1//! String manipulation.
2//!
3//! For more details, see the [`std::str`] module.
4//!
5//! [`std::str`]: ../../std/str/index.html
6
7#![stable(feature = "rust1", since = "1.0.0")]
8
9mod converts;
10mod count;
11mod error;
12mod iter;
13mod traits;
14mod validations;
15
16use self::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher};
17use crate::char::{self, EscapeDebugExtArgs};
18use crate::ops::Range;
19use crate::slice::{self, SliceIndex};
20use crate::ub_checks::assert_unsafe_precondition;
21use crate::{ascii, mem};
22
23pub mod pattern;
24
25mod lossy;
26#[unstable(feature = "str_from_raw_parts", issue = "119206")]
27pub use converts::{from_raw_parts, from_raw_parts_mut};
28#[stable(feature = "rust1", since = "1.0.0")]
29pub use converts::{from_utf8, from_utf8_unchecked};
30#[stable(feature = "str_mut_extras", since = "1.20.0")]
31pub use converts::{from_utf8_mut, from_utf8_unchecked_mut};
32#[stable(feature = "rust1", since = "1.0.0")]
33pub use error::{ParseBoolError, Utf8Error};
34#[stable(feature = "encode_utf16", since = "1.8.0")]
35pub use iter::EncodeUtf16;
36#[stable(feature = "rust1", since = "1.0.0")]
37#[allow(deprecated)]
38pub use iter::LinesAny;
39#[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
40pub use iter::SplitAsciiWhitespace;
41#[stable(feature = "split_inclusive", since = "1.51.0")]
42pub use iter::SplitInclusive;
43#[stable(feature = "rust1", since = "1.0.0")]
44pub use iter::{Bytes, CharIndices, Chars, Lines, SplitWhitespace};
45#[stable(feature = "str_escape", since = "1.34.0")]
46pub use iter::{EscapeDebug, EscapeDefault, EscapeUnicode};
47#[stable(feature = "str_match_indices", since = "1.5.0")]
48pub use iter::{MatchIndices, RMatchIndices};
49use iter::{MatchIndicesInternal, MatchesInternal, SplitInternal, SplitNInternal};
50#[stable(feature = "str_matches", since = "1.2.0")]
51pub use iter::{Matches, RMatches};
52#[stable(feature = "rust1", since = "1.0.0")]
53pub use iter::{RSplit, RSplitTerminator, Split, SplitTerminator};
54#[stable(feature = "rust1", since = "1.0.0")]
55pub use iter::{RSplitN, SplitN};
56#[stable(feature = "utf8_chunks", since = "1.79.0")]
57pub use lossy::{Utf8Chunk, Utf8Chunks};
58#[stable(feature = "rust1", since = "1.0.0")]
59pub use traits::FromStr;
60#[unstable(feature = "str_internals", issue = "none")]
61pub use validations::{next_code_point, utf8_char_width};
62
63#[inline(never)]
64#[cold]
65#[track_caller]
66#[rustc_allow_const_fn_unstable(const_eval_select)]
67#[cfg(not(feature = "panic_immediate_abort"))]
68const fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
69 crate::intrinsics::const_eval_select((s, begin, end), _called_in_const:slice_error_fail_ct, _called_at_rt:slice_error_fail_rt)
70}
71
72#[cfg(feature = "panic_immediate_abort")]
73const fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
74 slice_error_fail_ct(s, begin, end)
75}
76
77#[track_caller]
78const fn slice_error_fail_ct(_: &str, _: usize, _: usize) -> ! {
79 panic!("failed to slice string");
80}
81
82#[track_caller]
83fn slice_error_fail_rt(s: &str, begin: usize, end: usize) -> ! {
84 const MAX_DISPLAY_LENGTH: usize = 256;
85 let trunc_len = s.floor_char_boundary(MAX_DISPLAY_LENGTH);
86 let s_trunc = &s[..trunc_len];
87 let ellipsis = if trunc_len < s.len() { "[...]" } else { "" };
88
89 // 1. out of bounds
90 if begin > s.len() || end > s.len() {
91 let oob_index = if begin > s.len() { begin } else { end };
92 panic!("byte index {oob_index} is out of bounds of `{s_trunc}`{ellipsis}");
93 }
94
95 // 2. begin <= end
96 assert!(
97 begin <= end,
98 "begin <= end ({} <= {}) when slicing `{}`{}",
99 begin,
100 end,
101 s_trunc,
102 ellipsis
103 );
104
105 // 3. character boundary
106 let index = if !s.is_char_boundary(begin) { begin } else { end };
107 // find the character
108 let char_start = s.floor_char_boundary(index);
109 // `char_start` must be less than len and a char boundary
110 let ch = s[char_start..].chars().next().unwrap();
111 let char_range = char_start..char_start + ch.len_utf8();
112 panic!(
113 "byte index {} is not a char boundary; it is inside {:?} (bytes {:?}) of `{}`{}",
114 index, ch, char_range, s_trunc, ellipsis
115 );
116}
117
118impl str {
119 /// Returns the length of `self`.
120 ///
121 /// This length is in bytes, not [`char`]s or graphemes. In other words,
122 /// it might not be what a human considers the length of the string.
123 ///
124 /// [`char`]: prim@char
125 ///
126 /// # Examples
127 ///
128 /// ```
129 /// let len = "foo".len();
130 /// assert_eq!(3, len);
131 ///
132 /// assert_eq!("ƒoo".len(), 4); // fancy f!
133 /// assert_eq!("ƒoo".chars().count(), 3);
134 /// ```
135 #[stable(feature = "rust1", since = "1.0.0")]
136 #[rustc_const_stable(feature = "const_str_len", since = "1.39.0")]
137 #[rustc_diagnostic_item = "str_len"]
138 #[rustc_no_implicit_autorefs]
139 #[must_use]
140 #[inline]
141 pub const fn len(&self) -> usize {
142 self.as_bytes().len()
143 }
144
145 /// Returns `true` if `self` has a length of zero bytes.
146 ///
147 /// # Examples
148 ///
149 /// ```
150 /// let s = "";
151 /// assert!(s.is_empty());
152 ///
153 /// let s = "not empty";
154 /// assert!(!s.is_empty());
155 /// ```
156 #[stable(feature = "rust1", since = "1.0.0")]
157 #[rustc_const_stable(feature = "const_str_is_empty", since = "1.39.0")]
158 #[rustc_no_implicit_autorefs]
159 #[must_use]
160 #[inline]
161 pub const fn is_empty(&self) -> bool {
162 self.len() == 0
163 }
164
165 /// Converts a slice of bytes to a string slice.
166 ///
167 /// A string slice ([`&str`]) is made of bytes ([`u8`]), and a byte slice
168 /// ([`&[u8]`][byteslice]) is made of bytes, so this function converts between
169 /// the two. Not all byte slices are valid string slices, however: [`&str`] requires
170 /// that it is valid UTF-8. `from_utf8()` checks to ensure that the bytes are valid
171 /// UTF-8, and then does the conversion.
172 ///
173 /// [`&str`]: str
174 /// [byteslice]: prim@slice
175 ///
176 /// If you are sure that the byte slice is valid UTF-8, and you don't want to
177 /// incur the overhead of the validity check, there is an unsafe version of
178 /// this function, [`from_utf8_unchecked`], which has the same
179 /// behavior but skips the check.
180 ///
181 /// If you need a `String` instead of a `&str`, consider
182 /// [`String::from_utf8`][string].
183 ///
184 /// [string]: ../std/string/struct.String.html#method.from_utf8
185 ///
186 /// Because you can stack-allocate a `[u8; N]`, and you can take a
187 /// [`&[u8]`][byteslice] of it, this function is one way to have a
188 /// stack-allocated string. There is an example of this in the
189 /// examples section below.
190 ///
191 /// [byteslice]: slice
192 ///
193 /// # Errors
194 ///
195 /// Returns `Err` if the slice is not UTF-8 with a description as to why the
196 /// provided slice is not UTF-8.
197 ///
198 /// # Examples
199 ///
200 /// Basic usage:
201 ///
202 /// ```
203 /// // some bytes, in a vector
204 /// let sparkle_heart = vec![240, 159, 146, 150];
205 ///
206 /// // We can use the ? (try) operator to check if the bytes are valid
207 /// let sparkle_heart = str::from_utf8(&sparkle_heart)?;
208 ///
209 /// assert_eq!("💖", sparkle_heart);
210 /// # Ok::<_, std::str::Utf8Error>(())
211 /// ```
212 ///
213 /// Incorrect bytes:
214 ///
215 /// ```
216 /// // some invalid bytes, in a vector
217 /// let sparkle_heart = vec![0, 159, 146, 150];
218 ///
219 /// assert!(str::from_utf8(&sparkle_heart).is_err());
220 /// ```
221 ///
222 /// See the docs for [`Utf8Error`] for more details on the kinds of
223 /// errors that can be returned.
224 ///
225 /// A "stack allocated string":
226 ///
227 /// ```
228 /// // some bytes, in a stack-allocated array
229 /// let sparkle_heart = [240, 159, 146, 150];
230 ///
231 /// // We know these bytes are valid, so just use `unwrap()`.
232 /// let sparkle_heart: &str = str::from_utf8(&sparkle_heart).unwrap();
233 ///
234 /// assert_eq!("💖", sparkle_heart);
235 /// ```
236 #[stable(feature = "inherent_str_constructors", since = "1.87.0")]
237 #[rustc_const_stable(feature = "inherent_str_constructors", since = "1.87.0")]
238 #[rustc_diagnostic_item = "str_inherent_from_utf8"]
239 pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
240 converts::from_utf8(v)
241 }
242
243 /// Converts a mutable slice of bytes to a mutable string slice.
244 ///
245 /// # Examples
246 ///
247 /// Basic usage:
248 ///
249 /// ```
250 /// // "Hello, Rust!" as a mutable vector
251 /// let mut hellorust = vec![72, 101, 108, 108, 111, 44, 32, 82, 117, 115, 116, 33];
252 ///
253 /// // As we know these bytes are valid, we can use `unwrap()`
254 /// let outstr = str::from_utf8_mut(&mut hellorust).unwrap();
255 ///
256 /// assert_eq!("Hello, Rust!", outstr);
257 /// ```
258 ///
259 /// Incorrect bytes:
260 ///
261 /// ```
262 /// // Some invalid bytes in a mutable vector
263 /// let mut invalid = vec![128, 223];
264 ///
265 /// assert!(str::from_utf8_mut(&mut invalid).is_err());
266 /// ```
267 /// See the docs for [`Utf8Error`] for more details on the kinds of
268 /// errors that can be returned.
269 #[stable(feature = "inherent_str_constructors", since = "1.87.0")]
270 #[rustc_const_stable(feature = "const_str_from_utf8", since = "1.87.0")]
271 #[rustc_diagnostic_item = "str_inherent_from_utf8_mut"]
272 pub const fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
273 converts::from_utf8_mut(v)
274 }
275
276 /// Converts a slice of bytes to a string slice without checking
277 /// that the string contains valid UTF-8.
278 ///
279 /// See the safe version, [`from_utf8`], for more information.
280 ///
281 /// # Safety
282 ///
283 /// The bytes passed in must be valid UTF-8.
284 ///
285 /// # Examples
286 ///
287 /// Basic usage:
288 ///
289 /// ```
290 /// // some bytes, in a vector
291 /// let sparkle_heart = vec![240, 159, 146, 150];
292 ///
293 /// let sparkle_heart = unsafe {
294 /// str::from_utf8_unchecked(&sparkle_heart)
295 /// };
296 ///
297 /// assert_eq!("💖", sparkle_heart);
298 /// ```
299 #[inline]
300 #[must_use]
301 #[stable(feature = "inherent_str_constructors", since = "1.87.0")]
302 #[rustc_const_stable(feature = "inherent_str_constructors", since = "1.87.0")]
303 #[rustc_diagnostic_item = "str_inherent_from_utf8_unchecked"]
304 pub const unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
305 // SAFETY: converts::from_utf8_unchecked has the same safety requirements as this function.
306 unsafe { converts::from_utf8_unchecked(v) }
307 }
308
309 /// Converts a slice of bytes to a string slice without checking
310 /// that the string contains valid UTF-8; mutable version.
311 ///
312 /// See the immutable version, [`from_utf8_unchecked()`] for documentation and safety requirements.
313 ///
314 /// # Examples
315 ///
316 /// Basic usage:
317 ///
318 /// ```
319 /// let mut heart = vec![240, 159, 146, 150];
320 /// let heart = unsafe { str::from_utf8_unchecked_mut(&mut heart) };
321 ///
322 /// assert_eq!("💖", heart);
323 /// ```
324 #[inline]
325 #[must_use]
326 #[stable(feature = "inherent_str_constructors", since = "1.87.0")]
327 #[rustc_const_stable(feature = "inherent_str_constructors", since = "1.87.0")]
328 #[rustc_diagnostic_item = "str_inherent_from_utf8_unchecked_mut"]
329 pub const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
330 // SAFETY: converts::from_utf8_unchecked_mut has the same safety requirements as this function.
331 unsafe { converts::from_utf8_unchecked_mut(v) }
332 }
333
334 /// Checks that `index`-th byte is the first byte in a UTF-8 code point
335 /// sequence or the end of the string.
336 ///
337 /// The start and end of the string (when `index == self.len()`) are
338 /// considered to be boundaries.
339 ///
340 /// Returns `false` if `index` is greater than `self.len()`.
341 ///
342 /// # Examples
343 ///
344 /// ```
345 /// let s = "Löwe 老虎 Léopard";
346 /// assert!(s.is_char_boundary(0));
347 /// // start of `老`
348 /// assert!(s.is_char_boundary(6));
349 /// assert!(s.is_char_boundary(s.len()));
350 ///
351 /// // second byte of `ö`
352 /// assert!(!s.is_char_boundary(2));
353 ///
354 /// // third byte of `老`
355 /// assert!(!s.is_char_boundary(8));
356 /// ```
357 #[must_use]
358 #[stable(feature = "is_char_boundary", since = "1.9.0")]
359 #[rustc_const_stable(feature = "const_is_char_boundary", since = "1.86.0")]
360 #[inline]
361 pub const fn is_char_boundary(&self, index: usize) -> bool {
362 // 0 is always ok.
363 // Test for 0 explicitly so that it can optimize out the check
364 // easily and skip reading string data for that case.
365 // Note that optimizing `self.get(..index)` relies on this.
366 if index == 0 {
367 return true;
368 }
369
370 if index >= self.len() {
371 // For `true` we have two options:
372 //
373 // - index == self.len()
374 // Empty strings are valid, so return true
375 // - index > self.len()
376 // In this case return false
377 //
378 // The check is placed exactly here, because it improves generated
379 // code on higher opt-levels. See PR #84751 for more details.
380 index == self.len()
381 } else {
382 self.as_bytes()[index].is_utf8_char_boundary()
383 }
384 }
385
386 /// Finds the closest `x` not exceeding `index` where [`is_char_boundary(x)`] is `true`.
387 ///
388 /// This method can help you truncate a string so that it's still valid UTF-8, but doesn't
389 /// exceed a given number of bytes. Note that this is done purely at the character level
390 /// and can still visually split graphemes, even though the underlying characters aren't
391 /// split. For example, the emoji 🧑‍🔬 (scientist) could be split so that the string only
392 /// includes 🧑 (person) instead.
393 ///
394 /// [`is_char_boundary(x)`]: Self::is_char_boundary
395 ///
396 /// # Examples
397 ///
398 /// ```
399 /// #![feature(round_char_boundary)]
400 /// let s = "❤️🧡💛💚💙💜";
401 /// assert_eq!(s.len(), 26);
402 /// assert!(!s.is_char_boundary(13));
403 ///
404 /// let closest = s.floor_char_boundary(13);
405 /// assert_eq!(closest, 10);
406 /// assert_eq!(&s[..closest], "❤️🧡");
407 /// ```
408 #[unstable(feature = "round_char_boundary", issue = "93743")]
409 #[inline]
410 pub fn floor_char_boundary(&self, index: usize) -> usize {
411 if index >= self.len() {
412 self.len()
413 } else {
414 let lower_bound = index.saturating_sub(3);
415 let new_index = self.as_bytes()[lower_bound..=index]
416 .iter()
417 .rposition(|b| b.is_utf8_char_boundary());
418
419 // SAFETY: we know that the character boundary will be within four bytes
420 unsafe { lower_bound + new_index.unwrap_unchecked() }
421 }
422 }
423
424 /// Finds the closest `x` not below `index` where [`is_char_boundary(x)`] is `true`.
425 ///
426 /// If `index` is greater than the length of the string, this returns the length of the string.
427 ///
428 /// This method is the natural complement to [`floor_char_boundary`]. See that method
429 /// for more details.
430 ///
431 /// [`floor_char_boundary`]: str::floor_char_boundary
432 /// [`is_char_boundary(x)`]: Self::is_char_boundary
433 ///
434 /// # Examples
435 ///
436 /// ```
437 /// #![feature(round_char_boundary)]
438 /// let s = "❤️🧡💛💚💙💜";
439 /// assert_eq!(s.len(), 26);
440 /// assert!(!s.is_char_boundary(13));
441 ///
442 /// let closest = s.ceil_char_boundary(13);
443 /// assert_eq!(closest, 14);
444 /// assert_eq!(&s[..closest], "❤️🧡💛");
445 /// ```
446 #[unstable(feature = "round_char_boundary", issue = "93743")]
447 #[inline]
448 pub fn ceil_char_boundary(&self, index: usize) -> usize {
449 if index > self.len() {
450 self.len()
451 } else {
452 let upper_bound = Ord::min(index + 4, self.len());
453 self.as_bytes()[index..upper_bound]
454 .iter()
455 .position(|b| b.is_utf8_char_boundary())
456 .map_or(upper_bound, |pos| pos + index)
457 }
458 }
459
460 /// Converts a string slice to a byte slice. To convert the byte slice back
461 /// into a string slice, use the [`from_utf8`] function.
462 ///
463 /// # Examples
464 ///
465 /// ```
466 /// let bytes = "bors".as_bytes();
467 /// assert_eq!(b"bors", bytes);
468 /// ```
469 #[stable(feature = "rust1", since = "1.0.0")]
470 #[rustc_const_stable(feature = "str_as_bytes", since = "1.39.0")]
471 #[must_use]
472 #[inline(always)]
473 #[allow(unused_attributes)]
474 pub const fn as_bytes(&self) -> &[u8] {
475 // SAFETY: const sound because we transmute two types with the same layout
476 unsafe { mem::transmute(self) }
477 }
478
479 /// Converts a mutable string slice to a mutable byte slice.
480 ///
481 /// # Safety
482 ///
483 /// The caller must ensure that the content of the slice is valid UTF-8
484 /// before the borrow ends and the underlying `str` is used.
485 ///
486 /// Use of a `str` whose contents are not valid UTF-8 is undefined behavior.
487 ///
488 /// # Examples
489 ///
490 /// Basic usage:
491 ///
492 /// ```
493 /// let mut s = String::from("Hello");
494 /// let bytes = unsafe { s.as_bytes_mut() };
495 ///
496 /// assert_eq!(b"Hello", bytes);
497 /// ```
498 ///
499 /// Mutability:
500 ///
501 /// ```
502 /// let mut s = String::from("🗻∈🌏");
503 ///
504 /// unsafe {
505 /// let bytes = s.as_bytes_mut();
506 ///
507 /// bytes[0] = 0xF0;
508 /// bytes[1] = 0x9F;
509 /// bytes[2] = 0x8D;
510 /// bytes[3] = 0x94;
511 /// }
512 ///
513 /// assert_eq!("🍔∈🌏", s);
514 /// ```
515 #[stable(feature = "str_mut_extras", since = "1.20.0")]
516 #[rustc_const_stable(feature = "const_str_as_mut", since = "1.83.0")]
517 #[must_use]
518 #[inline(always)]
519 pub const unsafe fn as_bytes_mut(&mut self) -> &mut [u8] {
520 // SAFETY: the cast from `&str` to `&[u8]` is safe since `str`
521 // has the same layout as `&[u8]` (only std can make this guarantee).
522 // The pointer dereference is safe since it comes from a mutable reference which
523 // is guaranteed to be valid for writes.
524 unsafe { &mut *(self as *mut str as *mut [u8]) }
525 }
526
527 /// Converts a string slice to a raw pointer.
528 ///
529 /// As string slices are a slice of bytes, the raw pointer points to a
530 /// [`u8`]. This pointer will be pointing to the first byte of the string
531 /// slice.
532 ///
533 /// The caller must ensure that the returned pointer is never written to.
534 /// If you need to mutate the contents of the string slice, use [`as_mut_ptr`].
535 ///
536 /// [`as_mut_ptr`]: str::as_mut_ptr
537 ///
538 /// # Examples
539 ///
540 /// ```
541 /// let s = "Hello";
542 /// let ptr = s.as_ptr();
543 /// ```
544 #[stable(feature = "rust1", since = "1.0.0")]
545 #[rustc_const_stable(feature = "rustc_str_as_ptr", since = "1.32.0")]
546 #[rustc_never_returns_null_ptr]
547 #[rustc_as_ptr]
548 #[must_use]
549 #[inline(always)]
550 pub const fn as_ptr(&self) -> *const u8 {
551 self as *const str as *const u8
552 }
553
554 /// Converts a mutable string slice to a raw pointer.
555 ///
556 /// As string slices are a slice of bytes, the raw pointer points to a
557 /// [`u8`]. This pointer will be pointing to the first byte of the string
558 /// slice.
559 ///
560 /// It is your responsibility to make sure that the string slice only gets
561 /// modified in a way that it remains valid UTF-8.
562 #[stable(feature = "str_as_mut_ptr", since = "1.36.0")]
563 #[rustc_const_stable(feature = "const_str_as_mut", since = "1.83.0")]
564 #[rustc_never_returns_null_ptr]
565 #[rustc_as_ptr]
566 #[must_use]
567 #[inline(always)]
568 pub const fn as_mut_ptr(&mut self) -> *mut u8 {
569 self as *mut str as *mut u8
570 }
571
572 /// Returns a subslice of `str`.
573 ///
574 /// This is the non-panicking alternative to indexing the `str`. Returns
575 /// [`None`] whenever equivalent indexing operation would panic.
576 ///
577 /// # Examples
578 ///
579 /// ```
580 /// let v = String::from("🗻∈🌏");
581 ///
582 /// assert_eq!(Some("🗻"), v.get(0..4));
583 ///
584 /// // indices not on UTF-8 sequence boundaries
585 /// assert!(v.get(1..).is_none());
586 /// assert!(v.get(..8).is_none());
587 ///
588 /// // out of bounds
589 /// assert!(v.get(..42).is_none());
590 /// ```
591 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
592 #[inline]
593 pub fn get<I: SliceIndex<str>>(&self, i: I) -> Option<&I::Output> {
594 i.get(self)
595 }
596
597 /// Returns a mutable subslice of `str`.
598 ///
599 /// This is the non-panicking alternative to indexing the `str`. Returns
600 /// [`None`] whenever equivalent indexing operation would panic.
601 ///
602 /// # Examples
603 ///
604 /// ```
605 /// let mut v = String::from("hello");
606 /// // correct length
607 /// assert!(v.get_mut(0..5).is_some());
608 /// // out of bounds
609 /// assert!(v.get_mut(..42).is_none());
610 /// assert_eq!(Some("he"), v.get_mut(0..2).map(|v| &*v));
611 ///
612 /// assert_eq!("hello", v);
613 /// {
614 /// let s = v.get_mut(0..2);
615 /// let s = s.map(|s| {
616 /// s.make_ascii_uppercase();
617 /// &*s
618 /// });
619 /// assert_eq!(Some("HE"), s);
620 /// }
621 /// assert_eq!("HEllo", v);
622 /// ```
623 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
624 #[inline]
625 pub fn get_mut<I: SliceIndex<str>>(&mut self, i: I) -> Option<&mut I::Output> {
626 i.get_mut(self)
627 }
628
629 /// Returns an unchecked subslice of `str`.
630 ///
631 /// This is the unchecked alternative to indexing the `str`.
632 ///
633 /// # Safety
634 ///
635 /// Callers of this function are responsible that these preconditions are
636 /// satisfied:
637 ///
638 /// * The starting index must not exceed the ending index;
639 /// * Indexes must be within bounds of the original slice;
640 /// * Indexes must lie on UTF-8 sequence boundaries.
641 ///
642 /// Failing that, the returned string slice may reference invalid memory or
643 /// violate the invariants communicated by the `str` type.
644 ///
645 /// # Examples
646 ///
647 /// ```
648 /// let v = "🗻∈🌏";
649 /// unsafe {
650 /// assert_eq!("🗻", v.get_unchecked(0..4));
651 /// assert_eq!("∈", v.get_unchecked(4..7));
652 /// assert_eq!("🌏", v.get_unchecked(7..11));
653 /// }
654 /// ```
655 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
656 #[inline]
657 pub unsafe fn get_unchecked<I: SliceIndex<str>>(&self, i: I) -> &I::Output {
658 // SAFETY: the caller must uphold the safety contract for `get_unchecked`;
659 // the slice is dereferenceable because `self` is a safe reference.
660 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
661 unsafe { &*i.get_unchecked(self) }
662 }
663
664 /// Returns a mutable, unchecked subslice of `str`.
665 ///
666 /// This is the unchecked alternative to indexing the `str`.
667 ///
668 /// # Safety
669 ///
670 /// Callers of this function are responsible that these preconditions are
671 /// satisfied:
672 ///
673 /// * The starting index must not exceed the ending index;
674 /// * Indexes must be within bounds of the original slice;
675 /// * Indexes must lie on UTF-8 sequence boundaries.
676 ///
677 /// Failing that, the returned string slice may reference invalid memory or
678 /// violate the invariants communicated by the `str` type.
679 ///
680 /// # Examples
681 ///
682 /// ```
683 /// let mut v = String::from("🗻∈🌏");
684 /// unsafe {
685 /// assert_eq!("🗻", v.get_unchecked_mut(0..4));
686 /// assert_eq!("∈", v.get_unchecked_mut(4..7));
687 /// assert_eq!("🌏", v.get_unchecked_mut(7..11));
688 /// }
689 /// ```
690 #[stable(feature = "str_checked_slicing", since = "1.20.0")]
691 #[inline]
692 pub unsafe fn get_unchecked_mut<I: SliceIndex<str>>(&mut self, i: I) -> &mut I::Output {
693 // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`;
694 // the slice is dereferenceable because `self` is a safe reference.
695 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
696 unsafe { &mut *i.get_unchecked_mut(self) }
697 }
698
699 /// Creates a string slice from another string slice, bypassing safety
700 /// checks.
701 ///
702 /// This is generally not recommended, use with caution! For a safe
703 /// alternative see [`str`] and [`Index`].
704 ///
705 /// [`Index`]: crate::ops::Index
706 ///
707 /// This new slice goes from `begin` to `end`, including `begin` but
708 /// excluding `end`.
709 ///
710 /// To get a mutable string slice instead, see the
711 /// [`slice_mut_unchecked`] method.
712 ///
713 /// [`slice_mut_unchecked`]: str::slice_mut_unchecked
714 ///
715 /// # Safety
716 ///
717 /// Callers of this function are responsible that three preconditions are
718 /// satisfied:
719 ///
720 /// * `begin` must not exceed `end`.
721 /// * `begin` and `end` must be byte positions within the string slice.
722 /// * `begin` and `end` must lie on UTF-8 sequence boundaries.
723 ///
724 /// # Examples
725 ///
726 /// ```
727 /// let s = "Löwe 老虎 Léopard";
728 ///
729 /// unsafe {
730 /// assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
731 /// }
732 ///
733 /// let s = "Hello, world!";
734 ///
735 /// unsafe {
736 /// assert_eq!("world", s.slice_unchecked(7, 12));
737 /// }
738 /// ```
739 #[stable(feature = "rust1", since = "1.0.0")]
740 #[deprecated(since = "1.29.0", note = "use `get_unchecked(begin..end)` instead")]
741 #[must_use]
742 #[inline]
743 pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str {
744 // SAFETY: the caller must uphold the safety contract for `get_unchecked`;
745 // the slice is dereferenceable because `self` is a safe reference.
746 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
747 unsafe { &*(begin..end).get_unchecked(self) }
748 }
749
750 /// Creates a string slice from another string slice, bypassing safety
751 /// checks.
752 ///
753 /// This is generally not recommended, use with caution! For a safe
754 /// alternative see [`str`] and [`IndexMut`].
755 ///
756 /// [`IndexMut`]: crate::ops::IndexMut
757 ///
758 /// This new slice goes from `begin` to `end`, including `begin` but
759 /// excluding `end`.
760 ///
761 /// To get an immutable string slice instead, see the
762 /// [`slice_unchecked`] method.
763 ///
764 /// [`slice_unchecked`]: str::slice_unchecked
765 ///
766 /// # Safety
767 ///
768 /// Callers of this function are responsible that three preconditions are
769 /// satisfied:
770 ///
771 /// * `begin` must not exceed `end`.
772 /// * `begin` and `end` must be byte positions within the string slice.
773 /// * `begin` and `end` must lie on UTF-8 sequence boundaries.
774 #[stable(feature = "str_slice_mut", since = "1.5.0")]
775 #[deprecated(since = "1.29.0", note = "use `get_unchecked_mut(begin..end)` instead")]
776 #[inline]
777 pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str {
778 // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`;
779 // the slice is dereferenceable because `self` is a safe reference.
780 // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is.
781 unsafe { &mut *(begin..end).get_unchecked_mut(self) }
782 }
783
784 /// Divides one string slice into two at an index.
785 ///
786 /// The argument, `mid`, should be a byte offset from the start of the
787 /// string. It must also be on the boundary of a UTF-8 code point.
788 ///
789 /// The two slices returned go from the start of the string slice to `mid`,
790 /// and from `mid` to the end of the string slice.
791 ///
792 /// To get mutable string slices instead, see the [`split_at_mut`]
793 /// method.
794 ///
795 /// [`split_at_mut`]: str::split_at_mut
796 ///
797 /// # Panics
798 ///
799 /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is past
800 /// the end of the last code point of the string slice. For a non-panicking
801 /// alternative see [`split_at_checked`](str::split_at_checked).
802 ///
803 /// # Examples
804 ///
805 /// ```
806 /// let s = "Per Martin-Löf";
807 ///
808 /// let (first, last) = s.split_at(3);
809 ///
810 /// assert_eq!("Per", first);
811 /// assert_eq!(" Martin-Löf", last);
812 /// ```
813 #[inline]
814 #[must_use]
815 #[stable(feature = "str_split_at", since = "1.4.0")]
816 #[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
817 pub const fn split_at(&self, mid: usize) -> (&str, &str) {
818 match self.split_at_checked(mid) {
819 None => slice_error_fail(self, 0, mid),
820 Some(pair) => pair,
821 }
822 }
823
824 /// Divides one mutable string slice into two at an index.
825 ///
826 /// The argument, `mid`, should be a byte offset from the start of the
827 /// string. It must also be on the boundary of a UTF-8 code point.
828 ///
829 /// The two slices returned go from the start of the string slice to `mid`,
830 /// and from `mid` to the end of the string slice.
831 ///
832 /// To get immutable string slices instead, see the [`split_at`] method.
833 ///
834 /// [`split_at`]: str::split_at
835 ///
836 /// # Panics
837 ///
838 /// Panics if `mid` is not on a UTF-8 code point boundary, or if it is past
839 /// the end of the last code point of the string slice. For a non-panicking
840 /// alternative see [`split_at_mut_checked`](str::split_at_mut_checked).
841 ///
842 /// # Examples
843 ///
844 /// ```
845 /// let mut s = "Per Martin-Löf".to_string();
846 /// {
847 /// let (first, last) = s.split_at_mut(3);
848 /// first.make_ascii_uppercase();
849 /// assert_eq!("PER", first);
850 /// assert_eq!(" Martin-Löf", last);
851 /// }
852 /// assert_eq!("PER Martin-Löf", s);
853 /// ```
854 #[inline]
855 #[must_use]
856 #[stable(feature = "str_split_at", since = "1.4.0")]
857 #[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
858 pub const fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str) {
859 // is_char_boundary checks that the index is in [0, .len()]
860 if self.is_char_boundary(mid) {
861 // SAFETY: just checked that `mid` is on a char boundary.
862 unsafe { self.split_at_mut_unchecked(mid) }
863 } else {
864 slice_error_fail(self, 0, mid)
865 }
866 }
867
868 /// Divides one string slice into two at an index.
869 ///
870 /// The argument, `mid`, should be a valid byte offset from the start of the
871 /// string. It must also be on the boundary of a UTF-8 code point. The
872 /// method returns `None` if that’s not the case.
873 ///
874 /// The two slices returned go from the start of the string slice to `mid`,
875 /// and from `mid` to the end of the string slice.
876 ///
877 /// To get mutable string slices instead, see the [`split_at_mut_checked`]
878 /// method.
879 ///
880 /// [`split_at_mut_checked`]: str::split_at_mut_checked
881 ///
882 /// # Examples
883 ///
884 /// ```
885 /// let s = "Per Martin-Löf";
886 ///
887 /// let (first, last) = s.split_at_checked(3).unwrap();
888 /// assert_eq!("Per", first);
889 /// assert_eq!(" Martin-Löf", last);
890 ///
891 /// assert_eq!(None, s.split_at_checked(13)); // Inside “ö”
892 /// assert_eq!(None, s.split_at_checked(16)); // Beyond the string length
893 /// ```
894 #[inline]
895 #[must_use]
896 #[stable(feature = "split_at_checked", since = "1.80.0")]
897 #[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
898 pub const fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)> {
899 // is_char_boundary checks that the index is in [0, .len()]
900 if self.is_char_boundary(mid) {
901 // SAFETY: just checked that `mid` is on a char boundary.
902 Some(unsafe { self.split_at_unchecked(mid) })
903 } else {
904 None
905 }
906 }
907
908 /// Divides one mutable string slice into two at an index.
909 ///
910 /// The argument, `mid`, should be a valid byte offset from the start of the
911 /// string. It must also be on the boundary of a UTF-8 code point. The
912 /// method returns `None` if that’s not the case.
913 ///
914 /// The two slices returned go from the start of the string slice to `mid`,
915 /// and from `mid` to the end of the string slice.
916 ///
917 /// To get immutable string slices instead, see the [`split_at_checked`] method.
918 ///
919 /// [`split_at_checked`]: str::split_at_checked
920 ///
921 /// # Examples
922 ///
923 /// ```
924 /// let mut s = "Per Martin-Löf".to_string();
925 /// if let Some((first, last)) = s.split_at_mut_checked(3) {
926 /// first.make_ascii_uppercase();
927 /// assert_eq!("PER", first);
928 /// assert_eq!(" Martin-Löf", last);
929 /// }
930 /// assert_eq!("PER Martin-Löf", s);
931 ///
932 /// assert_eq!(None, s.split_at_mut_checked(13)); // Inside “ö”
933 /// assert_eq!(None, s.split_at_mut_checked(16)); // Beyond the string length
934 /// ```
935 #[inline]
936 #[must_use]
937 #[stable(feature = "split_at_checked", since = "1.80.0")]
938 #[rustc_const_stable(feature = "const_str_split_at", since = "1.86.0")]
939 pub const fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str)> {
940 // is_char_boundary checks that the index is in [0, .len()]
941 if self.is_char_boundary(mid) {
942 // SAFETY: just checked that `mid` is on a char boundary.
943 Some(unsafe { self.split_at_mut_unchecked(mid) })
944 } else {
945 None
946 }
947 }
948
949 /// Divides one string slice into two at an index.
950 ///
951 /// # Safety
952 ///
953 /// The caller must ensure that `mid` is a valid byte offset from the start
954 /// of the string and falls on the boundary of a UTF-8 code point.
955 const unsafe fn split_at_unchecked(&self, mid: usize) -> (&str, &str) {
956 let len = self.len();
957 let ptr = self.as_ptr();
958 // SAFETY: caller guarantees `mid` is on a char boundary.
959 unsafe {
960 (
961 from_utf8_unchecked(slice::from_raw_parts(ptr, mid)),
962 from_utf8_unchecked(slice::from_raw_parts(ptr.add(mid), len - mid)),
963 )
964 }
965 }
966
967 /// Divides one string slice into two at an index.
968 ///
969 /// # Safety
970 ///
971 /// The caller must ensure that `mid` is a valid byte offset from the start
972 /// of the string and falls on the boundary of a UTF-8 code point.
973 const unsafe fn split_at_mut_unchecked(&mut self, mid: usize) -> (&mut str, &mut str) {
974 let len = self.len();
975 let ptr = self.as_mut_ptr();
976 // SAFETY: caller guarantees `mid` is on a char boundary.
977 unsafe {
978 (
979 from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, mid)),
980 from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr.add(mid), len - mid)),
981 )
982 }
983 }
984
985 /// Returns an iterator over the [`char`]s of a string slice.
986 ///
987 /// As a string slice consists of valid UTF-8, we can iterate through a
988 /// string slice by [`char`]. This method returns such an iterator.
989 ///
990 /// It's important to remember that [`char`] represents a Unicode Scalar
991 /// Value, and might not match your idea of what a 'character' is. Iteration
992 /// over grapheme clusters may be what you actually want. This functionality
993 /// is not provided by Rust's standard library, check crates.io instead.
994 ///
995 /// # Examples
996 ///
997 /// Basic usage:
998 ///
999 /// ```
1000 /// let word = "goodbye";
1001 ///
1002 /// let count = word.chars().count();
1003 /// assert_eq!(7, count);
1004 ///
1005 /// let mut chars = word.chars();
1006 ///
1007 /// assert_eq!(Some('g'), chars.next());
1008 /// assert_eq!(Some('o'), chars.next());
1009 /// assert_eq!(Some('o'), chars.next());
1010 /// assert_eq!(Some('d'), chars.next());
1011 /// assert_eq!(Some('b'), chars.next());
1012 /// assert_eq!(Some('y'), chars.next());
1013 /// assert_eq!(Some('e'), chars.next());
1014 ///
1015 /// assert_eq!(None, chars.next());
1016 /// ```
1017 ///
1018 /// Remember, [`char`]s might not match your intuition about characters:
1019 ///
1020 /// [`char`]: prim@char
1021 ///
1022 /// ```
1023 /// let y = "y̆";
1024 ///
1025 /// let mut chars = y.chars();
1026 ///
1027 /// assert_eq!(Some('y'), chars.next()); // not 'y̆'
1028 /// assert_eq!(Some('\u{0306}'), chars.next());
1029 ///
1030 /// assert_eq!(None, chars.next());
1031 /// ```
1032 #[stable(feature = "rust1", since = "1.0.0")]
1033 #[inline]
1034 #[rustc_diagnostic_item = "str_chars"]
1035 pub fn chars(&self) -> Chars<'_> {
1036 Chars { iter: self.as_bytes().iter() }
1037 }
1038
1039 /// Returns an iterator over the [`char`]s of a string slice, and their
1040 /// positions.
1041 ///
1042 /// As a string slice consists of valid UTF-8, we can iterate through a
1043 /// string slice by [`char`]. This method returns an iterator of both
1044 /// these [`char`]s, as well as their byte positions.
1045 ///
1046 /// The iterator yields tuples. The position is first, the [`char`] is
1047 /// second.
1048 ///
1049 /// # Examples
1050 ///
1051 /// Basic usage:
1052 ///
1053 /// ```
1054 /// let word = "goodbye";
1055 ///
1056 /// let count = word.char_indices().count();
1057 /// assert_eq!(7, count);
1058 ///
1059 /// let mut char_indices = word.char_indices();
1060 ///
1061 /// assert_eq!(Some((0, 'g')), char_indices.next());
1062 /// assert_eq!(Some((1, 'o')), char_indices.next());
1063 /// assert_eq!(Some((2, 'o')), char_indices.next());
1064 /// assert_eq!(Some((3, 'd')), char_indices.next());
1065 /// assert_eq!(Some((4, 'b')), char_indices.next());
1066 /// assert_eq!(Some((5, 'y')), char_indices.next());
1067 /// assert_eq!(Some((6, 'e')), char_indices.next());
1068 ///
1069 /// assert_eq!(None, char_indices.next());
1070 /// ```
1071 ///
1072 /// Remember, [`char`]s might not match your intuition about characters:
1073 ///
1074 /// [`char`]: prim@char
1075 ///
1076 /// ```
1077 /// let yes = "y̆es";
1078 ///
1079 /// let mut char_indices = yes.char_indices();
1080 ///
1081 /// assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
1082 /// assert_eq!(Some((1, '\u{0306}')), char_indices.next());
1083 ///
1084 /// // note the 3 here - the previous character took up two bytes
1085 /// assert_eq!(Some((3, 'e')), char_indices.next());
1086 /// assert_eq!(Some((4, 's')), char_indices.next());
1087 ///
1088 /// assert_eq!(None, char_indices.next());
1089 /// ```
1090 #[stable(feature = "rust1", since = "1.0.0")]
1091 #[inline]
1092 pub fn char_indices(&self) -> CharIndices<'_> {
1093 CharIndices { front_offset: 0, iter: self.chars() }
1094 }
1095
1096 /// Returns an iterator over the bytes of a string slice.
1097 ///
1098 /// As a string slice consists of a sequence of bytes, we can iterate
1099 /// through a string slice by byte. This method returns such an iterator.
1100 ///
1101 /// # Examples
1102 ///
1103 /// ```
1104 /// let mut bytes = "bors".bytes();
1105 ///
1106 /// assert_eq!(Some(b'b'), bytes.next());
1107 /// assert_eq!(Some(b'o'), bytes.next());
1108 /// assert_eq!(Some(b'r'), bytes.next());
1109 /// assert_eq!(Some(b's'), bytes.next());
1110 ///
1111 /// assert_eq!(None, bytes.next());
1112 /// ```
1113 #[stable(feature = "rust1", since = "1.0.0")]
1114 #[inline]
1115 pub fn bytes(&self) -> Bytes<'_> {
1116 Bytes(self.as_bytes().iter().copied())
1117 }
1118
1119 /// Splits a string slice by whitespace.
1120 ///
1121 /// The iterator returned will return string slices that are sub-slices of
1122 /// the original string slice, separated by any amount of whitespace.
1123 ///
1124 /// 'Whitespace' is defined according to the terms of the Unicode Derived
1125 /// Core Property `White_Space`. If you only want to split on ASCII whitespace
1126 /// instead, use [`split_ascii_whitespace`].
1127 ///
1128 /// [`split_ascii_whitespace`]: str::split_ascii_whitespace
1129 ///
1130 /// # Examples
1131 ///
1132 /// Basic usage:
1133 ///
1134 /// ```
1135 /// let mut iter = "A few words".split_whitespace();
1136 ///
1137 /// assert_eq!(Some("A"), iter.next());
1138 /// assert_eq!(Some("few"), iter.next());
1139 /// assert_eq!(Some("words"), iter.next());
1140 ///
1141 /// assert_eq!(None, iter.next());
1142 /// ```
1143 ///
1144 /// All kinds of whitespace are considered:
1145 ///
1146 /// ```
1147 /// let mut iter = " Mary had\ta\u{2009}little \n\t lamb".split_whitespace();
1148 /// assert_eq!(Some("Mary"), iter.next());
1149 /// assert_eq!(Some("had"), iter.next());
1150 /// assert_eq!(Some("a"), iter.next());
1151 /// assert_eq!(Some("little"), iter.next());
1152 /// assert_eq!(Some("lamb"), iter.next());
1153 ///
1154 /// assert_eq!(None, iter.next());
1155 /// ```
1156 ///
1157 /// If the string is empty or all whitespace, the iterator yields no string slices:
1158 /// ```
1159 /// assert_eq!("".split_whitespace().next(), None);
1160 /// assert_eq!(" ".split_whitespace().next(), None);
1161 /// ```
1162 #[must_use = "this returns the split string as an iterator, \
1163 without modifying the original"]
1164 #[stable(feature = "split_whitespace", since = "1.1.0")]
1165 #[rustc_diagnostic_item = "str_split_whitespace"]
1166 #[inline]
1167 pub fn split_whitespace(&self) -> SplitWhitespace<'_> {
1168 SplitWhitespace { inner: self.split(IsWhitespace).filter(IsNotEmpty) }
1169 }
1170
1171 /// Splits a string slice by ASCII whitespace.
1172 ///
1173 /// The iterator returned will return string slices that are sub-slices of
1174 /// the original string slice, separated by any amount of ASCII whitespace.
1175 ///
1176 /// This uses the same definition as [`char::is_ascii_whitespace`].
1177 /// To split by Unicode `Whitespace` instead, use [`split_whitespace`].
1178 ///
1179 /// [`split_whitespace`]: str::split_whitespace
1180 ///
1181 /// # Examples
1182 ///
1183 /// Basic usage:
1184 ///
1185 /// ```
1186 /// let mut iter = "A few words".split_ascii_whitespace();
1187 ///
1188 /// assert_eq!(Some("A"), iter.next());
1189 /// assert_eq!(Some("few"), iter.next());
1190 /// assert_eq!(Some("words"), iter.next());
1191 ///
1192 /// assert_eq!(None, iter.next());
1193 /// ```
1194 ///
1195 /// Various kinds of ASCII whitespace are considered
1196 /// (see [`char::is_ascii_whitespace`]):
1197 ///
1198 /// ```
1199 /// let mut iter = " Mary had\ta little \n\t lamb".split_ascii_whitespace();
1200 /// assert_eq!(Some("Mary"), iter.next());
1201 /// assert_eq!(Some("had"), iter.next());
1202 /// assert_eq!(Some("a"), iter.next());
1203 /// assert_eq!(Some("little"), iter.next());
1204 /// assert_eq!(Some("lamb"), iter.next());
1205 ///
1206 /// assert_eq!(None, iter.next());
1207 /// ```
1208 ///
1209 /// If the string is empty or all ASCII whitespace, the iterator yields no string slices:
1210 /// ```
1211 /// assert_eq!("".split_ascii_whitespace().next(), None);
1212 /// assert_eq!(" ".split_ascii_whitespace().next(), None);
1213 /// ```
1214 #[must_use = "this returns the split string as an iterator, \
1215 without modifying the original"]
1216 #[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
1217 #[inline]
1218 pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace<'_> {
1219 let inner =
1220 self.as_bytes().split(IsAsciiWhitespace).filter(BytesIsNotEmpty).map(UnsafeBytesToStr);
1221 SplitAsciiWhitespace { inner }
1222 }
1223
1224 /// Returns an iterator over the lines of a string, as string slices.
1225 ///
1226 /// Lines are split at line endings that are either newlines (`\n`) or
1227 /// sequences of a carriage return followed by a line feed (`\r\n`).
1228 ///
1229 /// Line terminators are not included in the lines returned by the iterator.
1230 ///
1231 /// Note that any carriage return (`\r`) not immediately followed by a
1232 /// line feed (`\n`) does not split a line. These carriage returns are
1233 /// thereby included in the produced lines.
1234 ///
1235 /// The final line ending is optional. A string that ends with a final line
1236 /// ending will return the same lines as an otherwise identical string
1237 /// without a final line ending.
1238 ///
1239 /// # Examples
1240 ///
1241 /// Basic usage:
1242 ///
1243 /// ```
1244 /// let text = "foo\r\nbar\n\nbaz\r";
1245 /// let mut lines = text.lines();
1246 ///
1247 /// assert_eq!(Some("foo"), lines.next());
1248 /// assert_eq!(Some("bar"), lines.next());
1249 /// assert_eq!(Some(""), lines.next());
1250 /// // Trailing carriage return is included in the last line
1251 /// assert_eq!(Some("baz\r"), lines.next());
1252 ///
1253 /// assert_eq!(None, lines.next());
1254 /// ```
1255 ///
1256 /// The final line does not require any ending:
1257 ///
1258 /// ```
1259 /// let text = "foo\nbar\n\r\nbaz";
1260 /// let mut lines = text.lines();
1261 ///
1262 /// assert_eq!(Some("foo"), lines.next());
1263 /// assert_eq!(Some("bar"), lines.next());
1264 /// assert_eq!(Some(""), lines.next());
1265 /// assert_eq!(Some("baz"), lines.next());
1266 ///
1267 /// assert_eq!(None, lines.next());
1268 /// ```
1269 #[stable(feature = "rust1", since = "1.0.0")]
1270 #[inline]
1271 pub fn lines(&self) -> Lines<'_> {
1272 Lines(self.split_inclusive('\n').map(LinesMap))
1273 }
1274
1275 /// Returns an iterator over the lines of a string.
1276 #[stable(feature = "rust1", since = "1.0.0")]
1277 #[deprecated(since = "1.4.0", note = "use lines() instead now", suggestion = "lines")]
1278 #[inline]
1279 #[allow(deprecated)]
1280 pub fn lines_any(&self) -> LinesAny<'_> {
1281 LinesAny(self.lines())
1282 }
1283
1284 /// Returns an iterator of `u16` over the string encoded
1285 /// as native endian UTF-16 (without byte-order mark).
1286 ///
1287 /// # Examples
1288 ///
1289 /// ```
1290 /// let text = "Zażółć gęślą jaźń";
1291 ///
1292 /// let utf8_len = text.len();
1293 /// let utf16_len = text.encode_utf16().count();
1294 ///
1295 /// assert!(utf16_len <= utf8_len);
1296 /// ```
1297 #[must_use = "this returns the encoded string as an iterator, \
1298 without modifying the original"]
1299 #[stable(feature = "encode_utf16", since = "1.8.0")]
1300 pub fn encode_utf16(&self) -> EncodeUtf16<'_> {
1301 EncodeUtf16 { chars: self.chars(), extra: 0 }
1302 }
1303
1304 /// Returns `true` if the given pattern matches a sub-slice of
1305 /// this string slice.
1306 ///
1307 /// Returns `false` if it does not.
1308 ///
1309 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1310 /// function or closure that determines if a character matches.
1311 ///
1312 /// [`char`]: prim@char
1313 /// [pattern]: self::pattern
1314 ///
1315 /// # Examples
1316 ///
1317 /// ```
1318 /// let bananas = "bananas";
1319 ///
1320 /// assert!(bananas.contains("nana"));
1321 /// assert!(!bananas.contains("apples"));
1322 /// ```
1323 #[stable(feature = "rust1", since = "1.0.0")]
1324 #[inline]
1325 pub fn contains<P: Pattern>(&self, pat: P) -> bool {
1326 pat.is_contained_in(self)
1327 }
1328
1329 /// Returns `true` if the given pattern matches a prefix of this
1330 /// string slice.
1331 ///
1332 /// Returns `false` if it does not.
1333 ///
1334 /// The [pattern] can be a `&str`, in which case this function will return true if
1335 /// the `&str` is a prefix of this string slice.
1336 ///
1337 /// The [pattern] can also be a [`char`], a slice of [`char`]s, or a
1338 /// function or closure that determines if a character matches.
1339 /// These will only be checked against the first character of this string slice.
1340 /// Look at the second example below regarding behavior for slices of [`char`]s.
1341 ///
1342 /// [`char`]: prim@char
1343 /// [pattern]: self::pattern
1344 ///
1345 /// # Examples
1346 ///
1347 /// ```
1348 /// let bananas = "bananas";
1349 ///
1350 /// assert!(bananas.starts_with("bana"));
1351 /// assert!(!bananas.starts_with("nana"));
1352 /// ```
1353 ///
1354 /// ```
1355 /// let bananas = "bananas";
1356 ///
1357 /// // Note that both of these assert successfully.
1358 /// assert!(bananas.starts_with(&['b', 'a', 'n', 'a']));
1359 /// assert!(bananas.starts_with(&['a', 'b', 'c', 'd']));
1360 /// ```
1361 #[stable(feature = "rust1", since = "1.0.0")]
1362 #[rustc_diagnostic_item = "str_starts_with"]
1363 pub fn starts_with<P: Pattern>(&self, pat: P) -> bool {
1364 pat.is_prefix_of(self)
1365 }
1366
1367 /// Returns `true` if the given pattern matches a suffix of this
1368 /// string slice.
1369 ///
1370 /// Returns `false` if it does not.
1371 ///
1372 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1373 /// function or closure that determines if a character matches.
1374 ///
1375 /// [`char`]: prim@char
1376 /// [pattern]: self::pattern
1377 ///
1378 /// # Examples
1379 ///
1380 /// ```
1381 /// let bananas = "bananas";
1382 ///
1383 /// assert!(bananas.ends_with("anas"));
1384 /// assert!(!bananas.ends_with("nana"));
1385 /// ```
1386 #[stable(feature = "rust1", since = "1.0.0")]
1387 #[rustc_diagnostic_item = "str_ends_with"]
1388 pub fn ends_with<P: Pattern>(&self, pat: P) -> bool
1389 where
1390 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
1391 {
1392 pat.is_suffix_of(self)
1393 }
1394
1395 /// Returns the byte index of the first character of this string slice that
1396 /// matches the pattern.
1397 ///
1398 /// Returns [`None`] if the pattern doesn't match.
1399 ///
1400 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1401 /// function or closure that determines if a character matches.
1402 ///
1403 /// [`char`]: prim@char
1404 /// [pattern]: self::pattern
1405 ///
1406 /// # Examples
1407 ///
1408 /// Simple patterns:
1409 ///
1410 /// ```
1411 /// let s = "Löwe 老虎 Léopard Gepardi";
1412 ///
1413 /// assert_eq!(s.find('L'), Some(0));
1414 /// assert_eq!(s.find('é'), Some(14));
1415 /// assert_eq!(s.find("pard"), Some(17));
1416 /// ```
1417 ///
1418 /// More complex patterns using point-free style and closures:
1419 ///
1420 /// ```
1421 /// let s = "Löwe 老虎 Léopard";
1422 ///
1423 /// assert_eq!(s.find(char::is_whitespace), Some(5));
1424 /// assert_eq!(s.find(char::is_lowercase), Some(1));
1425 /// assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
1426 /// assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));
1427 /// ```
1428 ///
1429 /// Not finding the pattern:
1430 ///
1431 /// ```
1432 /// let s = "Löwe 老虎 Léopard";
1433 /// let x: &[_] = &['1', '2'];
1434 ///
1435 /// assert_eq!(s.find(x), None);
1436 /// ```
1437 #[stable(feature = "rust1", since = "1.0.0")]
1438 #[inline]
1439 pub fn find<P: Pattern>(&self, pat: P) -> Option<usize> {
1440 pat.into_searcher(self).next_match().map(|(i, _)| i)
1441 }
1442
1443 /// Returns the byte index for the first character of the last match of the pattern in
1444 /// this string slice.
1445 ///
1446 /// Returns [`None`] if the pattern doesn't match.
1447 ///
1448 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1449 /// function or closure that determines if a character matches.
1450 ///
1451 /// [`char`]: prim@char
1452 /// [pattern]: self::pattern
1453 ///
1454 /// # Examples
1455 ///
1456 /// Simple patterns:
1457 ///
1458 /// ```
1459 /// let s = "Löwe 老虎 Léopard Gepardi";
1460 ///
1461 /// assert_eq!(s.rfind('L'), Some(13));
1462 /// assert_eq!(s.rfind('é'), Some(14));
1463 /// assert_eq!(s.rfind("pard"), Some(24));
1464 /// ```
1465 ///
1466 /// More complex patterns with closures:
1467 ///
1468 /// ```
1469 /// let s = "Löwe 老虎 Léopard";
1470 ///
1471 /// assert_eq!(s.rfind(char::is_whitespace), Some(12));
1472 /// assert_eq!(s.rfind(char::is_lowercase), Some(20));
1473 /// ```
1474 ///
1475 /// Not finding the pattern:
1476 ///
1477 /// ```
1478 /// let s = "Löwe 老虎 Léopard";
1479 /// let x: &[_] = &['1', '2'];
1480 ///
1481 /// assert_eq!(s.rfind(x), None);
1482 /// ```
1483 #[stable(feature = "rust1", since = "1.0.0")]
1484 #[inline]
1485 pub fn rfind<P: Pattern>(&self, pat: P) -> Option<usize>
1486 where
1487 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
1488 {
1489 pat.into_searcher(self).next_match_back().map(|(i, _)| i)
1490 }
1491
1492 /// Returns an iterator over substrings of this string slice, separated by
1493 /// characters matched by a pattern.
1494 ///
1495 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1496 /// function or closure that determines if a character matches.
1497 ///
1498 /// [`char`]: prim@char
1499 /// [pattern]: self::pattern
1500 ///
1501 /// # Iterator behavior
1502 ///
1503 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1504 /// allows a reverse search and forward/reverse search yields the same
1505 /// elements. This is true for, e.g., [`char`], but not for `&str`.
1506 ///
1507 /// If the pattern allows a reverse search but its results might differ
1508 /// from a forward search, the [`rsplit`] method can be used.
1509 ///
1510 /// [`rsplit`]: str::rsplit
1511 ///
1512 /// # Examples
1513 ///
1514 /// Simple patterns:
1515 ///
1516 /// ```
1517 /// let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
1518 /// assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);
1519 ///
1520 /// let v: Vec<&str> = "".split('X').collect();
1521 /// assert_eq!(v, [""]);
1522 ///
1523 /// let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
1524 /// assert_eq!(v, ["lion", "", "tiger", "leopard"]);
1525 ///
1526 /// let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
1527 /// assert_eq!(v, ["lion", "tiger", "leopard"]);
1528 ///
1529 /// let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
1530 /// assert_eq!(v, ["abc", "def", "ghi"]);
1531 ///
1532 /// let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
1533 /// assert_eq!(v, ["lion", "tiger", "leopard"]);
1534 /// ```
1535 ///
1536 /// If the pattern is a slice of chars, split on each occurrence of any of the characters:
1537 ///
1538 /// ```
1539 /// let v: Vec<&str> = "2020-11-03 23:59".split(&['-', ' ', ':', '@'][..]).collect();
1540 /// assert_eq!(v, ["2020", "11", "03", "23", "59"]);
1541 /// ```
1542 ///
1543 /// A more complex pattern, using a closure:
1544 ///
1545 /// ```
1546 /// let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
1547 /// assert_eq!(v, ["abc", "def", "ghi"]);
1548 /// ```
1549 ///
1550 /// If a string contains multiple contiguous separators, you will end up
1551 /// with empty strings in the output:
1552 ///
1553 /// ```
1554 /// let x = "||||a||b|c".to_string();
1555 /// let d: Vec<_> = x.split('|').collect();
1556 ///
1557 /// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
1558 /// ```
1559 ///
1560 /// Contiguous separators are separated by the empty string.
1561 ///
1562 /// ```
1563 /// let x = "(///)".to_string();
1564 /// let d: Vec<_> = x.split('/').collect();
1565 ///
1566 /// assert_eq!(d, &["(", "", "", ")"]);
1567 /// ```
1568 ///
1569 /// Separators at the start or end of a string are neighbored
1570 /// by empty strings.
1571 ///
1572 /// ```
1573 /// let d: Vec<_> = "010".split("0").collect();
1574 /// assert_eq!(d, &["", "1", ""]);
1575 /// ```
1576 ///
1577 /// When the empty string is used as a separator, it separates
1578 /// every character in the string, along with the beginning
1579 /// and end of the string.
1580 ///
1581 /// ```
1582 /// let f: Vec<_> = "rust".split("").collect();
1583 /// assert_eq!(f, &["", "r", "u", "s", "t", ""]);
1584 /// ```
1585 ///
1586 /// Contiguous separators can lead to possibly surprising behavior
1587 /// when whitespace is used as the separator. This code is correct:
1588 ///
1589 /// ```
1590 /// let x = " a b c".to_string();
1591 /// let d: Vec<_> = x.split(' ').collect();
1592 ///
1593 /// assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
1594 /// ```
1595 ///
1596 /// It does _not_ give you:
1597 ///
1598 /// ```,ignore
1599 /// assert_eq!(d, &["a", "b", "c"]);
1600 /// ```
1601 ///
1602 /// Use [`split_whitespace`] for this behavior.
1603 ///
1604 /// [`split_whitespace`]: str::split_whitespace
1605 #[stable(feature = "rust1", since = "1.0.0")]
1606 #[inline]
1607 pub fn split<P: Pattern>(&self, pat: P) -> Split<'_, P> {
1608 Split(SplitInternal {
1609 start: 0,
1610 end: self.len(),
1611 matcher: pat.into_searcher(self),
1612 allow_trailing_empty: true,
1613 finished: false,
1614 })
1615 }
1616
1617 /// Returns an iterator over substrings of this string slice, separated by
1618 /// characters matched by a pattern.
1619 ///
1620 /// Differs from the iterator produced by `split` in that `split_inclusive`
1621 /// leaves the matched part as the terminator of the substring.
1622 ///
1623 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1624 /// function or closure that determines if a character matches.
1625 ///
1626 /// [`char`]: prim@char
1627 /// [pattern]: self::pattern
1628 ///
1629 /// # Examples
1630 ///
1631 /// ```
1632 /// let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb."
1633 /// .split_inclusive('\n').collect();
1634 /// assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb."]);
1635 /// ```
1636 ///
1637 /// If the last element of the string is matched,
1638 /// that element will be considered the terminator of the preceding substring.
1639 /// That substring will be the last item returned by the iterator.
1640 ///
1641 /// ```
1642 /// let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb.\n"
1643 /// .split_inclusive('\n').collect();
1644 /// assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb.\n"]);
1645 /// ```
1646 #[stable(feature = "split_inclusive", since = "1.51.0")]
1647 #[inline]
1648 pub fn split_inclusive<P: Pattern>(&self, pat: P) -> SplitInclusive<'_, P> {
1649 SplitInclusive(SplitInternal {
1650 start: 0,
1651 end: self.len(),
1652 matcher: pat.into_searcher(self),
1653 allow_trailing_empty: false,
1654 finished: false,
1655 })
1656 }
1657
1658 /// Returns an iterator over substrings of the given string slice, separated
1659 /// by characters matched by a pattern and yielded in reverse order.
1660 ///
1661 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1662 /// function or closure that determines if a character matches.
1663 ///
1664 /// [`char`]: prim@char
1665 /// [pattern]: self::pattern
1666 ///
1667 /// # Iterator behavior
1668 ///
1669 /// The returned iterator requires that the pattern supports a reverse
1670 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1671 /// search yields the same elements.
1672 ///
1673 /// For iterating from the front, the [`split`] method can be used.
1674 ///
1675 /// [`split`]: str::split
1676 ///
1677 /// # Examples
1678 ///
1679 /// Simple patterns:
1680 ///
1681 /// ```
1682 /// let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
1683 /// assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);
1684 ///
1685 /// let v: Vec<&str> = "".rsplit('X').collect();
1686 /// assert_eq!(v, [""]);
1687 ///
1688 /// let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
1689 /// assert_eq!(v, ["leopard", "tiger", "", "lion"]);
1690 ///
1691 /// let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
1692 /// assert_eq!(v, ["leopard", "tiger", "lion"]);
1693 /// ```
1694 ///
1695 /// A more complex pattern, using a closure:
1696 ///
1697 /// ```
1698 /// let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
1699 /// assert_eq!(v, ["ghi", "def", "abc"]);
1700 /// ```
1701 #[stable(feature = "rust1", since = "1.0.0")]
1702 #[inline]
1703 pub fn rsplit<P: Pattern>(&self, pat: P) -> RSplit<'_, P>
1704 where
1705 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
1706 {
1707 RSplit(self.split(pat).0)
1708 }
1709
1710 /// Returns an iterator over substrings of the given string slice, separated
1711 /// by characters matched by a pattern.
1712 ///
1713 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1714 /// function or closure that determines if a character matches.
1715 ///
1716 /// [`char`]: prim@char
1717 /// [pattern]: self::pattern
1718 ///
1719 /// Equivalent to [`split`], except that the trailing substring
1720 /// is skipped if empty.
1721 ///
1722 /// [`split`]: str::split
1723 ///
1724 /// This method can be used for string data that is _terminated_,
1725 /// rather than _separated_ by a pattern.
1726 ///
1727 /// # Iterator behavior
1728 ///
1729 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1730 /// allows a reverse search and forward/reverse search yields the same
1731 /// elements. This is true for, e.g., [`char`], but not for `&str`.
1732 ///
1733 /// If the pattern allows a reverse search but its results might differ
1734 /// from a forward search, the [`rsplit_terminator`] method can be used.
1735 ///
1736 /// [`rsplit_terminator`]: str::rsplit_terminator
1737 ///
1738 /// # Examples
1739 ///
1740 /// ```
1741 /// let v: Vec<&str> = "A.B.".split_terminator('.').collect();
1742 /// assert_eq!(v, ["A", "B"]);
1743 ///
1744 /// let v: Vec<&str> = "A..B..".split_terminator(".").collect();
1745 /// assert_eq!(v, ["A", "", "B", ""]);
1746 ///
1747 /// let v: Vec<&str> = "A.B:C.D".split_terminator(&['.', ':'][..]).collect();
1748 /// assert_eq!(v, ["A", "B", "C", "D"]);
1749 /// ```
1750 #[stable(feature = "rust1", since = "1.0.0")]
1751 #[inline]
1752 pub fn split_terminator<P: Pattern>(&self, pat: P) -> SplitTerminator<'_, P> {
1753 SplitTerminator(SplitInternal { allow_trailing_empty: false, ..self.split(pat).0 })
1754 }
1755
1756 /// Returns an iterator over substrings of `self`, separated by characters
1757 /// matched by a pattern and yielded in reverse order.
1758 ///
1759 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1760 /// function or closure that determines if a character matches.
1761 ///
1762 /// [`char`]: prim@char
1763 /// [pattern]: self::pattern
1764 ///
1765 /// Equivalent to [`split`], except that the trailing substring is
1766 /// skipped if empty.
1767 ///
1768 /// [`split`]: str::split
1769 ///
1770 /// This method can be used for string data that is _terminated_,
1771 /// rather than _separated_ by a pattern.
1772 ///
1773 /// # Iterator behavior
1774 ///
1775 /// The returned iterator requires that the pattern supports a
1776 /// reverse search, and it will be double ended if a forward/reverse
1777 /// search yields the same elements.
1778 ///
1779 /// For iterating from the front, the [`split_terminator`] method can be
1780 /// used.
1781 ///
1782 /// [`split_terminator`]: str::split_terminator
1783 ///
1784 /// # Examples
1785 ///
1786 /// ```
1787 /// let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
1788 /// assert_eq!(v, ["B", "A"]);
1789 ///
1790 /// let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
1791 /// assert_eq!(v, ["", "B", "", "A"]);
1792 ///
1793 /// let v: Vec<&str> = "A.B:C.D".rsplit_terminator(&['.', ':'][..]).collect();
1794 /// assert_eq!(v, ["D", "C", "B", "A"]);
1795 /// ```
1796 #[stable(feature = "rust1", since = "1.0.0")]
1797 #[inline]
1798 pub fn rsplit_terminator<P: Pattern>(&self, pat: P) -> RSplitTerminator<'_, P>
1799 where
1800 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
1801 {
1802 RSplitTerminator(self.split_terminator(pat).0)
1803 }
1804
1805 /// Returns an iterator over substrings of the given string slice, separated
1806 /// by a pattern, restricted to returning at most `n` items.
1807 ///
1808 /// If `n` substrings are returned, the last substring (the `n`th substring)
1809 /// will contain the remainder of the string.
1810 ///
1811 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1812 /// function or closure that determines if a character matches.
1813 ///
1814 /// [`char`]: prim@char
1815 /// [pattern]: self::pattern
1816 ///
1817 /// # Iterator behavior
1818 ///
1819 /// The returned iterator will not be double ended, because it is
1820 /// not efficient to support.
1821 ///
1822 /// If the pattern allows a reverse search, the [`rsplitn`] method can be
1823 /// used.
1824 ///
1825 /// [`rsplitn`]: str::rsplitn
1826 ///
1827 /// # Examples
1828 ///
1829 /// Simple patterns:
1830 ///
1831 /// ```
1832 /// let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
1833 /// assert_eq!(v, ["Mary", "had", "a little lambda"]);
1834 ///
1835 /// let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
1836 /// assert_eq!(v, ["lion", "", "tigerXleopard"]);
1837 ///
1838 /// let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
1839 /// assert_eq!(v, ["abcXdef"]);
1840 ///
1841 /// let v: Vec<&str> = "".splitn(1, 'X').collect();
1842 /// assert_eq!(v, [""]);
1843 /// ```
1844 ///
1845 /// A more complex pattern, using a closure:
1846 ///
1847 /// ```
1848 /// let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
1849 /// assert_eq!(v, ["abc", "defXghi"]);
1850 /// ```
1851 #[stable(feature = "rust1", since = "1.0.0")]
1852 #[inline]
1853 pub fn splitn<P: Pattern>(&self, n: usize, pat: P) -> SplitN<'_, P> {
1854 SplitN(SplitNInternal { iter: self.split(pat).0, count: n })
1855 }
1856
1857 /// Returns an iterator over substrings of this string slice, separated by a
1858 /// pattern, starting from the end of the string, restricted to returning at
1859 /// most `n` items.
1860 ///
1861 /// If `n` substrings are returned, the last substring (the `n`th substring)
1862 /// will contain the remainder of the string.
1863 ///
1864 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1865 /// function or closure that determines if a character matches.
1866 ///
1867 /// [`char`]: prim@char
1868 /// [pattern]: self::pattern
1869 ///
1870 /// # Iterator behavior
1871 ///
1872 /// The returned iterator will not be double ended, because it is not
1873 /// efficient to support.
1874 ///
1875 /// For splitting from the front, the [`splitn`] method can be used.
1876 ///
1877 /// [`splitn`]: str::splitn
1878 ///
1879 /// # Examples
1880 ///
1881 /// Simple patterns:
1882 ///
1883 /// ```
1884 /// let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
1885 /// assert_eq!(v, ["lamb", "little", "Mary had a"]);
1886 ///
1887 /// let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
1888 /// assert_eq!(v, ["leopard", "tiger", "lionX"]);
1889 ///
1890 /// let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
1891 /// assert_eq!(v, ["leopard", "lion::tiger"]);
1892 /// ```
1893 ///
1894 /// A more complex pattern, using a closure:
1895 ///
1896 /// ```
1897 /// let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
1898 /// assert_eq!(v, ["ghi", "abc1def"]);
1899 /// ```
1900 #[stable(feature = "rust1", since = "1.0.0")]
1901 #[inline]
1902 pub fn rsplitn<P: Pattern>(&self, n: usize, pat: P) -> RSplitN<'_, P>
1903 where
1904 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
1905 {
1906 RSplitN(self.splitn(n, pat).0)
1907 }
1908
1909 /// Splits the string on the first occurrence of the specified delimiter and
1910 /// returns prefix before delimiter and suffix after delimiter.
1911 ///
1912 /// # Examples
1913 ///
1914 /// ```
1915 /// assert_eq!("cfg".split_once('='), None);
1916 /// assert_eq!("cfg=".split_once('='), Some(("cfg", "")));
1917 /// assert_eq!("cfg=foo".split_once('='), Some(("cfg", "foo")));
1918 /// assert_eq!("cfg=foo=bar".split_once('='), Some(("cfg", "foo=bar")));
1919 /// ```
1920 #[stable(feature = "str_split_once", since = "1.52.0")]
1921 #[inline]
1922 pub fn split_once<P: Pattern>(&self, delimiter: P) -> Option<(&'_ str, &'_ str)> {
1923 let (start, end) = delimiter.into_searcher(self).next_match()?;
1924 // SAFETY: `Searcher` is known to return valid indices.
1925 unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
1926 }
1927
1928 /// Splits the string on the last occurrence of the specified delimiter and
1929 /// returns prefix before delimiter and suffix after delimiter.
1930 ///
1931 /// # Examples
1932 ///
1933 /// ```
1934 /// assert_eq!("cfg".rsplit_once('='), None);
1935 /// assert_eq!("cfg=foo".rsplit_once('='), Some(("cfg", "foo")));
1936 /// assert_eq!("cfg=foo=bar".rsplit_once('='), Some(("cfg=foo", "bar")));
1937 /// ```
1938 #[stable(feature = "str_split_once", since = "1.52.0")]
1939 #[inline]
1940 pub fn rsplit_once<P: Pattern>(&self, delimiter: P) -> Option<(&'_ str, &'_ str)>
1941 where
1942 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
1943 {
1944 let (start, end) = delimiter.into_searcher(self).next_match_back()?;
1945 // SAFETY: `Searcher` is known to return valid indices.
1946 unsafe { Some((self.get_unchecked(..start), self.get_unchecked(end..))) }
1947 }
1948
1949 /// Returns an iterator over the disjoint matches of a pattern within the
1950 /// given string slice.
1951 ///
1952 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1953 /// function or closure that determines if a character matches.
1954 ///
1955 /// [`char`]: prim@char
1956 /// [pattern]: self::pattern
1957 ///
1958 /// # Iterator behavior
1959 ///
1960 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
1961 /// allows a reverse search and forward/reverse search yields the same
1962 /// elements. This is true for, e.g., [`char`], but not for `&str`.
1963 ///
1964 /// If the pattern allows a reverse search but its results might differ
1965 /// from a forward search, the [`rmatches`] method can be used.
1966 ///
1967 /// [`rmatches`]: str::rmatches
1968 ///
1969 /// # Examples
1970 ///
1971 /// ```
1972 /// let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
1973 /// assert_eq!(v, ["abc", "abc", "abc"]);
1974 ///
1975 /// let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
1976 /// assert_eq!(v, ["1", "2", "3"]);
1977 /// ```
1978 #[stable(feature = "str_matches", since = "1.2.0")]
1979 #[inline]
1980 pub fn matches<P: Pattern>(&self, pat: P) -> Matches<'_, P> {
1981 Matches(MatchesInternal(pat.into_searcher(self)))
1982 }
1983
1984 /// Returns an iterator over the disjoint matches of a pattern within this
1985 /// string slice, yielded in reverse order.
1986 ///
1987 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
1988 /// function or closure that determines if a character matches.
1989 ///
1990 /// [`char`]: prim@char
1991 /// [pattern]: self::pattern
1992 ///
1993 /// # Iterator behavior
1994 ///
1995 /// The returned iterator requires that the pattern supports a reverse
1996 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
1997 /// search yields the same elements.
1998 ///
1999 /// For iterating from the front, the [`matches`] method can be used.
2000 ///
2001 /// [`matches`]: str::matches
2002 ///
2003 /// # Examples
2004 ///
2005 /// ```
2006 /// let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
2007 /// assert_eq!(v, ["abc", "abc", "abc"]);
2008 ///
2009 /// let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
2010 /// assert_eq!(v, ["3", "2", "1"]);
2011 /// ```
2012 #[stable(feature = "str_matches", since = "1.2.0")]
2013 #[inline]
2014 pub fn rmatches<P: Pattern>(&self, pat: P) -> RMatches<'_, P>
2015 where
2016 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
2017 {
2018 RMatches(self.matches(pat).0)
2019 }
2020
2021 /// Returns an iterator over the disjoint matches of a pattern within this string
2022 /// slice as well as the index that the match starts at.
2023 ///
2024 /// For matches of `pat` within `self` that overlap, only the indices
2025 /// corresponding to the first match are returned.
2026 ///
2027 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2028 /// function or closure that determines if a character matches.
2029 ///
2030 /// [`char`]: prim@char
2031 /// [pattern]: self::pattern
2032 ///
2033 /// # Iterator behavior
2034 ///
2035 /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
2036 /// allows a reverse search and forward/reverse search yields the same
2037 /// elements. This is true for, e.g., [`char`], but not for `&str`.
2038 ///
2039 /// If the pattern allows a reverse search but its results might differ
2040 /// from a forward search, the [`rmatch_indices`] method can be used.
2041 ///
2042 /// [`rmatch_indices`]: str::rmatch_indices
2043 ///
2044 /// # Examples
2045 ///
2046 /// ```
2047 /// let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
2048 /// assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);
2049 ///
2050 /// let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
2051 /// assert_eq!(v, [(1, "abc"), (4, "abc")]);
2052 ///
2053 /// let v: Vec<_> = "ababa".match_indices("aba").collect();
2054 /// assert_eq!(v, [(0, "aba")]); // only the first `aba`
2055 /// ```
2056 #[stable(feature = "str_match_indices", since = "1.5.0")]
2057 #[inline]
2058 pub fn match_indices<P: Pattern>(&self, pat: P) -> MatchIndices<'_, P> {
2059 MatchIndices(MatchIndicesInternal(pat.into_searcher(self)))
2060 }
2061
2062 /// Returns an iterator over the disjoint matches of a pattern within `self`,
2063 /// yielded in reverse order along with the index of the match.
2064 ///
2065 /// For matches of `pat` within `self` that overlap, only the indices
2066 /// corresponding to the last match are returned.
2067 ///
2068 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2069 /// function or closure that determines if a character matches.
2070 ///
2071 /// [`char`]: prim@char
2072 /// [pattern]: self::pattern
2073 ///
2074 /// # Iterator behavior
2075 ///
2076 /// The returned iterator requires that the pattern supports a reverse
2077 /// search, and it will be a [`DoubleEndedIterator`] if a forward/reverse
2078 /// search yields the same elements.
2079 ///
2080 /// For iterating from the front, the [`match_indices`] method can be used.
2081 ///
2082 /// [`match_indices`]: str::match_indices
2083 ///
2084 /// # Examples
2085 ///
2086 /// ```
2087 /// let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
2088 /// assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);
2089 ///
2090 /// let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
2091 /// assert_eq!(v, [(4, "abc"), (1, "abc")]);
2092 ///
2093 /// let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
2094 /// assert_eq!(v, [(2, "aba")]); // only the last `aba`
2095 /// ```
2096 #[stable(feature = "str_match_indices", since = "1.5.0")]
2097 #[inline]
2098 pub fn rmatch_indices<P: Pattern>(&self, pat: P) -> RMatchIndices<'_, P>
2099 where
2100 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
2101 {
2102 RMatchIndices(self.match_indices(pat).0)
2103 }
2104
2105 /// Returns a string slice with leading and trailing whitespace removed.
2106 ///
2107 /// 'Whitespace' is defined according to the terms of the Unicode Derived
2108 /// Core Property `White_Space`, which includes newlines.
2109 ///
2110 /// # Examples
2111 ///
2112 /// ```
2113 /// let s = "\n Hello\tworld\t\n";
2114 ///
2115 /// assert_eq!("Hello\tworld", s.trim());
2116 /// ```
2117 #[inline]
2118 #[must_use = "this returns the trimmed string as a slice, \
2119 without modifying the original"]
2120 #[stable(feature = "rust1", since = "1.0.0")]
2121 #[rustc_diagnostic_item = "str_trim"]
2122 pub fn trim(&self) -> &str {
2123 self.trim_matches(char::is_whitespace)
2124 }
2125
2126 /// Returns a string slice with leading whitespace removed.
2127 ///
2128 /// 'Whitespace' is defined according to the terms of the Unicode Derived
2129 /// Core Property `White_Space`, which includes newlines.
2130 ///
2131 /// # Text directionality
2132 ///
2133 /// A string is a sequence of bytes. `start` in this context means the first
2134 /// position of that byte string; for a left-to-right language like English or
2135 /// Russian, this will be left side, and for right-to-left languages like
2136 /// Arabic or Hebrew, this will be the right side.
2137 ///
2138 /// # Examples
2139 ///
2140 /// Basic usage:
2141 ///
2142 /// ```
2143 /// let s = "\n Hello\tworld\t\n";
2144 /// assert_eq!("Hello\tworld\t\n", s.trim_start());
2145 /// ```
2146 ///
2147 /// Directionality:
2148 ///
2149 /// ```
2150 /// let s = " English ";
2151 /// assert!(Some('E') == s.trim_start().chars().next());
2152 ///
2153 /// let s = " עברית ";
2154 /// assert!(Some('ע') == s.trim_start().chars().next());
2155 /// ```
2156 #[inline]
2157 #[must_use = "this returns the trimmed string as a new slice, \
2158 without modifying the original"]
2159 #[stable(feature = "trim_direction", since = "1.30.0")]
2160 #[rustc_diagnostic_item = "str_trim_start"]
2161 pub fn trim_start(&self) -> &str {
2162 self.trim_start_matches(char::is_whitespace)
2163 }
2164
2165 /// Returns a string slice with trailing whitespace removed.
2166 ///
2167 /// 'Whitespace' is defined according to the terms of the Unicode Derived
2168 /// Core Property `White_Space`, which includes newlines.
2169 ///
2170 /// # Text directionality
2171 ///
2172 /// A string is a sequence of bytes. `end` in this context means the last
2173 /// position of that byte string; for a left-to-right language like English or
2174 /// Russian, this will be right side, and for right-to-left languages like
2175 /// Arabic or Hebrew, this will be the left side.
2176 ///
2177 /// # Examples
2178 ///
2179 /// Basic usage:
2180 ///
2181 /// ```
2182 /// let s = "\n Hello\tworld\t\n";
2183 /// assert_eq!("\n Hello\tworld", s.trim_end());
2184 /// ```
2185 ///
2186 /// Directionality:
2187 ///
2188 /// ```
2189 /// let s = " English ";
2190 /// assert!(Some('h') == s.trim_end().chars().rev().next());
2191 ///
2192 /// let s = " עברית ";
2193 /// assert!(Some('ת') == s.trim_end().chars().rev().next());
2194 /// ```
2195 #[inline]
2196 #[must_use = "this returns the trimmed string as a new slice, \
2197 without modifying the original"]
2198 #[stable(feature = "trim_direction", since = "1.30.0")]
2199 #[rustc_diagnostic_item = "str_trim_end"]
2200 pub fn trim_end(&self) -> &str {
2201 self.trim_end_matches(char::is_whitespace)
2202 }
2203
2204 /// Returns a string slice with leading whitespace removed.
2205 ///
2206 /// 'Whitespace' is defined according to the terms of the Unicode Derived
2207 /// Core Property `White_Space`.
2208 ///
2209 /// # Text directionality
2210 ///
2211 /// A string is a sequence of bytes. 'Left' in this context means the first
2212 /// position of that byte string; for a language like Arabic or Hebrew
2213 /// which are 'right to left' rather than 'left to right', this will be
2214 /// the _right_ side, not the left.
2215 ///
2216 /// # Examples
2217 ///
2218 /// Basic usage:
2219 ///
2220 /// ```
2221 /// let s = " Hello\tworld\t";
2222 ///
2223 /// assert_eq!("Hello\tworld\t", s.trim_left());
2224 /// ```
2225 ///
2226 /// Directionality:
2227 ///
2228 /// ```
2229 /// let s = " English";
2230 /// assert!(Some('E') == s.trim_left().chars().next());
2231 ///
2232 /// let s = " עברית";
2233 /// assert!(Some('ע') == s.trim_left().chars().next());
2234 /// ```
2235 #[must_use = "this returns the trimmed string as a new slice, \
2236 without modifying the original"]
2237 #[inline]
2238 #[stable(feature = "rust1", since = "1.0.0")]
2239 #[deprecated(since = "1.33.0", note = "superseded by `trim_start`", suggestion = "trim_start")]
2240 pub fn trim_left(&self) -> &str {
2241 self.trim_start()
2242 }
2243
2244 /// Returns a string slice with trailing whitespace removed.
2245 ///
2246 /// 'Whitespace' is defined according to the terms of the Unicode Derived
2247 /// Core Property `White_Space`.
2248 ///
2249 /// # Text directionality
2250 ///
2251 /// A string is a sequence of bytes. 'Right' in this context means the last
2252 /// position of that byte string; for a language like Arabic or Hebrew
2253 /// which are 'right to left' rather than 'left to right', this will be
2254 /// the _left_ side, not the right.
2255 ///
2256 /// # Examples
2257 ///
2258 /// Basic usage:
2259 ///
2260 /// ```
2261 /// let s = " Hello\tworld\t";
2262 ///
2263 /// assert_eq!(" Hello\tworld", s.trim_right());
2264 /// ```
2265 ///
2266 /// Directionality:
2267 ///
2268 /// ```
2269 /// let s = "English ";
2270 /// assert!(Some('h') == s.trim_right().chars().rev().next());
2271 ///
2272 /// let s = "עברית ";
2273 /// assert!(Some('ת') == s.trim_right().chars().rev().next());
2274 /// ```
2275 #[must_use = "this returns the trimmed string as a new slice, \
2276 without modifying the original"]
2277 #[inline]
2278 #[stable(feature = "rust1", since = "1.0.0")]
2279 #[deprecated(since = "1.33.0", note = "superseded by `trim_end`", suggestion = "trim_end")]
2280 pub fn trim_right(&self) -> &str {
2281 self.trim_end()
2282 }
2283
2284 /// Returns a string slice with all prefixes and suffixes that match a
2285 /// pattern repeatedly removed.
2286 ///
2287 /// The [pattern] can be a [`char`], a slice of [`char`]s, or a function
2288 /// or closure that determines if a character matches.
2289 ///
2290 /// [`char`]: prim@char
2291 /// [pattern]: self::pattern
2292 ///
2293 /// # Examples
2294 ///
2295 /// Simple patterns:
2296 ///
2297 /// ```
2298 /// assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
2299 /// assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");
2300 ///
2301 /// let x: &[_] = &['1', '2'];
2302 /// assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");
2303 /// ```
2304 ///
2305 /// A more complex pattern, using a closure:
2306 ///
2307 /// ```
2308 /// assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");
2309 /// ```
2310 #[must_use = "this returns the trimmed string as a new slice, \
2311 without modifying the original"]
2312 #[stable(feature = "rust1", since = "1.0.0")]
2313 pub fn trim_matches<P: Pattern>(&self, pat: P) -> &str
2314 where
2315 for<'a> P::Searcher<'a>: DoubleEndedSearcher<'a>,
2316 {
2317 let mut i = 0;
2318 let mut j = 0;
2319 let mut matcher = pat.into_searcher(self);
2320 if let Some((a, b)) = matcher.next_reject() {
2321 i = a;
2322 j = b; // Remember earliest known match, correct it below if
2323 // last match is different
2324 }
2325 if let Some((_, b)) = matcher.next_reject_back() {
2326 j = b;
2327 }
2328 // SAFETY: `Searcher` is known to return valid indices.
2329 unsafe { self.get_unchecked(i..j) }
2330 }
2331
2332 /// Returns a string slice with all prefixes that match a pattern
2333 /// repeatedly removed.
2334 ///
2335 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2336 /// function or closure that determines if a character matches.
2337 ///
2338 /// [`char`]: prim@char
2339 /// [pattern]: self::pattern
2340 ///
2341 /// # Text directionality
2342 ///
2343 /// A string is a sequence of bytes. `start` in this context means the first
2344 /// position of that byte string; for a left-to-right language like English or
2345 /// Russian, this will be left side, and for right-to-left languages like
2346 /// Arabic or Hebrew, this will be the right side.
2347 ///
2348 /// # Examples
2349 ///
2350 /// ```
2351 /// assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
2352 /// assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");
2353 ///
2354 /// let x: &[_] = &['1', '2'];
2355 /// assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");
2356 /// ```
2357 #[must_use = "this returns the trimmed string as a new slice, \
2358 without modifying the original"]
2359 #[stable(feature = "trim_direction", since = "1.30.0")]
2360 pub fn trim_start_matches<P: Pattern>(&self, pat: P) -> &str {
2361 let mut i = self.len();
2362 let mut matcher = pat.into_searcher(self);
2363 if let Some((a, _)) = matcher.next_reject() {
2364 i = a;
2365 }
2366 // SAFETY: `Searcher` is known to return valid indices.
2367 unsafe { self.get_unchecked(i..self.len()) }
2368 }
2369
2370 /// Returns a string slice with the prefix removed.
2371 ///
2372 /// If the string starts with the pattern `prefix`, returns the substring after the prefix,
2373 /// wrapped in `Some`. Unlike [`trim_start_matches`], this method removes the prefix exactly once.
2374 ///
2375 /// If the string does not start with `prefix`, returns `None`.
2376 ///
2377 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2378 /// function or closure that determines if a character matches.
2379 ///
2380 /// [`char`]: prim@char
2381 /// [pattern]: self::pattern
2382 /// [`trim_start_matches`]: Self::trim_start_matches
2383 ///
2384 /// # Examples
2385 ///
2386 /// ```
2387 /// assert_eq!("foo:bar".strip_prefix("foo:"), Some("bar"));
2388 /// assert_eq!("foo:bar".strip_prefix("bar"), None);
2389 /// assert_eq!("foofoo".strip_prefix("foo"), Some("foo"));
2390 /// ```
2391 #[must_use = "this returns the remaining substring as a new slice, \
2392 without modifying the original"]
2393 #[stable(feature = "str_strip", since = "1.45.0")]
2394 pub fn strip_prefix<P: Pattern>(&self, prefix: P) -> Option<&str> {
2395 prefix.strip_prefix_of(self)
2396 }
2397
2398 /// Returns a string slice with the suffix removed.
2399 ///
2400 /// If the string ends with the pattern `suffix`, returns the substring before the suffix,
2401 /// wrapped in `Some`. Unlike [`trim_end_matches`], this method removes the suffix exactly once.
2402 ///
2403 /// If the string does not end with `suffix`, returns `None`.
2404 ///
2405 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2406 /// function or closure that determines if a character matches.
2407 ///
2408 /// [`char`]: prim@char
2409 /// [pattern]: self::pattern
2410 /// [`trim_end_matches`]: Self::trim_end_matches
2411 ///
2412 /// # Examples
2413 ///
2414 /// ```
2415 /// assert_eq!("bar:foo".strip_suffix(":foo"), Some("bar"));
2416 /// assert_eq!("bar:foo".strip_suffix("bar"), None);
2417 /// assert_eq!("foofoo".strip_suffix("foo"), Some("foo"));
2418 /// ```
2419 #[must_use = "this returns the remaining substring as a new slice, \
2420 without modifying the original"]
2421 #[stable(feature = "str_strip", since = "1.45.0")]
2422 pub fn strip_suffix<P: Pattern>(&self, suffix: P) -> Option<&str>
2423 where
2424 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
2425 {
2426 suffix.strip_suffix_of(self)
2427 }
2428
2429 /// Returns a string slice with all suffixes that match a pattern
2430 /// repeatedly removed.
2431 ///
2432 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2433 /// function or closure that determines if a character matches.
2434 ///
2435 /// [`char`]: prim@char
2436 /// [pattern]: self::pattern
2437 ///
2438 /// # Text directionality
2439 ///
2440 /// A string is a sequence of bytes. `end` in this context means the last
2441 /// position of that byte string; for a left-to-right language like English or
2442 /// Russian, this will be right side, and for right-to-left languages like
2443 /// Arabic or Hebrew, this will be the left side.
2444 ///
2445 /// # Examples
2446 ///
2447 /// Simple patterns:
2448 ///
2449 /// ```
2450 /// assert_eq!("11foo1bar11".trim_end_matches('1'), "11foo1bar");
2451 /// assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");
2452 ///
2453 /// let x: &[_] = &['1', '2'];
2454 /// assert_eq!("12foo1bar12".trim_end_matches(x), "12foo1bar");
2455 /// ```
2456 ///
2457 /// A more complex pattern, using a closure:
2458 ///
2459 /// ```
2460 /// assert_eq!("1fooX".trim_end_matches(|c| c == '1' || c == 'X'), "1foo");
2461 /// ```
2462 #[must_use = "this returns the trimmed string as a new slice, \
2463 without modifying the original"]
2464 #[stable(feature = "trim_direction", since = "1.30.0")]
2465 pub fn trim_end_matches<P: Pattern>(&self, pat: P) -> &str
2466 where
2467 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
2468 {
2469 let mut j = 0;
2470 let mut matcher = pat.into_searcher(self);
2471 if let Some((_, b)) = matcher.next_reject_back() {
2472 j = b;
2473 }
2474 // SAFETY: `Searcher` is known to return valid indices.
2475 unsafe { self.get_unchecked(0..j) }
2476 }
2477
2478 /// Returns a string slice with all prefixes that match a pattern
2479 /// repeatedly removed.
2480 ///
2481 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2482 /// function or closure that determines if a character matches.
2483 ///
2484 /// [`char`]: prim@char
2485 /// [pattern]: self::pattern
2486 ///
2487 /// # Text directionality
2488 ///
2489 /// A string is a sequence of bytes. 'Left' in this context means the first
2490 /// position of that byte string; for a language like Arabic or Hebrew
2491 /// which are 'right to left' rather than 'left to right', this will be
2492 /// the _right_ side, not the left.
2493 ///
2494 /// # Examples
2495 ///
2496 /// ```
2497 /// assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
2498 /// assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");
2499 ///
2500 /// let x: &[_] = &['1', '2'];
2501 /// assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");
2502 /// ```
2503 #[stable(feature = "rust1", since = "1.0.0")]
2504 #[deprecated(
2505 since = "1.33.0",
2506 note = "superseded by `trim_start_matches`",
2507 suggestion = "trim_start_matches"
2508 )]
2509 pub fn trim_left_matches<P: Pattern>(&self, pat: P) -> &str {
2510 self.trim_start_matches(pat)
2511 }
2512
2513 /// Returns a string slice with all suffixes that match a pattern
2514 /// repeatedly removed.
2515 ///
2516 /// The [pattern] can be a `&str`, [`char`], a slice of [`char`]s, or a
2517 /// function or closure that determines if a character matches.
2518 ///
2519 /// [`char`]: prim@char
2520 /// [pattern]: self::pattern
2521 ///
2522 /// # Text directionality
2523 ///
2524 /// A string is a sequence of bytes. 'Right' in this context means the last
2525 /// position of that byte string; for a language like Arabic or Hebrew
2526 /// which are 'right to left' rather than 'left to right', this will be
2527 /// the _left_ side, not the right.
2528 ///
2529 /// # Examples
2530 ///
2531 /// Simple patterns:
2532 ///
2533 /// ```
2534 /// assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
2535 /// assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");
2536 ///
2537 /// let x: &[_] = &['1', '2'];
2538 /// assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");
2539 /// ```
2540 ///
2541 /// A more complex pattern, using a closure:
2542 ///
2543 /// ```
2544 /// assert_eq!("1fooX".trim_right_matches(|c| c == '1' || c == 'X'), "1foo");
2545 /// ```
2546 #[stable(feature = "rust1", since = "1.0.0")]
2547 #[deprecated(
2548 since = "1.33.0",
2549 note = "superseded by `trim_end_matches`",
2550 suggestion = "trim_end_matches"
2551 )]
2552 pub fn trim_right_matches<P: Pattern>(&self, pat: P) -> &str
2553 where
2554 for<'a> P::Searcher<'a>: ReverseSearcher<'a>,
2555 {
2556 self.trim_end_matches(pat)
2557 }
2558
2559 /// Parses this string slice into another type.
2560 ///
2561 /// Because `parse` is so general, it can cause problems with type
2562 /// inference. As such, `parse` is one of the few times you'll see
2563 /// the syntax affectionately known as the 'turbofish': `::<>`. This
2564 /// helps the inference algorithm understand specifically which type
2565 /// you're trying to parse into.
2566 ///
2567 /// `parse` can parse into any type that implements the [`FromStr`] trait.
2568
2569 ///
2570 /// # Errors
2571 ///
2572 /// Will return [`Err`] if it's not possible to parse this string slice into
2573 /// the desired type.
2574 ///
2575 /// [`Err`]: FromStr::Err
2576 ///
2577 /// # Examples
2578 ///
2579 /// Basic usage:
2580 ///
2581 /// ```
2582 /// let four: u32 = "4".parse().unwrap();
2583 ///
2584 /// assert_eq!(4, four);
2585 /// ```
2586 ///
2587 /// Using the 'turbofish' instead of annotating `four`:
2588 ///
2589 /// ```
2590 /// let four = "4".parse::<u32>();
2591 ///
2592 /// assert_eq!(Ok(4), four);
2593 /// ```
2594 ///
2595 /// Failing to parse:
2596 ///
2597 /// ```
2598 /// let nope = "j".parse::<u32>();
2599 ///
2600 /// assert!(nope.is_err());
2601 /// ```
2602 #[inline]
2603 #[stable(feature = "rust1", since = "1.0.0")]
2604 pub fn parse<F: FromStr>(&self) -> Result<F, F::Err> {
2605 FromStr::from_str(self)
2606 }
2607
2608 /// Checks if all characters in this string are within the ASCII range.
2609 ///
2610 /// # Examples
2611 ///
2612 /// ```
2613 /// let ascii = "hello!\n";
2614 /// let non_ascii = "Grüße, Jürgen ❤";
2615 ///
2616 /// assert!(ascii.is_ascii());
2617 /// assert!(!non_ascii.is_ascii());
2618 /// ```
2619 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2620 #[rustc_const_stable(feature = "const_slice_is_ascii", since = "1.74.0")]
2621 #[must_use]
2622 #[inline]
2623 pub const fn is_ascii(&self) -> bool {
2624 // We can treat each byte as character here: all multibyte characters
2625 // start with a byte that is not in the ASCII range, so we will stop
2626 // there already.
2627 self.as_bytes().is_ascii()
2628 }
2629
2630 /// If this string slice [`is_ascii`](Self::is_ascii), returns it as a slice
2631 /// of [ASCII characters](`ascii::Char`), otherwise returns `None`.
2632 #[unstable(feature = "ascii_char", issue = "110998")]
2633 #[must_use]
2634 #[inline]
2635 pub const fn as_ascii(&self) -> Option<&[ascii::Char]> {
2636 // Like in `is_ascii`, we can work on the bytes directly.
2637 self.as_bytes().as_ascii()
2638 }
2639
2640 /// Converts this string slice into a slice of [ASCII characters](ascii::Char),
2641 /// without checking whether they are valid.
2642 ///
2643 /// # Safety
2644 ///
2645 /// Every character in this string must be ASCII, or else this is UB.
2646 #[unstable(feature = "ascii_char", issue = "110998")]
2647 #[must_use]
2648 #[inline]
2649 pub const unsafe fn as_ascii_unchecked(&self) -> &[ascii::Char] {
2650 assert_unsafe_precondition!(
2651 check_library_ub,
2652 "as_ascii_unchecked requires that the string is valid ASCII",
2653 (it: &str = self) => it.is_ascii()
2654 );
2655
2656 // SAFETY: the caller promised that every byte of this string slice
2657 // is ASCII.
2658 unsafe { self.as_bytes().as_ascii_unchecked() }
2659 }
2660
2661 /// Checks that two strings are an ASCII case-insensitive match.
2662 ///
2663 /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
2664 /// but without allocating and copying temporaries.
2665 ///
2666 /// # Examples
2667 ///
2668 /// ```
2669 /// assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
2670 /// assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
2671 /// assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));
2672 /// ```
2673 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2674 #[rustc_const_stable(feature = "const_eq_ignore_ascii_case", since = "CURRENT_RUSTC_VERSION")]
2675 #[must_use]
2676 #[inline]
2677 pub const fn eq_ignore_ascii_case(&self, other: &str) -> bool {
2678 self.as_bytes().eq_ignore_ascii_case(other.as_bytes())
2679 }
2680
2681 /// Converts this string to its ASCII upper case equivalent in-place.
2682 ///
2683 /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
2684 /// but non-ASCII letters are unchanged.
2685 ///
2686 /// To return a new uppercased value without modifying the existing one, use
2687 /// [`to_ascii_uppercase()`].
2688 ///
2689 /// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
2690 ///
2691 /// # Examples
2692 ///
2693 /// ```
2694 /// let mut s = String::from("Grüße, Jürgen ❤");
2695 ///
2696 /// s.make_ascii_uppercase();
2697 ///
2698 /// assert_eq!("GRüßE, JüRGEN ❤", s);
2699 /// ```
2700 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2701 #[rustc_const_stable(feature = "const_make_ascii", since = "1.84.0")]
2702 #[inline]
2703 pub const fn make_ascii_uppercase(&mut self) {
2704 // SAFETY: changing ASCII letters only does not invalidate UTF-8.
2705 let me = unsafe { self.as_bytes_mut() };
2706 me.make_ascii_uppercase()
2707 }
2708
2709 /// Converts this string to its ASCII lower case equivalent in-place.
2710 ///
2711 /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
2712 /// but non-ASCII letters are unchanged.
2713 ///
2714 /// To return a new lowercased value without modifying the existing one, use
2715 /// [`to_ascii_lowercase()`].
2716 ///
2717 /// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
2718 ///
2719 /// # Examples
2720 ///
2721 /// ```
2722 /// let mut s = String::from("GRÜßE, JÜRGEN ❤");
2723 ///
2724 /// s.make_ascii_lowercase();
2725 ///
2726 /// assert_eq!("grÜße, jÜrgen ❤", s);
2727 /// ```
2728 #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
2729 #[rustc_const_stable(feature = "const_make_ascii", since = "1.84.0")]
2730 #[inline]
2731 pub const fn make_ascii_lowercase(&mut self) {
2732 // SAFETY: changing ASCII letters only does not invalidate UTF-8.
2733 let me = unsafe { self.as_bytes_mut() };
2734 me.make_ascii_lowercase()
2735 }
2736
2737 /// Returns a string slice with leading ASCII whitespace removed.
2738 ///
2739 /// 'Whitespace' refers to the definition used by
2740 /// [`u8::is_ascii_whitespace`].
2741 ///
2742 /// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
2743 ///
2744 /// # Examples
2745 ///
2746 /// ```
2747 /// assert_eq!(" \t \u{3000}hello world\n".trim_ascii_start(), "\u{3000}hello world\n");
2748 /// assert_eq!(" ".trim_ascii_start(), "");
2749 /// assert_eq!("".trim_ascii_start(), "");
2750 /// ```
2751 #[must_use = "this returns the trimmed string as a new slice, \
2752 without modifying the original"]
2753 #[stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
2754 #[rustc_const_stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
2755 #[inline]
2756 pub const fn trim_ascii_start(&self) -> &str {
2757 // SAFETY: Removing ASCII characters from a `&str` does not invalidate
2758 // UTF-8.
2759 unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii_start()) }
2760 }
2761
2762 /// Returns a string slice with trailing ASCII whitespace removed.
2763 ///
2764 /// 'Whitespace' refers to the definition used by
2765 /// [`u8::is_ascii_whitespace`].
2766 ///
2767 /// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
2768 ///
2769 /// # Examples
2770 ///
2771 /// ```
2772 /// assert_eq!("\r hello world\u{3000}\n ".trim_ascii_end(), "\r hello world\u{3000}");
2773 /// assert_eq!(" ".trim_ascii_end(), "");
2774 /// assert_eq!("".trim_ascii_end(), "");
2775 /// ```
2776 #[must_use = "this returns the trimmed string as a new slice, \
2777 without modifying the original"]
2778 #[stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
2779 #[rustc_const_stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
2780 #[inline]
2781 pub const fn trim_ascii_end(&self) -> &str {
2782 // SAFETY: Removing ASCII characters from a `&str` does not invalidate
2783 // UTF-8.
2784 unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii_end()) }
2785 }
2786
2787 /// Returns a string slice with leading and trailing ASCII whitespace
2788 /// removed.
2789 ///
2790 /// 'Whitespace' refers to the definition used by
2791 /// [`u8::is_ascii_whitespace`].
2792 ///
2793 /// [`u8::is_ascii_whitespace`]: u8::is_ascii_whitespace
2794 ///
2795 /// # Examples
2796 ///
2797 /// ```
2798 /// assert_eq!("\r hello world\n ".trim_ascii(), "hello world");
2799 /// assert_eq!(" ".trim_ascii(), "");
2800 /// assert_eq!("".trim_ascii(), "");
2801 /// ```
2802 #[must_use = "this returns the trimmed string as a new slice, \
2803 without modifying the original"]
2804 #[stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
2805 #[rustc_const_stable(feature = "byte_slice_trim_ascii", since = "1.80.0")]
2806 #[inline]
2807 pub const fn trim_ascii(&self) -> &str {
2808 // SAFETY: Removing ASCII characters from a `&str` does not invalidate
2809 // UTF-8.
2810 unsafe { core::str::from_utf8_unchecked(self.as_bytes().trim_ascii()) }
2811 }
2812
2813 /// Returns an iterator that escapes each char in `self` with [`char::escape_debug`].
2814 ///
2815 /// Note: only extended grapheme codepoints that begin the string will be
2816 /// escaped.
2817 ///
2818 /// # Examples
2819 ///
2820 /// As an iterator:
2821 ///
2822 /// ```
2823 /// for c in "❤\n!".escape_debug() {
2824 /// print!("{c}");
2825 /// }
2826 /// println!();
2827 /// ```
2828 ///
2829 /// Using `println!` directly:
2830 ///
2831 /// ```
2832 /// println!("{}", "❤\n!".escape_debug());
2833 /// ```
2834 ///
2835 ///
2836 /// Both are equivalent to:
2837 ///
2838 /// ```
2839 /// println!("❤\\n!");
2840 /// ```
2841 ///
2842 /// Using `to_string`:
2843 ///
2844 /// ```
2845 /// assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");
2846 /// ```
2847 #[must_use = "this returns the escaped string as an iterator, \
2848 without modifying the original"]
2849 #[stable(feature = "str_escape", since = "1.34.0")]
2850 pub fn escape_debug(&self) -> EscapeDebug<'_> {
2851 let mut chars = self.chars();
2852 EscapeDebug {
2853 inner: chars
2854 .next()
2855 .map(|first| first.escape_debug_ext(EscapeDebugExtArgs::ESCAPE_ALL))
2856 .into_iter()
2857 .flatten()
2858 .chain(chars.flat_map(CharEscapeDebugContinue)),
2859 }
2860 }
2861
2862 /// Returns an iterator that escapes each char in `self` with [`char::escape_default`].
2863 ///
2864 /// # Examples
2865 ///
2866 /// As an iterator:
2867 ///
2868 /// ```
2869 /// for c in "❤\n!".escape_default() {
2870 /// print!("{c}");
2871 /// }
2872 /// println!();
2873 /// ```
2874 ///
2875 /// Using `println!` directly:
2876 ///
2877 /// ```
2878 /// println!("{}", "❤\n!".escape_default());
2879 /// ```
2880 ///
2881 ///
2882 /// Both are equivalent to:
2883 ///
2884 /// ```
2885 /// println!("\\u{{2764}}\\n!");
2886 /// ```
2887 ///
2888 /// Using `to_string`:
2889 ///
2890 /// ```
2891 /// assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");
2892 /// ```
2893 #[must_use = "this returns the escaped string as an iterator, \
2894 without modifying the original"]
2895 #[stable(feature = "str_escape", since = "1.34.0")]
2896 pub fn escape_default(&self) -> EscapeDefault<'_> {
2897 EscapeDefault { inner: self.chars().flat_map(CharEscapeDefault) }
2898 }
2899
2900 /// Returns an iterator that escapes each char in `self` with [`char::escape_unicode`].
2901 ///
2902 /// # Examples
2903 ///
2904 /// As an iterator:
2905 ///
2906 /// ```
2907 /// for c in "❤\n!".escape_unicode() {
2908 /// print!("{c}");
2909 /// }
2910 /// println!();
2911 /// ```
2912 ///
2913 /// Using `println!` directly:
2914 ///
2915 /// ```
2916 /// println!("{}", "❤\n!".escape_unicode());
2917 /// ```
2918 ///
2919 ///
2920 /// Both are equivalent to:
2921 ///
2922 /// ```
2923 /// println!("\\u{{2764}}\\u{{a}}\\u{{21}}");
2924 /// ```
2925 ///
2926 /// Using `to_string`:
2927 ///
2928 /// ```
2929 /// assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");
2930 /// ```
2931 #[must_use = "this returns the escaped string as an iterator, \
2932 without modifying the original"]
2933 #[stable(feature = "str_escape", since = "1.34.0")]
2934 pub fn escape_unicode(&self) -> EscapeUnicode<'_> {
2935 EscapeUnicode { inner: self.chars().flat_map(CharEscapeUnicode) }
2936 }
2937
2938 /// Returns the range that a substring points to.
2939 ///
2940 /// Returns `None` if `substr` does not point within `self`.
2941 ///
2942 /// Unlike [`str::find`], **this does not search through the string**.
2943 /// Instead, it uses pointer arithmetic to find where in the string
2944 /// `substr` is derived from.
2945 ///
2946 /// This is useful for extending [`str::split`] and similar methods.
2947 ///
2948 /// Note that this method may return false positives (typically either
2949 /// `Some(0..0)` or `Some(self.len()..self.len())`) if `substr` is a
2950 /// zero-length `str` that points at the beginning or end of another,
2951 /// independent, `str`.
2952 ///
2953 /// # Examples
2954 /// ```
2955 /// #![feature(substr_range)]
2956 ///
2957 /// let data = "a, b, b, a";
2958 /// let mut iter = data.split(", ").map(|s| data.substr_range(s).unwrap());
2959 ///
2960 /// assert_eq!(iter.next(), Some(0..1));
2961 /// assert_eq!(iter.next(), Some(3..4));
2962 /// assert_eq!(iter.next(), Some(6..7));
2963 /// assert_eq!(iter.next(), Some(9..10));
2964 /// ```
2965 #[must_use]
2966 #[unstable(feature = "substr_range", issue = "126769")]
2967 pub fn substr_range(&self, substr: &str) -> Option<Range<usize>> {
2968 self.as_bytes().subslice_range(substr.as_bytes())
2969 }
2970
2971 /// Returns the same string as a string slice `&str`.
2972 ///
2973 /// This method is redundant when used directly on `&str`, but
2974 /// it helps dereferencing other string-like types to string slices,
2975 /// for example references to `Box<str>` or `Arc<str>`.
2976 #[inline]
2977 #[unstable(feature = "str_as_str", issue = "130366")]
2978 pub fn as_str(&self) -> &str {
2979 self
2980 }
2981}
2982
2983#[stable(feature = "rust1", since = "1.0.0")]
2984impl AsRef<[u8]> for str {
2985 #[inline]
2986 fn as_ref(&self) -> &[u8] {
2987 self.as_bytes()
2988 }
2989}
2990
2991#[stable(feature = "rust1", since = "1.0.0")]
2992impl Default for &str {
2993 /// Creates an empty str
2994 #[inline]
2995 fn default() -> Self {
2996 ""
2997 }
2998}
2999
3000#[stable(feature = "default_mut_str", since = "1.28.0")]
3001impl Default for &mut str {
3002 /// Creates an empty mutable str
3003 #[inline]
3004 fn default() -> Self {
3005 // SAFETY: The empty string is valid UTF-8.
3006 unsafe { from_utf8_unchecked_mut(&mut []) }
3007 }
3008}
3009
3010impl_fn_for_zst! {
3011 /// A nameable, cloneable fn type
3012 #[derive(Clone)]
3013 struct LinesMap impl<'a> Fn = |line: &'a str| -> &'a str {
3014 let Some(line) = line.strip_suffix('\n') else { return line };
3015 let Some(line) = line.strip_suffix('\r') else { return line };
3016 line
3017 };
3018
3019 #[derive(Clone)]
3020 struct CharEscapeDebugContinue impl Fn = |c: char| -> char::EscapeDebug {
3021 c.escape_debug_ext(EscapeDebugExtArgs {
3022 escape_grapheme_extended: false,
3023 escape_single_quote: true,
3024 escape_double_quote: true
3025 })
3026 };
3027
3028 #[derive(Clone)]
3029 struct CharEscapeUnicode impl Fn = |c: char| -> char::EscapeUnicode {
3030 c.escape_unicode()
3031 };
3032 #[derive(Clone)]
3033 struct CharEscapeDefault impl Fn = |c: char| -> char::EscapeDefault {
3034 c.escape_default()
3035 };
3036
3037 #[derive(Clone)]
3038 struct IsWhitespace impl Fn = |c: char| -> bool {
3039 c.is_whitespace()
3040 };
3041
3042 #[derive(Clone)]
3043 struct IsAsciiWhitespace impl Fn = |byte: &u8| -> bool {
3044 byte.is_ascii_whitespace()
3045 };
3046
3047 #[derive(Clone)]
3048 struct IsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b str| -> bool {
3049 !s.is_empty()
3050 };
3051
3052 #[derive(Clone)]
3053 struct BytesIsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b [u8]| -> bool {
3054 !s.is_empty()
3055 };
3056
3057 #[derive(Clone)]
3058 struct UnsafeBytesToStr impl<'a> Fn = |bytes: &'a [u8]| -> &'a str {
3059 // SAFETY: not safe
3060 unsafe { from_utf8_unchecked(bytes) }
3061 };
3062}
3063
3064// This is required to make `impl From<&str> for Box<dyn Error>` and `impl<E> From<E> for Box<dyn Error>` not overlap.
3065#[stable(feature = "error_in_core_neg_impl", since = "1.65.0")]
3066impl !crate::error::Error for &str {}
3067