core/ptr/
non_null.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
use crate::cmp::Ordering;
use crate::marker::Unsize;
use crate::mem::{MaybeUninit, SizedTypeProperties};
use crate::num::NonZero;
use crate::ops::{CoerceUnsized, DispatchFromDyn};
use crate::pin::PinCoerceUnsized;
use crate::ptr::Unique;
use crate::slice::{self, SliceIndex};
use crate::ub_checks::assert_unsafe_precondition;
use crate::{fmt, hash, intrinsics, mem, ptr};

/// `*mut T` but non-zero and [covariant].
///
/// This is often the correct thing to use when building data structures using
/// raw pointers, but is ultimately more dangerous to use because of its additional
/// properties. If you're not sure if you should use `NonNull<T>`, just use `*mut T`!
///
/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
/// is never dereferenced. This is so that enums may use this forbidden value
/// as a discriminant -- `Option<NonNull<T>>` has the same size as `*mut T`.
/// However the pointer may still dangle if it isn't dereferenced.
///
/// Unlike `*mut T`, `NonNull<T>` was chosen to be covariant over `T`. This makes it
/// possible to use `NonNull<T>` when building covariant types, but introduces the
/// risk of unsoundness if used in a type that shouldn't actually be covariant.
/// (The opposite choice was made for `*mut T` even though technically the unsoundness
/// could only be caused by calling unsafe functions.)
///
/// Covariance is correct for most safe abstractions, such as `Box`, `Rc`, `Arc`, `Vec`,
/// and `LinkedList`. This is the case because they provide a public API that follows the
/// normal shared XOR mutable rules of Rust.
///
/// If your type cannot safely be covariant, you must ensure it contains some
/// additional field to provide invariance. Often this field will be a [`PhantomData`]
/// type like `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
///
/// Notice that `NonNull<T>` has a `From` instance for `&T`. However, this does
/// not change the fact that mutating through a (pointer derived from a) shared
/// reference is undefined behavior unless the mutation happens inside an
/// [`UnsafeCell<T>`]. The same goes for creating a mutable reference from a shared
/// reference. When using this `From` instance without an `UnsafeCell<T>`,
/// it is your responsibility to ensure that `as_mut` is never called, and `as_ptr`
/// is never used for mutation.
///
/// # Representation
///
/// Thanks to the [null pointer optimization],
/// `NonNull<T>` and `Option<NonNull<T>>`
/// are guaranteed to have the same size and alignment:
///
/// ```
/// # use std::mem::{size_of, align_of};
/// use std::ptr::NonNull;
///
/// assert_eq!(size_of::<NonNull<i16>>(), size_of::<Option<NonNull<i16>>>());
/// assert_eq!(align_of::<NonNull<i16>>(), align_of::<Option<NonNull<i16>>>());
///
/// assert_eq!(size_of::<NonNull<str>>(), size_of::<Option<NonNull<str>>>());
/// assert_eq!(align_of::<NonNull<str>>(), align_of::<Option<NonNull<str>>>());
/// ```
///
/// [covariant]: https://doc.rust-lang.org/reference/subtyping.html
/// [`PhantomData`]: crate::marker::PhantomData
/// [`UnsafeCell<T>`]: crate::cell::UnsafeCell
/// [null pointer optimization]: crate::option#representation
#[stable(feature = "nonnull", since = "1.25.0")]
#[repr(transparent)]
#[rustc_layout_scalar_valid_range_start(1)]
#[rustc_nonnull_optimization_guaranteed]
#[rustc_diagnostic_item = "NonNull"]
pub struct NonNull<T: ?Sized> {
    // Remember to use `.as_ptr()` instead of `.pointer`, as field projecting to
    // this is banned by <https://github.com/rust-lang/compiler-team/issues/807>.
    pointer: *const T,
}

/// `NonNull` pointers are not `Send` because the data they reference may be aliased.
// N.B., this impl is unnecessary, but should provide better error messages.
#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> !Send for NonNull<T> {}

/// `NonNull` pointers are not `Sync` because the data they reference may be aliased.
// N.B., this impl is unnecessary, but should provide better error messages.
#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> !Sync for NonNull<T> {}

impl<T: Sized> NonNull<T> {
    /// Creates a new `NonNull` that is dangling, but well-aligned.
    ///
    /// This is useful for initializing types which lazily allocate, like
    /// `Vec::new` does.
    ///
    /// Note that the pointer value may potentially represent a valid pointer to
    /// a `T`, which means this must not be used as a "not yet initialized"
    /// sentinel value. Types that lazily allocate must track initialization by
    /// some other means.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let ptr = NonNull::<u32>::dangling();
    /// // Important: don't try to access the value of `ptr` without
    /// // initializing it first! The pointer is not null but isn't valid either!
    /// ```
    #[stable(feature = "nonnull", since = "1.25.0")]
    #[rustc_const_stable(feature = "const_nonnull_dangling", since = "1.36.0")]
    #[must_use]
    #[inline]
    pub const fn dangling() -> Self {
        // SAFETY: ptr::dangling_mut() returns a non-null well-aligned pointer.
        unsafe {
            let ptr = crate::ptr::dangling_mut::<T>();
            NonNull::new_unchecked(ptr)
        }
    }

    /// Returns a shared references to the value. In contrast to [`as_ref`], this does not require
    /// that the value has to be initialized.
    ///
    /// For the mutable counterpart see [`as_uninit_mut`].
    ///
    /// [`as_ref`]: NonNull::as_ref
    /// [`as_uninit_mut`]: NonNull::as_uninit_mut
    ///
    /// # Safety
    ///
    /// When calling this method, you have to ensure that
    /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
    /// Note that because the created reference is to `MaybeUninit<T>`, the
    /// source pointer can point to uninitialized memory.
    #[inline]
    #[must_use]
    #[unstable(feature = "ptr_as_uninit", issue = "75402")]
    pub const unsafe fn as_uninit_ref<'a>(self) -> &'a MaybeUninit<T> {
        // SAFETY: the caller must guarantee that `self` meets all the
        // requirements for a reference.
        unsafe { &*self.cast().as_ptr() }
    }

    /// Returns a unique references to the value. In contrast to [`as_mut`], this does not require
    /// that the value has to be initialized.
    ///
    /// For the shared counterpart see [`as_uninit_ref`].
    ///
    /// [`as_mut`]: NonNull::as_mut
    /// [`as_uninit_ref`]: NonNull::as_uninit_ref
    ///
    /// # Safety
    ///
    /// When calling this method, you have to ensure that
    /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
    /// Note that because the created reference is to `MaybeUninit<T>`, the
    /// source pointer can point to uninitialized memory.
    #[inline]
    #[must_use]
    #[unstable(feature = "ptr_as_uninit", issue = "75402")]
    pub const unsafe fn as_uninit_mut<'a>(self) -> &'a mut MaybeUninit<T> {
        // SAFETY: the caller must guarantee that `self` meets all the
        // requirements for a reference.
        unsafe { &mut *self.cast().as_ptr() }
    }
}

impl<T: ?Sized> NonNull<T> {
    /// Creates a new `NonNull`.
    ///
    /// # Safety
    ///
    /// `ptr` must be non-null.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let mut x = 0u32;
    /// let ptr = unsafe { NonNull::new_unchecked(&mut x as *mut _) };
    /// ```
    ///
    /// *Incorrect* usage of this function:
    ///
    /// ```rust,no_run
    /// use std::ptr::NonNull;
    ///
    /// // NEVER DO THAT!!! This is undefined behavior. ⚠️
    /// let ptr = unsafe { NonNull::<u32>::new_unchecked(std::ptr::null_mut()) };
    /// ```
    #[stable(feature = "nonnull", since = "1.25.0")]
    #[rustc_const_stable(feature = "const_nonnull_new_unchecked", since = "1.25.0")]
    #[inline]
    pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
        // SAFETY: the caller must guarantee that `ptr` is non-null.
        unsafe {
            assert_unsafe_precondition!(
                check_language_ub,
                "NonNull::new_unchecked requires that the pointer is non-null",
                (ptr: *mut () = ptr as *mut ()) => !ptr.is_null()
            );
            NonNull { pointer: ptr as _ }
        }
    }

    /// Creates a new `NonNull` if `ptr` is non-null.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let mut x = 0u32;
    /// let ptr = NonNull::<u32>::new(&mut x as *mut _).expect("ptr is null!");
    ///
    /// if let Some(ptr) = NonNull::<u32>::new(std::ptr::null_mut()) {
    ///     unreachable!();
    /// }
    /// ```
    #[stable(feature = "nonnull", since = "1.25.0")]
    #[rustc_const_unstable(feature = "const_nonnull_new", issue = "93235")]
    #[inline]
    pub const fn new(ptr: *mut T) -> Option<Self> {
        if !ptr.is_null() {
            // SAFETY: The pointer is already checked and is not null
            Some(unsafe { Self::new_unchecked(ptr) })
        } else {
            None
        }
    }

    /// Converts a reference to a `NonNull` pointer.
    #[unstable(feature = "non_null_from_ref", issue = "130823")]
    #[inline]
    pub const fn from_ref(r: &T) -> Self {
        // SAFETY: A reference cannot be null.
        unsafe { NonNull { pointer: r as *const T } }
    }

    /// Converts a mutable reference to a `NonNull` pointer.
    #[unstable(feature = "non_null_from_ref", issue = "130823")]
    #[inline]
    pub const fn from_mut(r: &mut T) -> Self {
        // SAFETY: A mutable reference cannot be null.
        unsafe { NonNull { pointer: r as *mut T } }
    }

    /// Performs the same functionality as [`std::ptr::from_raw_parts`], except that a
    /// `NonNull` pointer is returned, as opposed to a raw `*const` pointer.
    ///
    /// See the documentation of [`std::ptr::from_raw_parts`] for more details.
    ///
    /// [`std::ptr::from_raw_parts`]: crate::ptr::from_raw_parts
    #[unstable(feature = "ptr_metadata", issue = "81513")]
    #[inline]
    pub const fn from_raw_parts(
        data_pointer: NonNull<impl super::Thin>,
        metadata: <T as super::Pointee>::Metadata,
    ) -> NonNull<T> {
        // SAFETY: The result of `ptr::from::raw_parts_mut` is non-null because `data_pointer` is.
        unsafe {
            NonNull::new_unchecked(super::from_raw_parts_mut(data_pointer.as_ptr(), metadata))
        }
    }

    /// Decompose a (possibly wide) pointer into its data pointer and metadata components.
    ///
    /// The pointer can be later reconstructed with [`NonNull::from_raw_parts`].
    #[unstable(feature = "ptr_metadata", issue = "81513")]
    #[must_use = "this returns the result of the operation, \
                  without modifying the original"]
    #[inline]
    pub const fn to_raw_parts(self) -> (NonNull<()>, <T as super::Pointee>::Metadata) {
        (self.cast(), super::metadata(self.as_ptr()))
    }

    /// Gets the "address" portion of the pointer.
    ///
    /// For more details see the equivalent method on a raw pointer, [`pointer::addr`].
    ///
    /// This is a [Strict Provenance][crate::ptr#strict-provenance] API.
    #[must_use]
    #[inline]
    #[stable(feature = "strict_provenance", since = "1.84.0")]
    pub fn addr(self) -> NonZero<usize> {
        // SAFETY: The pointer is guaranteed by the type to be non-null,
        // meaning that the address will be non-zero.
        unsafe { NonZero::new_unchecked(self.as_ptr().addr()) }
    }

    /// Creates a new pointer with the given address and the [provenance][crate::ptr#provenance] of
    /// `self`.
    ///
    /// For more details see the equivalent method on a raw pointer, [`pointer::with_addr`].
    ///
    /// This is a [Strict Provenance][crate::ptr#strict-provenance] API.
    #[must_use]
    #[inline]
    #[stable(feature = "strict_provenance", since = "1.84.0")]
    pub fn with_addr(self, addr: NonZero<usize>) -> Self {
        // SAFETY: The result of `ptr::from::with_addr` is non-null because `addr` is guaranteed to be non-zero.
        unsafe { NonNull::new_unchecked(self.as_ptr().with_addr(addr.get()) as *mut _) }
    }

    /// Creates a new pointer by mapping `self`'s address to a new one, preserving the
    /// [provenance][crate::ptr#provenance] of `self`.
    ///
    /// For more details see the equivalent method on a raw pointer, [`pointer::map_addr`].
    ///
    /// This is a [Strict Provenance][crate::ptr#strict-provenance] API.
    #[must_use]
    #[inline]
    #[stable(feature = "strict_provenance", since = "1.84.0")]
    pub fn map_addr(self, f: impl FnOnce(NonZero<usize>) -> NonZero<usize>) -> Self {
        self.with_addr(f(self.addr()))
    }

    /// Acquires the underlying `*mut` pointer.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let mut x = 0u32;
    /// let ptr = NonNull::new(&mut x).expect("ptr is null!");
    ///
    /// let x_value = unsafe { *ptr.as_ptr() };
    /// assert_eq!(x_value, 0);
    ///
    /// unsafe { *ptr.as_ptr() += 2; }
    /// let x_value = unsafe { *ptr.as_ptr() };
    /// assert_eq!(x_value, 2);
    /// ```
    #[stable(feature = "nonnull", since = "1.25.0")]
    #[rustc_const_stable(feature = "const_nonnull_as_ptr", since = "1.32.0")]
    #[rustc_never_returns_null_ptr]
    #[must_use]
    #[inline(always)]
    pub const fn as_ptr(self) -> *mut T {
        // This is a transmute for the same reasons as `NonZero::get`.

        // SAFETY: `NonNull` is `transparent` over a `*const T`, and `*const T`
        // and `*mut T` have the same layout, so transitively we can transmute
        // our `NonNull` to a `*mut T` directly.
        unsafe { mem::transmute::<Self, *mut T>(self) }
    }

    /// Returns a shared reference to the value. If the value may be uninitialized, [`as_uninit_ref`]
    /// must be used instead.
    ///
    /// For the mutable counterpart see [`as_mut`].
    ///
    /// [`as_uninit_ref`]: NonNull::as_uninit_ref
    /// [`as_mut`]: NonNull::as_mut
    ///
    /// # Safety
    ///
    /// When calling this method, you have to ensure that
    /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let mut x = 0u32;
    /// let ptr = NonNull::new(&mut x as *mut _).expect("ptr is null!");
    ///
    /// let ref_x = unsafe { ptr.as_ref() };
    /// println!("{ref_x}");
    /// ```
    ///
    /// [the module documentation]: crate::ptr#safety
    #[stable(feature = "nonnull", since = "1.25.0")]
    #[rustc_const_stable(feature = "const_nonnull_as_ref", since = "1.73.0")]
    #[must_use]
    #[inline(always)]
    pub const unsafe fn as_ref<'a>(&self) -> &'a T {
        // SAFETY: the caller must guarantee that `self` meets all the
        // requirements for a reference.
        // `cast_const` avoids a mutable raw pointer deref.
        unsafe { &*self.as_ptr().cast_const() }
    }

    /// Returns a unique reference to the value. If the value may be uninitialized, [`as_uninit_mut`]
    /// must be used instead.
    ///
    /// For the shared counterpart see [`as_ref`].
    ///
    /// [`as_uninit_mut`]: NonNull::as_uninit_mut
    /// [`as_ref`]: NonNull::as_ref
    ///
    /// # Safety
    ///
    /// When calling this method, you have to ensure that
    /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let mut x = 0u32;
    /// let mut ptr = NonNull::new(&mut x).expect("null pointer");
    ///
    /// let x_ref = unsafe { ptr.as_mut() };
    /// assert_eq!(*x_ref, 0);
    /// *x_ref += 2;
    /// assert_eq!(*x_ref, 2);
    /// ```
    ///
    /// [the module documentation]: crate::ptr#safety
    #[stable(feature = "nonnull", since = "1.25.0")]
    #[rustc_const_stable(feature = "const_ptr_as_ref", since = "1.83.0")]
    #[must_use]
    #[inline(always)]
    pub const unsafe fn as_mut<'a>(&mut self) -> &'a mut T {
        // SAFETY: the caller must guarantee that `self` meets all the
        // requirements for a mutable reference.
        unsafe { &mut *self.as_ptr() }
    }

    /// Casts to a pointer of another type.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let mut x = 0u32;
    /// let ptr = NonNull::new(&mut x as *mut _).expect("null pointer");
    ///
    /// let casted_ptr = ptr.cast::<i8>();
    /// let raw_ptr: *mut i8 = casted_ptr.as_ptr();
    /// ```
    #[stable(feature = "nonnull_cast", since = "1.27.0")]
    #[rustc_const_stable(feature = "const_nonnull_cast", since = "1.36.0")]
    #[must_use = "this returns the result of the operation, \
                  without modifying the original"]
    #[inline]
    pub const fn cast<U>(self) -> NonNull<U> {
        // SAFETY: `self` is a `NonNull` pointer which is necessarily non-null
        unsafe { NonNull { pointer: self.as_ptr() as *mut U } }
    }

    /// Adds an offset to a pointer.
    ///
    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
    /// offset of `3 * size_of::<T>()` bytes.
    ///
    /// # Safety
    ///
    /// If any of the following conditions are violated, the result is Undefined Behavior:
    ///
    /// * The computed offset, `count * size_of::<T>()` bytes, must not overflow `isize`.
    ///
    /// * If the computed offset is non-zero, then `self` must be derived from a pointer to some
    ///   [allocated object], and the entire memory range between `self` and the result must be in
    ///   bounds of that allocated object. In particular, this range must not "wrap around" the edge
    ///   of the address space.
    ///
    /// Allocated objects can never be larger than `isize::MAX` bytes, so if the computed offset
    /// stays in bounds of the allocated object, it is guaranteed to satisfy the first requirement.
    /// This implies, for instance, that `vec.as_ptr().add(vec.len())` (for `vec: Vec<T>`) is always
    /// safe.
    ///
    /// [allocated object]: crate::ptr#allocated-object
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let mut s = [1, 2, 3];
    /// let ptr: NonNull<u32> = NonNull::new(s.as_mut_ptr()).unwrap();
    ///
    /// unsafe {
    ///     println!("{}", ptr.offset(1).read());
    ///     println!("{}", ptr.offset(2).read());
    /// }
    /// ```
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[must_use = "returns a new pointer rather than modifying its argument"]
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn offset(self, count: isize) -> Self
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `offset`.
        // Additionally safety contract of `offset` guarantees that the resulting pointer is
        // pointing to an allocation, there can't be an allocation at null, thus it's safe to
        // construct `NonNull`.
        unsafe { NonNull { pointer: intrinsics::offset(self.as_ptr(), count) } }
    }

    /// Calculates the offset from a pointer in bytes.
    ///
    /// `count` is in units of **bytes**.
    ///
    /// This is purely a convenience for casting to a `u8` pointer and
    /// using [offset][pointer::offset] on it. See that method for documentation
    /// and safety requirements.
    ///
    /// For non-`Sized` pointees this operation changes only the data pointer,
    /// leaving the metadata untouched.
    #[must_use]
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn byte_offset(self, count: isize) -> Self {
        // SAFETY: the caller must uphold the safety contract for `offset` and `byte_offset` has
        // the same safety contract.
        // Additionally safety contract of `offset` guarantees that the resulting pointer is
        // pointing to an allocation, there can't be an allocation at null, thus it's safe to
        // construct `NonNull`.
        unsafe { NonNull { pointer: self.as_ptr().byte_offset(count) } }
    }

    /// Adds an offset to a pointer (convenience for `.offset(count as isize)`).
    ///
    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
    /// offset of `3 * size_of::<T>()` bytes.
    ///
    /// # Safety
    ///
    /// If any of the following conditions are violated, the result is Undefined Behavior:
    ///
    /// * The computed offset, `count * size_of::<T>()` bytes, must not overflow `isize`.
    ///
    /// * If the computed offset is non-zero, then `self` must be derived from a pointer to some
    ///   [allocated object], and the entire memory range between `self` and the result must be in
    ///   bounds of that allocated object. In particular, this range must not "wrap around" the edge
    ///   of the address space.
    ///
    /// Allocated objects can never be larger than `isize::MAX` bytes, so if the computed offset
    /// stays in bounds of the allocated object, it is guaranteed to satisfy the first requirement.
    /// This implies, for instance, that `vec.as_ptr().add(vec.len())` (for `vec: Vec<T>`) is always
    /// safe.
    ///
    /// [allocated object]: crate::ptr#allocated-object
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let s: &str = "123";
    /// let ptr: NonNull<u8> = NonNull::new(s.as_ptr().cast_mut()).unwrap();
    ///
    /// unsafe {
    ///     println!("{}", ptr.add(1).read() as char);
    ///     println!("{}", ptr.add(2).read() as char);
    /// }
    /// ```
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[must_use = "returns a new pointer rather than modifying its argument"]
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn add(self, count: usize) -> Self
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `offset`.
        // Additionally safety contract of `offset` guarantees that the resulting pointer is
        // pointing to an allocation, there can't be an allocation at null, thus it's safe to
        // construct `NonNull`.
        unsafe { NonNull { pointer: intrinsics::offset(self.as_ptr(), count) } }
    }

    /// Calculates the offset from a pointer in bytes (convenience for `.byte_offset(count as isize)`).
    ///
    /// `count` is in units of bytes.
    ///
    /// This is purely a convenience for casting to a `u8` pointer and
    /// using [`add`][NonNull::add] on it. See that method for documentation
    /// and safety requirements.
    ///
    /// For non-`Sized` pointees this operation changes only the data pointer,
    /// leaving the metadata untouched.
    #[must_use]
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn byte_add(self, count: usize) -> Self {
        // SAFETY: the caller must uphold the safety contract for `add` and `byte_add` has the same
        // safety contract.
        // Additionally safety contract of `add` guarantees that the resulting pointer is pointing
        // to an allocation, there can't be an allocation at null, thus it's safe to construct
        // `NonNull`.
        unsafe { NonNull { pointer: self.as_ptr().byte_add(count) } }
    }

    /// Subtracts an offset from a pointer (convenience for
    /// `.offset((count as isize).wrapping_neg())`).
    ///
    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
    /// offset of `3 * size_of::<T>()` bytes.
    ///
    /// # Safety
    ///
    /// If any of the following conditions are violated, the result is Undefined Behavior:
    ///
    /// * The computed offset, `count * size_of::<T>()` bytes, must not overflow `isize`.
    ///
    /// * If the computed offset is non-zero, then `self` must be derived from a pointer to some
    ///   [allocated object], and the entire memory range between `self` and the result must be in
    ///   bounds of that allocated object. In particular, this range must not "wrap around" the edge
    ///   of the address space.
    ///
    /// Allocated objects can never be larger than `isize::MAX` bytes, so if the computed offset
    /// stays in bounds of the allocated object, it is guaranteed to satisfy the first requirement.
    /// This implies, for instance, that `vec.as_ptr().add(vec.len())` (for `vec: Vec<T>`) is always
    /// safe.
    ///
    /// [allocated object]: crate::ptr#allocated-object
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let s: &str = "123";
    ///
    /// unsafe {
    ///     let end: NonNull<u8> = NonNull::new(s.as_ptr().cast_mut()).unwrap().add(3);
    ///     println!("{}", end.sub(1).read() as char);
    ///     println!("{}", end.sub(2).read() as char);
    /// }
    /// ```
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[must_use = "returns a new pointer rather than modifying its argument"]
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn sub(self, count: usize) -> Self
    where
        T: Sized,
    {
        if T::IS_ZST {
            // Pointer arithmetic does nothing when the pointee is a ZST.
            self
        } else {
            // SAFETY: the caller must uphold the safety contract for `offset`.
            // Because the pointee is *not* a ZST, that means that `count` is
            // at most `isize::MAX`, and thus the negation cannot overflow.
            unsafe { self.offset((count as isize).unchecked_neg()) }
        }
    }

    /// Calculates the offset from a pointer in bytes (convenience for
    /// `.byte_offset((count as isize).wrapping_neg())`).
    ///
    /// `count` is in units of bytes.
    ///
    /// This is purely a convenience for casting to a `u8` pointer and
    /// using [`sub`][NonNull::sub] on it. See that method for documentation
    /// and safety requirements.
    ///
    /// For non-`Sized` pointees this operation changes only the data pointer,
    /// leaving the metadata untouched.
    #[must_use]
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn byte_sub(self, count: usize) -> Self {
        // SAFETY: the caller must uphold the safety contract for `sub` and `byte_sub` has the same
        // safety contract.
        // Additionally safety contract of `sub` guarantees that the resulting pointer is pointing
        // to an allocation, there can't be an allocation at null, thus it's safe to construct
        // `NonNull`.
        unsafe { NonNull { pointer: self.as_ptr().byte_sub(count) } }
    }

    /// Calculates the distance between two pointers within the same allocation. The returned value is in
    /// units of T: the distance in bytes divided by `mem::size_of::<T>()`.
    ///
    /// This is equivalent to `(self as isize - origin as isize) / (mem::size_of::<T>() as isize)`,
    /// except that it has a lot more opportunities for UB, in exchange for the compiler
    /// better understanding what you are doing.
    ///
    /// The primary motivation of this method is for computing the `len` of an array/slice
    /// of `T` that you are currently representing as a "start" and "end" pointer
    /// (and "end" is "one past the end" of the array).
    /// In that case, `end.offset_from(start)` gets you the length of the array.
    ///
    /// All of the following safety requirements are trivially satisfied for this usecase.
    ///
    /// [`offset`]: #method.offset
    ///
    /// # Safety
    ///
    /// If any of the following conditions are violated, the result is Undefined Behavior:
    ///
    /// * `self` and `origin` must either
    ///
    ///   * point to the same address, or
    ///   * both be *derived from* a pointer to the same [allocated object], and the memory range between
    ///     the two pointers must be in bounds of that object. (See below for an example.)
    ///
    /// * The distance between the pointers, in bytes, must be an exact multiple
    ///   of the size of `T`.
    ///
    /// As a consequence, the absolute distance between the pointers, in bytes, computed on
    /// mathematical integers (without "wrapping around"), cannot overflow an `isize`. This is
    /// implied by the in-bounds requirement, and the fact that no allocated object can be larger
    /// than `isize::MAX` bytes.
    ///
    /// The requirement for pointers to be derived from the same allocated object is primarily
    /// needed for `const`-compatibility: the distance between pointers into *different* allocated
    /// objects is not known at compile-time. However, the requirement also exists at
    /// runtime and may be exploited by optimizations. If you wish to compute the difference between
    /// pointers that are not guaranteed to be from the same allocation, use `(self as isize -
    /// origin as isize) / mem::size_of::<T>()`.
    // FIXME: recommend `addr()` instead of `as usize` once that is stable.
    ///
    /// [`add`]: #method.add
    /// [allocated object]: crate::ptr#allocated-object
    ///
    /// # Panics
    ///
    /// This function panics if `T` is a Zero-Sized Type ("ZST").
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// let a = [0; 5];
    /// let ptr1: NonNull<u32> = NonNull::from(&a[1]);
    /// let ptr2: NonNull<u32> = NonNull::from(&a[3]);
    /// unsafe {
    ///     assert_eq!(ptr2.offset_from(ptr1), 2);
    ///     assert_eq!(ptr1.offset_from(ptr2), -2);
    ///     assert_eq!(ptr1.offset(2), ptr2);
    ///     assert_eq!(ptr2.offset(-2), ptr1);
    /// }
    /// ```
    ///
    /// *Incorrect* usage:
    ///
    /// ```rust,no_run
    /// use std::ptr::NonNull;
    ///
    /// let ptr1 = NonNull::new(Box::into_raw(Box::new(0u8))).unwrap();
    /// let ptr2 = NonNull::new(Box::into_raw(Box::new(1u8))).unwrap();
    /// let diff = (ptr2.addr().get() as isize).wrapping_sub(ptr1.addr().get() as isize);
    /// // Make ptr2_other an "alias" of ptr2.add(1), but derived from ptr1.
    /// let diff_plus_1 = diff.wrapping_add(1);
    /// let ptr2_other = NonNull::new(ptr1.as_ptr().wrapping_byte_offset(diff_plus_1)).unwrap();
    /// assert_eq!(ptr2.addr(), ptr2_other.addr());
    /// // Since ptr2_other and ptr2 are derived from pointers to different objects,
    /// // computing their offset is undefined behavior, even though
    /// // they point to addresses that are in-bounds of the same object!
    ///
    /// let one = unsafe { ptr2_other.offset_from(ptr2) }; // Undefined Behavior! ⚠️
    /// ```
    #[inline]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn offset_from(self, origin: NonNull<T>) -> isize
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `offset_from`.
        unsafe { self.as_ptr().offset_from(origin.as_ptr()) }
    }

    /// Calculates the distance between two pointers within the same allocation. The returned value is in
    /// units of **bytes**.
    ///
    /// This is purely a convenience for casting to a `u8` pointer and
    /// using [`offset_from`][NonNull::offset_from] on it. See that method for
    /// documentation and safety requirements.
    ///
    /// For non-`Sized` pointees this operation considers only the data pointers,
    /// ignoring the metadata.
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn byte_offset_from<U: ?Sized>(self, origin: NonNull<U>) -> isize {
        // SAFETY: the caller must uphold the safety contract for `byte_offset_from`.
        unsafe { self.as_ptr().byte_offset_from(origin.as_ptr()) }
    }

    // N.B. `wrapping_offset``, `wrapping_add`, etc are not implemented because they can wrap to null

    /// Calculates the distance between two pointers within the same allocation, *where it's known that
    /// `self` is equal to or greater than `origin`*. The returned value is in
    /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
    ///
    /// This computes the same value that [`offset_from`](#method.offset_from)
    /// would compute, but with the added precondition that the offset is
    /// guaranteed to be non-negative.  This method is equivalent to
    /// `usize::try_from(self.offset_from(origin)).unwrap_unchecked()`,
    /// but it provides slightly more information to the optimizer, which can
    /// sometimes allow it to optimize slightly better with some backends.
    ///
    /// This method can be though of as recovering the `count` that was passed
    /// to [`add`](#method.add) (or, with the parameters in the other order,
    /// to [`sub`](#method.sub)).  The following are all equivalent, assuming
    /// that their safety preconditions are met:
    /// ```rust
    /// # #![feature(ptr_sub_ptr)]
    /// # unsafe fn blah(ptr: std::ptr::NonNull<u32>, origin: std::ptr::NonNull<u32>, count: usize) -> bool {
    /// ptr.sub_ptr(origin) == count
    /// # &&
    /// origin.add(count) == ptr
    /// # &&
    /// ptr.sub(count) == origin
    /// # }
    /// ```
    ///
    /// # Safety
    ///
    /// - The distance between the pointers must be non-negative (`self >= origin`)
    ///
    /// - *All* the safety conditions of [`offset_from`](#method.offset_from)
    ///   apply to this method as well; see it for the full details.
    ///
    /// Importantly, despite the return type of this method being able to represent
    /// a larger offset, it's still *not permitted* to pass pointers which differ
    /// by more than `isize::MAX` *bytes*.  As such, the result of this method will
    /// always be less than or equal to `isize::MAX as usize`.
    ///
    /// # Panics
    ///
    /// This function panics if `T` is a Zero-Sized Type ("ZST").
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(ptr_sub_ptr)]
    /// use std::ptr::NonNull;
    ///
    /// let a = [0; 5];
    /// let ptr1: NonNull<u32> = NonNull::from(&a[1]);
    /// let ptr2: NonNull<u32> = NonNull::from(&a[3]);
    /// unsafe {
    ///     assert_eq!(ptr2.sub_ptr(ptr1), 2);
    ///     assert_eq!(ptr1.add(2), ptr2);
    ///     assert_eq!(ptr2.sub(2), ptr1);
    ///     assert_eq!(ptr2.sub_ptr(ptr2), 0);
    /// }
    ///
    /// // This would be incorrect, as the pointers are not correctly ordered:
    /// // ptr1.sub_ptr(ptr2)
    /// ```
    #[inline]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[unstable(feature = "ptr_sub_ptr", issue = "95892")]
    #[rustc_const_unstable(feature = "const_ptr_sub_ptr", issue = "95892")]
    pub const unsafe fn sub_ptr(self, subtracted: NonNull<T>) -> usize
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `sub_ptr`.
        unsafe { self.as_ptr().sub_ptr(subtracted.as_ptr()) }
    }

    /// Calculates the distance between two pointers within the same allocation, *where it's known that
    /// `self` is equal to or greater than `origin`*. The returned value is in
    /// units of **bytes**.
    ///
    /// This is purely a convenience for casting to a `u8` pointer and
    /// using [`sub_ptr`][NonNull::sub_ptr] on it. See that method for
    /// documentation and safety requirements.
    ///
    /// For non-`Sized` pointees this operation considers only the data pointers,
    /// ignoring the metadata.
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[unstable(feature = "ptr_sub_ptr", issue = "95892")]
    #[rustc_const_unstable(feature = "const_ptr_sub_ptr", issue = "95892")]
    pub const unsafe fn byte_sub_ptr<U: ?Sized>(self, origin: NonNull<U>) -> usize {
        // SAFETY: the caller must uphold the safety contract for `byte_sub_ptr`.
        unsafe { self.as_ptr().byte_sub_ptr(origin.as_ptr()) }
    }

    /// Reads the value from `self` without moving it. This leaves the
    /// memory in `self` unchanged.
    ///
    /// See [`ptr::read`] for safety concerns and examples.
    ///
    /// [`ptr::read`]: crate::ptr::read()
    #[inline]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn read(self) -> T
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `read`.
        unsafe { ptr::read(self.as_ptr()) }
    }

    /// Performs a volatile read of the value from `self` without moving it. This
    /// leaves the memory in `self` unchanged.
    ///
    /// Volatile operations are intended to act on I/O memory, and are guaranteed
    /// to not be elided or reordered by the compiler across other volatile
    /// operations.
    ///
    /// See [`ptr::read_volatile`] for safety concerns and examples.
    ///
    /// [`ptr::read_volatile`]: crate::ptr::read_volatile()
    #[inline]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    pub unsafe fn read_volatile(self) -> T
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `read_volatile`.
        unsafe { ptr::read_volatile(self.as_ptr()) }
    }

    /// Reads the value from `self` without moving it. This leaves the
    /// memory in `self` unchanged.
    ///
    /// Unlike `read`, the pointer may be unaligned.
    ///
    /// See [`ptr::read_unaligned`] for safety concerns and examples.
    ///
    /// [`ptr::read_unaligned`]: crate::ptr::read_unaligned()
    #[inline]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "non_null_convenience", since = "1.80.0")]
    pub const unsafe fn read_unaligned(self) -> T
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `read_unaligned`.
        unsafe { ptr::read_unaligned(self.as_ptr()) }
    }

    /// Copies `count * size_of<T>` bytes from `self` to `dest`. The source
    /// and destination may overlap.
    ///
    /// NOTE: this has the *same* argument order as [`ptr::copy`].
    ///
    /// See [`ptr::copy`] for safety concerns and examples.
    ///
    /// [`ptr::copy`]: crate::ptr::copy()
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
    pub const unsafe fn copy_to(self, dest: NonNull<T>, count: usize)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `copy`.
        unsafe { ptr::copy(self.as_ptr(), dest.as_ptr(), count) }
    }

    /// Copies `count * size_of<T>` bytes from `self` to `dest`. The source
    /// and destination may *not* overlap.
    ///
    /// NOTE: this has the *same* argument order as [`ptr::copy_nonoverlapping`].
    ///
    /// See [`ptr::copy_nonoverlapping`] for safety concerns and examples.
    ///
    /// [`ptr::copy_nonoverlapping`]: crate::ptr::copy_nonoverlapping()
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
    pub const unsafe fn copy_to_nonoverlapping(self, dest: NonNull<T>, count: usize)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `copy_nonoverlapping`.
        unsafe { ptr::copy_nonoverlapping(self.as_ptr(), dest.as_ptr(), count) }
    }

    /// Copies `count * size_of<T>` bytes from `src` to `self`. The source
    /// and destination may overlap.
    ///
    /// NOTE: this has the *opposite* argument order of [`ptr::copy`].
    ///
    /// See [`ptr::copy`] for safety concerns and examples.
    ///
    /// [`ptr::copy`]: crate::ptr::copy()
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
    pub const unsafe fn copy_from(self, src: NonNull<T>, count: usize)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `copy`.
        unsafe { ptr::copy(src.as_ptr(), self.as_ptr(), count) }
    }

    /// Copies `count * size_of<T>` bytes from `src` to `self`. The source
    /// and destination may *not* overlap.
    ///
    /// NOTE: this has the *opposite* argument order of [`ptr::copy_nonoverlapping`].
    ///
    /// See [`ptr::copy_nonoverlapping`] for safety concerns and examples.
    ///
    /// [`ptr::copy_nonoverlapping`]: crate::ptr::copy_nonoverlapping()
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
    pub const unsafe fn copy_from_nonoverlapping(self, src: NonNull<T>, count: usize)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `copy_nonoverlapping`.
        unsafe { ptr::copy_nonoverlapping(src.as_ptr(), self.as_ptr(), count) }
    }

    /// Executes the destructor (if any) of the pointed-to value.
    ///
    /// See [`ptr::drop_in_place`] for safety concerns and examples.
    ///
    /// [`ptr::drop_in_place`]: crate::ptr::drop_in_place()
    #[inline(always)]
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    pub unsafe fn drop_in_place(self) {
        // SAFETY: the caller must uphold the safety contract for `drop_in_place`.
        unsafe { ptr::drop_in_place(self.as_ptr()) }
    }

    /// Overwrites a memory location with the given value without reading or
    /// dropping the old value.
    ///
    /// See [`ptr::write`] for safety concerns and examples.
    ///
    /// [`ptr::write`]: crate::ptr::write()
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
    pub const unsafe fn write(self, val: T)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `write`.
        unsafe { ptr::write(self.as_ptr(), val) }
    }

    /// Invokes memset on the specified pointer, setting `count * size_of::<T>()`
    /// bytes of memory starting at `self` to `val`.
    ///
    /// See [`ptr::write_bytes`] for safety concerns and examples.
    ///
    /// [`ptr::write_bytes`]: crate::ptr::write_bytes()
    #[inline(always)]
    #[doc(alias = "memset")]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
    pub const unsafe fn write_bytes(self, val: u8, count: usize)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `write_bytes`.
        unsafe { ptr::write_bytes(self.as_ptr(), val, count) }
    }

    /// Performs a volatile write of a memory location with the given value without
    /// reading or dropping the old value.
    ///
    /// Volatile operations are intended to act on I/O memory, and are guaranteed
    /// to not be elided or reordered by the compiler across other volatile
    /// operations.
    ///
    /// See [`ptr::write_volatile`] for safety concerns and examples.
    ///
    /// [`ptr::write_volatile`]: crate::ptr::write_volatile()
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    pub unsafe fn write_volatile(self, val: T)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `write_volatile`.
        unsafe { ptr::write_volatile(self.as_ptr(), val) }
    }

    /// Overwrites a memory location with the given value without reading or
    /// dropping the old value.
    ///
    /// Unlike `write`, the pointer may be unaligned.
    ///
    /// See [`ptr::write_unaligned`] for safety concerns and examples.
    ///
    /// [`ptr::write_unaligned`]: crate::ptr::write_unaligned()
    #[inline(always)]
    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
    pub const unsafe fn write_unaligned(self, val: T)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `write_unaligned`.
        unsafe { ptr::write_unaligned(self.as_ptr(), val) }
    }

    /// Replaces the value at `self` with `src`, returning the old
    /// value, without dropping either.
    ///
    /// See [`ptr::replace`] for safety concerns and examples.
    ///
    /// [`ptr::replace`]: crate::ptr::replace()
    #[inline(always)]
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    pub unsafe fn replace(self, src: T) -> T
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `replace`.
        unsafe { ptr::replace(self.as_ptr(), src) }
    }

    /// Swaps the values at two mutable locations of the same type, without
    /// deinitializing either. They may overlap, unlike `mem::swap` which is
    /// otherwise equivalent.
    ///
    /// See [`ptr::swap`] for safety concerns and examples.
    ///
    /// [`ptr::swap`]: crate::ptr::swap()
    #[inline(always)]
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    #[rustc_const_unstable(feature = "const_swap", issue = "83163")]
    pub const unsafe fn swap(self, with: NonNull<T>)
    where
        T: Sized,
    {
        // SAFETY: the caller must uphold the safety contract for `swap`.
        unsafe { ptr::swap(self.as_ptr(), with.as_ptr()) }
    }

    /// Computes the offset that needs to be applied to the pointer in order to make it aligned to
    /// `align`.
    ///
    /// If it is not possible to align the pointer, the implementation returns
    /// `usize::MAX`.
    ///
    /// The offset is expressed in number of `T` elements, and not bytes.
    ///
    /// There are no guarantees whatsoever that offsetting the pointer will not overflow or go
    /// beyond the allocation that the pointer points into. It is up to the caller to ensure that
    /// the returned offset is correct in all terms other than alignment.
    ///
    /// When this is called during compile-time evaluation (which is unstable), the implementation
    /// may return `usize::MAX` in cases where that can never happen at runtime. This is because the
    /// actual alignment of pointers is not known yet during compile-time, so an offset with
    /// guaranteed alignment can sometimes not be computed. For example, a buffer declared as `[u8;
    /// N]` might be allocated at an odd or an even address, but at compile-time this is not yet
    /// known, so the execution has to be correct for either choice. It is therefore impossible to
    /// find an offset that is guaranteed to be 2-aligned. (This behavior is subject to change, as usual
    /// for unstable APIs.)
    ///
    /// # Panics
    ///
    /// The function panics if `align` is not a power-of-two.
    ///
    /// # Examples
    ///
    /// Accessing adjacent `u8` as `u16`
    ///
    /// ```
    /// use std::mem::align_of;
    /// use std::ptr::NonNull;
    ///
    /// # unsafe {
    /// let x = [5_u8, 6, 7, 8, 9];
    /// let ptr = NonNull::new(x.as_ptr() as *mut u8).unwrap();
    /// let offset = ptr.align_offset(align_of::<u16>());
    ///
    /// if offset < x.len() - 1 {
    ///     let u16_ptr = ptr.add(offset).cast::<u16>();
    ///     assert!(u16_ptr.read() == u16::from_ne_bytes([5, 6]) || u16_ptr.read() == u16::from_ne_bytes([6, 7]));
    /// } else {
    ///     // while the pointer can be aligned via `offset`, it would point
    ///     // outside the allocation
    /// }
    /// # }
    /// ```
    #[inline]
    #[must_use]
    #[stable(feature = "non_null_convenience", since = "1.80.0")]
    pub fn align_offset(self, align: usize) -> usize
    where
        T: Sized,
    {
        if !align.is_power_of_two() {
            panic!("align_offset: align is not a power-of-two");
        }

        {
            // SAFETY: `align` has been checked to be a power of 2 above.
            unsafe { ptr::align_offset(self.as_ptr(), align) }
        }
    }

    /// Returns whether the pointer is properly aligned for `T`.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::ptr::NonNull;
    ///
    /// // On some platforms, the alignment of i32 is less than 4.
    /// #[repr(align(4))]
    /// struct AlignedI32(i32);
    ///
    /// let data = AlignedI32(42);
    /// let ptr = NonNull::<AlignedI32>::from(&data);
    ///
    /// assert!(ptr.is_aligned());
    /// assert!(!NonNull::new(ptr.as_ptr().wrapping_byte_add(1)).unwrap().is_aligned());
    /// ```
    #[inline]
    #[must_use]
    #[stable(feature = "pointer_is_aligned", since = "1.79.0")]
    pub fn is_aligned(self) -> bool
    where
        T: Sized,
    {
        self.as_ptr().is_aligned()
    }

    /// Returns whether the pointer is aligned to `align`.
    ///
    /// For non-`Sized` pointees this operation considers only the data pointer,
    /// ignoring the metadata.
    ///
    /// # Panics
    ///
    /// The function panics if `align` is not a power-of-two (this includes 0).
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(pointer_is_aligned_to)]
    ///
    /// // On some platforms, the alignment of i32 is less than 4.
    /// #[repr(align(4))]
    /// struct AlignedI32(i32);
    ///
    /// let data = AlignedI32(42);
    /// let ptr = &data as *const AlignedI32;
    ///
    /// assert!(ptr.is_aligned_to(1));
    /// assert!(ptr.is_aligned_to(2));
    /// assert!(ptr.is_aligned_to(4));
    ///
    /// assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
    /// assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
    ///
    /// assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
    /// ```
    #[inline]
    #[must_use]
    #[unstable(feature = "pointer_is_aligned_to", issue = "96284")]
    pub fn is_aligned_to(self, align: usize) -> bool {
        self.as_ptr().is_aligned_to(align)
    }
}

impl<T> NonNull<[T]> {
    /// Creates a non-null raw slice from a thin pointer and a length.
    ///
    /// The `len` argument is the number of **elements**, not the number of bytes.
    ///
    /// This function is safe, but dereferencing the return value is unsafe.
    /// See the documentation of [`slice::from_raw_parts`] for slice safety requirements.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use std::ptr::NonNull;
    ///
    /// // create a slice pointer when starting out with a pointer to the first element
    /// let mut x = [5, 6, 7];
    /// let nonnull_pointer = NonNull::new(x.as_mut_ptr()).unwrap();
    /// let slice = NonNull::slice_from_raw_parts(nonnull_pointer, 3);
    /// assert_eq!(unsafe { slice.as_ref()[2] }, 7);
    /// ```
    ///
    /// (Note that this example artificially demonstrates a use of this method,
    /// but `let slice = NonNull::from(&x[..]);` would be a better way to write code like this.)
    #[stable(feature = "nonnull_slice_from_raw_parts", since = "1.70.0")]
    #[rustc_const_stable(feature = "const_slice_from_raw_parts_mut", since = "1.83.0")]
    #[must_use]
    #[inline]
    pub const fn slice_from_raw_parts(data: NonNull<T>, len: usize) -> Self {
        // SAFETY: `data` is a `NonNull` pointer which is necessarily non-null
        unsafe { Self::new_unchecked(super::slice_from_raw_parts_mut(data.as_ptr(), len)) }
    }

    /// Returns the length of a non-null raw slice.
    ///
    /// The returned value is the number of **elements**, not the number of bytes.
    ///
    /// This function is safe, even when the non-null raw slice cannot be dereferenced to a slice
    /// because the pointer does not have a valid address.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use std::ptr::NonNull;
    ///
    /// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
    /// assert_eq!(slice.len(), 3);
    /// ```
    #[stable(feature = "slice_ptr_len_nonnull", since = "1.63.0")]
    #[rustc_const_stable(feature = "const_slice_ptr_len_nonnull", since = "1.63.0")]
    #[must_use]
    #[inline]
    pub const fn len(self) -> usize {
        self.as_ptr().len()
    }

    /// Returns `true` if the non-null raw slice has a length of 0.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use std::ptr::NonNull;
    ///
    /// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
    /// assert!(!slice.is_empty());
    /// ```
    #[stable(feature = "slice_ptr_is_empty_nonnull", since = "1.79.0")]
    #[rustc_const_stable(feature = "const_slice_ptr_is_empty_nonnull", since = "1.79.0")]
    #[must_use]
    #[inline]
    pub const fn is_empty(self) -> bool {
        self.len() == 0
    }

    /// Returns a non-null pointer to the slice's buffer.
    ///
    /// # Examples
    ///
    /// ```rust
    /// #![feature(slice_ptr_get)]
    /// use std::ptr::NonNull;
    ///
    /// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
    /// assert_eq!(slice.as_non_null_ptr(), NonNull::<i8>::dangling());
    /// ```
    #[inline]
    #[must_use]
    #[unstable(feature = "slice_ptr_get", issue = "74265")]
    pub const fn as_non_null_ptr(self) -> NonNull<T> {
        self.cast()
    }

    /// Returns a raw pointer to the slice's buffer.
    ///
    /// # Examples
    ///
    /// ```rust
    /// #![feature(slice_ptr_get)]
    /// use std::ptr::NonNull;
    ///
    /// let slice: NonNull<[i8]> = NonNull::slice_from_raw_parts(NonNull::dangling(), 3);
    /// assert_eq!(slice.as_mut_ptr(), NonNull::<i8>::dangling().as_ptr());
    /// ```
    #[inline]
    #[must_use]
    #[unstable(feature = "slice_ptr_get", issue = "74265")]
    #[rustc_never_returns_null_ptr]
    pub const fn as_mut_ptr(self) -> *mut T {
        self.as_non_null_ptr().as_ptr()
    }

    /// Returns a shared reference to a slice of possibly uninitialized values. In contrast to
    /// [`as_ref`], this does not require that the value has to be initialized.
    ///
    /// For the mutable counterpart see [`as_uninit_slice_mut`].
    ///
    /// [`as_ref`]: NonNull::as_ref
    /// [`as_uninit_slice_mut`]: NonNull::as_uninit_slice_mut
    ///
    /// # Safety
    ///
    /// When calling this method, you have to ensure that all of the following is true:
    ///
    /// * The pointer must be [valid] for reads for `ptr.len() * mem::size_of::<T>()` many bytes,
    ///   and it must be properly aligned. This means in particular:
    ///
    ///     * The entire memory range of this slice must be contained within a single allocated object!
    ///       Slices can never span across multiple allocated objects.
    ///
    ///     * The pointer must be aligned even for zero-length slices. One
    ///       reason for this is that enum layout optimizations may rely on references
    ///       (including slices of any length) being aligned and non-null to distinguish
    ///       them from other data. You can obtain a pointer that is usable as `data`
    ///       for zero-length slices using [`NonNull::dangling()`].
    ///
    /// * The total size `ptr.len() * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`.
    ///   See the safety documentation of [`pointer::offset`].
    ///
    /// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
    ///   arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
    ///   In particular, while this reference exists, the memory the pointer points to must
    ///   not get mutated (except inside `UnsafeCell`).
    ///
    /// This applies even if the result of this method is unused!
    ///
    /// See also [`slice::from_raw_parts`].
    ///
    /// [valid]: crate::ptr#safety
    #[inline]
    #[must_use]
    #[unstable(feature = "ptr_as_uninit", issue = "75402")]
    pub const unsafe fn as_uninit_slice<'a>(self) -> &'a [MaybeUninit<T>] {
        // SAFETY: the caller must uphold the safety contract for `as_uninit_slice`.
        unsafe { slice::from_raw_parts(self.cast().as_ptr(), self.len()) }
    }

    /// Returns a unique reference to a slice of possibly uninitialized values. In contrast to
    /// [`as_mut`], this does not require that the value has to be initialized.
    ///
    /// For the shared counterpart see [`as_uninit_slice`].
    ///
    /// [`as_mut`]: NonNull::as_mut
    /// [`as_uninit_slice`]: NonNull::as_uninit_slice
    ///
    /// # Safety
    ///
    /// When calling this method, you have to ensure that all of the following is true:
    ///
    /// * The pointer must be [valid] for reads and writes for `ptr.len() * mem::size_of::<T>()`
    ///   many bytes, and it must be properly aligned. This means in particular:
    ///
    ///     * The entire memory range of this slice must be contained within a single allocated object!
    ///       Slices can never span across multiple allocated objects.
    ///
    ///     * The pointer must be aligned even for zero-length slices. One
    ///       reason for this is that enum layout optimizations may rely on references
    ///       (including slices of any length) being aligned and non-null to distinguish
    ///       them from other data. You can obtain a pointer that is usable as `data`
    ///       for zero-length slices using [`NonNull::dangling()`].
    ///
    /// * The total size `ptr.len() * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`.
    ///   See the safety documentation of [`pointer::offset`].
    ///
    /// * You must enforce Rust's aliasing rules, since the returned lifetime `'a` is
    ///   arbitrarily chosen and does not necessarily reflect the actual lifetime of the data.
    ///   In particular, while this reference exists, the memory the pointer points to must
    ///   not get accessed (read or written) through any other pointer.
    ///
    /// This applies even if the result of this method is unused!
    ///
    /// See also [`slice::from_raw_parts_mut`].
    ///
    /// [valid]: crate::ptr#safety
    ///
    /// # Examples
    ///
    /// ```rust
    /// #![feature(allocator_api, ptr_as_uninit)]
    ///
    /// use std::alloc::{Allocator, Layout, Global};
    /// use std::mem::MaybeUninit;
    /// use std::ptr::NonNull;
    ///
    /// let memory: NonNull<[u8]> = Global.allocate(Layout::new::<[u8; 32]>())?;
    /// // This is safe as `memory` is valid for reads and writes for `memory.len()` many bytes.
    /// // Note that calling `memory.as_mut()` is not allowed here as the content may be uninitialized.
    /// # #[allow(unused_variables)]
    /// let slice: &mut [MaybeUninit<u8>] = unsafe { memory.as_uninit_slice_mut() };
    /// # // Prevent leaks for Miri.
    /// # unsafe { Global.deallocate(memory.cast(), Layout::new::<[u8; 32]>()); }
    /// # Ok::<_, std::alloc::AllocError>(())
    /// ```
    #[inline]
    #[must_use]
    #[unstable(feature = "ptr_as_uninit", issue = "75402")]
    pub const unsafe fn as_uninit_slice_mut<'a>(self) -> &'a mut [MaybeUninit<T>] {
        // SAFETY: the caller must uphold the safety contract for `as_uninit_slice_mut`.
        unsafe { slice::from_raw_parts_mut(self.cast().as_ptr(), self.len()) }
    }

    /// Returns a raw pointer to an element or subslice, without doing bounds
    /// checking.
    ///
    /// Calling this method with an out-of-bounds index or when `self` is not dereferenceable
    /// is *[undefined behavior]* even if the resulting pointer is not used.
    ///
    /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
    ///
    /// # Examples
    ///
    /// ```
    /// #![feature(slice_ptr_get)]
    /// use std::ptr::NonNull;
    ///
    /// let x = &mut [1, 2, 4];
    /// let x = NonNull::slice_from_raw_parts(NonNull::new(x.as_mut_ptr()).unwrap(), x.len());
    ///
    /// unsafe {
    ///     assert_eq!(x.get_unchecked_mut(1).as_ptr(), x.as_non_null_ptr().as_ptr().add(1));
    /// }
    /// ```
    #[unstable(feature = "slice_ptr_get", issue = "74265")]
    #[inline]
    pub unsafe fn get_unchecked_mut<I>(self, index: I) -> NonNull<I::Output>
    where
        I: SliceIndex<[T]>,
    {
        // SAFETY: the caller ensures that `self` is dereferenceable and `index` in-bounds.
        // As a consequence, the resulting pointer cannot be null.
        unsafe { NonNull::new_unchecked(self.as_ptr().get_unchecked_mut(index)) }
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> Clone for NonNull<T> {
    #[inline(always)]
    fn clone(&self) -> Self {
        *self
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> Copy for NonNull<T> {}

#[unstable(feature = "coerce_unsized", issue = "18598")]
impl<T: ?Sized, U: ?Sized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> {}

#[unstable(feature = "dispatch_from_dyn", issue = "none")]
impl<T: ?Sized, U: ?Sized> DispatchFromDyn<NonNull<U>> for NonNull<T> where T: Unsize<U> {}

#[stable(feature = "pin", since = "1.33.0")]
unsafe impl<T: ?Sized> PinCoerceUnsized for NonNull<T> {}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> fmt::Debug for NonNull<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Pointer::fmt(&self.as_ptr(), f)
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> fmt::Pointer for NonNull<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Pointer::fmt(&self.as_ptr(), f)
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> Eq for NonNull<T> {}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> PartialEq for NonNull<T> {
    #[inline]
    #[allow(ambiguous_wide_pointer_comparisons)]
    fn eq(&self, other: &Self) -> bool {
        self.as_ptr() == other.as_ptr()
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> Ord for NonNull<T> {
    #[inline]
    #[allow(ambiguous_wide_pointer_comparisons)]
    fn cmp(&self, other: &Self) -> Ordering {
        self.as_ptr().cmp(&other.as_ptr())
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> PartialOrd for NonNull<T> {
    #[inline]
    #[allow(ambiguous_wide_pointer_comparisons)]
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        self.as_ptr().partial_cmp(&other.as_ptr())
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> hash::Hash for NonNull<T> {
    #[inline]
    fn hash<H: hash::Hasher>(&self, state: &mut H) {
        self.as_ptr().hash(state)
    }
}

#[unstable(feature = "ptr_internals", issue = "none")]
impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
    #[inline]
    fn from(unique: Unique<T>) -> Self {
        unique.as_non_null_ptr()
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> From<&mut T> for NonNull<T> {
    /// Converts a `&mut T` to a `NonNull<T>`.
    ///
    /// This conversion is safe and infallible since references cannot be null.
    #[inline]
    fn from(r: &mut T) -> Self {
        NonNull::from_mut(r)
    }
}

#[stable(feature = "nonnull", since = "1.25.0")]
impl<T: ?Sized> From<&T> for NonNull<T> {
    /// Converts a `&T` to a `NonNull<T>`.
    ///
    /// This conversion is safe and infallible since references cannot be null.
    #[inline]
    fn from(r: &T) -> Self {
        NonNull::from_ref(r)
    }
}