Auto merge of #126557 - GrigorenkoPV:vec_track_caller, r=<try>

Add `#[track_caller]` to allocating methods of `Vec` & `VecDeque`

Part 4 in a lengthy saga.
r? `@joshtriplett` because they were the reviewer the last 3 times.
`@bors` rollup=never "[just in case this has perf effects, Vec is hot](#79323 (comment))"

This was first attempted in #79323 by `@nvzqz.` It got approval from `@joshtriplett,` but rotted with merge conflicts and got closed.

Then it got picked up by `@Dylan-DPC-zz` in #83359. A benchmark was run[^perf], the results (after a bit of thinking[^thinking]) were deemed ok[^ok], but there was a typo[^typo] and the PR was made from a wrong remote in the first place[^remote], so #83909 was opened instead.

By the time #83909 rolled around, the methods in question had received some optimizations[^optimizations], so another perf run was conducted[^perf2]. The results were ok[^ok2]. There was a suggestion to add regression tests for panic behavior [^tests], but before it could be addressed, the PR fell victim to merge conflicts[^conflicts] and died again[^rip].

3 years have passed, and (from what I can tell) this has not been tried again, so here I am now, reviving this old effort.

Given how much time has passed and the fact that I've also touched `VecDeque` this time, it probably makes sense to
`@bors` try `@rust-timer`

[^perf]: #83359 (comment)
[^thinking]: #83359 (comment)
[^ok]: #83359 (comment)
[^typo]: #83359 (comment)
[^remote]: #83359 (comment)
[^optimizations]: #83909 (comment)
[^perf2]: #83909 (comment)
[^ok2]: #83909 (comment)
[^tests]: #83909 (comment)
[^conflicts]: #83909 (comment)
[^rip]: #83909 (comment)

Author: bors

Diff for: library/alloc/src/collections/vec_deque/mod.rs

@@ -107,6 +107,7 @@ pub struct VecDeque<
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Clone, A: Allocator + Clone> Clone for VecDeque<T, A> {
+    #[track_caller]
     fn clone(&self) -> Self {
         let mut deq = Self::with_capacity_in(self.len(), self.allocator().clone());
         deq.extend(self.iter().cloned());
@@ -117,6 +118,7 @@ impl<T: Clone, A: Allocator + Clone> Clone for VecDeque<T, A> {
     ///
     /// This method is preferred over simply assigning `source.clone()` to `self`,
     /// as it avoids reallocation if possible.
+    #[track_caller]
     fn clone_from(&mut self, source: &Self) {
         self.clear();
         self.extend(source.iter().cloned());
@@ -480,6 +482,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// Frobs the head and tail sections around to handle the fact that we
     /// just reallocated. Unsafe because it trusts old_capacity.
     #[inline]
+    #[track_caller]
     unsafe fn handle_capacity_increase(&mut self, old_capacity: usize) {
         let new_capacity = self.capacity();
         debug_assert!(new_capacity >= old_capacity);
@@ -560,6 +563,7 @@ impl<T> VecDeque<T> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use]
+    #[track_caller]
     pub fn with_capacity(capacity: usize) -> VecDeque<T> {
         Self::with_capacity_in(capacity, Global)
     }
@@ -615,6 +619,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// let deque: VecDeque<u32> = VecDeque::with_capacity(10);
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
+    #[track_caller]
     pub fn with_capacity_in(capacity: usize, alloc: A) -> VecDeque<T, A> {
         VecDeque { head: 0, len: 0, buf: RawVec::with_capacity_in(capacity, alloc) }
     }
@@ -779,6 +784,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// [`reserve`]: VecDeque::reserve
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[track_caller]
     pub fn reserve_exact(&mut self, additional: usize) {
         let new_cap = self.len.checked_add(additional).expect("capacity overflow");
         let old_cap = self.capacity();
@@ -808,6 +814,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert!(buf.capacity() >= 11);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[track_caller]
     pub fn reserve(&mut self, additional: usize) {
         let new_cap = self.len.checked_add(additional).expect("capacity overflow");
         let old_cap = self.capacity();
@@ -939,6 +946,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert!(buf.capacity() >= 4);
     /// ```
     #[stable(feature = "deque_extras_15", since = "1.5.0")]
+    #[track_caller]
     pub fn shrink_to_fit(&mut self) {
         self.shrink_to(0);
     }
@@ -964,6 +972,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert!(buf.capacity() >= 4);
     /// ```
     #[stable(feature = "shrink_to", since = "1.56.0")]
+    #[track_caller]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         let target_cap = min_capacity.max(self.len);
 
@@ -1729,6 +1738,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(d.front(), Some(&2));
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[track_caller]
     pub fn push_front(&mut self, value: T) {
         if self.is_full() {
             self.grow();
@@ -1756,6 +1766,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_confusables("push", "put", "append")]
+    #[track_caller]
     pub fn push_back(&mut self, value: T) {
         if self.is_full() {
             self.grow();
@@ -1865,6 +1876,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(vec_deque, &['a', 'd', 'b', 'c']);
     /// ```
     #[stable(feature = "deque_extras_15", since = "1.5.0")]
+    #[track_caller]
     pub fn insert(&mut self, index: usize, value: T) {
         assert!(index <= self.len(), "index out of bounds");
         if self.is_full() {
@@ -1968,6 +1980,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     #[inline]
     #[must_use = "use `.truncate()` if you don't need the other half"]
     #[stable(feature = "split_off", since = "1.4.0")]
+    #[track_caller]
     pub fn split_off(&mut self, at: usize) -> Self
     where
         A: Clone,
@@ -2034,6 +2047,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// ```
     #[inline]
     #[stable(feature = "append", since = "1.4.0")]
+    #[track_caller]
     pub fn append(&mut self, other: &mut Self) {
         if T::IS_ZST {
             self.len = self.len.checked_add(other.len).expect("capacity overflow");
@@ -2156,6 +2170,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     // be called in cold paths.
     // This may panic or abort
     #[inline(never)]
+    #[track_caller]
     fn grow(&mut self) {
         // Extend or possibly remove this assertion when valid use-cases for growing the
         // buffer without it being full emerge
@@ -2194,6 +2209,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(buf, [5, 10, 101, 102, 103]);
     /// ```
     #[stable(feature = "vec_resize_with", since = "1.33.0")]
+    #[track_caller]
     pub fn resize_with(&mut self, new_len: usize, generator: impl FnMut() -> T) {
         let len = self.len;
 
@@ -2740,6 +2756,7 @@ impl<T: Clone, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(buf, [5, 10, 20, 20, 20]);
     /// ```
     #[stable(feature = "deque_extras", since = "1.16.0")]
+    #[track_caller]
     pub fn resize(&mut self, new_len: usize, value: T) {
         if new_len > self.len() {
             let extra = new_len - self.len();
@@ -2859,6 +2876,7 @@ impl<T, A: Allocator> IndexMut<usize> for VecDeque<T, A> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> FromIterator<T> for VecDeque<T> {
+    #[track_caller]
     fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> VecDeque<T> {
         SpecFromIter::spec_from_iter(iter.into_iter())
     }
@@ -2898,33 +2916,39 @@ impl<'a, T, A: Allocator> IntoIterator for &'a mut VecDeque<T, A> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, A: Allocator> Extend<T> for VecDeque<T, A> {
+    #[track_caller]
     fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
         <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter());
     }
 
     #[inline]
+    #[track_caller]
     fn extend_one(&mut self, elem: T) {
         self.push_back(elem);
     }
 
     #[inline]
+    #[track_caller]
     fn extend_reserve(&mut self, additional: usize) {
         self.reserve(additional);
     }
 }
 
 #[stable(feature = "extend_ref", since = "1.2.0")]
 impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for VecDeque<T, A> {
+    #[track_caller]
     fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
         self.spec_extend(iter.into_iter());
     }
 
     #[inline]
+    #[track_caller]
     fn extend_one(&mut self, &elem: &'a T) {
         self.push_back(elem);
     }
 
     #[inline]
+    #[track_caller]
     fn extend_reserve(&mut self, additional: usize) {
         self.reserve(additional);
     }
@@ -3014,6 +3038,7 @@ impl<T, const N: usize> From<[T; N]> for VecDeque<T> {
     /// let deq2: VecDeque<_> = [1, 2, 3, 4].into();
     /// assert_eq!(deq1, deq2);
     /// ```
+    #[track_caller]
     fn from(arr: [T; N]) -> Self {
         let mut deq = VecDeque::with_capacity(N);
         let arr = ManuallyDrop::new(arr);

Diff for: library/alloc/src/collections/vec_deque/spec_extend.rs

@@ -7,13 +7,15 @@ use super::VecDeque;
 
 // Specialization trait used for VecDeque::extend
 pub(super) trait SpecExtend<T, I> {
+    #[track_caller]
     fn spec_extend(&mut self, iter: I);
 }
 
 impl<T, I, A: Allocator> SpecExtend<T, I> for VecDeque<T, A>
 where
     I: Iterator<Item = T>,
 {
+    #[track_caller]
     default fn spec_extend(&mut self, mut iter: I) {
         // This function should be the moral equivalent of:
         //
@@ -53,6 +55,7 @@ impl<T, I, A: Allocator> SpecExtend<T, I> for VecDeque<T, A>
 where
     I: TrustedLen<Item = T>,
 {
+    #[track_caller]
     default fn spec_extend(&mut self, iter: I) {
         // This is the case for a TrustedLen iterator.
         let (low, high) = iter.size_hint();
@@ -85,6 +88,7 @@ where
 }
 
 impl<T, A: Allocator> SpecExtend<T, vec::IntoIter<T>> for VecDeque<T, A> {
+    #[track_caller]
     fn spec_extend(&mut self, mut iterator: vec::IntoIter<T>) {
         let slice = iterator.as_slice();
         self.reserve(slice.len());
@@ -102,6 +106,7 @@ where
     I: Iterator<Item = &'a T>,
     T: Copy,
 {
+    #[track_caller]
     default fn spec_extend(&mut self, iterator: I) {
         self.spec_extend(iterator.copied())
     }
@@ -111,6 +116,7 @@ impl<'a, T: 'a, A: Allocator> SpecExtend<&'a T, slice::Iter<'a, T>> for VecDeque
 where
     T: Copy,
 {
+    #[track_caller]
     fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
         let slice = iterator.as_slice();
         self.reserve(slice.len());

Diff for: library/alloc/src/collections/vec_deque/spec_from_iter.rs

@@ -9,6 +9,7 @@ impl<T, I> SpecFromIter<T, I> for VecDeque<T>
 where
     I: Iterator<Item = T>,
 {
+    #[track_caller]
     default fn spec_from_iter(iterator: I) -> Self {
         // Since converting is O(1) now, just re-use the `Vec` logic for
         // anything where we can't do something extra-special for `VecDeque`,

Diff for: library/alloc/src/raw_vec.rs

@@ -21,7 +21,8 @@ mod tests;
 // only one location which panics rather than a bunch throughout the module.
 #[cfg(not(no_global_oom_handling))]
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
-fn capacity_overflow() -> ! {
+#[track_caller]
+pub(crate) fn capacity_overflow() -> ! {
     panic!("capacity overflow");
 }
 
@@ -113,6 +114,7 @@ impl<T> RawVec<T, Global> {
     #[cfg(not(any(no_global_oom_handling, test)))]
     #[must_use]
     #[inline]
+    #[track_caller]
     pub fn with_capacity(capacity: usize) -> Self {
         match Self::try_allocate_in(capacity, AllocInit::Uninitialized, Global) {
             Ok(res) => res,
@@ -124,6 +126,7 @@ impl<T> RawVec<T, Global> {
     #[cfg(not(any(no_global_oom_handling, test)))]
     #[must_use]
     #[inline]
+    #[track_caller]
     pub fn with_capacity_zeroed(capacity: usize) -> Self {
         Self::with_capacity_zeroed_in(capacity, Global)
     }
@@ -154,6 +157,7 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// allocator for the returned `RawVec`.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
+    #[track_caller]
     pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
         match Self::try_allocate_in(capacity, AllocInit::Uninitialized, alloc) {
             Ok(res) => res,
@@ -172,6 +176,7 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// of allocator for the returned `RawVec`.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
+    #[track_caller]
     pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self {
         match Self::try_allocate_in(capacity, AllocInit::Zeroed, alloc) {
             Ok(res) => res,
@@ -335,6 +340,7 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// Aborts on OOM.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
+    #[track_caller]
     pub fn reserve(&mut self, len: usize, additional: usize) {
         // Callers expect this function to be very cheap when there is already sufficient capacity.
         // Therefore, we move all the resizing and error-handling logic from grow_amortized and
@@ -360,6 +366,7 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// caller to ensure `len == self.capacity()`.
     #[cfg(not(no_global_oom_handling))]
     #[inline(never)]
+    #[track_caller]
     pub fn grow_one(&mut self) {
         if let Err(err) = self.grow_amortized(self.cap.0, 1) {
             handle_error(err);
@@ -396,6 +403,7 @@ impl<T, A: Allocator> RawVec<T, A> {
     ///
     /// Aborts on OOM.
     #[cfg(not(no_global_oom_handling))]
+    #[track_caller]
     pub fn reserve_exact(&mut self, len: usize, additional: usize) {
         if let Err(err) = self.try_reserve_exact(len, additional) {
             handle_error(err);
@@ -429,6 +437,7 @@ impl<T, A: Allocator> RawVec<T, A> {
     ///
     /// Aborts on OOM.
     #[cfg(not(no_global_oom_handling))]
+    #[track_caller]
     pub fn shrink_to_fit(&mut self, cap: usize) {
         if let Err(err) = self.shrink(cap) {
             handle_error(err);
@@ -510,7 +519,6 @@ impl<T, A: Allocator> RawVec<T, A> {
         Ok(())
     }
 
-    #[cfg(not(no_global_oom_handling))]
     fn shrink(&mut self, cap: usize) -> Result<(), TryReserveError> {
         assert!(cap <= self.capacity(), "Tried to shrink to a larger capacity");
 
@@ -588,6 +596,7 @@ unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawVec<T, A> {
 // Central function for reserve error handling.
 #[cfg(not(no_global_oom_handling))]
 #[cold]
+#[track_caller]
 fn handle_error(e: TryReserveError) -> ! {
     match e.kind() {
         CapacityOverflow => capacity_overflow(),

Diff for: library/alloc/src/vec/cow.rs

@@ -59,6 +59,7 @@ impl<'a, T> FromIterator<T> for Cow<'a, [T]>
 where
     T: Clone,
 {
+    #[track_caller]
     fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {
         Cow::Owned(FromIterator::from_iter(it))
     }

Diff for: library/alloc/src/vec/in_place_collect.rs

@@ -229,6 +229,7 @@ where
     I: Iterator<Item = T> + InPlaceCollect,
     <I as SourceIter>::Source: AsVecIntoIter,
 {
+    #[track_caller]
     default fn from_iter(iterator: I) -> Self {
         // Select the implementation in const eval to avoid codegen of the dead branch to improve compile times.
         let fun: fn(I) -> Vec<T> = const {
@@ -246,6 +247,7 @@ where
     }
 }
 
+#[track_caller]
 fn from_iter_in_place<I, T>(mut iterator: I) -> Vec<T>
 where
     I: Iterator<Item = T> + InPlaceCollect,