]>
Commit | Line | Data |
---|---|---|
6a06907d | 1 | #[doc = include_str!("panic.md")] |
5869c6ff XL |
2 | #[macro_export] |
3 | #[rustc_builtin_macro = "core_panic"] | |
4 | #[allow_internal_unstable(edition_panic)] | |
5 | #[stable(feature = "core", since = "1.6.0")] | |
6 | #[rustc_diagnostic_item = "core_panic_macro"] | |
7 | macro_rules! panic { | |
8 | // Expands to either `$crate::panic::panic_2015` or `$crate::panic::panic_2021` | |
9 | // depending on the edition of the caller. | |
10 | ($($arg:tt)*) => { | |
11 | /* compiler built-in */ | |
12 | }; | |
13 | } | |
14 | ||
041b39d2 | 15 | /// Asserts that two expressions are equal to each other (using [`PartialEq`]). |
1a4d82fc | 16 | /// |
c34b1796 AL |
17 | /// On panic, this macro will print the values of the expressions with their |
18 | /// debug representations. | |
1a4d82fc | 19 | /// |
041b39d2 | 20 | /// Like [`assert!`], this macro has a second form, where a custom |
32a655c1 SL |
21 | /// panic message can be provided. |
22 | /// | |
c34b1796 | 23 | /// # Examples |
1a4d82fc JJ |
24 | /// |
25 | /// ``` | |
85aaf69f SL |
26 | /// let a = 3; |
27 | /// let b = 1 + 2; | |
1a4d82fc | 28 | /// assert_eq!(a, b); |
32a655c1 SL |
29 | /// |
30 | /// assert_eq!(a, b, "we are testing addition with {} and {}", a, b); | |
1a4d82fc JJ |
31 | /// ``` |
32 | #[macro_export] | |
85aaf69f | 33 | #[stable(feature = "rust1", since = "1.0.0")] |
6a06907d | 34 | #[allow_internal_unstable(core_panic)] |
1a4d82fc | 35 | macro_rules! assert_eq { |
29967ef6 | 36 | ($left:expr, $right:expr $(,)?) => ({ |
a7813a04 | 37 | match (&$left, &$right) { |
1a4d82fc | 38 | (left_val, right_val) => { |
c34b1796 | 39 | if !(*left_val == *right_val) { |
6a06907d | 40 | let kind = $crate::panicking::AssertKind::Eq; |
9fa01778 XL |
41 | // The reborrows below are intentional. Without them, the stack slot for the |
42 | // borrow is initialized even before the values are compared, leading to a | |
43 | // noticeable slow down. | |
6a06907d | 44 | $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::None); |
1a4d82fc JJ |
45 | } |
46 | } | |
47 | } | |
3157f602 | 48 | }); |
8bb4bdeb | 49 | ($left:expr, $right:expr, $($arg:tt)+) => ({ |
6a06907d | 50 | match (&$left, &$right) { |
3157f602 XL |
51 | (left_val, right_val) => { |
52 | if !(*left_val == *right_val) { | |
6a06907d | 53 | let kind = $crate::panicking::AssertKind::Eq; |
9fa01778 XL |
54 | // The reborrows below are intentional. Without them, the stack slot for the |
55 | // borrow is initialized even before the values are compared, leading to a | |
56 | // noticeable slow down. | |
6a06907d | 57 | $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::Some($crate::format_args!($($arg)+))); |
3157f602 XL |
58 | } |
59 | } | |
60 | } | |
61 | }); | |
1a4d82fc JJ |
62 | } |
63 | ||
041b39d2 | 64 | /// Asserts that two expressions are not equal to each other (using [`PartialEq`]). |
9e0c209e SL |
65 | /// |
66 | /// On panic, this macro will print the values of the expressions with their | |
67 | /// debug representations. | |
68 | /// | |
041b39d2 | 69 | /// Like [`assert!`], this macro has a second form, where a custom |
32a655c1 SL |
70 | /// panic message can be provided. |
71 | /// | |
9e0c209e SL |
72 | /// # Examples |
73 | /// | |
74 | /// ``` | |
75 | /// let a = 3; | |
76 | /// let b = 2; | |
77 | /// assert_ne!(a, b); | |
32a655c1 SL |
78 | /// |
79 | /// assert_ne!(a, b, "we are testing that the values are not equal"); | |
9e0c209e SL |
80 | /// ``` |
81 | #[macro_export] | |
cc61c64b | 82 | #[stable(feature = "assert_ne", since = "1.13.0")] |
6a06907d | 83 | #[allow_internal_unstable(core_panic)] |
9e0c209e | 84 | macro_rules! assert_ne { |
29967ef6 | 85 | ($left:expr, $right:expr $(,)?) => ({ |
9e0c209e SL |
86 | match (&$left, &$right) { |
87 | (left_val, right_val) => { | |
88 | if *left_val == *right_val { | |
6a06907d | 89 | let kind = $crate::panicking::AssertKind::Ne; |
9fa01778 XL |
90 | // The reborrows below are intentional. Without them, the stack slot for the |
91 | // borrow is initialized even before the values are compared, leading to a | |
92 | // noticeable slow down. | |
6a06907d | 93 | $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::None); |
9e0c209e SL |
94 | } |
95 | } | |
96 | } | |
97 | }); | |
8bb4bdeb | 98 | ($left:expr, $right:expr, $($arg:tt)+) => ({ |
9e0c209e SL |
99 | match (&($left), &($right)) { |
100 | (left_val, right_val) => { | |
101 | if *left_val == *right_val { | |
6a06907d | 102 | let kind = $crate::panicking::AssertKind::Ne; |
9fa01778 XL |
103 | // The reborrows below are intentional. Without them, the stack slot for the |
104 | // borrow is initialized even before the values are compared, leading to a | |
105 | // noticeable slow down. | |
6a06907d | 106 | $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::Some($crate::format_args!($($arg)+))); |
9e0c209e SL |
107 | } |
108 | } | |
109 | } | |
110 | }); | |
111 | } | |
112 | ||
532ac7d7 | 113 | /// Asserts that a boolean expression is `true` at runtime. |
1a4d82fc | 114 | /// |
8bb4bdeb | 115 | /// This will invoke the [`panic!`] macro if the provided expression cannot be |
1a4d82fc JJ |
116 | /// evaluated to `true` at runtime. |
117 | /// | |
8bb4bdeb | 118 | /// Like [`assert!`], this macro also has a second version, where a custom panic |
92a42be0 SL |
119 | /// message can be provided. |
120 | /// | |
041b39d2 XL |
121 | /// # Uses |
122 | /// | |
8bb4bdeb | 123 | /// Unlike [`assert!`], `debug_assert!` statements are only enabled in non |
416331ca | 124 | /// optimized builds by default. An optimized build will not execute |
c34b1796 AL |
125 | /// `debug_assert!` statements unless `-C debug-assertions` is passed to the |
126 | /// compiler. This makes `debug_assert!` useful for checks that are too | |
127 | /// expensive to be present in a release build but may be helpful during | |
416331ca | 128 | /// development. The result of expanding `debug_assert!` is always type checked. |
1a4d82fc | 129 | /// |
5bcae85e SL |
130 | /// An unchecked assertion allows a program in an inconsistent state to keep |
131 | /// running, which might have unexpected consequences but does not introduce | |
132 | /// unsafety as long as this only happens in safe code. The performance cost | |
f035d41b | 133 | /// of assertions, however, is not measurable in general. Replacing [`assert!`] |
5bcae85e SL |
134 | /// with `debug_assert!` is thus only encouraged after thorough profiling, and |
135 | /// more importantly, only in safe code! | |
136 | /// | |
c34b1796 | 137 | /// # Examples |
1a4d82fc JJ |
138 | /// |
139 | /// ``` | |
140 | /// // the panic message for these assertions is the stringified value of the | |
141 | /// // expression given. | |
142 | /// debug_assert!(true); | |
85aaf69f SL |
143 | /// |
144 | /// fn some_expensive_computation() -> bool { true } // a very simple function | |
1a4d82fc JJ |
145 | /// debug_assert!(some_expensive_computation()); |
146 | /// | |
147 | /// // assert with a custom message | |
85aaf69f | 148 | /// let x = true; |
1a4d82fc | 149 | /// debug_assert!(x, "x wasn't true!"); |
85aaf69f SL |
150 | /// |
151 | /// let a = 3; let b = 27; | |
1a4d82fc JJ |
152 | /// debug_assert!(a + b == 30, "a = {}, b = {}", a, b); |
153 | /// ``` | |
154 | #[macro_export] | |
85aaf69f | 155 | #[stable(feature = "rust1", since = "1.0.0")] |
5869c6ff | 156 | #[rustc_diagnostic_item = "debug_assert_macro"] |
1a4d82fc | 157 | macro_rules! debug_assert { |
e1599b0c | 158 | ($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert!($($arg)*); }) |
1a4d82fc JJ |
159 | } |
160 | ||
9cc50fc6 | 161 | /// Asserts that two expressions are equal to each other. |
1a4d82fc | 162 | /// |
9cc50fc6 SL |
163 | /// On panic, this macro will print the values of the expressions with their |
164 | /// debug representations. | |
1a4d82fc | 165 | /// |
ea8adc8c | 166 | /// Unlike [`assert_eq!`], `debug_assert_eq!` statements are only enabled in non |
416331ca | 167 | /// optimized builds by default. An optimized build will not execute |
c34b1796 AL |
168 | /// `debug_assert_eq!` statements unless `-C debug-assertions` is passed to the |
169 | /// compiler. This makes `debug_assert_eq!` useful for checks that are too | |
170 | /// expensive to be present in a release build but may be helpful during | |
416331ca | 171 | /// development. The result of expanding `debug_assert_eq!` is always type checked. |
1a4d82fc | 172 | /// |
c34b1796 | 173 | /// # Examples |
1a4d82fc JJ |
174 | /// |
175 | /// ``` | |
85aaf69f SL |
176 | /// let a = 3; |
177 | /// let b = 1 + 2; | |
1a4d82fc JJ |
178 | /// debug_assert_eq!(a, b); |
179 | /// ``` | |
180 | #[macro_export] | |
92a42be0 | 181 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 182 | macro_rules! debug_assert_eq { |
e1599b0c | 183 | ($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert_eq!($($arg)*); }) |
1a4d82fc JJ |
184 | } |
185 | ||
9e0c209e SL |
186 | /// Asserts that two expressions are not equal to each other. |
187 | /// | |
188 | /// On panic, this macro will print the values of the expressions with their | |
189 | /// debug representations. | |
190 | /// | |
ea8adc8c | 191 | /// Unlike [`assert_ne!`], `debug_assert_ne!` statements are only enabled in non |
416331ca | 192 | /// optimized builds by default. An optimized build will not execute |
9e0c209e SL |
193 | /// `debug_assert_ne!` statements unless `-C debug-assertions` is passed to the |
194 | /// compiler. This makes `debug_assert_ne!` useful for checks that are too | |
195 | /// expensive to be present in a release build but may be helpful during | |
416331ca | 196 | /// development. The result of expanding `debug_assert_ne!` is always type checked. |
9e0c209e SL |
197 | /// |
198 | /// # Examples | |
199 | /// | |
200 | /// ``` | |
201 | /// let a = 3; | |
202 | /// let b = 2; | |
203 | /// debug_assert_ne!(a, b); | |
204 | /// ``` | |
205 | #[macro_export] | |
cc61c64b | 206 | #[stable(feature = "assert_ne", since = "1.13.0")] |
9e0c209e | 207 | macro_rules! debug_assert_ne { |
e1599b0c | 208 | ($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert_ne!($($arg)*); }) |
9e0c209e SL |
209 | } |
210 | ||
e74abb32 XL |
211 | /// Returns whether the given expression matches any of the given patterns. |
212 | /// | |
213 | /// Like in a `match` expression, the pattern can be optionally followed by `if` | |
214 | /// and a guard expression that has access to names bound by the pattern. | |
215 | /// | |
216 | /// # Examples | |
217 | /// | |
218 | /// ``` | |
e74abb32 XL |
219 | /// let foo = 'f'; |
220 | /// assert!(matches!(foo, 'A'..='Z' | 'a'..='z')); | |
221 | /// | |
222 | /// let bar = Some(4); | |
223 | /// assert!(matches!(bar, Some(x) if x > 2)); | |
224 | /// ``` | |
225 | #[macro_export] | |
dfeec247 | 226 | #[stable(feature = "matches_macro", since = "1.42.0")] |
e74abb32 | 227 | macro_rules! matches { |
1b1a35ee | 228 | ($expression:expr, $( $pattern:pat )|+ $( if $guard: expr )? $(,)?) => { |
e74abb32 XL |
229 | match $expression { |
230 | $( $pattern )|+ $( if $guard )? => true, | |
231 | _ => false | |
232 | } | |
233 | } | |
234 | } | |
235 | ||
532ac7d7 | 236 | /// Unwraps a result or propagates its error. |
9e0c209e | 237 | /// |
ea8adc8c | 238 | /// The `?` operator was added to replace `try!` and should be used instead. |
0731742a XL |
239 | /// Furthermore, `try` is a reserved word in Rust 2018, so if you must use |
240 | /// it, you will need to use the [raw-identifier syntax][ris]: `r#try`. | |
241 | /// | |
242 | /// [ris]: https://doc.rust-lang.org/nightly/rust-by-example/compatibility/raw_identifiers.html | |
9e0c209e | 243 | /// |
ea8adc8c | 244 | /// `try!` matches the given [`Result`]. In case of the `Ok` variant, the |
9e0c209e SL |
245 | /// expression has the value of the wrapped value. |
246 | /// | |
247 | /// In case of the `Err` variant, it retrieves the inner error. `try!` then | |
248 | /// performs conversion using `From`. This provides automatic conversion | |
249 | /// between specialized errors and more general ones. The resulting | |
250 | /// error is then immediately returned. | |
251 | /// | |
252 | /// Because of the early return, `try!` can only be used in functions that | |
ea8adc8c XL |
253 | /// return [`Result`]. |
254 | /// | |
92a42be0 SL |
255 | /// # Examples |
256 | /// | |
257 | /// ``` | |
258 | /// use std::io; | |
259 | /// use std::fs::File; | |
260 | /// use std::io::prelude::*; | |
261 | /// | |
9e0c209e SL |
262 | /// enum MyError { |
263 | /// FileWriteError | |
264 | /// } | |
265 | /// | |
266 | /// impl From<io::Error> for MyError { | |
267 | /// fn from(e: io::Error) -> MyError { | |
268 | /// MyError::FileWriteError | |
269 | /// } | |
270 | /// } | |
271 | /// | |
2c00a5a8 | 272 | /// // The preferred method of quick returning Errors |
ea8adc8c XL |
273 | /// fn write_to_file_question() -> Result<(), MyError> { |
274 | /// let mut file = File::create("my_best_friends.txt")?; | |
2c00a5a8 | 275 | /// file.write_all(b"This is a list of my best friends.")?; |
ea8adc8c XL |
276 | /// Ok(()) |
277 | /// } | |
278 | /// | |
279 | /// // The previous method of quick returning Errors | |
9e0c209e | 280 | /// fn write_to_file_using_try() -> Result<(), MyError> { |
a1dfa0c6 XL |
281 | /// let mut file = r#try!(File::create("my_best_friends.txt")); |
282 | /// r#try!(file.write_all(b"This is a list of my best friends.")); | |
92a42be0 SL |
283 | /// Ok(()) |
284 | /// } | |
ea8adc8c | 285 | /// |
92a42be0 | 286 | /// // This is equivalent to: |
9e0c209e | 287 | /// fn write_to_file_using_match() -> Result<(), MyError> { |
a1dfa0c6 | 288 | /// let mut file = r#try!(File::create("my_best_friends.txt")); |
92a42be0 | 289 | /// match file.write_all(b"This is a list of my best friends.") { |
a7813a04 | 290 | /// Ok(v) => v, |
9e0c209e | 291 | /// Err(e) => return Err(From::from(e)), |
92a42be0 | 292 | /// } |
92a42be0 SL |
293 | /// Ok(()) |
294 | /// } | |
295 | /// ``` | |
1a4d82fc | 296 | #[macro_export] |
92a42be0 | 297 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 298 | #[rustc_deprecated(since = "1.39.0", reason = "use the `?` operator instead")] |
83c7162d | 299 | #[doc(alias = "?")] |
a1dfa0c6 | 300 | macro_rules! r#try { |
29967ef6 | 301 | ($expr:expr $(,)?) => { |
60c5eb7d XL |
302 | match $expr { |
303 | $crate::result::Result::Ok(val) => val, | |
304 | $crate::result::Result::Err(err) => { | |
305 | return $crate::result::Result::Err($crate::convert::From::from(err)); | |
306 | } | |
1a4d82fc | 307 | } |
60c5eb7d | 308 | }; |
1a4d82fc JJ |
309 | } |
310 | ||
532ac7d7 | 311 | /// Writes formatted data into a buffer. |
b039eaaf | 312 | /// |
29967ef6 | 313 | /// This macro accepts a 'writer', a format string, and a list of arguments. Arguments will be |
cc61c64b XL |
314 | /// formatted according to the specified format string and the result will be passed to the writer. |
315 | /// The writer may be any value with a `write_fmt` method; generally this comes from an | |
1b1a35ee XL |
316 | /// implementation of either the [`fmt::Write`] or the [`io::Write`] trait. The macro |
317 | /// returns whatever the `write_fmt` method returns; commonly a [`fmt::Result`], or an | |
cc61c64b | 318 | /// [`io::Result`]. |
b039eaaf | 319 | /// |
cc61c64b | 320 | /// See [`std::fmt`] for more information on the format string syntax. |
5bcae85e | 321 | /// |
29967ef6 | 322 | /// [`std::fmt`]: ../std/fmt/index.html |
1b1a35ee XL |
323 | /// [`fmt::Write`]: crate::fmt::Write |
324 | /// [`io::Write`]: ../std/io/trait.Write.html | |
325 | /// [`fmt::Result`]: crate::fmt::Result | |
cc61c64b | 326 | /// [`io::Result`]: ../std/io/type.Result.html |
1a4d82fc | 327 | /// |
c34b1796 | 328 | /// # Examples |
1a4d82fc JJ |
329 | /// |
330 | /// ``` | |
c34b1796 | 331 | /// use std::io::Write; |
1a4d82fc | 332 | /// |
416331ca XL |
333 | /// fn main() -> std::io::Result<()> { |
334 | /// let mut w = Vec::new(); | |
335 | /// write!(&mut w, "test")?; | |
336 | /// write!(&mut w, "formatted {}", "arguments")?; | |
b039eaaf | 337 | /// |
416331ca XL |
338 | /// assert_eq!(w, b"testformatted arguments"); |
339 | /// Ok(()) | |
340 | /// } | |
1a4d82fc | 341 | /// ``` |
476ff2be SL |
342 | /// |
343 | /// A module can import both `std::fmt::Write` and `std::io::Write` and call `write!` on objects | |
344 | /// implementing either, as objects do not typically implement both. However, the module must | |
345 | /// import the traits qualified so their names do not conflict: | |
346 | /// | |
347 | /// ``` | |
348 | /// use std::fmt::Write as FmtWrite; | |
349 | /// use std::io::Write as IoWrite; | |
350 | /// | |
416331ca XL |
351 | /// fn main() -> Result<(), Box<dyn std::error::Error>> { |
352 | /// let mut s = String::new(); | |
353 | /// let mut v = Vec::new(); | |
354 | /// | |
355 | /// write!(&mut s, "{} {}", "abc", 123)?; // uses fmt::Write::write_fmt | |
356 | /// write!(&mut v, "s = {:?}", s)?; // uses io::Write::write_fmt | |
357 | /// assert_eq!(v, b"s = \"abc 123\""); | |
358 | /// Ok(()) | |
359 | /// } | |
476ff2be | 360 | /// ``` |
b7449926 | 361 | /// |
a1dfa0c6 XL |
362 | /// Note: This macro can be used in `no_std` setups as well. |
363 | /// In a `no_std` setup you are responsible for the implementation details of the components. | |
b7449926 XL |
364 | /// |
365 | /// ```no_run | |
366 | /// # extern crate core; | |
367 | /// use core::fmt::Write; | |
368 | /// | |
369 | /// struct Example; | |
370 | /// | |
371 | /// impl Write for Example { | |
372 | /// fn write_str(&mut self, _s: &str) -> core::fmt::Result { | |
373 | /// unimplemented!(); | |
374 | /// } | |
375 | /// } | |
376 | /// | |
377 | /// let mut m = Example{}; | |
378 | /// write!(&mut m, "Hello World").expect("Not written"); | |
379 | /// ``` | |
1a4d82fc | 380 | #[macro_export] |
cc61c64b | 381 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 382 | macro_rules! write { |
e1599b0c | 383 | ($dst:expr, $($arg:tt)*) => ($dst.write_fmt($crate::format_args!($($arg)*))) |
1a4d82fc JJ |
384 | } |
385 | ||
c30ab7b3 | 386 | /// Write formatted data into a buffer, with a newline appended. |
5bcae85e SL |
387 | /// |
388 | /// On all platforms, the newline is the LINE FEED character (`\n`/`U+000A`) alone | |
389 | /// (no additional CARRIAGE RETURN (`\r`/`U+000D`). | |
390 | /// | |
cc61c64b XL |
391 | /// For more information, see [`write!`]. For information on the format string syntax, see |
392 | /// [`std::fmt`]. | |
5bcae85e | 393 | /// |
5869c6ff | 394 | /// [`std::fmt`]: ../std/fmt/index.html |
b039eaaf SL |
395 | /// |
396 | /// # Examples | |
397 | /// | |
398 | /// ``` | |
416331ca | 399 | /// use std::io::{Write, Result}; |
b039eaaf | 400 | /// |
416331ca XL |
401 | /// fn main() -> Result<()> { |
402 | /// let mut w = Vec::new(); | |
403 | /// writeln!(&mut w)?; | |
404 | /// writeln!(&mut w, "test")?; | |
405 | /// writeln!(&mut w, "formatted {}", "arguments")?; | |
b039eaaf | 406 | /// |
416331ca XL |
407 | /// assert_eq!(&w[..], "\ntest\nformatted arguments\n".as_bytes()); |
408 | /// Ok(()) | |
409 | /// } | |
b039eaaf | 410 | /// ``` |
476ff2be SL |
411 | /// |
412 | /// A module can import both `std::fmt::Write` and `std::io::Write` and call `write!` on objects | |
413 | /// implementing either, as objects do not typically implement both. However, the module must | |
414 | /// import the traits qualified so their names do not conflict: | |
415 | /// | |
416 | /// ``` | |
417 | /// use std::fmt::Write as FmtWrite; | |
418 | /// use std::io::Write as IoWrite; | |
419 | /// | |
416331ca XL |
420 | /// fn main() -> Result<(), Box<dyn std::error::Error>> { |
421 | /// let mut s = String::new(); | |
422 | /// let mut v = Vec::new(); | |
423 | /// | |
424 | /// writeln!(&mut s, "{} {}", "abc", 123)?; // uses fmt::Write::write_fmt | |
425 | /// writeln!(&mut v, "s = {:?}", s)?; // uses io::Write::write_fmt | |
426 | /// assert_eq!(v, b"s = \"abc 123\\n\"\n"); | |
427 | /// Ok(()) | |
428 | /// } | |
476ff2be | 429 | /// ``` |
1a4d82fc | 430 | #[macro_export] |
85aaf69f | 431 | #[stable(feature = "rust1", since = "1.0.0")] |
532ac7d7 | 432 | #[allow_internal_unstable(format_args_nl)] |
1a4d82fc | 433 | macro_rules! writeln { |
29967ef6 | 434 | ($dst:expr $(,)?) => ( |
48663c56 | 435 | $crate::write!($dst, "\n") |
32a655c1 | 436 | ); |
b7449926 | 437 | ($dst:expr, $($arg:tt)*) => ( |
e1599b0c | 438 | $dst.write_fmt($crate::format_args_nl!($($arg)*)) |
1a4d82fc JJ |
439 | ); |
440 | } | |
441 | ||
532ac7d7 | 442 | /// Indicates unreachable code. |
1a4d82fc JJ |
443 | /// |
444 | /// This is useful any time that the compiler can't determine that some code is unreachable. For | |
445 | /// example: | |
446 | /// | |
447 | /// * Match arms with guard conditions. | |
448 | /// * Loops that dynamically terminate. | |
449 | /// * Iterators that dynamically terminate. | |
450 | /// | |
ea8adc8c | 451 | /// If the determination that the code is unreachable proves incorrect, the |
dc9dc135 XL |
452 | /// program immediately terminates with a [`panic!`]. |
453 | /// | |
454 | /// The unsafe counterpart of this macro is the [`unreachable_unchecked`] function, which | |
455 | /// will cause undefined behavior if the code is reached. | |
ea8adc8c | 456 | /// |
3dfed10e | 457 | /// [`unreachable_unchecked`]: crate::hint::unreachable_unchecked |
ea8adc8c | 458 | /// |
1a4d82fc JJ |
459 | /// # Panics |
460 | /// | |
fc512014 | 461 | /// This will always [`panic!`]. |
1a4d82fc JJ |
462 | /// |
463 | /// # Examples | |
464 | /// | |
465 | /// Match arms: | |
466 | /// | |
c34b1796 | 467 | /// ``` |
92a42be0 | 468 | /// # #[allow(dead_code)] |
c34b1796 | 469 | /// fn foo(x: Option<i32>) { |
1a4d82fc JJ |
470 | /// match x { |
471 | /// Some(n) if n >= 0 => println!("Some(Non-negative)"), | |
472 | /// Some(n) if n < 0 => println!("Some(Negative)"), | |
473 | /// Some(_) => unreachable!(), // compile error if commented out | |
474 | /// None => println!("None") | |
475 | /// } | |
476 | /// } | |
477 | /// ``` | |
478 | /// | |
479 | /// Iterators: | |
480 | /// | |
c34b1796 | 481 | /// ``` |
92a42be0 | 482 | /// # #[allow(dead_code)] |
1a4d82fc | 483 | /// fn divide_by_three(x: u32) -> u32 { // one of the poorest implementations of x/3 |
c34b1796 | 484 | /// for i in 0.. { |
1a4d82fc JJ |
485 | /// if 3*i < i { panic!("u32 overflow"); } |
486 | /// if x < 3*i { return i-1; } | |
487 | /// } | |
488 | /// unreachable!(); | |
489 | /// } | |
490 | /// ``` | |
491 | #[macro_export] | |
cc61c64b | 492 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
493 | macro_rules! unreachable { |
494 | () => ({ | |
fc512014 | 495 | $crate::panic!("internal error: entered unreachable code") |
1a4d82fc | 496 | }); |
29967ef6 | 497 | ($msg:expr $(,)?) => ({ |
48663c56 | 498 | $crate::unreachable!("{}", $msg) |
1a4d82fc JJ |
499 | }); |
500 | ($fmt:expr, $($arg:tt)*) => ({ | |
fc512014 | 501 | $crate::panic!($crate::concat!("internal error: entered unreachable code: ", $fmt), $($arg)*) |
1a4d82fc JJ |
502 | }); |
503 | } | |
504 | ||
dfeec247 | 505 | /// Indicates unimplemented code by panicking with a message of "not implemented". |
e9174d1e | 506 | /// |
dfeec247 | 507 | /// This allows your code to type-check, which is useful if you are prototyping or |
e74abb32 XL |
508 | /// implementing a trait that requires multiple methods which you don't plan of using all of. |
509 | /// | |
fc512014 | 510 | /// The difference between `unimplemented!` and [`todo!`] is that while `todo!` |
dfeec247 XL |
511 | /// conveys an intent of implementing the functionality later and the message is "not yet |
512 | /// implemented", `unimplemented!` makes no such claims. Its message is "not implemented". | |
513 | /// Also some IDEs will mark `todo!`s. | |
e9174d1e | 514 | /// |
ea8adc8c XL |
515 | /// # Panics |
516 | /// | |
fc512014 XL |
517 | /// This will always [`panic!`] because `unimplemented!` is just a shorthand for `panic!` with a |
518 | /// fixed, specific message. | |
e74abb32 XL |
519 | /// |
520 | /// Like `panic!`, this macro has a second form for displaying custom values. | |
ea8adc8c | 521 | /// |
e9174d1e SL |
522 | /// # Examples |
523 | /// | |
dfeec247 | 524 | /// Say we have a trait `Foo`: |
e9174d1e SL |
525 | /// |
526 | /// ``` | |
527 | /// trait Foo { | |
e74abb32 | 528 | /// fn bar(&self) -> u8; |
e9174d1e | 529 | /// fn baz(&self); |
e74abb32 | 530 | /// fn qux(&self) -> Result<u64, ()>; |
e9174d1e SL |
531 | /// } |
532 | /// ``` | |
533 | /// | |
dfeec247 XL |
534 | /// We want to implement `Foo` for 'MyStruct', but for some reason it only makes sense |
535 | /// to implement the `bar()` function. `baz()` and `qux()` will still need to be defined | |
e74abb32 XL |
536 | /// in our implementation of `Foo`, but we can use `unimplemented!` in their definitions |
537 | /// to allow our code to compile. | |
538 | /// | |
dfeec247 XL |
539 | /// We still want to have our program stop running if the unimplemented methods are |
540 | /// reached. | |
e9174d1e SL |
541 | /// |
542 | /// ``` | |
543 | /// # trait Foo { | |
e74abb32 | 544 | /// # fn bar(&self) -> u8; |
92a42be0 | 545 | /// # fn baz(&self); |
e74abb32 | 546 | /// # fn qux(&self) -> Result<u64, ()>; |
e9174d1e SL |
547 | /// # } |
548 | /// struct MyStruct; | |
549 | /// | |
550 | /// impl Foo for MyStruct { | |
e74abb32 XL |
551 | /// fn bar(&self) -> u8 { |
552 | /// 1 + 1 | |
e9174d1e SL |
553 | /// } |
554 | /// | |
92a42be0 | 555 | /// fn baz(&self) { |
dfeec247 XL |
556 | /// // It makes no sense to `baz` a `MyStruct`, so we have no logic here |
557 | /// // at all. | |
558 | /// // This will display "thread 'main' panicked at 'not implemented'". | |
e9174d1e SL |
559 | /// unimplemented!(); |
560 | /// } | |
e74abb32 XL |
561 | /// |
562 | /// fn qux(&self) -> Result<u64, ()> { | |
e74abb32 | 563 | /// // We have some logic here, |
dfeec247 | 564 | /// // We can add a message to unimplemented! to display our omission. |
e74abb32 | 565 | /// // This will display: |
dfeec247 XL |
566 | /// // "thread 'main' panicked at 'not implemented: MyStruct isn't quxable'". |
567 | /// unimplemented!("MyStruct isn't quxable"); | |
e74abb32 | 568 | /// } |
e9174d1e SL |
569 | /// } |
570 | /// | |
571 | /// fn main() { | |
572 | /// let s = MyStruct; | |
92a42be0 | 573 | /// s.bar(); |
e9174d1e SL |
574 | /// } |
575 | /// ``` | |
1a4d82fc | 576 | #[macro_export] |
cc61c64b | 577 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 578 | macro_rules! unimplemented { |
fc512014 XL |
579 | () => ($crate::panic!("not implemented")); |
580 | ($($arg:tt)+) => ($crate::panic!("not implemented: {}", $crate::format_args!($($arg)+))); | |
1a4d82fc | 581 | } |
c30ab7b3 | 582 | |
532ac7d7 XL |
583 | /// Indicates unfinished code. |
584 | /// | |
585 | /// This can be useful if you are prototyping and are just looking to have your | |
e74abb32 XL |
586 | /// code typecheck. |
587 | /// | |
dfeec247 XL |
588 | /// The difference between [`unimplemented!`] and `todo!` is that while `todo!` conveys |
589 | /// an intent of implementing the functionality later and the message is "not yet | |
590 | /// implemented", `unimplemented!` makes no such claims. Its message is "not implemented". | |
591 | /// Also some IDEs will mark `todo!`s. | |
592 | /// | |
532ac7d7 XL |
593 | /// # Panics |
594 | /// | |
fc512014 | 595 | /// This will always [`panic!`]. |
532ac7d7 XL |
596 | /// |
597 | /// # Examples | |
598 | /// | |
599 | /// Here's an example of some in-progress code. We have a trait `Foo`: | |
600 | /// | |
601 | /// ``` | |
602 | /// trait Foo { | |
603 | /// fn bar(&self); | |
604 | /// fn baz(&self); | |
605 | /// } | |
606 | /// ``` | |
607 | /// | |
608 | /// We want to implement `Foo` on one of our types, but we also want to work on | |
609 | /// just `bar()` first. In order for our code to compile, we need to implement | |
610 | /// `baz()`, so we can use `todo!`: | |
611 | /// | |
612 | /// ``` | |
532ac7d7 XL |
613 | /// # trait Foo { |
614 | /// # fn bar(&self); | |
615 | /// # fn baz(&self); | |
616 | /// # } | |
617 | /// struct MyStruct; | |
618 | /// | |
619 | /// impl Foo for MyStruct { | |
620 | /// fn bar(&self) { | |
621 | /// // implementation goes here | |
622 | /// } | |
623 | /// | |
624 | /// fn baz(&self) { | |
625 | /// // let's not worry about implementing baz() for now | |
626 | /// todo!(); | |
627 | /// } | |
628 | /// } | |
629 | /// | |
630 | /// fn main() { | |
631 | /// let s = MyStruct; | |
632 | /// s.bar(); | |
633 | /// | |
dfeec247 | 634 | /// // we aren't even using baz(), so this is fine. |
532ac7d7 XL |
635 | /// } |
636 | /// ``` | |
637 | #[macro_export] | |
dfeec247 | 638 | #[stable(feature = "todo_macro", since = "1.40.0")] |
532ac7d7 | 639 | macro_rules! todo { |
fc512014 XL |
640 | () => ($crate::panic!("not yet implemented")); |
641 | ($($arg:tt)+) => ($crate::panic!("not yet implemented: {}", $crate::format_args!($($arg)+))); | |
416331ca XL |
642 | } |
643 | ||
644 | /// Definitions of built-in macros. | |
c30ab7b3 | 645 | /// |
416331ca XL |
646 | /// Most of the macro properties (stability, visibility, etc.) are taken from the source code here, |
647 | /// with exception of expansion functions transforming macro inputs into outputs, | |
648 | /// those functions are provided by the compiler. | |
416331ca | 649 | pub(crate) mod builtin { |
041b39d2 | 650 | |
532ac7d7 | 651 | /// Causes compilation to fail with the given error message when encountered. |
041b39d2 | 652 | /// |
416331ca XL |
653 | /// This macro should be used when a crate uses a conditional compilation strategy to provide |
654 | /// better error messages for erroneous conditions. It's the compiler-level form of [`panic!`], | |
655 | /// but emits an error during *compilation* rather than at *runtime*. | |
656 | /// | |
657 | /// # Examples | |
658 | /// | |
659 | /// Two such examples are macros and `#[cfg]` environments. | |
660 | /// | |
661 | /// Emit better compiler error if a macro is passed invalid values. Without the final branch, | |
662 | /// the compiler would still emit an error, but the error's message would not mention the two | |
663 | /// valid values. | |
041b39d2 | 664 | /// |
416331ca XL |
665 | /// ```compile_fail |
666 | /// macro_rules! give_me_foo_or_bar { | |
667 | /// (foo) => {}; | |
668 | /// (bar) => {}; | |
669 | /// ($x:ident) => { | |
670 | /// compile_error!("This macro only accepts `foo` or `bar`"); | |
671 | /// } | |
672 | /// } | |
673 | /// | |
674 | /// give_me_foo_or_bar!(neither); | |
675 | /// // ^ will fail at compile time with message "This macro only accepts `foo` or `bar`" | |
676 | /// ``` | |
677 | /// | |
678 | /// Emit compiler error if one of a number of features isn't available. | |
679 | /// | |
680 | /// ```compile_fail | |
681 | /// #[cfg(not(any(feature = "foo", feature = "bar")))] | |
682 | /// compile_error!("Either feature \"foo\" or \"bar\" must be enabled for this crate."); | |
683 | /// ``` | |
041b39d2 | 684 | #[stable(feature = "compile_error_macro", since = "1.20.0")] |
416331ca XL |
685 | #[rustc_builtin_macro] |
686 | #[macro_export] | |
0531ce1d | 687 | macro_rules! compile_error { |
29967ef6 | 688 | ($msg:expr $(,)?) => {{ /* compiler built-in */ }}; |
0531ce1d | 689 | } |
041b39d2 | 690 | |
532ac7d7 | 691 | /// Constructs parameters for the other string-formatting macros. |
c30ab7b3 | 692 | /// |
416331ca XL |
693 | /// This macro functions by taking a formatting string literal containing |
694 | /// `{}` for each additional argument passed. `format_args!` prepares the | |
695 | /// additional parameters to ensure the output can be interpreted as a string | |
696 | /// and canonicalizes the arguments into a single type. Any value that implements | |
697 | /// the [`Display`] trait can be passed to `format_args!`, as can any | |
698 | /// [`Debug`] implementation be passed to a `{:?}` within the formatting string. | |
699 | /// | |
700 | /// This macro produces a value of type [`fmt::Arguments`]. This value can be | |
701 | /// passed to the macros within [`std::fmt`] for performing useful redirection. | |
702 | /// All other formatting macros ([`format!`], [`write!`], [`println!`], etc) are | |
703 | /// proxied through this one. `format_args!`, unlike its derived macros, avoids | |
704 | /// heap allocations. | |
705 | /// | |
706 | /// You can use the [`fmt::Arguments`] value that `format_args!` returns | |
707 | /// in `Debug` and `Display` contexts as seen below. The example also shows | |
708 | /// that `Debug` and `Display` format to the same thing: the interpolated | |
709 | /// format string in `format_args!`. | |
710 | /// | |
711 | /// ```rust | |
712 | /// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2)); | |
713 | /// let display = format!("{}", format_args!("{} foo {:?}", 1, 2)); | |
714 | /// assert_eq!("1 foo 2", display); | |
715 | /// assert_eq!(display, debug); | |
716 | /// ``` | |
c30ab7b3 | 717 | /// |
416331ca XL |
718 | /// For more information, see the documentation in [`std::fmt`]. |
719 | /// | |
3dfed10e XL |
720 | /// [`Display`]: crate::fmt::Display |
721 | /// [`Debug`]: crate::fmt::Debug | |
722 | /// [`fmt::Arguments`]: crate::fmt::Arguments | |
5869c6ff | 723 | /// [`std::fmt`]: ../std/fmt/index.html |
416331ca | 724 | /// [`format!`]: ../std/macro.format.html |
416331ca XL |
725 | /// [`println!`]: ../std/macro.println.html |
726 | /// | |
727 | /// # Examples | |
728 | /// | |
729 | /// ``` | |
730 | /// use std::fmt; | |
731 | /// | |
732 | /// let s = fmt::format(format_args!("hello {}", "world")); | |
733 | /// assert_eq!(s, format!("hello {}", "world")); | |
734 | /// ``` | |
c30ab7b3 | 735 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
736 | #[allow_internal_unstable(fmt_internals)] |
737 | #[rustc_builtin_macro] | |
738 | #[macro_export] | |
ff7c6d11 | 739 | macro_rules! format_args { |
60c5eb7d XL |
740 | ($fmt:expr) => {{ /* compiler built-in */ }}; |
741 | ($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }}; | |
416331ca XL |
742 | } |
743 | ||
744 | /// Same as `format_args`, but adds a newline in the end. | |
60c5eb7d XL |
745 | #[unstable( |
746 | feature = "format_args_nl", | |
dfeec247 | 747 | issue = "none", |
60c5eb7d XL |
748 | reason = "`format_args_nl` is only for internal \ |
749 | language use and is subject to change" | |
750 | )] | |
416331ca XL |
751 | #[allow_internal_unstable(fmt_internals)] |
752 | #[rustc_builtin_macro] | |
753 | #[macro_export] | |
416331ca | 754 | macro_rules! format_args_nl { |
60c5eb7d XL |
755 | ($fmt:expr) => {{ /* compiler built-in */ }}; |
756 | ($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }}; | |
ff7c6d11 | 757 | } |
c30ab7b3 | 758 | |
532ac7d7 | 759 | /// Inspects an environment variable at compile time. |
c30ab7b3 | 760 | /// |
416331ca XL |
761 | /// This macro will expand to the value of the named environment variable at |
762 | /// compile time, yielding an expression of type `&'static str`. | |
763 | /// | |
764 | /// If the environment variable is not defined, then a compilation error | |
765 | /// will be emitted. To not emit a compile error, use the [`option_env!`] | |
766 | /// macro instead. | |
c30ab7b3 | 767 | /// |
416331ca XL |
768 | /// # Examples |
769 | /// | |
770 | /// ``` | |
771 | /// let path: &'static str = env!("PATH"); | |
772 | /// println!("the $PATH variable at the time of compiling was: {}", path); | |
773 | /// ``` | |
774 | /// | |
775 | /// You can customize the error message by passing a string as the second | |
776 | /// parameter: | |
777 | /// | |
778 | /// ```compile_fail | |
779 | /// let doc: &'static str = env!("documentation", "what's that?!"); | |
780 | /// ``` | |
781 | /// | |
782 | /// If the `documentation` environment variable is not defined, you'll get | |
783 | /// the following error: | |
784 | /// | |
785 | /// ```text | |
786 | /// error: what's that?! | |
787 | /// ``` | |
c30ab7b3 | 788 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
789 | #[rustc_builtin_macro] |
790 | #[macro_export] | |
ff7c6d11 | 791 | macro_rules! env { |
29967ef6 | 792 | ($name:expr $(,)?) => {{ /* compiler built-in */ }}; |
6a06907d | 793 | ($name:expr, $error_msg:expr $(,)?) => {{ /* compiler built-in */ }}; |
ff7c6d11 | 794 | } |
c30ab7b3 | 795 | |
532ac7d7 | 796 | /// Optionally inspects an environment variable at compile time. |
c30ab7b3 | 797 | /// |
416331ca XL |
798 | /// If the named environment variable is present at compile time, this will |
799 | /// expand into an expression of type `Option<&'static str>` whose value is | |
800 | /// `Some` of the value of the environment variable. If the environment | |
801 | /// variable is not present, then this will expand to `None`. See | |
3dfed10e | 802 | /// [`Option<T>`][Option] for more information on this type. |
416331ca XL |
803 | /// |
804 | /// A compile time error is never emitted when using this macro regardless | |
805 | /// of whether the environment variable is present or not. | |
c30ab7b3 | 806 | /// |
416331ca XL |
807 | /// # Examples |
808 | /// | |
809 | /// ``` | |
810 | /// let key: Option<&'static str> = option_env!("SECRET_KEY"); | |
811 | /// println!("the secret key might be: {:?}", key); | |
812 | /// ``` | |
c30ab7b3 | 813 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
814 | #[rustc_builtin_macro] |
815 | #[macro_export] | |
0531ce1d | 816 | macro_rules! option_env { |
29967ef6 | 817 | ($name:expr $(,)?) => {{ /* compiler built-in */ }}; |
0531ce1d | 818 | } |
c30ab7b3 | 819 | |
532ac7d7 | 820 | /// Concatenates identifiers into one identifier. |
c30ab7b3 | 821 | /// |
416331ca XL |
822 | /// This macro takes any number of comma-separated identifiers, and |
823 | /// concatenates them all into one, yielding an expression which is a new | |
824 | /// identifier. Note that hygiene makes it such that this macro cannot | |
825 | /// capture local variables. Also, as a general rule, macros are only | |
826 | /// allowed in item, statement or expression position. That means while | |
827 | /// you may use this macro for referring to existing variables, functions or | |
828 | /// modules etc, you cannot define a new one with it. | |
829 | /// | |
830 | /// # Examples | |
831 | /// | |
832 | /// ``` | |
833 | /// #![feature(concat_idents)] | |
c30ab7b3 | 834 | /// |
416331ca XL |
835 | /// # fn main() { |
836 | /// fn foobar() -> u32 { 23 } | |
837 | /// | |
838 | /// let f = concat_idents!(foo, bar); | |
839 | /// println!("{}", f()); | |
840 | /// | |
841 | /// // fn concat_idents!(new, fun, name) { } // not usable in this way! | |
842 | /// # } | |
843 | /// ``` | |
60c5eb7d XL |
844 | #[unstable( |
845 | feature = "concat_idents", | |
846 | issue = "29599", | |
847 | reason = "`concat_idents` is not stable enough for use and is subject to change" | |
848 | )] | |
416331ca XL |
849 | #[rustc_builtin_macro] |
850 | #[macro_export] | |
c30ab7b3 | 851 | macro_rules! concat_idents { |
29967ef6 | 852 | ($($e:ident),+ $(,)?) => {{ /* compiler built-in */ }}; |
c30ab7b3 SL |
853 | } |
854 | ||
855 | /// Concatenates literals into a static string slice. | |
856 | /// | |
416331ca XL |
857 | /// This macro takes any number of comma-separated literals, yielding an |
858 | /// expression of type `&'static str` which represents all of the literals | |
859 | /// concatenated left-to-right. | |
860 | /// | |
861 | /// Integer and floating point literals are stringified in order to be | |
862 | /// concatenated. | |
c30ab7b3 | 863 | /// |
416331ca XL |
864 | /// # Examples |
865 | /// | |
866 | /// ``` | |
867 | /// let s = concat!("test", 10, 'b', true); | |
868 | /// assert_eq!(s, "test10btrue"); | |
869 | /// ``` | |
c30ab7b3 | 870 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
871 | #[rustc_builtin_macro] |
872 | #[macro_export] | |
ff7c6d11 | 873 | macro_rules! concat { |
29967ef6 | 874 | ($($e:expr),* $(,)?) => {{ /* compiler built-in */ }}; |
ff7c6d11 | 875 | } |
c30ab7b3 | 876 | |
532ac7d7 | 877 | /// Expands to the line number on which it was invoked. |
c30ab7b3 | 878 | /// |
416331ca XL |
879 | /// With [`column!`] and [`file!`], these macros provide debugging information for |
880 | /// developers about the location within the source. | |
881 | /// | |
882 | /// The expanded expression has type `u32` and is 1-based, so the first line | |
883 | /// in each file evaluates to 1, the second to 2, etc. This is consistent | |
884 | /// with error messages by common compilers or popular editors. | |
885 | /// The returned line is *not necessarily* the line of the `line!` invocation itself, | |
886 | /// but rather the first macro invocation leading up to the invocation | |
887 | /// of the `line!` macro. | |
888 | /// | |
416331ca | 889 | /// # Examples |
c30ab7b3 | 890 | /// |
416331ca XL |
891 | /// ``` |
892 | /// let current_line = line!(); | |
893 | /// println!("defined on line: {}", current_line); | |
894 | /// ``` | |
c30ab7b3 | 895 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
896 | #[rustc_builtin_macro] |
897 | #[macro_export] | |
60c5eb7d XL |
898 | macro_rules! line { |
899 | () => { | |
900 | /* compiler built-in */ | |
901 | }; | |
902 | } | |
c30ab7b3 | 903 | |
416331ca XL |
904 | /// Expands to the column number at which it was invoked. |
905 | /// | |
906 | /// With [`line!`] and [`file!`], these macros provide debugging information for | |
907 | /// developers about the location within the source. | |
908 | /// | |
909 | /// The expanded expression has type `u32` and is 1-based, so the first column | |
910 | /// in each line evaluates to 1, the second to 2, etc. This is consistent | |
911 | /// with error messages by common compilers or popular editors. | |
912 | /// The returned column is *not necessarily* the line of the `column!` invocation itself, | |
913 | /// but rather the first macro invocation leading up to the invocation | |
914 | /// of the `column!` macro. | |
915 | /// | |
416331ca | 916 | /// # Examples |
c30ab7b3 | 917 | /// |
416331ca XL |
918 | /// ``` |
919 | /// let current_col = column!(); | |
920 | /// println!("defined on column: {}", current_col); | |
921 | /// ``` | |
c30ab7b3 | 922 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
923 | #[rustc_builtin_macro] |
924 | #[macro_export] | |
60c5eb7d XL |
925 | macro_rules! column { |
926 | () => { | |
927 | /* compiler built-in */ | |
928 | }; | |
929 | } | |
c30ab7b3 | 930 | |
416331ca XL |
931 | /// Expands to the file name in which it was invoked. |
932 | /// | |
933 | /// With [`line!`] and [`column!`], these macros provide debugging information for | |
934 | /// developers about the location within the source. | |
935 | /// | |
416331ca XL |
936 | /// The expanded expression has type `&'static str`, and the returned file |
937 | /// is not the invocation of the `file!` macro itself, but rather the | |
938 | /// first macro invocation leading up to the invocation of the `file!` | |
939 | /// macro. | |
c30ab7b3 | 940 | /// |
416331ca XL |
941 | /// # Examples |
942 | /// | |
943 | /// ``` | |
944 | /// let this_file = file!(); | |
945 | /// println!("defined in file: {}", this_file); | |
946 | /// ``` | |
c30ab7b3 | 947 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
948 | #[rustc_builtin_macro] |
949 | #[macro_export] | |
60c5eb7d XL |
950 | macro_rules! file { |
951 | () => { | |
952 | /* compiler built-in */ | |
953 | }; | |
954 | } | |
c30ab7b3 | 955 | |
532ac7d7 | 956 | /// Stringifies its arguments. |
c30ab7b3 | 957 | /// |
416331ca XL |
958 | /// This macro will yield an expression of type `&'static str` which is the |
959 | /// stringification of all the tokens passed to the macro. No restrictions | |
960 | /// are placed on the syntax of the macro invocation itself. | |
961 | /// | |
962 | /// Note that the expanded results of the input tokens may change in the | |
963 | /// future. You should be careful if you rely on the output. | |
c30ab7b3 | 964 | /// |
416331ca XL |
965 | /// # Examples |
966 | /// | |
967 | /// ``` | |
968 | /// let one_plus_one = stringify!(1 + 1); | |
969 | /// assert_eq!(one_plus_one, "1 + 1"); | |
970 | /// ``` | |
c30ab7b3 | 971 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
972 | #[rustc_builtin_macro] |
973 | #[macro_export] | |
60c5eb7d XL |
974 | macro_rules! stringify { |
975 | ($($t:tt)*) => { | |
976 | /* compiler built-in */ | |
977 | }; | |
978 | } | |
c30ab7b3 | 979 | |
3dfed10e | 980 | /// Includes a UTF-8 encoded file as a string. |
c30ab7b3 | 981 | /// |
ba9703b0 XL |
982 | /// The file is located relative to the current file (similarly to how |
983 | /// modules are found). The provided path is interpreted in a platform-specific | |
984 | /// way at compile time. So, for instance, an invocation with a Windows path | |
985 | /// containing backslashes `\` would not compile correctly on Unix. | |
416331ca XL |
986 | /// |
987 | /// This macro will yield an expression of type `&'static str` which is the | |
988 | /// contents of the file. | |
c30ab7b3 | 989 | /// |
416331ca XL |
990 | /// # Examples |
991 | /// | |
992 | /// Assume there are two files in the same directory with the following | |
993 | /// contents: | |
994 | /// | |
995 | /// File 'spanish.in': | |
996 | /// | |
997 | /// ```text | |
998 | /// adiós | |
999 | /// ``` | |
1000 | /// | |
1001 | /// File 'main.rs': | |
1002 | /// | |
1003 | /// ```ignore (cannot-doctest-external-file-dependency) | |
1004 | /// fn main() { | |
1005 | /// let my_str = include_str!("spanish.in"); | |
1006 | /// assert_eq!(my_str, "adiós\n"); | |
1007 | /// print!("{}", my_str); | |
1008 | /// } | |
1009 | /// ``` | |
1010 | /// | |
1011 | /// Compiling 'main.rs' and running the resulting binary will print "adiós". | |
c30ab7b3 | 1012 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
1013 | #[rustc_builtin_macro] |
1014 | #[macro_export] | |
0531ce1d | 1015 | macro_rules! include_str { |
29967ef6 | 1016 | ($file:expr $(,)?) => {{ /* compiler built-in */ }}; |
0531ce1d | 1017 | } |
c30ab7b3 SL |
1018 | |
1019 | /// Includes a file as a reference to a byte array. | |
1020 | /// | |
ba9703b0 XL |
1021 | /// The file is located relative to the current file (similarly to how |
1022 | /// modules are found). The provided path is interpreted in a platform-specific | |
1023 | /// way at compile time. So, for instance, an invocation with a Windows path | |
1024 | /// containing backslashes `\` would not compile correctly on Unix. | |
416331ca XL |
1025 | /// |
1026 | /// This macro will yield an expression of type `&'static [u8; N]` which is | |
1027 | /// the contents of the file. | |
c30ab7b3 | 1028 | /// |
416331ca XL |
1029 | /// # Examples |
1030 | /// | |
1031 | /// Assume there are two files in the same directory with the following | |
1032 | /// contents: | |
1033 | /// | |
1034 | /// File 'spanish.in': | |
1035 | /// | |
1036 | /// ```text | |
1037 | /// adiós | |
1038 | /// ``` | |
1039 | /// | |
1040 | /// File 'main.rs': | |
1041 | /// | |
1042 | /// ```ignore (cannot-doctest-external-file-dependency) | |
1043 | /// fn main() { | |
1044 | /// let bytes = include_bytes!("spanish.in"); | |
1045 | /// assert_eq!(bytes, b"adi\xc3\xb3s\n"); | |
1046 | /// print!("{}", String::from_utf8_lossy(bytes)); | |
1047 | /// } | |
1048 | /// ``` | |
1049 | /// | |
1050 | /// Compiling 'main.rs' and running the resulting binary will print "adiós". | |
c30ab7b3 | 1051 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
1052 | #[rustc_builtin_macro] |
1053 | #[macro_export] | |
0531ce1d | 1054 | macro_rules! include_bytes { |
29967ef6 | 1055 | ($file:expr $(,)?) => {{ /* compiler built-in */ }}; |
0531ce1d | 1056 | } |
c30ab7b3 SL |
1057 | |
1058 | /// Expands to a string that represents the current module path. | |
1059 | /// | |
416331ca XL |
1060 | /// The current module path can be thought of as the hierarchy of modules |
1061 | /// leading back up to the crate root. The first component of the path | |
1062 | /// returned is the name of the crate currently being compiled. | |
1063 | /// | |
1064 | /// # Examples | |
1065 | /// | |
1066 | /// ``` | |
1067 | /// mod test { | |
1068 | /// pub fn foo() { | |
1069 | /// assert!(module_path!().ends_with("test")); | |
1070 | /// } | |
1071 | /// } | |
c30ab7b3 | 1072 | /// |
416331ca XL |
1073 | /// test::foo(); |
1074 | /// ``` | |
c30ab7b3 | 1075 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
1076 | #[rustc_builtin_macro] |
1077 | #[macro_export] | |
60c5eb7d XL |
1078 | macro_rules! module_path { |
1079 | () => { | |
1080 | /* compiler built-in */ | |
1081 | }; | |
1082 | } | |
c30ab7b3 | 1083 | |
416331ca | 1084 | /// Evaluates boolean combinations of configuration flags at compile-time. |
c30ab7b3 | 1085 | /// |
416331ca XL |
1086 | /// In addition to the `#[cfg]` attribute, this macro is provided to allow |
1087 | /// boolean expression evaluation of configuration flags. This frequently | |
1088 | /// leads to less duplicated code. | |
c30ab7b3 | 1089 | /// |
416331ca XL |
1090 | /// The syntax given to this macro is the same syntax as the [`cfg`] |
1091 | /// attribute. | |
1092 | /// | |
f9f354fc XL |
1093 | /// `cfg!`, unlike `#[cfg]`, does not remove any code and only evaluates to true or false. For |
1094 | /// example, all blocks in an if/else expression need to be valid when `cfg!` is used for | |
1095 | /// the condition, regardless of what `cfg!` is evaluating. | |
1096 | /// | |
416331ca XL |
1097 | /// [`cfg`]: ../reference/conditional-compilation.html#the-cfg-attribute |
1098 | /// | |
1099 | /// # Examples | |
1100 | /// | |
1101 | /// ``` | |
1102 | /// let my_directory = if cfg!(windows) { | |
1103 | /// "windows-specific-directory" | |
1104 | /// } else { | |
1105 | /// "unix-directory" | |
1106 | /// }; | |
1107 | /// ``` | |
c30ab7b3 | 1108 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
1109 | #[rustc_builtin_macro] |
1110 | #[macro_export] | |
60c5eb7d XL |
1111 | macro_rules! cfg { |
1112 | ($($cfg:tt)*) => { | |
1113 | /* compiler built-in */ | |
1114 | }; | |
1115 | } | |
c30ab7b3 | 1116 | |
532ac7d7 | 1117 | /// Parses a file as an expression or an item according to the context. |
c30ab7b3 | 1118 | /// |
416331ca | 1119 | /// The file is located relative to the current file (similarly to how |
ba9703b0 XL |
1120 | /// modules are found). The provided path is interpreted in a platform-specific |
1121 | /// way at compile time. So, for instance, an invocation with a Windows path | |
1122 | /// containing backslashes `\` would not compile correctly on Unix. | |
416331ca XL |
1123 | /// |
1124 | /// Using this macro is often a bad idea, because if the file is | |
1125 | /// parsed as an expression, it is going to be placed in the | |
1126 | /// surrounding code unhygienically. This could result in variables | |
1127 | /// or functions being different from what the file expected if | |
1128 | /// there are variables or functions that have the same name in | |
1129 | /// the current file. | |
1130 | /// | |
1131 | /// # Examples | |
1132 | /// | |
1133 | /// Assume there are two files in the same directory with the following | |
1134 | /// contents: | |
1135 | /// | |
1136 | /// File 'monkeys.in': | |
c30ab7b3 | 1137 | /// |
416331ca XL |
1138 | /// ```ignore (only-for-syntax-highlight) |
1139 | /// ['🙈', '🙊', '🙉'] | |
1140 | /// .iter() | |
1141 | /// .cycle() | |
1142 | /// .take(6) | |
1143 | /// .collect::<String>() | |
1144 | /// ``` | |
1145 | /// | |
1146 | /// File 'main.rs': | |
1147 | /// | |
1148 | /// ```ignore (cannot-doctest-external-file-dependency) | |
1149 | /// fn main() { | |
1150 | /// let my_string = include!("monkeys.in"); | |
1151 | /// assert_eq!("🙈🙊🙉🙈🙊🙉", my_string); | |
1152 | /// println!("{}", my_string); | |
1153 | /// } | |
1154 | /// ``` | |
1155 | /// | |
1156 | /// Compiling 'main.rs' and running the resulting binary will print | |
1157 | /// "🙈🙊🙉🙈🙊🙉". | |
c30ab7b3 | 1158 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
1159 | #[rustc_builtin_macro] |
1160 | #[macro_export] | |
0531ce1d | 1161 | macro_rules! include { |
29967ef6 | 1162 | ($file:expr $(,)?) => {{ /* compiler built-in */ }}; |
0531ce1d XL |
1163 | } |
1164 | ||
532ac7d7 | 1165 | /// Asserts that a boolean expression is `true` at runtime. |
0531ce1d | 1166 | /// |
416331ca XL |
1167 | /// This will invoke the [`panic!`] macro if the provided expression cannot be |
1168 | /// evaluated to `true` at runtime. | |
1169 | /// | |
1170 | /// # Uses | |
1171 | /// | |
1172 | /// Assertions are always checked in both debug and release builds, and cannot | |
1173 | /// be disabled. See [`debug_assert!`] for assertions that are not enabled in | |
1174 | /// release builds by default. | |
1175 | /// | |
f9f354fc | 1176 | /// Unsafe code may rely on `assert!` to enforce run-time invariants that, if |
416331ca XL |
1177 | /// violated could lead to unsafety. |
1178 | /// | |
1179 | /// Other use-cases of `assert!` include testing and enforcing run-time | |
1180 | /// invariants in safe code (whose violation cannot result in unsafety). | |
1181 | /// | |
1182 | /// # Custom Messages | |
1183 | /// | |
1184 | /// This macro has a second form, where a custom panic message can | |
1185 | /// be provided with or without arguments for formatting. See [`std::fmt`] | |
6a06907d XL |
1186 | /// for syntax for this form. Expressions used as format arguments will only |
1187 | /// be evaluated if the assertion fails. | |
416331ca | 1188 | /// |
5869c6ff | 1189 | /// [`std::fmt`]: ../std/fmt/index.html |
416331ca XL |
1190 | /// |
1191 | /// # Examples | |
1192 | /// | |
1193 | /// ``` | |
1194 | /// // the panic message for these assertions is the stringified value of the | |
1195 | /// // expression given. | |
1196 | /// assert!(true); | |
1197 | /// | |
1198 | /// fn some_computation() -> bool { true } // a very simple function | |
1199 | /// | |
1200 | /// assert!(some_computation()); | |
1201 | /// | |
1202 | /// // assert with a custom message | |
1203 | /// let x = true; | |
1204 | /// assert!(x, "x wasn't true!"); | |
0531ce1d | 1205 | /// |
416331ca XL |
1206 | /// let a = 3; let b = 27; |
1207 | /// assert!(a + b == 30, "a = {}, b = {}", a, b); | |
1208 | /// ``` | |
0531ce1d | 1209 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca XL |
1210 | #[rustc_builtin_macro] |
1211 | #[macro_export] | |
5869c6ff XL |
1212 | #[rustc_diagnostic_item = "assert_macro"] |
1213 | #[allow_internal_unstable(core_panic, edition_panic)] | |
0531ce1d | 1214 | macro_rules! assert { |
29967ef6 | 1215 | ($cond:expr $(,)?) => {{ /* compiler built-in */ }}; |
60c5eb7d | 1216 | ($cond:expr, $($arg:tt)+) => {{ /* compiler built-in */ }}; |
0531ce1d | 1217 | } |
416331ca XL |
1218 | |
1219 | /// Inline assembly. | |
60c5eb7d XL |
1220 | /// |
1221 | /// Read the [unstable book] for the usage. | |
1222 | /// | |
1223 | /// [unstable book]: ../unstable-book/library-features/asm.html | |
1224 | #[unstable( | |
1225 | feature = "asm", | |
f9f354fc | 1226 | issue = "72016", |
60c5eb7d XL |
1227 | reason = "inline assembly is not stable enough for use and is subject to change" |
1228 | )] | |
416331ca XL |
1229 | #[rustc_builtin_macro] |
1230 | #[macro_export] | |
60c5eb7d | 1231 | macro_rules! asm { |
f9f354fc XL |
1232 | ("assembly template", |
1233 | $(operands,)* | |
1234 | $(options($(option),*))? | |
1235 | ) => { | |
60c5eb7d XL |
1236 | /* compiler built-in */ |
1237 | }; | |
1238 | } | |
416331ca | 1239 | |
f9f354fc | 1240 | /// LLVM-style inline assembly. |
ba9703b0 XL |
1241 | /// |
1242 | /// Read the [unstable book] for the usage. | |
1243 | /// | |
f9f354fc | 1244 | /// [unstable book]: ../unstable-book/library-features/llvm-asm.html |
ba9703b0 XL |
1245 | #[unstable( |
1246 | feature = "llvm_asm", | |
1247 | issue = "70173", | |
f9f354fc | 1248 | reason = "prefer using the new asm! syntax instead" |
ba9703b0 XL |
1249 | )] |
1250 | #[rustc_builtin_macro] | |
1251 | #[macro_export] | |
1252 | macro_rules! llvm_asm { | |
1253 | ("assembly template" | |
1254 | : $("output"(operand),)* | |
1255 | : $("input"(operand),)* | |
1256 | : $("clobbers",)* | |
1257 | : $("options",)*) => { | |
1258 | /* compiler built-in */ | |
1259 | }; | |
1260 | } | |
1261 | ||
416331ca | 1262 | /// Module-level inline assembly. |
60c5eb7d XL |
1263 | #[unstable( |
1264 | feature = "global_asm", | |
1265 | issue = "35119", | |
1266 | reason = "`global_asm!` is not stable enough for use and is subject to change" | |
1267 | )] | |
416331ca XL |
1268 | #[rustc_builtin_macro] |
1269 | #[macro_export] | |
60c5eb7d XL |
1270 | macro_rules! global_asm { |
1271 | ("assembly") => { | |
1272 | /* compiler built-in */ | |
1273 | }; | |
1274 | } | |
416331ca XL |
1275 | |
1276 | /// Prints passed tokens into the standard output. | |
60c5eb7d XL |
1277 | #[unstable( |
1278 | feature = "log_syntax", | |
1279 | issue = "29598", | |
1280 | reason = "`log_syntax!` is not stable enough for use and is subject to change" | |
1281 | )] | |
416331ca XL |
1282 | #[rustc_builtin_macro] |
1283 | #[macro_export] | |
60c5eb7d XL |
1284 | macro_rules! log_syntax { |
1285 | ($($arg:tt)*) => { | |
1286 | /* compiler built-in */ | |
1287 | }; | |
1288 | } | |
416331ca XL |
1289 | |
1290 | /// Enables or disables tracing functionality used for debugging other macros. | |
60c5eb7d XL |
1291 | #[unstable( |
1292 | feature = "trace_macros", | |
1293 | issue = "29598", | |
1294 | reason = "`trace_macros` is not stable enough for use and is subject to change" | |
1295 | )] | |
416331ca XL |
1296 | #[rustc_builtin_macro] |
1297 | #[macro_export] | |
1298 | macro_rules! trace_macros { | |
60c5eb7d XL |
1299 | (true) => {{ /* compiler built-in */ }}; |
1300 | (false) => {{ /* compiler built-in */ }}; | |
416331ca XL |
1301 | } |
1302 | ||
6a06907d XL |
1303 | /// Attribute macro used to apply derive macros. |
1304 | #[cfg(not(bootstrap))] | |
1305 | #[stable(feature = "rust1", since = "1.0.0")] | |
1306 | #[rustc_builtin_macro] | |
1307 | pub macro derive($item:item) { | |
1308 | /* compiler built-in */ | |
1309 | } | |
1310 | ||
416331ca XL |
1311 | /// Attribute macro applied to a function to turn it into a unit test. |
1312 | #[stable(feature = "rust1", since = "1.0.0")] | |
1313 | #[allow_internal_unstable(test, rustc_attrs)] | |
1314 | #[rustc_builtin_macro] | |
60c5eb7d XL |
1315 | pub macro test($item:item) { |
1316 | /* compiler built-in */ | |
1317 | } | |
416331ca XL |
1318 | |
1319 | /// Attribute macro applied to a function to turn it into a benchmark test. | |
60c5eb7d XL |
1320 | #[unstable( |
1321 | feature = "test", | |
1322 | issue = "50297", | |
1323 | soft, | |
1324 | reason = "`bench` is a part of custom test frameworks which are unstable" | |
1325 | )] | |
416331ca XL |
1326 | #[allow_internal_unstable(test, rustc_attrs)] |
1327 | #[rustc_builtin_macro] | |
60c5eb7d XL |
1328 | pub macro bench($item:item) { |
1329 | /* compiler built-in */ | |
1330 | } | |
416331ca XL |
1331 | |
1332 | /// An implementation detail of the `#[test]` and `#[bench]` macros. | |
60c5eb7d XL |
1333 | #[unstable( |
1334 | feature = "custom_test_frameworks", | |
1335 | issue = "50297", | |
1336 | reason = "custom test frameworks are an unstable feature" | |
1337 | )] | |
416331ca XL |
1338 | #[allow_internal_unstable(test, rustc_attrs)] |
1339 | #[rustc_builtin_macro] | |
60c5eb7d XL |
1340 | pub macro test_case($item:item) { |
1341 | /* compiler built-in */ | |
1342 | } | |
416331ca XL |
1343 | |
1344 | /// Attribute macro applied to a static to register it as a global allocator. | |
29967ef6 XL |
1345 | /// |
1346 | /// See also [`std::alloc::GlobalAlloc`](../std/alloc/trait.GlobalAlloc.html). | |
416331ca XL |
1347 | #[stable(feature = "global_allocator", since = "1.28.0")] |
1348 | #[allow_internal_unstable(rustc_attrs)] | |
1349 | #[rustc_builtin_macro] | |
60c5eb7d XL |
1350 | pub macro global_allocator($item:item) { |
1351 | /* compiler built-in */ | |
1352 | } | |
416331ca | 1353 | |
ba9703b0 | 1354 | /// Keeps the item it's applied to if the passed path is accessible, and removes it otherwise. |
ba9703b0 XL |
1355 | #[unstable( |
1356 | feature = "cfg_accessible", | |
1357 | issue = "64797", | |
1358 | reason = "`cfg_accessible` is not fully implemented" | |
1359 | )] | |
1360 | #[rustc_builtin_macro] | |
1361 | pub macro cfg_accessible($item:item) { | |
1362 | /* compiler built-in */ | |
1363 | } | |
1364 | ||
6a06907d XL |
1365 | /// Expands all `#[cfg]` and `#[cfg_attr]` attributes in the code fragment it's applied to. |
1366 | #[cfg(not(bootstrap))] | |
1367 | #[unstable( | |
1368 | feature = "cfg_eval", | |
1369 | issue = "82679", | |
1370 | reason = "`cfg_eval` is a recently implemented feature" | |
1371 | )] | |
1372 | #[rustc_builtin_macro] | |
1373 | pub macro cfg_eval($($tt:tt)*) { | |
1374 | /* compiler built-in */ | |
1375 | } | |
1376 | ||
416331ca XL |
1377 | /// Unstable implementation detail of the `rustc` compiler, do not use. |
1378 | #[rustc_builtin_macro] | |
416331ca XL |
1379 | #[stable(feature = "rust1", since = "1.0.0")] |
1380 | #[allow_internal_unstable(core_intrinsics, libstd_sys_internals)] | |
6a06907d XL |
1381 | #[rustc_deprecated( |
1382 | since = "1.52.0", | |
1383 | reason = "rustc-serialize is deprecated and no longer supported" | |
1384 | )] | |
60c5eb7d XL |
1385 | pub macro RustcDecodable($item:item) { |
1386 | /* compiler built-in */ | |
1387 | } | |
416331ca XL |
1388 | |
1389 | /// Unstable implementation detail of the `rustc` compiler, do not use. | |
1390 | #[rustc_builtin_macro] | |
416331ca XL |
1391 | #[stable(feature = "rust1", since = "1.0.0")] |
1392 | #[allow_internal_unstable(core_intrinsics)] | |
6a06907d XL |
1393 | #[rustc_deprecated( |
1394 | since = "1.52.0", | |
1395 | reason = "rustc-serialize is deprecated and no longer supported" | |
1396 | )] | |
60c5eb7d XL |
1397 | pub macro RustcEncodable($item:item) { |
1398 | /* compiler built-in */ | |
1399 | } | |
c30ab7b3 | 1400 | } |