Auto merge of #74235 - Manishearth:rollup-bgs3q14, r=Manishearth

Rollup of 19 pull requests

Successful merges:

 - #71322 (Accept tuple.0.0 as tuple indexing (take 2))
 - #72303 (Add core::future::{poll_fn, PollFn})
 - #73862 (Stabilize casts and coercions to `&[T]` in const fn)
 - #73887 (stabilize const mem::forget)
 - #73989 (adjust ub-enum test to be endianess-independent)
 - #74045 (Explain effects of debugging options from config.toml)
 - #74076 (Add `read_exact_at` and `write_all_at` to WASI's `FileExt`)
 - #74099 (Add VecDeque::range* methods)
 - #74100 (Use str::strip* in bootstrap)
 - #74103 (Only add CFGuard on `windows-msvc` targets)
 - #74109 (Only allow `repr(i128/u128)` on enum)
 - #74122 (Start-up clean-up)
 - #74125 (Correctly mark the ending span of a match arm)
 - #74127 (Avoid "whitelist")
 - #74129 (:arrow_up: rust-analyzer)
 - #74135 (Update books)
 - #74145 (Update rust-installer to latest version)
 - #74161 (Fix  disabled dockerfiles)
 - #74162 (take self by value in ToPredicate)

Failed merges:

r? @ghost

3 files changed, 163 insertions, 13 deletions

diff --git a/src/liballoc/collections/vec_deque.rs b/src/liballoc/collections/vec_deque.rs
index 15f3a94ca2d..2efb94e8afe 100644
--- a/src/liballoc/collections/vec_deque.rs
+++ b/src/liballoc/collections/vec_deque.rs
@@ -1084,6 +1084,108 @@ impl<T> VecDeque<T> {
         self.tail == self.head
     }
 
+    fn range_start_end<R>(&self, range: R) -> (usize, usize)
+    where
+        R: RangeBounds<usize>,
+    {
+        let len = self.len();
+        let start = match range.start_bound() {
+            Included(&n) => n,
+            Excluded(&n) => n + 1,
+            Unbounded => 0,
+        };
+        let end = match range.end_bound() {
+            Included(&n) => n + 1,
+            Excluded(&n) => n,
+            Unbounded => len,
+        };
+        assert!(start <= end, "lower bound was too large");
+        assert!(end <= len, "upper bound was too large");
+        (start, end)
+    }
+
+    /// Creates an iterator that covers the specified range in the `VecDeque`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the starting point is greater than the end point or if
+    /// the end point is greater than the length of the vector.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(deque_range)]
+    ///
+    /// use std::collections::VecDeque;
+    ///
+    /// let v: VecDeque<_> = vec![1, 2, 3].into_iter().collect();
+    /// let range = v.range(2..).copied().collect::<VecDeque<_>>();
+    /// assert_eq!(range, [3]);
+    ///
+    /// // A full range covers all contents
+    /// let all = v.range(..);
+    /// assert_eq!(all.len(), 3);
+    /// ```
+    #[inline]
+    #[unstable(feature = "deque_range", issue = "74217")]
+    pub fn range<R>(&self, range: R) -> Iter<'_, T>
+    where
+        R: RangeBounds<usize>,
+    {
+        let (start, end) = self.range_start_end(range);
+        let tail = self.wrap_add(self.tail, start);
+        let head = self.wrap_add(self.tail, end);
+        Iter {
+            tail,
+            head,
+            // The shared reference we have in &self is maintained in the '_ of Iter.
+            ring: unsafe { self.buffer_as_slice() },
+        }
+    }
+
+    /// Creates an iterator that covers the specified mutable range in the `VecDeque`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the starting point is greater than the end point or if
+    /// the end point is greater than the length of the vector.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(deque_range)]
+    ///
+    /// use std::collections::VecDeque;
+    ///
+    /// let mut v: VecDeque<_> = vec![1, 2, 3].into_iter().collect();
+    /// for v in v.range_mut(2..) {
+    ///   *v *= 2;
+    /// }
+    /// assert_eq!(v, vec![1, 2, 6]);
+    ///
+    /// // A full range covers all contents
+    /// for v in v.range_mut(..) {
+    ///   *v *= 2;
+    /// }
+    /// assert_eq!(v, vec![2, 4, 12]);
+    /// ```
+    #[inline]
+    #[unstable(feature = "deque_range", issue = "74217")]
+    pub fn range_mut<R>(&mut self, range: R) -> IterMut<'_, T>
+    where
+        R: RangeBounds<usize>,
+    {
+        let (start, end) = self.range_start_end(range);
+        let tail = self.wrap_add(self.tail, start);
+        let head = self.wrap_add(self.tail, end);
+        IterMut {
+            tail,
+            head,
+            // The shared reference we have in &mut self is maintained in the '_ of IterMut.
+            ring: unsafe { self.buffer_as_mut_slice() },
+        }
+    }
+
     /// Creates a draining iterator that removes the specified range in the
     /// `VecDeque` and yields the removed items.
     ///
@@ -1129,19 +1231,7 @@ impl<T> VecDeque<T> {
         // When finished, the remaining data will be copied back to cover the hole,
         // and the head/tail values will be restored correctly.
         //
-        let len = self.len();
-        let start = match range.start_bound() {
-            Included(&n) => n,
-            Excluded(&n) => n + 1,
-            Unbounded => 0,
-        };
-        let end = match range.end_bound() {
-            Included(&n) => n + 1,
-            Excluded(&n) => n,
-            Unbounded => len,
-        };
-        assert!(start <= end, "drain lower bound was too large");
-        assert!(end <= len, "drain upper bound was too large");
+        let (start, end) = self.range_start_end(range);
 
         // The deque's elements are parted into three segments:
         // * self.tail  -> drain_tail
diff --git a/src/liballoc/collections/vec_deque/tests.rs b/src/liballoc/collections/vec_deque/tests.rs
index 960af4bfda0..e5edfe02a52 100644
--- a/src/liballoc/collections/vec_deque/tests.rs
+++ b/src/liballoc/collections/vec_deque/tests.rs
@@ -247,6 +247,65 @@ fn test_remove() {
 }
 
 #[test]
+fn test_range() {
+    let mut tester: VecDeque<usize> = VecDeque::with_capacity(7);
+
+    let cap = tester.capacity();
+    for len in 0..=cap {
+        for tail in 0..=cap {
+            for start in 0..=len {
+                for end in start..=len {
+                    tester.tail = tail;
+                    tester.head = tail;
+                    for i in 0..len {
+                        tester.push_back(i);
+                    }
+
+                    // Check that we iterate over the correct values
+                    let range: VecDeque<_> = tester.range(start..end).copied().collect();
+                    let expected: VecDeque<_> = (start..end).collect();
+                    assert_eq!(range, expected);
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn test_range_mut() {
+    let mut tester: VecDeque<usize> = VecDeque::with_capacity(7);
+
+    let cap = tester.capacity();
+    for len in 0..=cap {
+        for tail in 0..=cap {
+            for start in 0..=len {
+                for end in start..=len {
+                    tester.tail = tail;
+                    tester.head = tail;
+                    for i in 0..len {
+                        tester.push_back(i);
+                    }
+
+                    let head_was = tester.head;
+                    let tail_was = tester.tail;
+
+                    // Check that we iterate over the correct values
+                    let range: VecDeque<_> = tester.range_mut(start..end).map(|v| *v).collect();
+                    let expected: VecDeque<_> = (start..end).collect();
+                    assert_eq!(range, expected);
+
+                    // We shouldn't have changed the capacity or made the
+                    // head or tail out of bounds
+                    assert_eq!(tester.capacity(), cap);
+                    assert_eq!(tester.tail, tail_was);
+                    assert_eq!(tester.head, head_was);
+                }
+            }
+        }
+    }
+}
+
+#[test]
 fn test_drain() {
     let mut tester: VecDeque<usize> = VecDeque::with_capacity(7);
 
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 79bfd57a00f..2ec777ac85c 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -89,6 +89,7 @@
 #![feature(const_in_array_repeat_expressions)]
 #![cfg_attr(bootstrap, feature(const_if_match))]
 #![feature(cow_is_borrowed)]
+#![feature(deque_range)]
 #![feature(dispatch_from_dyn)]
 #![feature(core_intrinsics)]
 #![feature(container_error_extra)]