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
use crate::num::TryFromIntError;

mod private {
    /// This trait being unreachable from outside the crate
    /// prevents other implementations of the `FloatToInt` trait,
    /// which allows potentially adding more trait methods after the trait is `#[stable]`.
    #[unstable(feature = "convert_float_to_int", issue = "67057")]
    pub trait Sealed {}
}

/// Supporting trait for inherent methods of `f32` and `f64` such as `to_int_unchecked`.
/// Typically doesn’t need to be used directly.
#[unstable(feature = "convert_float_to_int", issue = "67057")]
pub trait FloatToInt<Int>: private::Sealed + Sized {
    #[unstable(feature = "convert_float_to_int", issue = "67057")]
    #[doc(hidden)]
    unsafe fn to_int_unchecked(self) -> Int;
}

macro_rules! impl_float_to_int {
    ($Float:ty => $($Int:ty),+) => {
        #[unstable(feature = "convert_float_to_int", issue = "67057")]
        impl private::Sealed for $Float {}
        $(
            #[unstable(feature = "convert_float_to_int", issue = "67057")]
            impl FloatToInt<$Int> for $Float {
                #[inline]
                unsafe fn to_int_unchecked(self) -> $Int {
                    // SAFETY: the safety contract must be upheld by the caller.
                    unsafe { crate::intrinsics::float_to_int_unchecked(self) }
                }
            }
        )+
    }
}

impl_float_to_int!(f16 => u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);
impl_float_to_int!(f32 => u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);
impl_float_to_int!(f64 => u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);
impl_float_to_int!(f128 => u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);

// Conversion traits for primitive integer and float types
// Conversions T -> T are covered by a blanket impl and therefore excluded
// Some conversions from and to usize/isize are not implemented due to portability concerns
macro_rules! impl_from {
    (bool => $Int:ty $(,)?) => {
        impl_from!(
            bool => $Int,
            #[stable(feature = "from_bool", since = "1.28.0")],
            concat!(
                "Converts a [`bool`] to [`", stringify!($Int), "`] losslessly.\n",
                "The resulting value is `0` for `false` and `1` for `true` values.\n",
                "\n",
                "# Examples\n",
                "\n",
                "```\n",
                "assert_eq!(", stringify!($Int), "::from(true), 1);\n",
                "assert_eq!(", stringify!($Int), "::from(false), 0);\n",
                "```\n",
            ),
        );
    };
    ($Small:ty => $Large:ty, #[$attr:meta] $(,)?) => {
        impl_from!(
            $Small => $Large,
            #[$attr],
            concat!("Converts [`", stringify!($Small), "`] to [`", stringify!($Large), "`] losslessly."),
        );
    };
    ($Small:ty => $Large:ty, #[$attr:meta], $doc:expr $(,)?) => {
        #[$attr]
        impl From<$Small> for $Large {
            // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
            // Rustdocs on functions do not.
            #[doc = $doc]
            #[inline(always)]
            fn from(small: $Small) -> Self {
                small as Self
            }
        }
    };
}

// boolean -> integer
impl_from!(bool => u8);
impl_from!(bool => u16);
impl_from!(bool => u32);
impl_from!(bool => u64);
impl_from!(bool => u128);
impl_from!(bool => usize);
impl_from!(bool => i8);
impl_from!(bool => i16);
impl_from!(bool => i32);
impl_from!(bool => i64);
impl_from!(bool => i128);
impl_from!(bool => isize);

// unsigned integer -> unsigned integer
impl_from!(u8 => u16, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u8 => u32, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u8 => u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u8 => u128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(u8 => usize, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u16 => u32, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u16 => u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u16 => u128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(u32 => u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u32 => u128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(u64 => u128, #[stable(feature = "i128", since = "1.26.0")]);

// signed integer -> signed integer
impl_from!(i8 => i16, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(i8 => i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(i8 => i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(i8 => i128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(i8 => isize, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(i16 => i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(i16 => i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(i16 => i128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(i32 => i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(i32 => i128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(i64 => i128, #[stable(feature = "i128", since = "1.26.0")]);

// unsigned integer -> signed integer
impl_from!(u8 => i16, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u8 => i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u8 => i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u8 => i128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(u16 => i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u16 => i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u16 => i128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(u32 => i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")]);
impl_from!(u32 => i128, #[stable(feature = "i128", since = "1.26.0")]);
impl_from!(u64 => i128, #[stable(feature = "i128", since = "1.26.0")]);

// The C99 standard defines bounds on INTPTR_MIN, INTPTR_MAX, and UINTPTR_MAX
// which imply that pointer-sized integers must be at least 16 bits:
// https://port70.net/~nsz/c/c99/n1256.html#7.18.2.4
impl_from!(u16 => usize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")]);
impl_from!(u8 => isize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")]);
impl_from!(i16 => isize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")]);

// RISC-V defines the possibility of a 128-bit address space (RV128).

// CHERI proposes 128-bit “capabilities”. Unclear if this would be relevant to usize/isize.
// https://www.cl.cam.ac.uk/research/security/ctsrd/pdfs/20171017a-cheri-poster.pdf
// https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-951.pdf

// Note: integers can only be represented with full precision in a float if
// they fit in the significand, which is 24 bits in f32 and 53 bits in f64.
// Lossy float conversions are not implemented at this time.

// signed integer -> float
impl_from!(i8 => f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(i8 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(i16 => f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(i16 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(i32 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);

// unsigned integer -> float
impl_from!(u8 => f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(u8 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(u16 => f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(u16 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(u32 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);

// float -> float
// FIXME(f16_f128): adding additional `From` impls for existing types breaks inference. See
// <https://github.com/rust-lang/rust/issues/123824>
impl_from!(f16 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(f32 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(f32 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(f64 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);

macro_rules! impl_float_from_bool {
    ($float:ty) => {
        #[stable(feature = "float_from_bool", since = "1.68.0")]
        impl From<bool> for $float {
            #[doc = concat!("Converts a [`bool`] to [`", stringify!($float),"`] losslessly.")]
            /// The resulting value is positive `0.0` for `false` and `1.0` for `true` values.
            ///
            /// # Examples
            /// ```
            #[doc = concat!("let x: ", stringify!($float)," = false.into();")]
            /// assert_eq!(x, 0.0);
            /// assert!(x.is_sign_positive());
            ///
            #[doc = concat!("let y: ", stringify!($float)," = true.into();")]
            /// assert_eq!(y, 1.0);
            /// ```
            #[inline]
            fn from(small: bool) -> Self {
                small as u8 as Self
            }
        }
    };
}

// boolean -> float
impl_float_from_bool!(f32);
impl_float_from_bool!(f64);

// no possible bounds violation
macro_rules! impl_try_from_unbounded {
    ($source:ty => $($target:ty),+) => {$(
        #[stable(feature = "try_from", since = "1.34.0")]
        impl TryFrom<$source> for $target {
            type Error = TryFromIntError;

            /// Try to create the target number type from a source
            /// number type. This returns an error if the source value
            /// is outside of the range of the target type.
            #[inline]
            fn try_from(value: $source) -> Result<Self, Self::Error> {
                Ok(value as Self)
            }
        }
    )*}
}

// only negative bounds
macro_rules! impl_try_from_lower_bounded {
    ($source:ty => $($target:ty),+) => {$(
        #[stable(feature = "try_from", since = "1.34.0")]
        impl TryFrom<$source> for $target {
            type Error = TryFromIntError;

            /// Try to create the target number type from a source
            /// number type. This returns an error if the source value
            /// is outside of the range of the target type.
            #[inline]
            fn try_from(u: $source) -> Result<Self, Self::Error> {
                if u >= 0 {
                    Ok(u as Self)
                } else {
                    Err(TryFromIntError(()))
                }
            }
        }
    )*}
}

// unsigned to signed (only positive bound)
macro_rules! impl_try_from_upper_bounded {
    ($source:ty => $($target:ty),+) => {$(
        #[stable(feature = "try_from", since = "1.34.0")]
        impl TryFrom<$source> for $target {
            type Error = TryFromIntError;

            /// Try to create the target number type from a source
            /// number type. This returns an error if the source value
            /// is outside of the range of the target type.
            #[inline]
            fn try_from(u: $source) -> Result<Self, Self::Error> {
                if u > (Self::MAX as $source) {
                    Err(TryFromIntError(()))
                } else {
                    Ok(u as Self)
                }
            }
        }
    )*}
}

// all other cases
macro_rules! impl_try_from_both_bounded {
    ($source:ty => $($target:ty),+) => {$(
        #[stable(feature = "try_from", since = "1.34.0")]
        impl TryFrom<$source> for $target {
            type Error = TryFromIntError;

            /// Try to create the target number type from a source
            /// number type. This returns an error if the source value
            /// is outside of the range of the target type.
            #[inline]
            fn try_from(u: $source) -> Result<Self, Self::Error> {
                let min = Self::MIN as $source;
                let max = Self::MAX as $source;
                if u < min || u > max {
                    Err(TryFromIntError(()))
                } else {
                    Ok(u as Self)
                }
            }
        }
    )*}
}

macro_rules! rev {
    ($mac:ident, $source:ty => $($target:ty),+) => {$(
        $mac!($target => $source);
    )*}
}

// unsigned integer -> unsigned integer
impl_try_from_upper_bounded!(u16 => u8);
impl_try_from_upper_bounded!(u32 => u8, u16);
impl_try_from_upper_bounded!(u64 => u8, u16, u32);
impl_try_from_upper_bounded!(u128 => u8, u16, u32, u64);

// signed integer -> signed integer
impl_try_from_both_bounded!(i16 => i8);
impl_try_from_both_bounded!(i32 => i8, i16);
impl_try_from_both_bounded!(i64 => i8, i16, i32);
impl_try_from_both_bounded!(i128 => i8, i16, i32, i64);

// unsigned integer -> signed integer
impl_try_from_upper_bounded!(u8 => i8);
impl_try_from_upper_bounded!(u16 => i8, i16);
impl_try_from_upper_bounded!(u32 => i8, i16, i32);
impl_try_from_upper_bounded!(u64 => i8, i16, i32, i64);
impl_try_from_upper_bounded!(u128 => i8, i16, i32, i64, i128);

// signed integer -> unsigned integer
impl_try_from_lower_bounded!(i8 => u8, u16, u32, u64, u128);
impl_try_from_both_bounded!(i16 => u8);
impl_try_from_lower_bounded!(i16 => u16, u32, u64, u128);
impl_try_from_both_bounded!(i32 => u8, u16);
impl_try_from_lower_bounded!(i32 => u32, u64, u128);
impl_try_from_both_bounded!(i64 => u8, u16, u32);
impl_try_from_lower_bounded!(i64 => u64, u128);
impl_try_from_both_bounded!(i128 => u8, u16, u32, u64);
impl_try_from_lower_bounded!(i128 => u128);

// usize/isize
impl_try_from_upper_bounded!(usize => isize);
impl_try_from_lower_bounded!(isize => usize);

#[cfg(target_pointer_width = "16")]
mod ptr_try_from_impls {
    use super::TryFromIntError;

    impl_try_from_upper_bounded!(usize => u8);
    impl_try_from_unbounded!(usize => u16, u32, u64, u128);
    impl_try_from_upper_bounded!(usize => i8, i16);
    impl_try_from_unbounded!(usize => i32, i64, i128);

    impl_try_from_both_bounded!(isize => u8);
    impl_try_from_lower_bounded!(isize => u16, u32, u64, u128);
    impl_try_from_both_bounded!(isize => i8);
    impl_try_from_unbounded!(isize => i16, i32, i64, i128);

    rev!(impl_try_from_upper_bounded, usize => u32, u64, u128);
    rev!(impl_try_from_lower_bounded, usize => i8, i16);
    rev!(impl_try_from_both_bounded, usize => i32, i64, i128);

    rev!(impl_try_from_upper_bounded, isize => u16, u32, u64, u128);
    rev!(impl_try_from_both_bounded, isize => i32, i64, i128);
}

#[cfg(target_pointer_width = "32")]
mod ptr_try_from_impls {
    use super::TryFromIntError;

    impl_try_from_upper_bounded!(usize => u8, u16);
    impl_try_from_unbounded!(usize => u32, u64, u128);
    impl_try_from_upper_bounded!(usize => i8, i16, i32);
    impl_try_from_unbounded!(usize => i64, i128);

    impl_try_from_both_bounded!(isize => u8, u16);
    impl_try_from_lower_bounded!(isize => u32, u64, u128);
    impl_try_from_both_bounded!(isize => i8, i16);
    impl_try_from_unbounded!(isize => i32, i64, i128);

    rev!(impl_try_from_unbounded, usize => u32);
    rev!(impl_try_from_upper_bounded, usize => u64, u128);
    rev!(impl_try_from_lower_bounded, usize => i8, i16, i32);
    rev!(impl_try_from_both_bounded, usize => i64, i128);

    rev!(impl_try_from_unbounded, isize => u16);
    rev!(impl_try_from_upper_bounded, isize => u32, u64, u128);
    rev!(impl_try_from_unbounded, isize => i32);
    rev!(impl_try_from_both_bounded, isize => i64, i128);
}

#[cfg(target_pointer_width = "64")]
mod ptr_try_from_impls {
    use super::TryFromIntError;

    impl_try_from_upper_bounded!(usize => u8, u16, u32);
    impl_try_from_unbounded!(usize => u64, u128);
    impl_try_from_upper_bounded!(usize => i8, i16, i32, i64);
    impl_try_from_unbounded!(usize => i128);

    impl_try_from_both_bounded!(isize => u8, u16, u32);
    impl_try_from_lower_bounded!(isize => u64, u128);
    impl_try_from_both_bounded!(isize => i8, i16, i32);
    impl_try_from_unbounded!(isize => i64, i128);

    rev!(impl_try_from_unbounded, usize => u32, u64);
    rev!(impl_try_from_upper_bounded, usize => u128);
    rev!(impl_try_from_lower_bounded, usize => i8, i16, i32, i64);
    rev!(impl_try_from_both_bounded, usize => i128);

    rev!(impl_try_from_unbounded, isize => u16, u32);
    rev!(impl_try_from_upper_bounded, isize => u64, u128);
    rev!(impl_try_from_unbounded, isize => i32, i64);
    rev!(impl_try_from_both_bounded, isize => i128);
}

// Conversion traits for non-zero integer types
use crate::num::NonZero;

macro_rules! impl_nonzero_int_from_nonzero_int {
    ($Small:ty => $Large:ty) => {
        #[stable(feature = "nz_int_conv", since = "1.41.0")]
        impl From<NonZero<$Small>> for NonZero<$Large> {
            // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
            // Rustdocs on functions do not.
            #[doc = concat!("Converts <code>[NonZero]\\<[", stringify!($Small), "]></code> ")]
            #[doc = concat!("to <code>[NonZero]\\<[", stringify!($Large), "]></code> losslessly.")]
            #[inline]
            fn from(small: NonZero<$Small>) -> Self {
                // SAFETY: input type guarantees the value is non-zero
                unsafe { Self::new_unchecked(From::from(small.get())) }
            }
        }
    };
}

// non-zero unsigned integer -> non-zero unsigned integer
impl_nonzero_int_from_nonzero_int!(u8 => u16);
impl_nonzero_int_from_nonzero_int!(u8 => u32);
impl_nonzero_int_from_nonzero_int!(u8 => u64);
impl_nonzero_int_from_nonzero_int!(u8 => u128);
impl_nonzero_int_from_nonzero_int!(u8 => usize);
impl_nonzero_int_from_nonzero_int!(u16 => u32);
impl_nonzero_int_from_nonzero_int!(u16 => u64);
impl_nonzero_int_from_nonzero_int!(u16 => u128);
impl_nonzero_int_from_nonzero_int!(u16 => usize);
impl_nonzero_int_from_nonzero_int!(u32 => u64);
impl_nonzero_int_from_nonzero_int!(u32 => u128);
impl_nonzero_int_from_nonzero_int!(u64 => u128);

// non-zero signed integer -> non-zero signed integer
impl_nonzero_int_from_nonzero_int!(i8 => i16);
impl_nonzero_int_from_nonzero_int!(i8 => i32);
impl_nonzero_int_from_nonzero_int!(i8 => i64);
impl_nonzero_int_from_nonzero_int!(i8 => i128);
impl_nonzero_int_from_nonzero_int!(i8 => isize);
impl_nonzero_int_from_nonzero_int!(i16 => i32);
impl_nonzero_int_from_nonzero_int!(i16 => i64);
impl_nonzero_int_from_nonzero_int!(i16 => i128);
impl_nonzero_int_from_nonzero_int!(i16 => isize);
impl_nonzero_int_from_nonzero_int!(i32 => i64);
impl_nonzero_int_from_nonzero_int!(i32 => i128);
impl_nonzero_int_from_nonzero_int!(i64 => i128);

// non-zero unsigned -> non-zero signed integer
impl_nonzero_int_from_nonzero_int!(u8 => i16);
impl_nonzero_int_from_nonzero_int!(u8 => i32);
impl_nonzero_int_from_nonzero_int!(u8 => i64);
impl_nonzero_int_from_nonzero_int!(u8 => i128);
impl_nonzero_int_from_nonzero_int!(u8 => isize);
impl_nonzero_int_from_nonzero_int!(u16 => i32);
impl_nonzero_int_from_nonzero_int!(u16 => i64);
impl_nonzero_int_from_nonzero_int!(u16 => i128);
impl_nonzero_int_from_nonzero_int!(u32 => i64);
impl_nonzero_int_from_nonzero_int!(u32 => i128);
impl_nonzero_int_from_nonzero_int!(u64 => i128);

macro_rules! impl_nonzero_int_try_from_int {
    ($Int:ty) => {
        #[stable(feature = "nzint_try_from_int_conv", since = "1.46.0")]
        impl TryFrom<$Int> for NonZero<$Int> {
            type Error = TryFromIntError;

            // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
            // Rustdocs on functions do not.
            #[doc = concat!("Attempts to convert [`", stringify!($Int), "`] ")]
            #[doc = concat!("to <code>[NonZero]\\<[", stringify!($Int), "]></code>.")]
            #[inline]
            fn try_from(value: $Int) -> Result<Self, Self::Error> {
                Self::new(value).ok_or(TryFromIntError(()))
            }
        }
    };
}

// integer -> non-zero integer
impl_nonzero_int_try_from_int!(u8);
impl_nonzero_int_try_from_int!(u16);
impl_nonzero_int_try_from_int!(u32);
impl_nonzero_int_try_from_int!(u64);
impl_nonzero_int_try_from_int!(u128);
impl_nonzero_int_try_from_int!(usize);
impl_nonzero_int_try_from_int!(i8);
impl_nonzero_int_try_from_int!(i16);
impl_nonzero_int_try_from_int!(i32);
impl_nonzero_int_try_from_int!(i64);
impl_nonzero_int_try_from_int!(i128);
impl_nonzero_int_try_from_int!(isize);

macro_rules! impl_nonzero_int_try_from_nonzero_int {
    ($source:ty => $($target:ty),+) => {$(
        #[stable(feature = "nzint_try_from_nzint_conv", since = "1.49.0")]
        impl TryFrom<NonZero<$source>> for NonZero<$target> {
            type Error = TryFromIntError;

            // Rustdocs on the impl block show a "[+] show undocumented items" toggle.
            // Rustdocs on functions do not.
            #[doc = concat!("Attempts to convert <code>[NonZero]\\<[", stringify!($source), "]></code> ")]
            #[doc = concat!("to <code>[NonZero]\\<[", stringify!($target), "]></code>.")]
            #[inline]
            fn try_from(value: NonZero<$source>) -> Result<Self, Self::Error> {
                // SAFETY: Input is guaranteed to be non-zero.
                Ok(unsafe { Self::new_unchecked(<$target>::try_from(value.get())?) })
            }
        }
    )*};
}

// unsigned non-zero integer -> unsigned non-zero integer
impl_nonzero_int_try_from_nonzero_int!(u16 => u8);
impl_nonzero_int_try_from_nonzero_int!(u32 => u8, u16, usize);
impl_nonzero_int_try_from_nonzero_int!(u64 => u8, u16, u32, usize);
impl_nonzero_int_try_from_nonzero_int!(u128 => u8, u16, u32, u64, usize);
impl_nonzero_int_try_from_nonzero_int!(usize => u8, u16, u32, u64, u128);

// signed non-zero integer -> signed non-zero integer
impl_nonzero_int_try_from_nonzero_int!(i16 => i8);
impl_nonzero_int_try_from_nonzero_int!(i32 => i8, i16, isize);
impl_nonzero_int_try_from_nonzero_int!(i64 => i8, i16, i32, isize);
impl_nonzero_int_try_from_nonzero_int!(i128 => i8, i16, i32, i64, isize);
impl_nonzero_int_try_from_nonzero_int!(isize => i8, i16, i32, i64, i128);

// unsigned non-zero integer -> signed non-zero integer
impl_nonzero_int_try_from_nonzero_int!(u8 => i8);
impl_nonzero_int_try_from_nonzero_int!(u16 => i8, i16, isize);
impl_nonzero_int_try_from_nonzero_int!(u32 => i8, i16, i32, isize);
impl_nonzero_int_try_from_nonzero_int!(u64 => i8, i16, i32, i64, isize);
impl_nonzero_int_try_from_nonzero_int!(u128 => i8, i16, i32, i64, i128, isize);
impl_nonzero_int_try_from_nonzero_int!(usize => i8, i16, i32, i64, i128, isize);

// signed non-zero integer -> unsigned non-zero integer
impl_nonzero_int_try_from_nonzero_int!(i8 => u8, u16, u32, u64, u128, usize);
impl_nonzero_int_try_from_nonzero_int!(i16 => u8, u16, u32, u64, u128, usize);
impl_nonzero_int_try_from_nonzero_int!(i32 => u8, u16, u32, u64, u128, usize);
impl_nonzero_int_try_from_nonzero_int!(i64 => u8, u16, u32, u64, u128, usize);
impl_nonzero_int_try_from_nonzero_int!(i128 => u8, u16, u32, u64, u128, usize);
impl_nonzero_int_try_from_nonzero_int!(isize => u8, u16, u32, u64, u128, usize);