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Commit 19a40ec

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Rollup merge of rust-lang#123107 - avandesa:vec_pop_if, r=joboet
Implement `Vec::pop_if` This PR adds `Vec::pop_if` to the public API, behind the `vec_pop_if` feature. ```rust impl<T> Vec<T> { pub fn pop_if<F>(&mut self, f: F) -> Option<T> where F: FnOnce(&mut T) -> bool; } ``` Tracking issue: rust-lang#122741 ## Open questions - [ ] Should the first unit test be split up? - [ ] I don't see any guidance on ordering of methods in impl blocks, should I move the method elsewhere?
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‎library/alloc/src/lib.rs‎

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#![feature(unicode_internals)]
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#![feature(unsize)]
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#![feature(utf8_chunks)]
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#![feature(vec_pop_if)]
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// tidy-alphabetical-end
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//
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// Language features:

‎library/alloc/src/vec/mod.rs‎

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}
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}
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/// Removes and returns the last element in a vector if the predicate
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/// returns `true`, or [`None`] if the predicate returns false or the vector
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/// is empty.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(vec_pop_if)]
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///
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/// let mut vec = vec![1, 2, 3, 4];
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/// let pred = |x: &mut i32| *x % 2 == 0;
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///
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/// assert_eq!(vec.pop_if(pred), Some(4));
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/// assert_eq!(vec, [1, 2, 3]);
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/// assert_eq!(vec.pop_if(pred), None);
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/// ```
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#[unstable(feature = "vec_pop_if", issue = "122741")]
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pub fn pop_if<F>(&mut self, f: F) -> Option<T>
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where
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F: FnOnce(&mut T) -> bool,
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{
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let last = self.last_mut()?;
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if f(last) { self.pop() } else { None }
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}
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/// Moves all the elements of `other` into `self`, leaving `other` empty.
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///
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/// # Panics

‎library/alloc/tests/lib.rs‎

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#![feature(strict_provenance)]
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#![feature(drain_keep_rest)]
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#![feature(local_waker)]
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#![feature(vec_pop_if)]
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#![allow(internal_features)]
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#![deny(fuzzy_provenance_casts)]
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#![deny(unsafe_op_in_unsafe_fn)]

‎library/alloc/tests/vec.rs‎

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assert_eq!(Vec::from(&mut [1, 2, 3]), vec![1, 2, 3]);
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}
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#[test]
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fn test_pop_if() {
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let mut v = vec![1, 2, 3, 4];
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let pred = |x: &mut i32| *x % 2 == 0;
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assert_eq!(v.pop_if(pred), Some(4));
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assert_eq!(v, [1, 2, 3]);
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assert_eq!(v.pop_if(pred), None);
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assert_eq!(v, [1, 2, 3]);
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}
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#[test]
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fn test_pop_if_empty() {
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let mut v = Vec::<i32>::new();
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assert_eq!(v.pop_if(|_| true), None);
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assert!(v.is_empty());
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}
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#[test]
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fn test_pop_if_mutates() {
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let mut v = vec![1];
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let pred = |x: &mut i32| {
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*x += 1;
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false
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};
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assert_eq!(v.pop_if(pred), None);
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assert_eq!(v, [2]);
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}
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/// This assortment of tests, in combination with miri, verifies we handle UB on fishy arguments
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/// in the stdlib. Draining and extending the allocation are fairly well-tested earlier, but
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/// `vec.insert(usize::MAX, val)` once slipped by!

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