fold(init, f)
3289	}
3290	}
3291	impl<K, V, A: Allocator> ExactSizeIterator for IntoIter<K, V, A> {
3292	#[cfg_attr(feature = "inline-more", inline)]
3293	fn len(&self) -> usize {
3294	self.inner.len()
3295	}
3296	}
3297	impl<K, V, A: Allocator> FusedIterator for IntoIter<K, V, A> {}
3298
3299	impl<K: Debug, V: Debug, A: Allocator> fmt::Debug for IntoIter<K, V, A> {
3300	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3301	f.debug_list().entries(self.iter()).finish()
3302	}
3303	}
3304
3305	impl<K, V> Default for Keys<'_, K, V> {
3306	#[cfg_attr(feature = "inline-more", inline)]
3307	fn default() -> Self {
3308	Self {
3309	inner: Default::default(),
3310	}
3311	}
3312	}
3313	impl<'a, K, V> Iterator for Keys<'a, K, V> {
3314	type Item = &'a K;
3315
3316	#[cfg_attr(feature = "inline-more", inline)]
3317	fn next(&mut self) -> Option<&'a K> {
3318	// Avoid `Option::map` because it bloats LLVM IR.
3319	match self.inner.next() {
3320	Some((k: &'a K, _)) => Some(k),
3321	None => None,
3322	}
3323	}
3324	#[cfg_attr(feature = "inline-more", inline)]
3325	fn size_hint(&self) -> (usize, Option<usize>) {
3326	self.inner.size_hint()
3327	}
3328	#[cfg_attr(feature = "inline-more", inline)]
3329	fn fold<B, F>(self, init: B, mut f: F) -> B
3330	where
3331	Self: Sized,
3332	F: FnMut(B, Self::Item) -> B,
3333	{
3334	self.inner.fold(init, \|acc: B, (k: &'a K, _)\| f(acc, k))
3335	}
3336	}
3337	impl<K, V> ExactSizeIterator for Keys<'_, K, V> {
3338	#[cfg_attr(feature = "inline-more", inline)]
3339	fn len(&self) -> usize {
3340	self.inner.len()
3341	}
3342	}
3343	impl<K, V> FusedIterator for Keys<'_, K, V> {}
3344
3345	impl<K, V> Default for Values<'_, K, V> {
3346	#[cfg_attr(feature = "inline-more", inline)]
3347	fn default() -> Self {
3348	Self {
3349	inner: Default::default(),
3350	}
3351	}
3352	}
3353	impl<'a, K, V> Iterator for Values<'a, K, V> {
3354	type Item = &'a V;
3355
3356	#[cfg_attr(feature = "inline-more", inline)]
3357	fn next(&mut self) -> Option<&'a V> {
3358	// Avoid `Option::map` because it bloats LLVM IR.
3359	match self.inner.next() {
3360	Some((_, v: &'a V)) => Some(v),
3361	None => None,
3362	}
3363	}
3364	#[cfg_attr(feature = "inline-more", inline)]
3365	fn size_hint(&self) -> (usize, Option<usize>) {
3366	self.inner.size_hint()
3367	}
3368	#[cfg_attr(feature = "inline-more", inline)]
3369	fn fold<B, F>(self, init: B, mut f: F) -> B
3370	where
3371	Self: Sized,
3372	F: FnMut(B, Self::Item) -> B,
3373	{
3374	self.inner.fold(init, \|acc: B, (_, v: &'a V)\| f(acc, v))
3375	}
3376	}
3377	impl<K, V> ExactSizeIterator for Values<'_, K, V> {
3378	#[cfg_attr(feature = "inline-more", inline)]
3379	fn len(&self) -> usize {
3380	self.inner.len()
3381	}
3382	}
3383	impl<K, V> FusedIterator for Values<'_, K, V> {}
3384
3385	impl<K, V> Default for ValuesMut<'_, K, V> {
3386	#[cfg_attr(feature = "inline-more", inline)]
3387	fn default() -> Self {
3388	Self {
3389	inner: Default::default(),
3390	}
3391	}
3392	}
3393	impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
3394	type Item = &'a mut V;
3395
3396	#[cfg_attr(feature = "inline-more", inline)]
3397	fn next(&mut self) -> Option<&'a mut V> {
3398	// Avoid `Option::map` because it bloats LLVM IR.
3399	match self.inner.next() {
3400	Some((_, v: &'a mut V)) => Some(v),
3401	None => None,
3402	}
3403	}
3404	#[cfg_attr(feature = "inline-more", inline)]
3405	fn size_hint(&self) -> (usize, Option<usize>) {
3406	self.inner.size_hint()
3407	}
3408	#[cfg_attr(feature = "inline-more", inline)]
3409	fn fold<B, F>(self, init: B, mut f: F) -> B
3410	where
3411	Self: Sized,
3412	F: FnMut(B, Self::Item) -> B,
3413	{
3414	self.inner.fold(init, \|acc: B, (_, v: &'a mut V)\| f(acc, v))
3415	}
3416	}
3417	impl<K, V> ExactSizeIterator for ValuesMut<'_, K, V> {
3418	#[cfg_attr(feature = "inline-more", inline)]
3419	fn len(&self) -> usize {
3420	self.inner.len()
3421	}
3422	}
3423	impl<K, V> FusedIterator for ValuesMut<'_, K, V> {}
3424
3425	impl<K, V: Debug> fmt::Debug for ValuesMut<'_, K, V> {
3426	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3427	f&mut DebugList<'_, '_>.debug_list()
3428	.entries(self.inner.iter().map(\|(_, val: &V)\| val))
3429	.finish()
3430	}
3431	}
3432
3433	impl<K, V, A: Allocator> Iterator for Drain<'_, K, V, A> {
3434	type Item = (K, V);
3435
3436	#[cfg_attr(feature = "inline-more", inline)]
3437	fn next(&mut self) -> Option<(K, V)> {
3438	self.inner.next()
3439	}
3440	#[cfg_attr(feature = "inline-more", inline)]
3441	fn size_hint(&self) -> (usize, Option<usize>) {
3442	self.inner.size_hint()
3443	}
3444	#[cfg_attr(feature = "inline-more", inline)]
3445	fn fold<B, F>(self, init: B, f: F) -> B
3446	where
3447	Self: Sized,
3448	F: FnMut(B, Self::Item) -> B,
3449	{
3450	self.inner.fold(init, f)
3451	}
3452	}
3453	impl<K, V, A: Allocator> ExactSizeIterator for Drain<'_, K, V, A> {
3454	#[cfg_attr(feature = "inline-more", inline)]
3455	fn len(&self) -> usize {
3456	self.inner.len()
3457	}
3458	}
3459	impl<K, V, A: Allocator> FusedIterator for Drain<'_, K, V, A> {}
3460
3461	impl<K, V, A> fmt::Debug for Drain<'_, K, V, A>
3462	where
3463	K: fmt::Debug,
3464	V: fmt::Debug,
3465	A: Allocator,
3466	{
3467	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
3468	f.debug_list().entries(self.iter()).finish()
3469	}
3470	}
3471
3472	impl<'a, K, V, S, A: Allocator> Entry<'a, K, V, S, A> {
3473	/// Sets the value of the entry, and returns an `OccupiedEntry`.
3474	///
3475	/// # Examples
3476	///
3477	/// ```
3478	/// use hashbrown::HashMap;
3479	///
3480	/// let mut map: HashMap<&str, u32> = HashMap::new();
3481	/// let entry = map.entry("horseyland").insert(`37`);
3482	///
3483	/// assert_eq!(entry.key(), &"horseyland");
3484	/// ```
3485	#[cfg_attr(feature = "inline-more", inline)]
3486	pub fn insert(self, value: V) -> OccupiedEntry<'a, K, V, S, A>
3487	where
3488	K: Hash,
3489	S: BuildHasher,
3490	{
3491	match self {
3492	Entry::Occupied(mut entry) => {
3493	entry.insert(value);
3494	entry
3495	}
3496	Entry::Vacant(entry) => entry.insert_entry(value),
3497	}
3498	}
3499
3500	/// Ensures a value is in the entry by inserting the default if empty, and returns
3501	/// a mutable reference to the value in the entry.
3502	///
3503	/// # Examples
3504	///
3505	/// ```
3506	/// use hashbrown::HashMap;
3507	///
3508	/// let mut map: HashMap<&str, u32> = HashMap::new();
3509	///
3510	/// // nonexistent key
3511	/// map.entry("poneyland").or_insert(`3`);
3512	/// assert_eq!(map["poneyland"], `3`);
3513	///
3514	/// // existing key
3515	/// map.entry("poneyland").or_insert(`10`) = `2`;
3516	/// assert_eq!(map["poneyland"], `6`);
3517	/// ```
3518	#[cfg_attr(feature = "inline-more", inline)]
3519	pub fn or_insert(self, default: V) -> &'a mut V
3520	where
3521	K: Hash,
3522	S: BuildHasher,
3523	{
3524	match self {
3525	Entry::Occupied(entry) => entry.into_mut(),
3526	Entry::Vacant(entry) => entry.insert(default),
3527	}
3528	}
3529
3530	/// Ensures a value is in the entry by inserting the result of the default function if empty,
3531	/// and returns a mutable reference to the value in the entry.
3532	///
3533	/// # Examples
3534	///
3535	/// ```
3536	/// use hashbrown::HashMap;
3537	///
3538	/// let mut map: HashMap<&str, u32> = HashMap::new();
3539	///
3540	/// // nonexistent key
3541	/// map.entry("poneyland").or_insert_with(\|\| `3`);
3542	/// assert_eq!(map["poneyland"], `3`);
3543	///
3544	/// // existing key
3545	/// map.entry("poneyland").or_insert_with(\|\| `10`) = `2`;
3546	/// assert_eq!(map["poneyland"], `6`);
3547	/// ```
3548	#[cfg_attr(feature = "inline-more", inline)]
3549	pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V
3550	where
3551	K: Hash,
3552	S: BuildHasher,
3553	{
3554	match self {
3555	Entry::Occupied(entry) => entry.into_mut(),
3556	Entry::Vacant(entry) => entry.insert(default()),
3557	}
3558	}
3559
3560	/// Ensures a value is in the entry by inserting, if empty, the result of the default function.
3561	/// This method allows for generating key-derived values for insertion by providing the default
3562	/// function a reference to the key that was moved during the `.entry(key)` method call.
3563	///
3564	/// The reference to the moved key is provided so that cloning or copying the key is
3565	/// unnecessary, unlike with `.or_insert_with(\|\| ... )`.
3566	///
3567	/// # Examples
3568	///
3569	/// ```
3570	/// use hashbrown::HashMap;
3571	///
3572	/// let mut map: HashMap<&str, usize> = HashMap::new();
3573	///
3574	/// // nonexistent key
3575	/// map.entry("poneyland").or_insert_with_key(\|key\| key.chars().count());
3576	/// assert_eq!(map["poneyland"], `9`);
3577	///
3578	/// // existing key
3579	/// map.entry("poneyland").or_insert_with_key(\|key\| key.chars().count() `10`) *= `2`;
3580	/// assert_eq!(map["poneyland"], `18`);
3581	/// ```
3582	#[cfg_attr(feature = "inline-more", inline)]
3583	pub fn or_insert_with_key<F: FnOnce(&K) -> V>(self, default: F) -> &'a mut V
3584	where
3585	K: Hash,
3586	S: BuildHasher,
3587	{
3588	match self {
3589	Entry::Occupied(entry) => entry.into_mut(),
3590	Entry::Vacant(entry) => {
3591	let value = default(entry.key());
3592	entry.insert(value)
3593	}
3594	}
3595	}
3596
3597	/// Returns a reference to this entry's key.
3598	///
3599	/// # Examples
3600	///
3601	/// ```
3602	/// use hashbrown::HashMap;
3603	///
3604	/// let mut map: HashMap<&str, u32> = HashMap::new();
3605	/// map.entry("poneyland").or_insert(`3`);
3606	/// // existing key
3607	/// assert_eq!(map.entry("poneyland").key(), &"poneyland");
3608	/// // nonexistent key
3609	/// assert_eq!(map.entry("horseland").key(), &"horseland");
3610	/// ```
3611	#[cfg_attr(feature = "inline-more", inline)]
3612	pub fn key(&self) -> &K {
3613	match *self {
3614	Entry::Occupied(ref entry) => entry.key(),
3615	Entry::Vacant(ref entry) => entry.key(),
3616	}
3617	}
3618
3619	/// Provides in-place mutable access to an occupied entry before any
3620	/// potential inserts into the map.
3621	///
3622	/// # Examples
3623	///
3624	/// ```
3625	/// use hashbrown::HashMap;
3626	///
3627	/// let mut map: HashMap<&str, u32> = HashMap::new();
3628	///
3629	/// map.entry("poneyland")
3630	/// .and_modify(\|e\| { *e += `1` })
3631	/// .or_insert(`42`);
3632	/// assert_eq!(map["poneyland"], `42`);
3633	///
3634	/// map.entry("poneyland")
3635	/// .and_modify(\|e\| { *e += `1` })
3636	/// .or_insert(`42`);
3637	/// assert_eq!(map["poneyland"], `43`);
3638	/// ```
3639	#[cfg_attr(feature = "inline-more", inline)]
3640	pub fn and_modify<F>(self, f: F) -> Self
3641	where
3642	F: FnOnce(&mut V),
3643	{
3644	match self {
3645	Entry::Occupied(mut entry) => {
3646	f(entry.get_mut());
3647	Entry::Occupied(entry)
3648	}
3649	Entry::Vacant(entry) => Entry::Vacant(entry),
3650	}
3651	}
3652
3653	/// Provides shared access to the key and owned access to the value of
3654	/// an occupied entry and allows to replace or remove it based on the
3655	/// value of the returned option.
3656	///
3657	/// # Examples
3658	///
3659	/// ```
3660	/// use hashbrown::HashMap;
3661	/// use hashbrown::hash_map::Entry;
3662	///
3663	/// let mut map: HashMap<&str, u32> = HashMap::new();
3664	///
3665	/// let entry = map
3666	/// .entry("poneyland")
3667	/// .and_replace_entry_with(\|_k, _v\| panic!());
3668	///
3669	/// match entry {
3670	/// Entry::Vacant(e) => {
3671	/// assert_eq!(e.key(), &"poneyland");
3672	/// }
3673	/// Entry::Occupied(_) => panic!(),
3674	/// }
3675	///
3676	/// map.insert("poneyland", `42`);
3677	///
3678	/// let entry = map
3679	/// .entry("poneyland")
3680	/// .and_replace_entry_with(\|k, v\| {
3681	/// assert_eq!(k, &"poneyland");
3682	/// assert_eq!(v, `42`);
3683	/// Some(v + `1`)
3684	/// });
3685	///
3686	/// match entry {
3687	/// Entry::Occupied(e) => {
3688	/// assert_eq!(e.key(), &"poneyland");
3689	/// assert_eq!(e.get(), &`43`);
3690	/// }
3691	/// Entry::Vacant(_) => panic!(),
3692	/// }
3693	///
3694	/// assert_eq!(map["poneyland"], `43`);
3695	///
3696	/// let entry = map
3697	/// .entry("poneyland")
3698	/// .and_replace_entry_with(\|_k, _v\| None);
3699	///
3700	/// match entry {
3701	/// Entry::Vacant(e) => assert_eq!(e.key(), &"poneyland"),
3702	/// Entry::Occupied(_) => panic!(),
3703	/// }
3704	///
3705	/// assert!(!map.contains_key("poneyland"));
3706	/// ```
3707	#[cfg_attr(feature = "inline-more", inline)]
3708	pub fn and_replace_entry_with<F>(self, f: F) -> Self
3709	where
3710	F: FnOnce(&K, V) -> Option<V>,
3711	{
3712	match self {
3713	Entry::Occupied(entry) => entry.replace_entry_with(f),
3714	Entry::Vacant(_) => self,
3715	}
3716	}
3717	}
3718
3719	impl<'a, K, V: Default, S, A: Allocator> Entry<'a, K, V, S, A> {
3720	/// Ensures a value is in the entry by inserting the default value if empty,
3721	/// and returns a mutable reference to the value in the entry.
3722	///
3723	/// # Examples
3724	///
3725	/// ```
3726	/// use hashbrown::HashMap;
3727	///
3728	/// let mut map: HashMap<&str, Option<u32>> = HashMap::new();
3729	///
3730	/// // nonexistent key
3731	/// map.entry("poneyland").or_default();
3732	/// assert_eq!(map["poneyland"], None);
3733	///
3734	/// map.insert("horseland", Some(`3`));
3735	///
3736	/// // existing key
3737	/// assert_eq!(map.entry("horseland").or_default(), &mut Some(`3`));
3738	/// ```
3739	#[cfg_attr(feature = "inline-more", inline)]
3740	pub fn or_default(self) -> &'a mut V
3741	where
3742	K: Hash,
3743	S: BuildHasher,
3744	{
3745	match self {
3746	Entry::Occupied(entry) => entry.into_mut(),
3747	Entry::Vacant(entry) => entry.insert(Default::default()),
3748	}
3749	}
3750	}
3751
3752	impl<'a, K, V, S, A: Allocator> OccupiedEntry<'a, K, V, S, A> {
3753	/// Gets a reference to the key in the entry.
3754	///
3755	/// # Examples
3756	///
3757	/// ```
3758	/// use hashbrown::hash_map::{Entry, HashMap};
3759	///
3760	/// let mut map: HashMap<&str, u32> = HashMap::new();
3761	/// map.entry("poneyland").or_insert(`12`);
3762	///
3763	/// match map.entry("poneyland") {
3764	/// Entry::Vacant(_) => panic!(),
3765	/// Entry::Occupied(entry) => assert_eq!(entry.key(), &"poneyland"),
3766	/// }
3767	/// ```
3768	#[cfg_attr(feature = "inline-more", inline)]
3769	pub fn key(&self) -> &K {
3770	unsafe { &self.elem.as_ref().0 }
3771	}
3772
3773	/// Take the ownership of the key and value from the map.
3774	/// Keeps the allocated memory for reuse.
3775	///
3776	/// # Examples
3777	///
3778	/// ```
3779	/// use hashbrown::HashMap;
3780	/// use hashbrown::hash_map::Entry;
3781	///
3782	/// let mut map: HashMap<&str, u32> = HashMap::new();
3783	/// // The map is empty
3784	/// assert!(map.is_empty() && map.capacity() == `0`);
3785	///
3786	/// map.entry("poneyland").or_insert(`12`);
3787	///
3788	/// if let Entry::Occupied(o) = map.entry("poneyland") {
3789	/// // We delete the entry from the map.
3790	/// assert_eq!(o.remove_entry(), ("poneyland", `12`));
3791	/// }
3792	///
3793	/// assert_eq!(map.contains_key("poneyland"), `false`);
3794	/// // Now map hold none elements
3795	/// assert!(map.is_empty());
3796	/// ```
3797	#[cfg_attr(feature = "inline-more", inline)]
3798	pub fn remove_entry(self) -> (K, V) {
3799	unsafe { self.table.table.remove(self.elem).0 }
3800	}
3801
3802	/// Gets a reference to the value in the entry.
3803	///
3804	/// # Examples
3805	///
3806	/// ```
3807	/// use hashbrown::HashMap;
3808	/// use hashbrown::hash_map::Entry;
3809	///
3810	/// let mut map: HashMap<&str, u32> = HashMap::new();
3811	/// map.entry("poneyland").or_insert(`12`);
3812	///
3813	/// match map.entry("poneyland") {
3814	/// Entry::Vacant(_) => panic!(),
3815	/// Entry::Occupied(entry) => assert_eq!(entry.get(), &`12`),
3816	/// }
3817	/// ```
3818	#[cfg_attr(feature = "inline-more", inline)]
3819	pub fn get(&self) -> &V {
3820	unsafe { &self.elem.as_ref().1 }
3821	}
3822
3823	/// Gets a mutable reference to the value in the entry.
3824	///
3825	/// If you need a reference to the `OccupiedEntry` which may outlive the
3826	/// destruction of the `Entry` value, see [`into_mut`].
3827	///
3828	/// [`into_mut`]: #method.into_mut
3829	///
3830	/// # Examples
3831	///
3832	/// ```
3833	/// use hashbrown::HashMap;
3834	/// use hashbrown::hash_map::Entry;
3835	///
3836	/// let mut map: HashMap<&str, u32> = HashMap::new();
3837	/// map.entry("poneyland").or_insert(`12`);
3838	///
3839	/// assert_eq!(map["poneyland"], `12`);
3840	/// if let Entry::Occupied(mut o) = map.entry("poneyland") {
3841	/// *o.get_mut() += `10`;
3842	/// assert_eq!(*o.get(), `22`);
3843	///
3844	/// // We can use the same Entry multiple times.
3845	/// *o.get_mut() += `2`;
3846	/// }
3847	///
3848	/// assert_eq!(map["poneyland"], `24`);
3849	/// ```
3850	#[cfg_attr(feature = "inline-more", inline)]
3851	pub fn get_mut(&mut self) -> &mut V {
3852	unsafe { &mut self.elem.as_mut().1 }
3853	}
3854
3855	/// Converts the `OccupiedEntry` into a mutable reference to the value in the entry
3856	/// with a lifetime bound to the map itself.
3857	///
3858	/// If you need multiple references to the `OccupiedEntry`, see [`get_mut`].
3859	///
3860	/// [`get_mut`]: #method.get_mut
3861	///
3862	/// # Examples
3863	///
3864	/// ```
3865	/// use hashbrown::hash_map::{Entry, HashMap};
3866	///
3867	/// let mut map: HashMap<&str, u32> = HashMap::new();
3868	/// map.entry("poneyland").or_insert(`12`);
3869	///
3870	/// assert_eq!(map["poneyland"], `12`);
3871	///
3872	/// let value: &mut u32;
3873	/// match map.entry("poneyland") {
3874	/// Entry::Occupied(entry) => value = entry.into_mut(),
3875	/// Entry::Vacant(_) => panic!(),
3876	/// }
3877	/// *value += `10`;
3878	///
3879	/// assert_eq!(map["poneyland"], `22`);
3880	/// ```
3881	#[cfg_attr(feature = "inline-more", inline)]
3882	pub fn into_mut(self) -> &'a mut V {
3883	unsafe { &mut self.elem.as_mut().1 }
3884	}
3885
3886	/// Sets the value of the entry, and returns the entry's old value.
3887	///
3888	/// # Examples
3889	///
3890	/// ```
3891	/// use hashbrown::HashMap;
3892	/// use hashbrown::hash_map::Entry;
3893	///
3894	/// let mut map: HashMap<&str, u32> = HashMap::new();
3895	/// map.entry("poneyland").or_insert(`12`);
3896	///
3897	/// if let Entry::Occupied(mut o) = map.entry("poneyland") {
3898	/// assert_eq!(o.insert(`15`), `12`);
3899	/// }
3900	///
3901	/// assert_eq!(map["poneyland"], `15`);
3902	/// ```
3903	#[cfg_attr(feature = "inline-more", inline)]
3904	pub fn insert(&mut self, value: V) -> V {
3905	mem::replace(self.get_mut(), value)
3906	}
3907
3908	/// Takes the value out of the entry, and returns it.
3909	/// Keeps the allocated memory for reuse.
3910	///
3911	/// # Examples
3912	///
3913	/// ```
3914	/// use hashbrown::HashMap;
3915	/// use hashbrown::hash_map::Entry;
3916	///
3917	/// let mut map: HashMap<&str, u32> = HashMap::new();
3918	/// // The map is empty
3919	/// assert!(map.is_empty() && map.capacity() == `0`);
3920	///
3921	/// map.entry("poneyland").or_insert(`12`);
3922	///
3923	/// if let Entry::Occupied(o) = map.entry("poneyland") {
3924	/// assert_eq!(o.remove(), `12`);
3925	/// }
3926	///
3927	/// assert_eq!(map.contains_key("poneyland"), `false`);
3928	/// // Now map hold none elements
3929	/// assert!(map.is_empty());
3930	/// ```
3931	#[cfg_attr(feature = "inline-more", inline)]
3932	pub fn remove(self) -> V {
3933	self.remove_entry().1
3934	}
3935
3936	/// Provides shared access to the key and owned access to the value of
3937	/// the entry and allows to replace or remove it based on the
3938	/// value of the returned option.
3939	///
3940	/// # Examples
3941	///
3942	/// ```
3943	/// use hashbrown::HashMap;
3944	/// use hashbrown::hash_map::Entry;
3945	///
3946	/// let mut map: HashMap<&str, u32> = HashMap::new();
3947	/// map.insert("poneyland", `42`);
3948	///
3949	/// let entry = match map.entry("poneyland") {
3950	/// Entry::Occupied(e) => {
3951	/// e.replace_entry_with(\|k, v\| {
3952	/// assert_eq!(k, &"poneyland");
3953	/// assert_eq!(v, `42`);
3954	/// Some(v + `1`)
3955	/// })
3956	/// }
3957	/// Entry::Vacant(_) => panic!(),
3958	/// };
3959	///
3960	/// match entry {
3961	/// Entry::Occupied(e) => {
3962	/// assert_eq!(e.key(), &"poneyland");
3963	/// assert_eq!(e.get(), &`43`);
3964	/// }
3965	/// Entry::Vacant(_) => panic!(),
3966	/// }
3967	///
3968	/// assert_eq!(map["poneyland"], `43`);
3969	///
3970	/// let entry = match map.entry("poneyland") {
3971	/// Entry::Occupied(e) => e.replace_entry_with(\|_k, _v\| None),
3972	/// Entry::Vacant(_) => panic!(),
3973	/// };
3974	///
3975	/// match entry {
3976	/// Entry::Vacant(e) => {
3977	/// assert_eq!(e.key(), &"poneyland");
3978	/// }
3979	/// Entry::Occupied(_) => panic!(),
3980	/// }
3981	///
3982	/// assert!(!map.contains_key("poneyland"));
3983	/// ```
3984	#[cfg_attr(feature = "inline-more", inline)]
3985	pub fn replace_entry_with<F>(self, f: F) -> Entry<'a, K, V, S, A>
3986	where
3987	F: FnOnce(&K, V) -> Option<V>,
3988	{
3989	unsafe {
3990	let mut spare_key = None;
3991
3992	self.table
3993	.table
3994	.replace_bucket_with(self.elem.clone(), \|(key, value)\| {
3995	if let Some(new_value) = f(&key, value) {
3996	Some((key, new_value))
3997	} else {
3998	spare_key = Some(key);
3999	None
4000	}
4001	});
4002
4003	if let Some(key) = spare_key {
4004	Entry::Vacant(VacantEntry {
4005	hash: self.hash,
4006	key,
4007	table: self.table,
4008	})
4009	} else {
4010	Entry::Occupied(self)
4011	}
4012	}
4013	}
4014	}
4015
4016	impl<'a, K, V, S, A: Allocator> VacantEntry<'a, K, V, S, A> {
4017	/// Gets a reference to the key that would be used when inserting a value
4018	/// through the `VacantEntry`.
4019	///
4020	/// # Examples
4021	///
4022	/// ```
4023	/// use hashbrown::HashMap;
4024	///
4025	/// let mut map: HashMap<&str, u32> = HashMap::new();
4026	/// assert_eq!(map.entry("poneyland").key(), &"poneyland");
4027	/// ```
4028	#[cfg_attr(feature = "inline-more", inline)]
4029	pub fn key(&self) -> &K {
4030	&self.key
4031	}
4032
4033	/// Take ownership of the key.
4034	///
4035	/// # Examples
4036	///
4037	/// ```
4038	/// use hashbrown::hash_map::{Entry, HashMap};
4039	///
4040	/// let mut map: HashMap<&str, u32> = HashMap::new();
4041	///
4042	/// match map.entry("poneyland") {
4043	/// Entry::Occupied(_) => panic!(),
4044	/// Entry::Vacant(v) => assert_eq!(v.into_key(), "poneyland"),
4045	/// }
4046	/// ```
4047	#[cfg_attr(feature = "inline-more", inline)]
4048	pub fn into_key(self) -> K {
4049	self.key
4050	}
4051
4052	/// Sets the value of the entry with the [`VacantEntry`]'s key,
4053	/// and returns a mutable reference to it.
4054	///
4055	/// # Examples
4056	///
4057	/// ```
4058	/// use hashbrown::HashMap;
4059	/// use hashbrown::hash_map::Entry;
4060	///
4061	/// let mut map: HashMap<&str, u32> = HashMap::new();
4062	///
4063	/// if let Entry::Vacant(o) = map.entry("poneyland") {
4064	/// o.insert(`37`);
4065	/// }
4066	/// assert_eq!(map["poneyland"], `37`);
4067	/// ```
4068	#[cfg_attr(feature = "inline-more", inline)]
4069	pub fn insert(self, value: V) -> &'a mut V
4070	where
4071	K: Hash,
4072	S: BuildHasher,
4073	{
4074	let table = &mut self.table.table;
4075	let entry = table.insert_entry(
4076	self.hash,
4077	(self.key, value),
4078	make_hasher::<_, V, S>(&self.table.hash_builder),
4079	);
4080	&mut entry.1
4081	}
4082
4083	/// Sets the value of the entry with the [`VacantEntry`]'s key,
4084	/// and returns an [`OccupiedEntry`].
4085	///
4086	/// # Examples
4087	///
4088	/// ```
4089	/// use hashbrown::HashMap;
4090	/// use hashbrown::hash_map::Entry;
4091	///
4092	/// let mut map: HashMap<&str, u32> = HashMap::new();
4093	///
4094	/// if let Entry::Vacant(v) = map.entry("poneyland") {
4095	/// let o = v.insert_entry(`37`);
4096	/// assert_eq!(o.get(), &`37`);
4097	/// }
4098	/// ```
4099	#[cfg_attr(feature = "inline-more", inline)]
4100	pub fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V, S, A>
4101	where
4102	K: Hash,
4103	S: BuildHasher,
4104	{
4105	let elem = self.table.table.insert(
4106	self.hash,
4107	(self.key, value),
4108	make_hasher::<_, V, S>(&self.table.hash_builder),
4109	);
4110	OccupiedEntry {
4111	hash: self.hash,
4112	elem,
4113	table: self.table,
4114	}
4115	}
4116	}
4117
4118	impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> EntryRef<'a, 'b, K, Q, V, S, A> {
4119	/// Sets the value of the entry, and returns an `OccupiedEntry`.
4120	///
4121	/// # Examples
4122	///
4123	/// ```
4124	/// use hashbrown::HashMap;
4125	///
4126	/// let mut map: HashMap<String, u32> = HashMap::new();
4127	/// let entry = map.entry_ref("horseyland").insert(`37`);
4128	///
4129	/// assert_eq!(entry.key(), "horseyland");
4130	/// ```
4131	#[cfg_attr(feature = "inline-more", inline)]
4132	pub fn insert(self, value: V) -> OccupiedEntry<'a, K, V, S, A>
4133	where
4134	K: Hash + From<&'b Q>,
4135	S: BuildHasher,
4136	{
4137	match self {
4138	EntryRef::Occupied(mut entry) => {
4139	entry.insert(value);
4140	entry
4141	}
4142	EntryRef::Vacant(entry) => entry.insert_entry(value),
4143	}
4144	}
4145
4146	/// Ensures a value is in the entry by inserting the default if empty, and returns
4147	/// a mutable reference to the value in the entry.
4148	///
4149	/// # Examples
4150	///
4151	/// ```
4152	/// use hashbrown::HashMap;
4153	///
4154	/// let mut map: HashMap<String, u32> = HashMap::new();
4155	///
4156	/// // nonexistent key
4157	/// map.entry_ref("poneyland").or_insert(`3`);
4158	/// assert_eq!(map["poneyland"], `3`);
4159	///
4160	/// // existing key
4161	/// map.entry_ref("poneyland").or_insert(`10`) = `2`;
4162	/// assert_eq!(map["poneyland"], `6`);
4163	/// ```
4164	#[cfg_attr(feature = "inline-more", inline)]
4165	pub fn or_insert(self, default: V) -> &'a mut V
4166	where
4167	K: Hash + From<&'b Q>,
4168	S: BuildHasher,
4169	{
4170	match self {
4171	EntryRef::Occupied(entry) => entry.into_mut(),
4172	EntryRef::Vacant(entry) => entry.insert(default),
4173	}
4174	}
4175
4176	/// Ensures a value is in the entry by inserting the result of the default function if empty,
4177	/// and returns a mutable reference to the value in the entry.
4178	///
4179	/// # Examples
4180	///
4181	/// ```
4182	/// use hashbrown::HashMap;
4183	///
4184	/// let mut map: HashMap<String, u32> = HashMap::new();
4185	///
4186	/// // nonexistent key
4187	/// map.entry_ref("poneyland").or_insert_with(\|\| `3`);
4188	/// assert_eq!(map["poneyland"], `3`);
4189	///
4190	/// // existing key
4191	/// map.entry_ref("poneyland").or_insert_with(\|\| `10`) = `2`;
4192	/// assert_eq!(map["poneyland"], `6`);
4193	/// ```
4194	#[cfg_attr(feature = "inline-more", inline)]
4195	pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V
4196	where
4197	K: Hash + From<&'b Q>,
4198	S: BuildHasher,
4199	{
4200	match self {
4201	EntryRef::Occupied(entry) => entry.into_mut(),
4202	EntryRef::Vacant(entry) => entry.insert(default()),
4203	}
4204	}
4205
4206	/// Ensures a value is in the entry by inserting, if empty, the result of the default function.
4207	/// This method allows for generating key-derived values for insertion by providing the default
4208	/// function an access to the borrower form of the key.
4209	///
4210	/// # Examples
4211	///
4212	/// ```
4213	/// use hashbrown::HashMap;
4214	///
4215	/// let mut map: HashMap<String, usize> = HashMap::new();
4216	///
4217	/// // nonexistent key
4218	/// map.entry_ref("poneyland").or_insert_with_key(\|key\| key.chars().count());
4219	/// assert_eq!(map["poneyland"], `9`);
4220	///
4221	/// // existing key
4222	/// map.entry_ref("poneyland").or_insert_with_key(\|key\| key.chars().count() `10`) *= `2`;
4223	/// assert_eq!(map["poneyland"], `18`);
4224	/// ```
4225	#[cfg_attr(feature = "inline-more", inline)]
4226	pub fn or_insert_with_key<F: FnOnce(&Q) -> V>(self, default: F) -> &'a mut V
4227	where
4228	K: Hash + Borrow<Q> + From<&'b Q>,
4229	S: BuildHasher,
4230	{
4231	match self {
4232	EntryRef::Occupied(entry) => entry.into_mut(),
4233	EntryRef::Vacant(entry) => {
4234	let value = default(entry.key);
4235	entry.insert(value)
4236	}
4237	}
4238	}
4239
4240	/// Returns a reference to this entry's key.
4241	///
4242	/// # Examples
4243	///
4244	/// ```
4245	/// use hashbrown::HashMap;
4246	///
4247	/// let mut map: HashMap<String, u32> = HashMap::new();
4248	/// map.entry_ref("poneyland").or_insert(`3`);
4249	/// // existing key
4250	/// assert_eq!(map.entry_ref("poneyland").key(), "poneyland");
4251	/// // nonexistent key
4252	/// assert_eq!(map.entry_ref("horseland").key(), "horseland");
4253	/// ```
4254	#[cfg_attr(feature = "inline-more", inline)]
4255	pub fn key(&self) -> &Q
4256	where
4257	K: Borrow<Q>,
4258	{
4259	match *self {
4260	EntryRef::Occupied(ref entry) => entry.key().borrow(),
4261	EntryRef::Vacant(ref entry) => entry.key(),
4262	}
4263	}
4264
4265	/// Provides in-place mutable access to an occupied entry before any
4266	/// potential inserts into the map.
4267	///
4268	/// # Examples
4269	///
4270	/// ```
4271	/// use hashbrown::HashMap;
4272	///
4273	/// let mut map: HashMap<String, u32> = HashMap::new();
4274	///
4275	/// map.entry_ref("poneyland")
4276	/// .and_modify(\|e\| { *e += `1` })
4277	/// .or_insert(`42`);
4278	/// assert_eq!(map["poneyland"], `42`);
4279	///
4280	/// map.entry_ref("poneyland")
4281	/// .and_modify(\|e\| { *e += `1` })
4282	/// .or_insert(`42`);
4283	/// assert_eq!(map["poneyland"], `43`);
4284	/// ```
4285	#[cfg_attr(feature = "inline-more", inline)]
4286	pub fn and_modify<F>(self, f: F) -> Self
4287	where
4288	F: FnOnce(&mut V),
4289	{
4290	match self {
4291	EntryRef::Occupied(mut entry) => {
4292	f(entry.get_mut());
4293	EntryRef::Occupied(entry)
4294	}
4295	EntryRef::Vacant(entry) => EntryRef::Vacant(entry),
4296	}
4297	}
4298	}
4299
4300	impl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator> EntryRef<'a, 'b, K, Q, V, S, A> {
4301	/// Ensures a value is in the entry by inserting the default value if empty,
4302	/// and returns a mutable reference to the value in the entry.
4303	///
4304	/// # Examples
4305	///
4306	/// ```
4307	/// use hashbrown::HashMap;
4308	///
4309	/// let mut map: HashMap<String, Option<u32>> = HashMap::new();
4310	///
4311	/// // nonexistent key
4312	/// map.entry_ref("poneyland").or_default();
4313	/// assert_eq!(map["poneyland"], None);
4314	///
4315	/// map.insert("horseland".to_string(), Some(`3`));
4316	///
4317	/// // existing key
4318	/// assert_eq!(map.entry_ref("horseland").or_default(), &mut Some(`3`));
4319	/// ```
4320	#[cfg_attr(feature = "inline-more", inline)]
4321	pub fn or_default(self) -> &'a mut V
4322	where
4323	K: Hash + From<&'b Q>,
4324	S: BuildHasher,
4325	{
4326	match self {
4327	EntryRef::Occupied(entry) => entry.into_mut(),
4328	EntryRef::Vacant(entry) => entry.insert(Default::default()),
4329	}
4330	}
4331	}
4332
4333	impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator> VacantEntryRef<'a, 'b, K, Q, V, S, A> {
4334	/// Gets a reference to the key that would be used when inserting a value
4335	/// through the `VacantEntryRef`.
4336	///
4337	/// # Examples
4338	///
4339	/// ```
4340	/// use hashbrown::HashMap;
4341	///
4342	/// let mut map: HashMap<String, u32> = HashMap::new();
4343	/// let key: &str = "poneyland";
4344	/// assert_eq!(map.entry_ref(key).key(), "poneyland");
4345	/// ```
4346	#[cfg_attr(feature = "inline-more", inline)]
4347	pub fn key(&self) -> &'b Q {
4348	self.key
4349	}
4350
4351	/// Sets the value of the entry with the `VacantEntryRef`'s key,
4352	/// and returns a mutable reference to it.
4353	///
4354	/// # Examples
4355	///
4356	/// ```
4357	/// use hashbrown::HashMap;
4358	/// use hashbrown::hash_map::EntryRef;
4359	///
4360	/// let mut map: HashMap<String, u32> = HashMap::new();
4361	/// let key: &str = "poneyland";
4362	///
4363	/// if let EntryRef::Vacant(o) = map.entry_ref(key) {
4364	/// o.insert(`37`);
4365	/// }
4366	/// assert_eq!(map["poneyland"], `37`);
4367	/// ```
4368	#[cfg_attr(feature = "inline-more", inline)]
4369	pub fn insert(self, value: V) -> &'a mut V
4370	where
4371	K: Hash + From<&'b Q>,
4372	S: BuildHasher,
4373	{
4374	let table = &mut self.table.table;
4375	let entry = table.insert_entry(
4376	self.hash,
4377	(self.key.into(), value),
4378	make_hasher::<_, V, S>(&self.table.hash_builder),
4379	);
4380	&mut entry.1
4381	}
4382
4383	/// Sets the value of the entry with the [`VacantEntryRef`]'s key,
4384	/// and returns an [`OccupiedEntry`].
4385	///
4386	/// # Examples
4387	///
4388	/// ```
4389	/// use hashbrown::HashMap;
4390	/// use hashbrown::hash_map::EntryRef;
4391	///
4392	/// let mut map: HashMap<&str, u32> = HashMap::new();
4393	///
4394	/// if let EntryRef::Vacant(v) = map.entry_ref("poneyland") {
4395	/// let o = v.insert_entry(`37`);
4396	/// assert_eq!(o.get(), &`37`);
4397	/// }
4398	/// ```
4399	#[cfg_attr(feature = "inline-more", inline)]
4400	pub fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V, S, A>
4401	where
4402	K: Hash + From<&'b Q>,
4403	S: BuildHasher,
4404	{
4405	let elem = self.table.table.insert(
4406	self.hash,
4407	(self.key.into(), value),
4408	make_hasher::<_, V, S>(&self.table.hash_builder),
4409	);
4410	OccupiedEntry {
4411	hash: self.hash,
4412	elem,
4413	table: self.table,
4414	}
4415	}
4416	}
4417
4418	impl<K, V, S, A> FromIterator<(K, V)> for HashMap<K, V, S, A>
4419	where
4420	K: Eq + Hash,
4421	S: BuildHasher + Default,
4422	A: Default + Allocator,
4423	{
4424	#[cfg_attr(feature = "inline-more", inline)]
4425	fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
4426	let iter: ::IntoIter = iter.into_iter();
4427	let mut map: HashMap =
4428	Self::with_capacity_and_hasher_in(capacity:iter.size_hint().0, S::default(), A::default());
4429	iter.for_each(\|(k: K, v: V)\| {
4430	map.insert(k, v);
4431	});
4432	map
4433	}
4434	}
4435
4436	/// Inserts all new key-values from the iterator and replaces values with existing
4437	/// keys with new values returned from the iterator.
4438	impl<K, V, S, A> Extend<(K, V)> for HashMap<K, V, S, A>
4439	where
4440	K: Eq + Hash,
4441	S: BuildHasher,
4442	A: Allocator,
4443	{
4444	/// Inserts all new key-values from the iterator to existing `HashMap<K, V, S, A>`.
4445	/// Replace values with existing keys with new values returned from the iterator.
4446	///
4447	/// # Examples
4448	///
4449	/// ```
4450	/// use hashbrown::hash_map::HashMap;
4451	///
4452	/// let mut map = HashMap::new();
4453	/// map.insert(`1`, `100`);
4454	///
4455	/// let some_iter = [(`1`, `1`), (`2`, `2`)].into_iter();
4456	/// map.extend(some_iter);
4457	/// // Replace values with existing keys with new values returned from the iterator.
4458	/// // So that the map.get(&1) doesn't return Some(&100).
4459	/// assert_eq!(map.get(&`1`), Some(&`1`));
4460	///
4461	/// let some_vec: Vec<_> = vec![(`3`, `3`), (`4`, `4`)];
4462	/// map.extend(some_vec);
4463	///
4464	/// let some_arr = [(`5`, `5`), (`6`, `6`)];
4465	/// map.extend(some_arr);
4466	/// let old_map_len = map.len();
4467	///
4468	/// // You can also extend from another HashMap
4469	/// let mut new_map = HashMap::new();
4470	/// new_map.extend(map);
4471	/// assert_eq!(new_map.len(), old_map_len);
4472	///
4473	/// let mut vec: Vec<_> = new_map.into_iter().collect();
4474	/// // The `IntoIter` iterator produces items in arbitrary order, so the
4475	/// // items must be sorted to test them against a sorted array.
4476	/// vec.sort_unstable();
4477	/// assert_eq!(vec, [(`1`, `1`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)]);
4478	/// ```
4479	#[cfg_attr(feature = "inline-more", inline)]
4480	fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
4481	// Keys may be already present or show multiple times in the iterator.
4482	// Reserve the entire hint lower bound if the map is empty.
4483	// Otherwise reserve half the hint (rounded up), so the map
4484	// will only resize twice in the worst case.
4485	let iter = iter.into_iter();
4486	let reserve = if self.is_empty() {
4487	iter.size_hint().0
4488	} else {
4489	(iter.size_hint().0 + `1`) / `2`
4490	};
4491	self.reserve(reserve);
4492	iter.for_each(move \|(k, v)\| {
4493	self.insert(k, v);
4494	});
4495	}
4496
4497	#[inline]
4498	#[cfg(feature = "nightly")]
4499	fn extend_one(&mut self, (k, v): (K, V)) {
4500	self.insert(k, v);
4501	}
4502
4503	#[inline]
4504	#[cfg(feature = "nightly")]
4505	fn extend_reserve(&mut self, additional: usize) {
4506	// Keys may be already present or show multiple times in the iterator.
4507	// Reserve the entire hint lower bound if the map is empty.
4508	// Otherwise reserve half the hint (rounded up), so the map
4509	// will only resize twice in the worst case.
4510	let reserve = if self.is_empty() {
4511	additional
4512	} else {
4513	(additional + `1`) / `2`
4514	};
4515	self.reserve(reserve);
4516	}
4517	}
4518
4519	/// Inserts all new key-values from the iterator and replaces values with existing
4520	/// keys with new values returned from the iterator.
4521	impl<'a, K, V, S, A> Extend<(&'a K, &'a V)> for HashMap<K, V, S, A>
4522	where
4523	K: Eq + Hash + Copy,
4524	V: Copy,
4525	S: BuildHasher,
4526	A: Allocator,
4527	{
4528	/// Inserts all new key-values from the iterator to existing `HashMap<K, V, S, A>`.
4529	/// Replace values with existing keys with new values returned from the iterator.
4530	/// The keys and values must implement [`Copy`] trait.
4531	///
4532	/// [`Copy`]: https://doc.rust-lang.org/core/marker/trait.Copy.html
4533	///
4534	/// # Examples
4535	///
4536	/// ```
4537	/// use hashbrown::hash_map::HashMap;
4538	///
4539	/// let mut map = HashMap::new();
4540	/// map.insert(`1`, `100`);
4541	///
4542	/// let arr = [(`1`, `1`), (`2`, `2`)];
4543	/// let some_iter = arr.iter().map(\|(k, v)\| (k, v));
4544	/// map.extend(some_iter);
4545	/// // Replace values with existing keys with new values returned from the iterator.
4546	/// // So that the map.get(&1) doesn't return Some(&100).
4547	/// assert_eq!(map.get(&`1`), Some(&`1`));
4548	///
4549	/// let some_vec: Vec<_> = vec![(`3`, `3`), (`4`, `4`)];
4550	/// map.extend(some_vec.iter().map(\|(k, v)\| (k, v)));
4551	///
4552	/// let some_arr = [(`5`, `5`), (`6`, `6`)];
4553	/// map.extend(some_arr.iter().map(\|(k, v)\| (k, v)));
4554	///
4555	/// // You can also extend from another HashMap
4556	/// let mut new_map = HashMap::new();
4557	/// new_map.extend(&map);
4558	/// assert_eq!(new_map, map);
4559	///
4560	/// let mut vec: Vec<_> = new_map.into_iter().collect();
4561	/// // The `IntoIter` iterator produces items in arbitrary order, so the
4562	/// // items must be sorted to test them against a sorted array.
4563	/// vec.sort_unstable();
4564	/// assert_eq!(vec, [(`1`, `1`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)]);
4565	/// ```
4566	#[cfg_attr(feature = "inline-more", inline)]
4567	fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T) {
4568	self.extend(iter.into_iter().map(\|(&key, &value)\| (key, value)));
4569	}
4570
4571	#[inline]
4572	#[cfg(feature = "nightly")]
4573	fn extend_one(&mut self, (k, v): (&'a K, &'a V)) {
4574	self.insert(k, v);
4575	}
4576
4577	#[inline]
4578	#[cfg(feature = "nightly")]
4579	fn extend_reserve(&mut self, additional: usize) {
4580	Extend::<(K, V)>::extend_reserve(self, additional);
4581	}
4582	}
4583
4584	/// Inserts all new key-values from the iterator and replaces values with existing
4585	/// keys with new values returned from the iterator.
4586	impl<'a, K, V, S, A> Extend<&'a (K, V)> for HashMap<K, V, S, A>
4587	where
4588	K: Eq + Hash + Copy,
4589	V: Copy,
4590	S: BuildHasher,
4591	A: Allocator,
4592	{
4593	/// Inserts all new key-values from the iterator to existing `HashMap<K, V, S, A>`.
4594	/// Replace values with existing keys with new values returned from the iterator.
4595	/// The keys and values must implement [`Copy`] trait.
4596	///
4597	/// [`Copy`]: https://doc.rust-lang.org/core/marker/trait.Copy.html
4598	///
4599	/// # Examples
4600	///
4601	/// ```
4602	/// use hashbrown::hash_map::HashMap;
4603	///
4604	/// let mut map = HashMap::new();
4605	/// map.insert(`1`, `100`);
4606	///
4607	/// let arr = [(`1`, `1`), (`2`, `2`)];
4608	/// let some_iter = arr.iter();
4609	/// map.extend(some_iter);
4610	/// // Replace values with existing keys with new values returned from the iterator.
4611	/// // So that the map.get(&1) doesn't return Some(&100).
4612	/// assert_eq!(map.get(&`1`), Some(&`1`));
4613	///
4614	/// let some_vec: Vec<_> = vec![(`3`, `3`), (`4`, `4`)];
4615	/// map.extend(&some_vec);
4616	///
4617	/// let some_arr = [(`5`, `5`), (`6`, `6`)];
4618	/// map.extend(&some_arr);
4619	///
4620	/// let mut vec: Vec<_> = map.into_iter().collect();
4621	/// // The `IntoIter` iterator produces items in arbitrary order, so the
4622	/// // items must be sorted to test them against a sorted array.
4623	/// vec.sort_unstable();
4624	/// assert_eq!(vec, [(`1`, `1`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)]);
4625	/// ```
4626	#[cfg_attr(feature = "inline-more", inline)]
4627	fn extend<T: IntoIterator<Item = &'a (K, V)>>(&mut self, iter: T) {
4628	self.extend(iter.into_iter().map(\|&(key, value)\| (key, value)));
4629	}
4630
4631	#[inline]
4632	#[cfg(feature = "nightly")]
4633	fn extend_one(&mut self, &(k, v): &'a (K, V)) {
4634	self.insert(k, v);
4635	}
4636
4637	#[inline]
4638	#[cfg(feature = "nightly")]
4639	fn extend_reserve(&mut self, additional: usize) {
4640	Extend::<(K, V)>::extend_reserve(self, additional);
4641	}
4642	}
4643
4644	#[allow(dead_code)]
4645	fn assert_covariance() {
4646	fn map_key<'new>(v: HashMap<&'static str, u8>) -> HashMap<&'new str, u8> {
4647	v
4648	}
4649	fn map_val<'new>(v: HashMap<u8, &'static str>) -> HashMap<u8, &'new str> {
4650	v
4651	}
4652	fn iter_key<'a, 'new>(v: Iter<'a, &'static str, u8>) -> Iter<'a, &'new str, u8> {
4653	v
4654	}
4655	fn iter_val<'a, 'new>(v: Iter<'a, u8, &'static str>) -> Iter<'a, u8, &'new str> {
4656	v
4657	}
4658	fn into_iter_key<'new, A: Allocator>(
4659	v: IntoIter<&'static str, u8, A>,
4660	) -> IntoIter<&'new str, u8, A> {
4661	v
4662	}
4663	fn into_iter_val<'new, A: Allocator>(
4664	v: IntoIter<u8, &'static str, A>,
4665	) -> IntoIter<u8, &'new str, A> {
4666	v
4667	}
4668	fn keys_key<'a, 'new>(v: Keys<'a, &'static str, u8>) -> Keys<'a, &'new str, u8> {
4669	v
4670	}
4671	fn keys_val<'a, 'new>(v: Keys<'a, u8, &'static str>) -> Keys<'a, u8, &'new str> {
4672	v
4673	}
4674	fn values_key<'a, 'new>(v: Values<'a, &'static str, u8>) -> Values<'a, &'new str, u8> {
4675	v
4676	}
4677	fn values_val<'a, 'new>(v: Values<'a, u8, &'static str>) -> Values<'a, u8, &'new str> {
4678	v
4679	}
4680	fn drain<'new>(
4681	d: Drain<'static, &'static str, &'static str>,
4682	) -> Drain<'new, &'new str, &'new str> {
4683	d
4684	}
4685	}
4686
4687	#[cfg(test)]
4688	mod test_map {
4689	use super::DefaultHashBuilder;
4690	use super::Entry::{Occupied, Vacant};
4691	use super::EntryRef;
4692	use super::HashMap;
4693	use alloc::string::{String, ToString};
4694	use alloc::sync::Arc;
4695	use allocator_api2::alloc::{AllocError, Allocator, Global};
4696	use core::alloc::Layout;
4697	use core::ptr::NonNull;
4698	use core::sync::atomic::{AtomicI8, Ordering};
4699	use rand::{rngs::SmallRng, Rng, SeedableRng};
4700	use std::borrow::ToOwned;
4701	use std::cell::RefCell;
4702	use std::vec::Vec;
4703
4704	#[test]
4705	fn test_zero_capacities() {
4706	type HM = HashMap<i32, i32>;
4707
4708	let m = HM::new();
4709	assert_eq!(m.capacity(), `0`);
4710
4711	let m = HM::default();
4712	assert_eq!(m.capacity(), `0`);
4713
4714	let m = HM::with_hasher(DefaultHashBuilder::default());
4715	assert_eq!(m.capacity(), `0`);
4716
4717	let m = HM::with_capacity(`0`);
4718	assert_eq!(m.capacity(), `0`);
4719
4720	let m = HM::with_capacity_and_hasher(`0`, DefaultHashBuilder::default());
4721	assert_eq!(m.capacity(), `0`);
4722
4723	let mut m = HM::new();
4724	m.insert(`1`, `1`);
4725	m.insert(`2`, `2`);
4726	m.remove(&`1`);
4727	m.remove(&`2`);
4728	m.shrink_to_fit();
4729	assert_eq!(m.capacity(), `0`);
4730
4731	let mut m = HM::new();
4732	m.reserve(`0`);
4733	assert_eq!(m.capacity(), `0`);
4734	}
4735
4736	#[test]
4737	fn test_create_capacity_zero() {
4738	let mut m = HashMap::with_capacity(`0`);
4739
4740	assert!(m.insert(`1`, `1`).is_none());
4741
4742	assert!(m.contains_key(&`1`));
4743	assert!(!m.contains_key(&`0`));
4744	}
4745
4746	#[test]
4747	fn test_insert() {
4748	let mut m = HashMap::new();
4749	assert_eq!(m.len(), `0`);
4750	assert!(m.insert(`1`, `2`).is_none());
4751	assert_eq!(m.len(), `1`);
4752	assert!(m.insert(`2`, `4`).is_none());
4753	assert_eq!(m.len(), `2`);
4754	assert_eq!(*m.get(&`1`).unwrap(), `2`);
4755	assert_eq!(*m.get(&`2`).unwrap(), `4`);
4756	}
4757
4758	#[test]
4759	fn test_clone() {
4760	let mut m = HashMap::new();
4761	assert_eq!(m.len(), `0`);
4762	assert!(m.insert(`1`, `2`).is_none());
4763	assert_eq!(m.len(), `1`);
4764	assert!(m.insert(`2`, `4`).is_none());
4765	assert_eq!(m.len(), `2`);
4766	#[allow(clippy::redundant_clone)]
4767	let m2 = m.clone();
4768	assert_eq!(*m2.get(&`1`).unwrap(), `2`);
4769	assert_eq!(*m2.get(&`2`).unwrap(), `4`);
4770	assert_eq!(m2.len(), `2`);
4771	}
4772
4773	#[test]
4774	fn test_clone_from() {
4775	let mut m = HashMap::new();
4776	let mut m2 = HashMap::new();
4777	assert_eq!(m.len(), `0`);
4778	assert!(m.insert(`1`, `2`).is_none());
4779	assert_eq!(m.len(), `1`);
4780	assert!(m.insert(`2`, `4`).is_none());
4781	assert_eq!(m.len(), `2`);
4782	m2.clone_from(&m);
4783	assert_eq!(*m2.get(&`1`).unwrap(), `2`);
4784	assert_eq!(*m2.get(&`2`).unwrap(), `4`);
4785	assert_eq!(m2.len(), `2`);
4786	}
4787
4788	thread_local! { static DROP_VECTOR: RefCell<Vec<i32>> = const { RefCell::new(Vec::new()) } }
4789
4790	#[derive(Hash, PartialEq, Eq)]
4791	struct Droppable {
4792	k: usize,
4793	}
4794
4795	impl Droppable {
4796	fn new(k: usize) -> Droppable {
4797	DROP_VECTOR.with(\|slot\| {
4798	slot.borrow_mut()[k] += `1`;
4799	});
4800
4801	Droppable { k }
4802	}
4803	}
4804
4805	impl Drop for Droppable {
4806	fn drop(&mut self) {
4807	DROP_VECTOR.with(\|slot\| {
4808	slot.borrow_mut()[self.k] -= `1`;
4809	});
4810	}
4811	}
4812
4813	impl Clone for Droppable {
4814	fn clone(&self) -> Self {
4815	Droppable::new(self.k)
4816	}
4817	}
4818
4819	#[test]
4820	fn test_drops() {
4821	DROP_VECTOR.with(\|slot\| {
4822	*slot.borrow_mut() = vec![`0`; `200`];
4823	});
4824
4825	{
4826	let mut m = HashMap::new();
4827
4828	DROP_VECTOR.with(\|v\| {
4829	for i in `0`..`200` {
4830	assert_eq!(v.borrow()[i], `0`);
4831	}
4832	});
4833
4834	for i in `0`..`100` {
4835	let d1 = Droppable::new(i);
4836	let d2 = Droppable::new(i + `100`);
4837	m.insert(d1, d2);
4838	}
4839
4840	DROP_VECTOR.with(\|v\| {
4841	for i in `0`..`200` {
4842	assert_eq!(v.borrow()[i], `1`);
4843	}
4844	});
4845
4846	for i in `0`..`50` {
4847	let k = Droppable::new(i);
4848	let v = m.remove(&k);
4849
4850	assert!(v.is_some());
4851
4852	DROP_VECTOR.with(\|v\| {
4853	assert_eq!(v.borrow()[i], `1`);
4854	assert_eq!(v.borrow()[i + `100`], `1`);
4855	});
4856	}
4857
4858	DROP_VECTOR.with(\|v\| {
4859	for i in `0`..`50` {
4860	assert_eq!(v.borrow()[i], `0`);
4861	assert_eq!(v.borrow()[i + `100`], `0`);
4862	}
4863
4864	for i in `50`..`100` {
4865	assert_eq!(v.borrow()[i], `1`);
4866	assert_eq!(v.borrow()[i + `100`], `1`);
4867	}
4868	});
4869	}
4870
4871	DROP_VECTOR.with(\|v\| {
4872	for i in `0`..`200` {
4873	assert_eq!(v.borrow()[i], `0`);
4874	}
4875	});
4876	}
4877
4878	#[test]
4879	fn test_into_iter_drops() {
4880	DROP_VECTOR.with(\|v\| {
4881	*v.borrow_mut() = vec![`0`; `200`];
4882	});
4883
4884	let hm = {
4885	let mut hm = HashMap::new();
4886
4887	DROP_VECTOR.with(\|v\| {
4888	for i in `0`..`200` {
4889	assert_eq!(v.borrow()[i], `0`);
4890	}
4891	});
4892
4893	for i in `0`..`100` {
4894	let d1 = Droppable::new(i);
4895	let d2 = Droppable::new(i + `100`);
4896	hm.insert(d1, d2);
4897	}
4898
4899	DROP_VECTOR.with(\|v\| {
4900	for i in `0`..`200` {
4901	assert_eq!(v.borrow()[i], `1`);
4902	}
4903	});
4904
4905	hm
4906	};
4907
4908	// By the way, ensure that cloning doesn't screw up the dropping.
4909	drop(hm.clone());
4910
4911	{
4912	let mut half = hm.into_iter().take(`50`);
4913
4914	DROP_VECTOR.with(\|v\| {
4915	for i in `0`..`200` {
4916	assert_eq!(v.borrow()[i], `1`);
4917	}
4918	});
4919
4920	for _ in half.by_ref() {}
4921
4922	DROP_VECTOR.with(\|v\| {
4923	let nk = (`0`..`100`).filter(\|&i\| v.borrow()[i] == `1`).count();
4924
4925	let nv = (`0`..`100`).filter(\|&i\| v.borrow()[i + `100`] == `1`).count();
4926
4927	assert_eq!(nk, `50`);
4928	assert_eq!(nv, `50`);
4929	});
4930	};
4931
4932	DROP_VECTOR.with(\|v\| {
4933	for i in `0`..`200` {
4934	assert_eq!(v.borrow()[i], `0`);
4935	}
4936	});
4937	}
4938
4939	#[test]
4940	fn test_empty_remove() {
4941	let mut m: HashMap<i32, bool> = HashMap::new();
4942	assert_eq!(m.remove(&`0`), None);
4943	}
4944
4945	#[test]
4946	fn test_empty_entry() {
4947	let mut m: HashMap<i32, bool> = HashMap::new();
4948	match m.entry(`0`) {
4949	Occupied(_) => panic!(),
4950	Vacant(_) => {}
4951	}
4952	assert!(*m.entry(`0`).or_insert(`true`));
4953	assert_eq!(m.len(), `1`);
4954	}
4955
4956	#[test]
4957	fn test_empty_entry_ref() {
4958	let mut m: HashMap<std::string::String, bool> = HashMap::new();
4959	match m.entry_ref("poneyland") {
4960	EntryRef::Occupied(_) => panic!(),
4961	EntryRef::Vacant(_) => {}
4962	}
4963	assert!(*m.entry_ref("poneyland").or_insert(`true`));
4964	assert_eq!(m.len(), `1`);
4965	}
4966
4967	#[test]
4968	fn test_empty_iter() {
4969	let mut m: HashMap<i32, bool> = HashMap::new();
4970	assert_eq!(m.drain().next(), None);
4971	assert_eq!(m.keys().next(), None);
4972	assert_eq!(m.values().next(), None);
4973	assert_eq!(m.values_mut().next(), None);
4974	assert_eq!(m.iter().next(), None);
4975	assert_eq!(m.iter_mut().next(), None);
4976	assert_eq!(m.len(), `0`);
4977	assert!(m.is_empty());
4978	assert_eq!(m.into_iter().next(), None);
4979	}
4980
4981	#[test]
4982	#[cfg_attr(miri, ignore)] // FIXME: takes too long
4983	fn test_lots_of_insertions() {
4984	let mut m = HashMap::new();
4985
4986	// Try this a few times to make sure we never screw up the hashmap's
4987	// internal state.
4988	for _ in `0`..`10` {
4989	assert!(m.is_empty());
4990
4991	for i in `1`..`1001` {
4992	assert!(m.insert(i, i).is_none());
4993
4994	for j in `1`..=i {
4995	let r = m.get(&j);
4996	assert_eq!(r, Some(&j));
4997	}
4998
4999	for j in i + `1`..`1001` {
5000	let r = m.get(&j);
5001	assert_eq!(r, None);
5002	}
5003	}
5004
5005	for i in `1001`..`2001` {
5006	assert!(!m.contains_key(&i));
5007	}
5008
5009	// remove forwards
5010	for i in `1`..`1001` {
5011	assert!(m.remove(&i).is_some());
5012
5013	for j in `1`..=i {
5014	assert!(!m.contains_key(&j));
5015	}
5016
5017	for j in i + `1`..`1001` {
5018	assert!(m.contains_key(&j));
5019	}
5020	}
5021
5022	for i in `1`..`1001` {
5023	assert!(!m.contains_key(&i));
5024	}
5025
5026	for i in `1`..`1001` {
5027	assert!(m.insert(i, i).is_none());
5028	}
5029
5030	// remove backwards
5031	for i in (`1`..`1001`).rev() {
5032	assert!(m.remove(&i).is_some());
5033
5034	for j in i..`1001` {
5035	assert!(!m.contains_key(&j));
5036	}
5037
5038	for j in `1`..i {
5039	assert!(m.contains_key(&j));
5040	}
5041	}
5042	}
5043	}
5044
5045	#[test]
5046	fn test_find_mut() {
5047	let mut m = HashMap::new();
5048	assert!(m.insert(`1`, `12`).is_none());
5049	assert!(m.insert(`2`, `8`).is_none());
5050	assert!(m.insert(`5`, `14`).is_none());
5051	let new = `100`;
5052	match m.get_mut(&`5`) {
5053	None => panic!(),
5054	Some(x) => *x = new,
5055	}
5056	assert_eq!(m.get(&`5`), Some(&new));
5057	}
5058
5059	#[test]
5060	fn test_insert_overwrite() {
5061	let mut m = HashMap::new();
5062	assert!(m.insert(`1`, `2`).is_none());
5063	assert_eq!(*m.get(&`1`).unwrap(), `2`);
5064	assert!(m.insert(`1`, `3`).is_some());
5065	assert_eq!(*m.get(&`1`).unwrap(), `3`);
5066	}
5067
5068	#[test]
5069	fn test_insert_conflicts() {
5070	let mut m = HashMap::with_capacity(`4`);
5071	assert!(m.insert(`1`, `2`).is_none());
5072	assert!(m.insert(`5`, `3`).is_none());
5073	assert!(m.insert(`9`, `4`).is_none());
5074	assert_eq!(*m.get(&`9`).unwrap(), `4`);
5075	assert_eq!(*m.get(&`5`).unwrap(), `3`);
5076	assert_eq!(*m.get(&`1`).unwrap(), `2`);
5077	}
5078
5079	#[test]
5080	fn test_conflict_remove() {
5081	let mut m = HashMap::with_capacity(`4`);
5082	assert!(m.insert(`1`, `2`).is_none());
5083	assert_eq!(*m.get(&`1`).unwrap(), `2`);
5084	assert!(m.insert(`5`, `3`).is_none());
5085	assert_eq!(*m.get(&`1`).unwrap(), `2`);
5086	assert_eq!(*m.get(&`5`).unwrap(), `3`);
5087	assert!(m.insert(`9`, `4`).is_none());
5088	assert_eq!(*m.get(&`1`).unwrap(), `2`);
5089	assert_eq!(*m.get(&`5`).unwrap(), `3`);
5090	assert_eq!(*m.get(&`9`).unwrap(), `4`);
5091	assert!(m.remove(&`1`).is_some());
5092	assert_eq!(*m.get(&`9`).unwrap(), `4`);
5093	assert_eq!(*m.get(&`5`).unwrap(), `3`);
5094	}
5095
5096	#[test]
5097	fn test_insert_unique_unchecked() {
5098	let mut map = HashMap::new();
5099	let (k1, v1) = unsafe { map.insert_unique_unchecked(`10`, `11`) };
5100	assert_eq!((&`10`, &mut `11`), (k1, v1));
5101	let (k2, v2) = unsafe { map.insert_unique_unchecked(`20`, `21`) };
5102	assert_eq!((&`20`, &mut `21`), (k2, v2));
5103	assert_eq!(Some(&`11`), map.get(&`10`));
5104	assert_eq!(Some(&`21`), map.get(&`20`));
5105	assert_eq!(None, map.get(&`30`));
5106	}
5107
5108	#[test]
5109	fn test_is_empty() {
5110	let mut m = HashMap::with_capacity(`4`);
5111	assert!(m.insert(`1`, `2`).is_none());
5112	assert!(!m.is_empty());
5113	assert!(m.remove(&`1`).is_some());
5114	assert!(m.is_empty());
5115	}
5116
5117	#[test]
5118	fn test_remove() {
5119	let mut m = HashMap::new();
5120	m.insert(`1`, `2`);
5121	assert_eq!(m.remove(&`1`), Some(`2`));
5122	assert_eq!(m.remove(&`1`), None);
5123	}
5124
5125	#[test]
5126	fn test_remove_entry() {
5127	let mut m = HashMap::new();
5128	m.insert(`1`, `2`);
5129	assert_eq!(m.remove_entry(&`1`), Some((`1`, `2`)));
5130	assert_eq!(m.remove(&`1`), None);
5131	}
5132
5133	#[test]
5134	fn test_iterate() {
5135	let mut m = HashMap::with_capacity(`4`);
5136	for i in `0`..`32` {
5137	assert!(m.insert(i, i * `2`).is_none());
5138	}
5139	assert_eq!(m.len(), `32`);
5140
5141	let mut observed: u32 = `0`;
5142
5143	for (k, v) in &m {
5144	assert_eq!(v, k * `2`);
5145	observed \|= `1` << *k;
5146	}
5147	assert_eq!(observed, `0xFFFF_FFFF`);
5148	}
5149
5150	#[test]
5151	fn test_keys() {
5152	let vec = vec![(`1`, 'a'), (`2`, 'b'), (`3`, 'c')];
5153	let map: HashMap<_, _> = vec.into_iter().collect();
5154	let keys: Vec<_> = map.keys().copied().collect();
5155	assert_eq!(keys.len(), `3`);
5156	assert!(keys.contains(&`1`));
5157	assert!(keys.contains(&`2`));
5158	assert!(keys.contains(&`3`));
5159	}
5160
5161	#[test]
5162	fn test_values() {
5163	let vec = vec![(`1`, 'a'), (`2`, 'b'), (`3`, 'c')];
5164	let map: HashMap<_, _> = vec.into_iter().collect();
5165	let values: Vec<_> = map.values().copied().collect();
5166	assert_eq!(values.len(), `3`);
5167	assert!(values.contains(&'a'));
5168	assert!(values.contains(&'b'));
5169	assert!(values.contains(&'c'));
5170	}
5171
5172	#[test]
5173	fn test_values_mut() {
5174	let vec = vec![(`1`, `1`), (`2`, `2`), (`3`, `3`)];
5175	let mut map: HashMap<_, _> = vec.into_iter().collect();
5176	for value in map.values_mut() {
5177	value = `2`;
5178	}
5179	let values: Vec<_> = map.values().copied().collect();
5180	assert_eq!(values.len(), `3`);
5181	assert!(values.contains(&`2`));
5182	assert!(values.contains(&`4`));
5183	assert!(values.contains(&`6`));
5184	}
5185
5186	#[test]
5187	fn test_into_keys() {
5188	let vec = vec![(`1`, 'a'), (`2`, 'b'), (`3`, 'c')];
5189	let map: HashMap<_, _> = vec.into_iter().collect();
5190	let keys: Vec<_> = map.into_keys().collect();
5191
5192	assert_eq!(keys.len(), `3`);
5193	assert!(keys.contains(&`1`));
5194	assert!(keys.contains(&`2`));
5195	assert!(keys.contains(&`3`));
5196	}
5197
5198	#[test]
5199	fn test_into_values() {
5200	let vec = vec![(`1`, 'a'), (`2`, 'b'), (`3`, 'c')];
5201	let map: HashMap<_, _> = vec.into_iter().collect();
5202	let values: Vec<_> = map.into_values().collect();
5203
5204	assert_eq!(values.len(), `3`);
5205	assert!(values.contains(&'a'));
5206	assert!(values.contains(&'b'));
5207	assert!(values.contains(&'c'));
5208	}
5209
5210	#[test]
5211	fn test_find() {
5212	let mut m = HashMap::new();
5213	assert!(m.get(&`1`).is_none());
5214	m.insert(`1`, `2`);
5215	match m.get(&`1`) {
5216	None => panic!(),
5217	Some(v) => assert_eq!(*v, `2`),
5218	}
5219	}
5220
5221	#[test]
5222	fn test_eq() {
5223	let mut m1 = HashMap::new();
5224	m1.insert(`1`, `2`);
5225	m1.insert(`2`, `3`);
5226	m1.insert(`3`, `4`);
5227
5228	let mut m2 = HashMap::new();
5229	m2.insert(`1`, `2`);
5230	m2.insert(`2`, `3`);
5231
5232	assert!(m1 != m2);
5233
5234	m2.insert(`3`, `4`);
5235
5236	assert_eq!(m1, m2);
5237	}
5238
5239	#[test]
5240	fn test_show() {
5241	let mut map = HashMap::new();
5242	let empty: HashMap<i32, i32> = HashMap::new();
5243
5244	map.insert(`1`, `2`);
5245	map.insert(`3`, `4`);
5246
5247	let map_str = format!("{map:?}");
5248
5249	assert!(map_str == "{1: 2, 3: 4}" \|\| map_str == "{3: 4, 1: 2}");
5250	assert_eq!(format!("{empty:?}"), "{}");
5251	}
5252
5253	#[test]
5254	fn test_expand() {
5255	let mut m = HashMap::new();
5256
5257	assert_eq!(m.len(), `0`);
5258	assert!(m.is_empty());
5259
5260	let mut i = `0`;
5261	let old_raw_cap = m.raw_capacity();
5262	while old_raw_cap == m.raw_capacity() {
5263	m.insert(i, i);
5264	i += `1`;
5265	}
5266
5267	assert_eq!(m.len(), i);
5268	assert!(!m.is_empty());
5269	}
5270
5271	#[test]
5272	fn test_behavior_resize_policy() {
5273	let mut m = HashMap::new();
5274
5275	assert_eq!(m.len(), `0`);
5276	assert_eq!(m.raw_capacity(), `1`);
5277	assert!(m.is_empty());
5278
5279	m.insert(`0`, `0`);
5280	m.remove(&`0`);
5281	assert!(m.is_empty());
5282	let initial_raw_cap = m.raw_capacity();
5283	m.reserve(initial_raw_cap);
5284	let raw_cap = m.raw_capacity();
5285
5286	assert_eq!(raw_cap, initial_raw_cap * `2`);
5287
5288	let mut i = `0`;
5289	for _ in `0`..raw_cap * `3` / `4` {
5290	m.insert(i, i);
5291	i += `1`;
5292	}
5293	// three quarters full
5294
5295	assert_eq!(m.len(), i);
5296	assert_eq!(m.raw_capacity(), raw_cap);
5297
5298	for _ in `0`..raw_cap / `4` {
5299	m.insert(i, i);
5300	i += `1`;
5301	}
5302	// half full
5303
5304	let new_raw_cap = m.raw_capacity();
5305	assert_eq!(new_raw_cap, raw_cap * `2`);
5306
5307	for _ in `0`..raw_cap / `2` - `1` {
5308	i -= `1`;
5309	m.remove(&i);
5310	assert_eq!(m.raw_capacity(), new_raw_cap);
5311	}
5312	// A little more than one quarter full.
5313	m.shrink_to_fit();
5314	assert_eq!(m.raw_capacity(), raw_cap);
5315	// again, a little more than half full
5316	for _ in `0`..raw_cap / `2` {
5317	i -= `1`;
5318	m.remove(&i);
5319	}
5320	m.shrink_to_fit();
5321
5322	assert_eq!(m.len(), i);
5323	assert!(!m.is_empty());
5324	assert_eq!(m.raw_capacity(), initial_raw_cap);
5325	}
5326
5327	#[test]
5328	fn test_reserve_shrink_to_fit() {
5329	let mut m = HashMap::new();
5330	m.insert(`0`, `0`);
5331	m.remove(&`0`);
5332	assert!(m.capacity() >= m.len());
5333	for i in `0`..`128` {
5334	m.insert(i, i);
5335	}
5336	m.reserve(`256`);
5337
5338	let usable_cap = m.capacity();
5339	for i in `128`..(`128` + `256`) {
5340	m.insert(i, i);
5341	assert_eq!(m.capacity(), usable_cap);
5342	}
5343
5344	for i in `100`..(`128` + `256`) {
5345	assert_eq!(m.remove(&i), Some(i));
5346	}
5347	m.shrink_to_fit();
5348
5349	assert_eq!(m.len(), `100`);
5350	assert!(!m.is_empty());
5351	assert!(m.capacity() >= m.len());
5352
5353	for i in `0`..`100` {
5354	assert_eq!(m.remove(&i), Some(i));
5355	}
5356	m.shrink_to_fit();
5357	m.insert(`0`, `0`);
5358
5359	assert_eq!(m.len(), `1`);
5360	assert!(m.capacity() >= m.len());
5361	assert_eq!(m.remove(&`0`), Some(`0`));
5362	}
5363
5364	#[test]
5365	fn test_from_iter() {
5366	let xs = [(`1`, `1`), (`2`, `2`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)];
5367
5368	let map: HashMap<_, _> = xs.iter().copied().collect();
5369
5370	for &(k, v) in &xs {
5371	assert_eq!(map.get(&k), Some(&v));
5372	}
5373
5374	assert_eq!(map.iter().len(), xs.len() - `1`);
5375	}
5376
5377	#[test]
5378	fn test_size_hint() {
5379	let xs = [(`1`, `1`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)];
5380
5381	let map: HashMap<_, _> = xs.iter().copied().collect();
5382
5383	let mut iter = map.iter();
5384
5385	for _ in iter.by_ref().take(`3`) {}
5386
5387	assert_eq!(iter.size_hint(), (`3`, Some(`3`)));
5388	}
5389
5390	#[test]
5391	fn test_iter_len() {
5392	let xs = [(`1`, `1`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)];
5393
5394	let map: HashMap<_, _> = xs.iter().copied().collect();
5395
5396	let mut iter = map.iter();
5397
5398	for _ in iter.by_ref().take(`3`) {}
5399
5400	assert_eq!(iter.len(), `3`);
5401	}
5402
5403	#[test]
5404	fn test_mut_size_hint() {
5405	let xs = [(`1`, `1`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)];
5406
5407	let mut map: HashMap<_, _> = xs.iter().copied().collect();
5408
5409	let mut iter = map.iter_mut();
5410
5411	for _ in iter.by_ref().take(`3`) {}
5412
5413	assert_eq!(iter.size_hint(), (`3`, Some(`3`)));
5414	}
5415
5416	#[test]
5417	fn test_iter_mut_len() {
5418	let xs = [(`1`, `1`), (`2`, `2`), (`3`, `3`), (`4`, `4`), (`5`, `5`), (`6`, `6`)];
5419
5420	let mut map: HashMap<_, _> = xs.iter().copied().collect();
5421
5422	let mut iter = map.iter_mut();
5423
5424	for _ in iter.by_ref().take(`3`) {}
5425
5426	assert_eq!(iter.len(), `3`);
5427	}
5428
5429	#[test]
5430	fn test_index() {
5431	let mut map = HashMap::new();
5432
5433	map.insert(`1`, `2`);
5434	map.insert(`2`, `1`);
5435	map.insert(`3`, `4`);
5436
5437	assert_eq!(map[&`2`], `1`);
5438	}
5439
5440	#[test]
5441	#[should_panic]
5442	fn test_index_nonexistent() {
5443	let mut map = HashMap::new();
5444
5445	map.insert(`1`, `2`);
5446	map.insert(`2`, `1`);
5447	map.insert(`3`, `4`);
5448
5449	#[allow(clippy::no_effect)] // false positive lint
5450	map[&`4`];
5451	}
5452
5453	#[test]
5454	fn test_entry() {
5455	let xs = [(`1`, `10`), (`2`, `20`), (`3`, `30`), (`4`, `40`), (`5`, `50`), (`6`, `60`)];
5456
5457	let mut map: HashMap<_, _> = xs.iter().copied().collect();
5458
5459	// Existing key (insert)
5460	match map.entry(`1`) {
5461	Vacant(_) => unreachable!(),
5462	Occupied(mut view) => {
5463	assert_eq!(view.get(), &`10`);
5464	assert_eq!(view.insert(`100`), `10`);
5465	}
5466	}
5467	assert_eq!(map.get(&`1`).unwrap(), &`100`);
5468	assert_eq!(map.len(), `6`);
5469
5470	// Existing key (update)
5471	match map.entry(`2`) {
5472	Vacant(_) => unreachable!(),
5473	Occupied(mut view) => {
5474	let v = view.get_mut();
5475	let new_v = (v) `10`;
5476	*v = new_v;
5477	}
5478	}
5479	assert_eq!(map.get(&`2`).unwrap(), &`200`);
5480	assert_eq!(map.len(), `6`);
5481
5482	// Existing key (take)
5483	match map.entry(`3`) {
5484	Vacant(_) => unreachable!(),
5485	Occupied(view) => {
5486	assert_eq!(view.remove(), `30`);
5487	}
5488	}
5489	assert_eq!(map.get(&`3`), None);
5490	assert_eq!(map.len(), `5`);
5491
5492	// Inexistent key (insert)
5493	match map.entry(`10`) {
5494	Occupied(_) => unreachable!(),
5495	Vacant(view) => {
5496	assert_eq!(*view.insert(`1000`), `1000`);
5497	}
5498	}
5499	assert_eq!(map.get(&`10`).unwrap(), &`1000`);
5500	assert_eq!(map.len(), `6`);
5501	}
5502
5503	#[test]
5504	fn test_entry_ref() {
5505	let xs = [
5506	("One".to_owned(), `10`),
5507	("Two".to_owned(), `20`),
5508	("Three".to_owned(), `30`),
5509	("Four".to_owned(), `40`),
5510	("Five".to_owned(), `50`),
5511	("Six".to_owned(), `60`),
5512	];
5513
5514	let mut map: HashMap<_, _> = xs.iter().cloned().collect();
5515
5516	// Existing key (insert)
5517	match map.entry_ref("One") {
5518	EntryRef::Vacant(_) => unreachable!(),
5519	EntryRef::Occupied(mut view) => {
5520	assert_eq!(view.get(), &`10`);
5521	assert_eq!(view.insert(`100`), `10`);
5522	}
5523	}
5524	assert_eq!(map.get("One").unwrap(), &`100`);
5525	assert_eq!(map.len(), `6`);
5526
5527	// Existing key (update)
5528	match map.entry_ref("Two") {
5529	EntryRef::Vacant(_) => unreachable!(),
5530	EntryRef::Occupied(mut view) => {
5531	let v = view.get_mut();
5532	let new_v = (v) `10`;
5533	*v = new_v;
5534	}
5535	}
5536	assert_eq!(map.get("Two").unwrap(), &`200`);
5537	assert_eq!(map.len(), `6`);
5538
5539	// Existing key (take)
5540	match map.entry_ref("Three") {
5541	EntryRef::Vacant(_) => unreachable!(),
5542	EntryRef::Occupied(view) => {
5543	assert_eq!(view.remove(), `30`);
5544	}
5545	}
5546	assert_eq!(map.get("Three"), None);
5547	assert_eq!(map.len(), `5`);
5548
5549	// Inexistent key (insert)
5550	match map.entry_ref("Ten") {
5551	EntryRef::Occupied(_) => unreachable!(),
5552	EntryRef::Vacant(view) => {
5553	assert_eq!(*view.insert(`1000`), `1000`);
5554	}
5555	}
5556	assert_eq!(map.get("Ten").unwrap(), &`1000`);
5557	assert_eq!(map.len(), `6`);
5558	}
5559
5560	#[test]
5561	fn test_entry_take_doesnt_corrupt() {
5562	#![allow(deprecated)] //rand
5563	// Test for #19292
5564	fn check(m: &HashMap<i32, ()>) {
5565	for k in m.keys() {
5566	assert!(m.contains_key(k), "{k} is in keys() but not in the map?");
5567	}
5568	}
5569
5570	let mut m = HashMap::new();
5571
5572	let mut rng = {
5573	let seed = u64::from_le_bytes(*b"testseed");
5574	SmallRng::seed_from_u64(seed)
5575	};
5576
5577	// Populate the map with some items.
5578	for _ in `0`..`50` {
5579	let x = rng.gen_range(`-10`..`10`);
5580	m.insert(x, ());
5581	}
5582
5583	for _ in `0`..`1000` {
5584	let x = rng.gen_range(`-10`..`10`);
5585	match m.entry(x) {
5586	Vacant(_) => {}
5587	Occupied(e) => {
5588	e.remove();
5589	}
5590	}
5591
5592	check(&m);
5593	}
5594	}
5595
5596	#[test]
5597	fn test_entry_ref_take_doesnt_corrupt() {
5598	#![allow(deprecated)] //rand
5599	// Test for #19292
5600	fn check(m: &HashMap<std::string::String, ()>) {
5601	for k in m.keys() {
5602	assert!(m.contains_key(k), "{k} is in keys() but not in the map?");
5603	}
5604	}
5605
5606	let mut m = HashMap::new();
5607
5608	let mut rng = {
5609	let seed = u64::from_le_bytes(*b"testseed");
5610	SmallRng::seed_from_u64(seed)
5611	};
5612
5613	// Populate the map with some items.
5614	for _ in `0`..`50` {
5615	let mut x = std::string::String::with_capacity(`1`);
5616	x.push(rng.gen_range('a'..='z'));
5617	m.insert(x, ());
5618	}
5619
5620	for _ in `0`..`1000` {
5621	let mut x = std::string::String::with_capacity(`1`);
5622	x.push(rng.gen_range('a'..='z'));
5623	match m.entry_ref(x.as_str()) {
5624	EntryRef::Vacant(_) => {}
5625	EntryRef::Occupied(e) => {
5626	e.remove();
5627	}
5628	}
5629
5630	check(&m);
5631	}
5632	}
5633
5634	#[test]
5635	fn test_extend_ref_k_ref_v() {
5636	let mut a = HashMap::new();
5637	a.insert(`1`, "one");
5638	let mut b = HashMap::new();
5639	b.insert(`2`, "two");
5640	b.insert(`3`, "three");
5641
5642	a.extend(&b);
5643
5644	assert_eq!(a.len(), `3`);
5645	assert_eq!(a[&`1`], "one");
5646	assert_eq!(a[&`2`], "two");
5647	assert_eq!(a[&`3`], "three");
5648	}
5649
5650	#[test]
5651	#[allow(clippy::needless_borrow)]
5652	fn test_extend_ref_kv_tuple() {
5653	use std::ops::AddAssign;
5654	let mut a = HashMap::new();
5655	a.insert(`0`, `0`);
5656
5657	fn create_arr<T: AddAssign<T> + Copy, const N: usize>(start: T, step: T) -> [(T, T); N] {
5658	let mut outs: [(T, T); N] = [(start, start); N];
5659	let mut element = step;
5660	outs.iter_mut().skip(`1`).for_each(\|(k, v)\| {
5661	*k += element;
5662	*v += element;
5663	element += step;
5664	});
5665	outs
5666	}
5667
5668	let for_iter: Vec<_> = (`0`..`100`).map(\|i\| (i, i)).collect();
5669	let iter = for_iter.iter();
5670	let vec: Vec<_> = (`100`..`200`).map(\|i\| (i, i)).collect();
5671	a.extend(iter);
5672	a.extend(&vec);
5673	a.extend(create_arr::<i32, `100`>(`200`, `1`));
5674
5675	assert_eq!(a.len(), `300`);
5676
5677	for item in `0`..`300` {
5678	assert_eq!(a[&item], item);
5679	}
5680	}
5681
5682	#[test]
5683	fn test_capacity_not_less_than_len() {
5684	let mut a = HashMap::new();
5685	let mut item = `0`;
5686
5687	for _ in `0`..`116` {
5688	a.insert(item, `0`);
5689	item += `1`;
5690	}
5691
5692	assert!(a.capacity() > a.len());
5693
5694	let free = a.capacity() - a.len();
5695	for _ in `0`..free {
5696	a.insert(item, `0`);
5697	item += `1`;
5698	}
5699
5700	assert_eq!(a.len(), a.capacity());
5701
5702	// Insert at capacity should cause allocation.
5703	a.insert(item, `0`);
5704	assert!(a.capacity() > a.len());
5705	}
5706
5707	#[test]
5708	fn test_occupied_entry_key() {
5709	let mut a = HashMap::new();
5710	let key = "hello there";
5711	let value = "value goes here";
5712	assert!(a.is_empty());
5713	a.insert(key, value);
5714	assert_eq!(a.len(), `1`);
5715	assert_eq!(a[key], value);
5716
5717	match a.entry(key) {
5718	Vacant(_) => panic!(),
5719	Occupied(e) => assert_eq!(key, *e.key()),
5720	}
5721	assert_eq!(a.len(), `1`);
5722	assert_eq!(a[key], value);
5723	}
5724
5725	#[test]
5726	fn test_occupied_entry_ref_key() {
5727	let mut a = HashMap::new();
5728	let key = "hello there";
5729	let value = "value goes here";
5730	assert!(a.is_empty());
5731	a.insert(key.to_owned(), value);
5732	assert_eq!(a.len(), `1`);
5733	assert_eq!(a[key], value);
5734
5735	match a.entry_ref(key) {
5736	EntryRef::Vacant(_) => panic!(),
5737	EntryRef::Occupied(e) => assert_eq!(key, e.key()),
5738	}
5739	assert_eq!(a.len(), `1`);
5740	assert_eq!(a[key], value);
5741	}
5742
5743	#[test]
5744	fn test_vacant_entry_key() {
5745	let mut a = HashMap::new();
5746	let key = "hello there";
5747	let value = "value goes here";
5748
5749	assert!(a.is_empty());
5750	match a.entry(key) {
5751	Occupied(_) => panic!(),
5752	Vacant(e) => {
5753	assert_eq!(key, *e.key());
5754	e.insert(value);
5755	}
5756	}
5757	assert_eq!(a.len(), `1`);
5758	assert_eq!(a[key], value);
5759	}
5760
5761	#[test]
5762	fn test_vacant_entry_ref_key() {
5763	let mut a: HashMap<std::string::String, &str> = HashMap::new();
5764	let key = "hello there";
5765	let value = "value goes here";
5766
5767	assert!(a.is_empty());
5768	match a.entry_ref(key) {
5769	EntryRef::Occupied(_) => panic!(),
5770	EntryRef::Vacant(e) => {
5771	assert_eq!(key, e.key());
5772	e.insert(value);
5773	}
5774	}
5775	assert_eq!(a.len(), `1`);
5776	assert_eq!(a[key], value);
5777	}
5778
5779	#[test]
5780	fn test_occupied_entry_replace_entry_with() {
5781	let mut a = HashMap::new();
5782
5783	let key = "a key";
5784	let value = "an initial value";
5785	let new_value = "a new value";
5786
5787	let entry = a.entry(key).insert(value).replace_entry_with(\|k, v\| {
5788	assert_eq!(k, &key);
5789	assert_eq!(v, value);
5790	Some(new_value)
5791	});
5792
5793	match entry {
5794	Occupied(e) => {
5795	assert_eq!(e.key(), &key);
5796	assert_eq!(e.get(), &new_value);
5797	}
5798	Vacant(_) => panic!(),
5799	}
5800
5801	assert_eq!(a[key], new_value);
5802	assert_eq!(a.len(), `1`);
5803
5804	let entry = match a.entry(key) {
5805	Occupied(e) => e.replace_entry_with(\|k, v\| {
5806	assert_eq!(k, &key);
5807	assert_eq!(v, new_value);
5808	None
5809	}),
5810	Vacant(_) => panic!(),
5811	};
5812
5813	match entry {
5814	Vacant(e) => assert_eq!(e.key(), &key),
5815	Occupied(_) => panic!(),
5816	}
5817
5818	assert!(!a.contains_key(key));
5819	assert_eq!(a.len(), `0`);
5820	}
5821
5822	#[test]
5823	fn test_entry_and_replace_entry_with() {
5824	let mut a = HashMap::new();
5825
5826	let key = "a key";
5827	let value = "an initial value";
5828	let new_value = "a new value";
5829
5830	let entry = a.entry(key).and_replace_entry_with(\|_, _\| panic!());
5831
5832	match entry {
5833	Vacant(e) => assert_eq!(e.key(), &key),
5834	Occupied(_) => panic!(),
5835	}
5836
5837	a.insert(key, value);
5838
5839	let entry = a.entry(key).and_replace_entry_with(\|k, v\| {
5840	assert_eq!(k, &key);
5841	assert_eq!(v, value);
5842	Some(new_value)
5843	});
5844
5845	match entry {
5846	Occupied(e) => {
5847	assert_eq!(e.key(), &key);
5848	assert_eq!(e.get(), &new_value);
5849	}
5850	Vacant(_) => panic!(),
5851	}
5852
5853	assert_eq!(a[key], new_value);
5854	assert_eq!(a.len(), `1`);
5855
5856	let entry = a.entry(key).and_replace_entry_with(\|k, v\| {
5857	assert_eq!(k, &key);
5858	assert_eq!(v, new_value);
5859	None
5860	});
5861
5862	match entry {
5863	Vacant(e) => assert_eq!(e.key(), &key),
5864	Occupied(_) => panic!(),
5865	}
5866
5867	assert!(!a.contains_key(key));
5868	assert_eq!(a.len(), `0`);
5869	}
5870
5871	#[test]
5872	fn test_replace_entry_with_doesnt_corrupt() {
5873	#![allow(deprecated)] //rand
5874	// Test for #19292
5875	fn check(m: &HashMap<i32, ()>) {
5876	for k in m.keys() {
5877	assert!(m.contains_key(k), "{k} is in keys() but not in the map?");
5878	}
5879	}
5880
5881	let mut m = HashMap::new();
5882
5883	let mut rng = {
5884	let seed = u64::from_le_bytes(*b"testseed");
5885	SmallRng::seed_from_u64(seed)
5886	};
5887
5888	// Populate the map with some items.
5889	for _ in `0`..`50` {
5890	let x = rng.gen_range(`-10`..`10`);
5891	m.insert(x, ());
5892	}
5893
5894	for _ in `0`..`1000` {
5895	let x = rng.gen_range(`-10`..`10`);
5896	m.entry(x).and_replace_entry_with(\|_, _\| None);
5897	check(&m);
5898	}
5899	}
5900
5901	#[test]
5902	fn test_retain() {
5903	let mut map: HashMap<i32, i32> = (`0`..`100`).map(\|x\| (x, x * `10`)).collect();
5904
5905	map.retain(\|&k, _\| k % `2` == `0`);
5906	assert_eq!(map.len(), `50`);
5907	assert_eq!(map[&`2`], `20`);
5908	assert_eq!(map[&`4`], `40`);
5909	assert_eq!(map[&`6`], `60`);
5910	}
5911
5912	#[test]
5913	fn test_extract_if() {
5914	{
5915	let mut map: HashMap<i32, i32> = (`0`..`8`).map(\|x\| (x, x * `10`)).collect();
5916	let drained = map.extract_if(\|&k, _\| k % `2` == `0`);
5917	let mut out = drained.collect::<Vec<_>>();
5918	out.sort_unstable();
5919	assert_eq!(vec![(`0`, `0`), (`2`, `20`), (`4`, `40`), (`6`, `60`)], out);
5920	assert_eq!(map.len(), `4`);
5921	}
5922	{
5923	let mut map: HashMap<i32, i32> = (`0`..`8`).map(\|x\| (x, x * `10`)).collect();
5924	map.extract_if(\|&k, _\| k % `2` == `0`).for_each(drop);
5925	assert_eq!(map.len(), `4`);
5926	}
5927	}
5928
5929	#[test]
5930	#[cfg_attr(miri, ignore)] // FIXME: no OOM signalling (https://github.com/rust-lang/miri/issues/613)
5931	fn test_try_reserve() {
5932	use crate::TryReserveError::{AllocError, CapacityOverflow};
5933
5934	const MAX_ISIZE: usize = isize::MAX as usize;
5935
5936	let mut empty_bytes: HashMap<u8, u8> = HashMap::new();
5937
5938	if let Err(CapacityOverflow) = empty_bytes.try_reserve(usize::MAX) {
5939	} else {
5940	panic!("usize::MAX should trigger an overflow!");
5941	}
5942
5943	if let Err(CapacityOverflow) = empty_bytes.try_reserve(MAX_ISIZE) {
5944	} else {
5945	panic!("isize::MAX should trigger an overflow!");
5946	}
5947
5948	if let Err(AllocError { .. }) = empty_bytes.try_reserve(MAX_ISIZE / `5`) {
5949	} else {
5950	// This may succeed if there is enough free memory. Attempt to
5951	// allocate a few more hashmaps to ensure the allocation will fail.
5952	let mut empty_bytes2: HashMap<u8, u8> = HashMap::new();
5953	let _ = empty_bytes2.try_reserve(MAX_ISIZE / `5`);
5954	let mut empty_bytes3: HashMap<u8, u8> = HashMap::new();
5955	let _ = empty_bytes3.try_reserve(MAX_ISIZE / `5`);
5956	let mut empty_bytes4: HashMap<u8, u8> = HashMap::new();
5957	if let Err(AllocError { .. }) = empty_bytes4.try_reserve(MAX_ISIZE / `5`) {
5958	} else {
5959	panic!("isize::MAX / 5 should trigger an OOM!");
5960	}
5961	}
5962	}
5963
5964	#[test]
5965	fn test_const_with_hasher() {
5966	use core::hash::BuildHasher;
5967	use std::collections::hash_map::DefaultHasher;
5968
5969	#[derive(Clone)]
5970	struct MyHasher;
5971	impl BuildHasher for MyHasher {
5972	type Hasher = DefaultHasher;
5973
5974	fn build_hasher(&self) -> DefaultHasher {
5975	DefaultHasher::new()
5976	}
5977	}
5978
5979	const EMPTY_MAP: HashMap<u32, std::string::String, MyHasher> =
5980	HashMap::with_hasher(MyHasher);
5981
5982	let mut map = EMPTY_MAP;
5983	map.insert(`17`, "seventeen".to_owned());
5984	assert_eq!("seventeen", map[&`17`]);
5985	}
5986
5987	#[test]
5988	fn test_get_many_mut() {
5989	let mut map = HashMap::new();
5990	map.insert("foo".to_owned(), `0`);
5991	map.insert("bar".to_owned(), `10`);
5992	map.insert("baz".to_owned(), `20`);
5993	map.insert("qux".to_owned(), `30`);
5994
5995	let xs = map.get_many_mut(["foo", "qux"]);
5996	assert_eq!(xs, [Some(&mut `0`), Some(&mut `30`)]);
5997
5998	let xs = map.get_many_mut(["foo", "dud"]);
5999	assert_eq!(xs, [Some(&mut `0`), None]);
6000
6001	let ys = map.get_many_key_value_mut(["bar", "baz"]);
6002	assert_eq!(
6003	ys,
6004	[
6005	Some((&"bar".to_owned(), &mut `10`)),
6006	Some((&"baz".to_owned(), &mut `20`))
6007	],
6008	);
6009
6010	let ys = map.get_many_key_value_mut(["bar", "dip"]);
6011	assert_eq!(ys, [Some((&"bar".to_string(), &mut `10`)), None]);
6012	}
6013
6014	#[test]
6015	#[should_panic = "duplicate keys found"]
6016	fn test_get_many_mut_duplicate() {
6017	let mut map = HashMap::new();
6018	map.insert("foo".to_owned(), `0`);
6019
6020	let _xs = map.get_many_mut(["foo", "foo"]);
6021	}
6022
6023	#[test]
6024	#[should_panic = "panic in drop"]
6025	fn test_clone_from_double_drop() {
6026	#[derive(Clone)]
6027	struct CheckedDrop {
6028	panic_in_drop: bool,
6029	dropped: bool,
6030	}
6031	impl Drop for CheckedDrop {
6032	fn drop(&mut self) {
6033	if self.panic_in_drop {
6034	self.dropped = `true`;
6035	panic!("panic in drop");
6036	}
6037	if self.dropped {
6038	panic!("double drop");
6039	}
6040	self.dropped = `true`;
6041	}
6042	}
6043	const DISARMED: CheckedDrop = CheckedDrop {
6044	panic_in_drop: `false`,
6045	dropped: `false`,
6046	};
6047	const ARMED: CheckedDrop = CheckedDrop {
6048	panic_in_drop: `true`,
6049	dropped: `false`,
6050	};
6051
6052	let mut map1 = HashMap::new();
6053	map1.insert(`1`, DISARMED);
6054	map1.insert(`2`, DISARMED);
6055	map1.insert(`3`, DISARMED);
6056	map1.insert(`4`, DISARMED);
6057
6058	let mut map2 = HashMap::new();
6059	map2.insert(`1`, DISARMED);
6060	map2.insert(`2`, ARMED);
6061	map2.insert(`3`, DISARMED);
6062	map2.insert(`4`, DISARMED);
6063
6064	map2.clone_from(&map1);
6065	}
6066
6067	#[test]
6068	#[should_panic = "panic in clone"]
6069	fn test_clone_from_memory_leaks() {
6070	use alloc::vec::Vec;
6071
6072	struct CheckedClone {
6073	panic_in_clone: bool,
6074	need_drop: Vec<i32>,
6075	}
6076	impl Clone for CheckedClone {
6077	fn clone(&self) -> Self {
6078	if self.panic_in_clone {
6079	panic!("panic in clone")
6080	}
6081	Self {
6082	panic_in_clone: self.panic_in_clone,
6083	need_drop: self.need_drop.clone(),
6084	}
6085	}
6086	}
6087	let mut map1 = HashMap::new();
6088	map1.insert(
6089	`1`,
6090	CheckedClone {
6091	panic_in_clone: `false`,
6092	need_drop: vec![`0`, `1`, `2`],
6093	},
6094	);
6095	map1.insert(
6096	`2`,
6097	CheckedClone {
6098	panic_in_clone: `false`,
6099	need_drop: vec![`3`, `4`, `5`],
6100	},
6101	);
6102	map1.insert(
6103	`3`,
6104	CheckedClone {
6105	panic_in_clone: `true`,
6106	need_drop: vec![`6`, `7`, `8`],
6107	},
6108	);
6109	let _map2 = map1.clone();
6110	}
6111
6112	struct MyAllocInner {
6113	drop_count: Arc<AtomicI8>,
6114	}
6115
6116	#[derive(Clone)]
6117	struct MyAlloc {
6118	_inner: Arc<MyAllocInner>,
6119	}
6120
6121	impl MyAlloc {
6122	fn new(drop_count: Arc<AtomicI8>) -> Self {
6123	MyAlloc {
6124	_inner: Arc::new(MyAllocInner { drop_count }),
6125	}
6126	}
6127	}
6128
6129	impl Drop for MyAllocInner {
6130	fn drop(&mut self) {
6131	println!("MyAlloc freed.");
6132	self.drop_count.fetch_sub(`1`, Ordering::SeqCst);
6133	}
6134	}
6135
6136	unsafe impl Allocator for MyAlloc {
6137	fn allocate(&self, layout: Layout) -> std::result::Result<NonNull<[u8]>, AllocError> {
6138	let g = Global;
6139	g.allocate(layout)
6140	}
6141
6142	unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
6143	let g = Global;
6144	g.deallocate(ptr, layout)
6145	}
6146	}
6147
6148	#[test]
6149	fn test_hashmap_into_iter_bug() {
6150	let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(`1`));
6151
6152	{
6153	let mut map = HashMap::with_capacity_in(`10`, MyAlloc::new(dropped.clone()));
6154	for i in `0`..`10` {
6155	map.entry(i).or_insert_with(\|\| "i".to_string());
6156	}
6157
6158	for (k, v) in map {
6159	println!("{}, {}", k, v);
6160	}
6161	}
6162
6163	// All allocator clones should already be dropped.
6164	assert_eq!(dropped.load(Ordering::SeqCst), `0`);
6165	}
6166
6167	#[derive(Debug)]
6168	struct CheckedCloneDrop<T> {
6169	panic_in_clone: bool,
6170	panic_in_drop: bool,
6171	dropped: bool,
6172	data: T,
6173	}
6174
6175	impl<T> CheckedCloneDrop<T> {
6176	fn new(panic_in_clone: bool, panic_in_drop: bool, data: T) -> Self {
6177	CheckedCloneDrop {
6178	panic_in_clone,
6179	panic_in_drop,
6180	dropped: `false`,
6181	data,
6182	}
6183	}
6184	}
6185
6186	impl<T: Clone> Clone for CheckedCloneDrop<T> {
6187	fn clone(&self) -> Self {
6188	if self.panic_in_clone {
6189	panic!("panic in clone")
6190	}
6191	Self {
6192	panic_in_clone: self.panic_in_clone,
6193	panic_in_drop: self.panic_in_drop,
6194	dropped: self.dropped,
6195	data: self.data.clone(),
6196	}
6197	}
6198	}
6199
6200	impl<T> Drop for CheckedCloneDrop<T> {
6201	fn drop(&mut self) {
6202	if self.panic_in_drop {
6203	self.dropped = `true`;
6204	panic!("panic in drop");
6205	}
6206	if self.dropped {
6207	panic!("double drop");
6208	}
6209	self.dropped = `true`;
6210	}
6211	}
6212
6213	/// Return hashmap with predefined distribution of elements.
6214	/// All elements will be located in the same order as elements
6215	/// returned by iterator.
6216	///
6217	/// This function does not panic, but returns an error as a `String`
6218	/// to distinguish between a test panic and an error in the input data.
6219	fn get_test_map<I, T, A>(
6220	iter: I,
6221	mut fun: impl FnMut(u64) -> T,
6222	alloc: A,
6223	) -> Result<HashMap<u64, CheckedCloneDrop<T>, DefaultHashBuilder, A>, String>
6224	where
6225	I: Iterator<Item = (bool, bool)> + Clone + ExactSizeIterator,
6226	A: Allocator,
6227	T: PartialEq + core::fmt::Debug,
6228	{
6229	use crate::scopeguard::guard;
6230
6231	let mut map: HashMap<u64, CheckedCloneDrop<T>, _, A> =
6232	HashMap::with_capacity_in(iter.size_hint().0, alloc);
6233	{
6234	let mut guard = guard(&mut map, \|map\| {
6235	for (_, value) in map.iter_mut() {
6236	value.panic_in_drop = `false`
6237	}
6238	});
6239
6240	let mut count = `0`;
6241	// Hash and Key must be equal to each other for controlling the elements placement.
6242	for (panic_in_clone, panic_in_drop) in iter.clone() {
6243	if core::mem::needs_drop::<T>() && panic_in_drop {
6244	return Err(String::from(
6245	"panic_in_drop can be set with a type that doesn't need to be dropped",
6246	));
6247	}
6248	guard.table.insert(
6249	count,
6250	(
6251	count,
6252	CheckedCloneDrop::new(panic_in_clone, panic_in_drop, fun(count)),
6253	),
6254	\|(k, _)\| *k,
6255	);
6256	count += `1`;
6257	}
6258
6259	// Let's check that all elements are located as we wanted
6260	let mut check_count = `0`;
6261	for ((key, value), (panic_in_clone, panic_in_drop)) in guard.iter().zip(iter) {
6262	if *key != check_count {
6263	return Err(format!(
6264	"key != check_count,`\n`key: `{}`,`\n`check_count: `{}`",
6265	key, check_count
6266	));
6267	}
6268	if value.dropped
6269	\|\| value.panic_in_clone != panic_in_clone
6270	\|\| value.panic_in_drop != panic_in_drop
6271	\|\| value.data != fun(check_count)
6272	{
6273	return Err(format!(
6274	"Value is not equal to expected,`\n`value: `{:?}`,`\n`expected: \
6275	`CheckedCloneDrop {{ panic_in_clone: {}, panic_in_drop: {}, dropped: {}, data: {:?} }}`",
6276	value, panic_in_clone, panic_in_drop, `false`, fun(check_count)
6277	));
6278	}
6279	check_count += `1`;
6280	}
6281
6282	if guard.len() != check_count as usize {
6283	return Err(format!(
6284	"map.len() != check_count,`\n`map.len(): `{}`,`\n`check_count: `{}`",
6285	guard.len(),
6286	check_count
6287	));
6288	}
6289
6290	if count != check_count {
6291	return Err(format!(
6292	"count != check_count,`\n`count: `{}`,`\n`check_count: `{}`",
6293	count, check_count
6294	));
6295	}
6296	core::mem::forget(guard);
6297	}
6298	Ok(map)
6299	}
6300
6301	const DISARMED: bool = `false`;
6302	const ARMED: bool = `true`;
6303
6304	const ARMED_FLAGS: [bool; `8`] = [
6305	DISARMED, DISARMED, DISARMED, ARMED, DISARMED, DISARMED, DISARMED, DISARMED,
6306	];
6307
6308	const DISARMED_FLAGS: [bool; `8`] = [
6309	DISARMED, DISARMED, DISARMED, DISARMED, DISARMED, DISARMED, DISARMED, DISARMED,
6310	];
6311
6312	#[test]
6313	#[should_panic = "panic in clone"]
6314	fn test_clone_memory_leaks_and_double_drop_one() {
6315	let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(`2`));
6316
6317	{
6318	assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
6319
6320	let map: HashMap<u64, CheckedCloneDrop<Vec<u64>>, DefaultHashBuilder, MyAlloc> =
6321	match get_test_map(
6322	ARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
6323	\|n\| vec![n],
6324	MyAlloc::new(dropped.clone()),
6325	) {
6326	Ok(map) => map,
6327	Err(msg) => panic!("{msg}"),
6328	};
6329
6330	// Clone should normally clone a few elements, and then (when the
6331	// clone function panics), deallocate both its own memory, memory
6332	// of `dropped: Arc<AtomicI8>` and the memory of already cloned
6333	// elements (Vec<i32> memory inside CheckedCloneDrop).
6334	let _map2 = map.clone();
6335	}
6336	}
6337
6338	#[test]
6339	#[should_panic = "panic in drop"]
6340	fn test_clone_memory_leaks_and_double_drop_two() {
6341	let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(`2`));
6342
6343	{
6344	assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
6345
6346	let map: HashMap<u64, CheckedCloneDrop<u64>, DefaultHashBuilder, _> = match get_test_map(
6347	DISARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
6348	\|n\| n,
6349	MyAlloc::new(dropped.clone()),
6350	) {
6351	Ok(map) => map,
6352	Err(msg) => panic!("{msg}"),
6353	};
6354
6355	let mut map2 = match get_test_map(
6356	DISARMED_FLAGS.into_iter().zip(ARMED_FLAGS),
6357	\|n\| n,
6358	MyAlloc::new(dropped.clone()),
6359	) {
6360	Ok(map) => map,
6361	Err(msg) => panic!("{msg}"),
6362	};
6363
6364	// The `clone_from` should try to drop the elements of `map2` without
6365	// double drop and leaking the allocator. Elements that have not been
6366	// dropped leak their memory.
6367	map2.clone_from(&map);
6368	}
6369	}
6370
6371	/// We check that we have a working table if the clone operation from another
6372	/// thread ended in a panic (when buckets of maps are equal to each other).
6373	#[test]
6374	fn test_catch_panic_clone_from_when_len_is_equal() {
6375	use std::thread;
6376
6377	let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(`2`));
6378
6379	{
6380	assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
6381
6382	let mut map = match get_test_map(
6383	DISARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
6384	\|n\| vec![n],
6385	MyAlloc::new(dropped.clone()),
6386	) {
6387	Ok(map) => map,
6388	Err(msg) => panic!("{msg}"),
6389	};
6390
6391	thread::scope(\|s\| {
6392	let result: thread::ScopedJoinHandle<'_, String> = s.spawn(\|\| {
6393	let scope_map =
6394	match get_test_map(ARMED_FLAGS.into_iter().zip(DISARMED_FLAGS), \|n\| vec![n * `2`], MyAlloc::new(dropped.clone())) {
6395	Ok(map) => map,
6396	Err(msg) => return msg,
6397	};
6398	if map.table.buckets() != scope_map.table.buckets() {
6399	return format!(
6400	"map.table.buckets() != scope_map.table.buckets(),`\n`left: `{}`,`\n`right: `{}`",
6401	map.table.buckets(), scope_map.table.buckets()
6402	);
6403	}
6404	map.clone_from(&scope_map);
6405	"We must fail the cloning!!!".to_owned()
6406	});
6407	if let Ok(msg) = result.join() {
6408	panic!("{msg}")
6409	}
6410	});
6411
6412	// Let's check that all iterators work fine and do not return elements
6413	// (especially `RawIterRange`, which does not depend on the number of
6414	// elements in the table, but looks directly at the control bytes)
6415	//
6416	// SAFETY: We know for sure that `RawTable` will outlive
6417	// the returned `RawIter / RawIterRange` iterator.
6418	assert_eq!(map.len(), `0`);
6419	assert_eq!(map.iter().count(), `0`);
6420	assert_eq!(unsafe { map.table.iter().count() }, `0`);
6421	assert_eq!(unsafe { map.table.iter().iter.count() }, `0`);
6422
6423	for idx in `0`..map.table.buckets() {
6424	let idx = idx as u64;
6425	assert!(
6426	map.table.find(idx, \|(k, _)\| *k == idx).is_none(),
6427	"Index: {idx}"
6428	);
6429	}
6430	}
6431
6432	// All allocator clones should already be dropped.
6433	assert_eq!(dropped.load(Ordering::SeqCst), `0`);
6434	}
6435
6436	/// We check that we have a working table if the clone operation from another
6437	/// thread ended in a panic (when buckets of maps are not equal to each other).
6438	#[test]
6439	fn test_catch_panic_clone_from_when_len_is_not_equal() {
6440	use std::thread;
6441
6442	let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(`2`));
6443
6444	{
6445	assert_eq!(ARMED_FLAGS.len(), DISARMED_FLAGS.len());
6446
6447	let mut map = match get_test_map(
6448	[DISARMED].into_iter().zip([DISARMED]),
6449	\|n\| vec![n],
6450	MyAlloc::new(dropped.clone()),
6451	) {
6452	Ok(map) => map,
6453	Err(msg) => panic!("{msg}"),
6454	};
6455
6456	thread::scope(\|s\| {
6457	let result: thread::ScopedJoinHandle<'_, String> = s.spawn(\|\| {
6458	let scope_map = match get_test_map(
6459	ARMED_FLAGS.into_iter().zip(DISARMED_FLAGS),
6460	\|n\| vec![n * `2`],
6461	MyAlloc::new(dropped.clone()),
6462	) {
6463	Ok(map) => map,
6464	Err(msg) => return msg,
6465	};
6466	if map.table.buckets() == scope_map.table.buckets() {
6467	return format!(
6468	"map.table.buckets() == scope_map.table.buckets(): `{}`",
6469	map.table.buckets()
6470	);
6471	}
6472	map.clone_from(&scope_map);
6473	"We must fail the cloning!!!".to_owned()
6474	});
6475	if let Ok(msg) = result.join() {
6476	panic!("{msg}")
6477	}
6478	});
6479
6480	// Let's check that all iterators work fine and do not return elements
6481	// (especially `RawIterRange`, which does not depend on the number of
6482	// elements in the table, but looks directly at the control bytes)
6483	//
6484	// SAFETY: We know for sure that `RawTable` will outlive
6485	// the returned `RawIter / RawIterRange` iterator.
6486	assert_eq!(map.len(), `0`);
6487	assert_eq!(map.iter().count(), `0`);
6488	assert_eq!(unsafe { map.table.iter().count() }, `0`);
6489	assert_eq!(unsafe { map.table.iter().iter.count() }, `0`);
6490
6491	for idx in `0`..map.table.buckets() {
6492	let idx = idx as u64;
6493	assert!(
6494	map.table.find(idx, \|(k, _)\| *k == idx).is_none(),
6495	"Index: {idx}"
6496	);
6497	}
6498	}
6499
6500	// All allocator clones should already be dropped.
6501	assert_eq!(dropped.load(Ordering::SeqCst), `0`);
6502	}
6503
6504	#[test]
6505	fn test_allocation_info() {
6506	assert_eq!(HashMap::<(), ()>::new().allocation_size(), `0`);
6507	assert_eq!(HashMap::<u32, u32>::new().allocation_size(), `0`);
6508	assert!(
6509	HashMap::<u32, u32>::with_capacity(`1`).allocation_size() > core::mem::size_of::<u32>()
6510	);
6511	}
6512	}
6513