bump Rust version (requires a patch for now)

Author: RalfJung

rust-src.diff

@@ -0,0 +1,250 @@
+diff --git a/library/alloc/src/collections/vec_deque.rs b/library/alloc/src/collections/vec_deque.rs
+index 253a3e9f2be..65cfe9a9b49 100644
+--- a/library/alloc/src/collections/vec_deque.rs
++++ b/library/alloc/src/collections/vec_deque.rs
+@@ -1089,11 +1089,7 @@ impl<T> VecDeque<T> {
+     where
+         R: RangeBounds<usize>,
+     {
+-        // SAFETY: This buffer is only used to check the range. It might be partially
+-        // uninitialized, but `check_range` needs a contiguous slice.
+-        // https://github.com/rust-lang/rust/pull/75207#discussion_r471193682
+-        let buffer = unsafe { slice::from_raw_parts(self.ptr(), self.len()) };
+-        let Range { start, end } = buffer.check_range(range);
++        let Range { start, end } = slice::check_range(self.len(), range);
+         let tail = self.wrap_add(self.tail, start);
+         let head = self.wrap_add(self.tail, end);
+         (tail, head)
+diff --git a/library/alloc/src/slice.rs b/library/alloc/src/slice.rs
+index 677bfdd2349..55afdd94f44 100644
+--- a/library/alloc/src/slice.rs
++++ b/library/alloc/src/slice.rs
+@@ -91,6 +91,8 @@ use crate::borrow::ToOwned;
+ use crate::boxed::Box;
+ use crate::vec::Vec;
+ 
++#[unstable(feature = "slice_check_range", issue = "76393")]
++pub use core::slice::check_range;
+ #[unstable(feature = "array_chunks", issue = "74985")]
+ pub use core::slice::ArrayChunks;
+ #[unstable(feature = "array_chunks", issue = "74985")]
+diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
+index e1724bf3c9a..2b0ce5ede56 100644
+--- a/library/alloc/src/string.rs
++++ b/library/alloc/src/string.rs
+@@ -49,6 +49,7 @@ use core::iter::{FromIterator, FusedIterator};
+ use core::ops::Bound::{Excluded, Included, Unbounded};
+ use core::ops::{self, Add, AddAssign, Index, IndexMut, Range, RangeBounds};
+ use core::ptr;
++use core::slice;
+ use core::str::{lossy, pattern::Pattern};
+ 
+ use crate::borrow::{Cow, ToOwned};
+@@ -1506,7 +1507,7 @@ impl String {
+         // of the vector version. The data is just plain bytes.
+         // Because the range removal happens in Drop, if the Drain iterator is leaked,
+         // the removal will not happen.
+-        let Range { start, end } = self.as_bytes().check_range(range);
++        let Range { start, end } = slice::check_range(self.len(), range);
+         assert!(self.is_char_boundary(start));
+         assert!(self.is_char_boundary(end));
+ 
+diff --git a/library/alloc/src/vec.rs b/library/alloc/src/vec.rs
+index baa6c0919de..3d48a06fd24 100644
+--- a/library/alloc/src/vec.rs
++++ b/library/alloc/src/vec.rs
+@@ -1310,7 +1310,7 @@ impl<T> Vec<T> {
+         // the hole, and the vector length is restored to the new length.
+         //
+         let len = self.len();
+-        let Range { start, end } = self.check_range(range);
++        let Range { start, end } = slice::check_range(len, range);
+ 
+         unsafe {
+             // set self.vec length's to start, to be safe in case Drain is leaked
+diff --git a/library/alloc/tests/vec.rs b/library/alloc/tests/vec.rs
+index 53b0d0a2718..f3e6eb62926 100644
+--- a/library/alloc/tests/vec.rs
++++ b/library/alloc/tests/vec.rs
+@@ -880,7 +880,7 @@ fn test_from_iter_partially_drained_in_place_specialization() {
+ #[test]
+ fn test_from_iter_specialization_with_iterator_adapters() {
+     fn assert_in_place_trait<T: InPlaceIterable>(_: &T) {};
+-    let src: Vec<usize> = vec![0usize; 65535];
++    let src: Vec<usize> = vec![0usize; if cfg!(miri) { 256 } else { 65535 }];
+     let srcptr = src.as_ptr();
+     let iter = src
+         .into_iter()
+diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
+index 4c027b23584..b4531f2d18c 100644
+--- a/library/core/src/slice/mod.rs
++++ b/library/core/src/slice/mod.rs
+@@ -354,79 +354,6 @@ impl<T> [T] {
+         unsafe { &mut *index.get_unchecked_mut(self) }
+     }
+ 
+-    /// Converts a range over this slice to [`Range`].
+-    ///
+-    /// The returned range is safe to pass to [`get_unchecked`] and [`get_unchecked_mut`].
+-    ///
+-    /// [`get_unchecked`]: #method.get_unchecked
+-    /// [`get_unchecked_mut`]: #method.get_unchecked_mut
+-    ///
+-    /// # Panics
+-    ///
+-    /// Panics if the range is out of bounds.
+-    ///
+-    /// # Examples
+-    ///
+-    /// ```
+-    /// #![feature(slice_check_range)]
+-    ///
+-    /// let v = [10, 40, 30];
+-    /// assert_eq!(1..2, v.check_range(1..2));
+-    /// assert_eq!(0..2, v.check_range(..2));
+-    /// assert_eq!(1..3, v.check_range(1..));
+-    /// ```
+-    ///
+-    /// Panics when [`Index::index`] would panic:
+-    ///
+-    /// ```should_panic
+-    /// #![feature(slice_check_range)]
+-    ///
+-    /// [10, 40, 30].check_range(2..1);
+-    /// ```
+-    ///
+-    /// ```should_panic
+-    /// #![feature(slice_check_range)]
+-    ///
+-    /// [10, 40, 30].check_range(1..4);
+-    /// ```
+-    ///
+-    /// ```should_panic
+-    /// #![feature(slice_check_range)]
+-    ///
+-    /// [10, 40, 30].check_range(1..=usize::MAX);
+-    /// ```
+-    ///
+-    /// [`Index::index`]: ops::Index::index
+-    #[track_caller]
+-    #[unstable(feature = "slice_check_range", issue = "76393")]
+-    pub fn check_range<R: RangeBounds<usize>>(&self, range: R) -> Range<usize> {
+-        let start = match range.start_bound() {
+-            Bound::Included(&start) => start,
+-            Bound::Excluded(start) => {
+-                start.checked_add(1).unwrap_or_else(|| slice_start_index_overflow_fail())
+-            }
+-            Bound::Unbounded => 0,
+-        };
+-
+-        let len = self.len();
+-        let end = match range.end_bound() {
+-            Bound::Included(end) => {
+-                end.checked_add(1).unwrap_or_else(|| slice_end_index_overflow_fail())
+-            }
+-            Bound::Excluded(&end) => end,
+-            Bound::Unbounded => len,
+-        };
+-
+-        if start > end {
+-            slice_index_order_fail(start, end);
+-        }
+-        if end > len {
+-            slice_end_index_len_fail(end, len);
+-        }
+-
+-        Range { start, end }
+-    }
+-
+     /// Returns a raw pointer to the slice's buffer.
+     ///
+     /// The caller must ensure that the slice outlives the pointer this
+@@ -2770,7 +2697,7 @@ impl<T> [T] {
+     where
+         T: Copy,
+     {
+-        let Range { start: src_start, end: src_end } = self.check_range(src);
++        let Range { start: src_start, end: src_end } = check_range(self.len(), src);
+         let count = src_end - src_start;
+         assert!(dest <= self.len() - count, "dest is out of bounds");
+         // SAFETY: the conditions for `ptr::copy` have all been checked above,
+@@ -6660,6 +6587,79 @@ unsafe impl<'a, T> TrustedRandomAccess for RChunksExactMut<'a, T> {
+ // Free functions
+ //
+ 
++/// Converts a range over this slice to [`Range`].
++///
++/// The returned range is safe to pass to [`get_unchecked`] and [`get_unchecked_mut`].
++///
++/// [`get_unchecked`]: #method.get_unchecked
++/// [`get_unchecked_mut`]: #method.get_unchecked_mut
++///
++/// # Panics
++///
++/// Panics if the range is out of bounds.
++///
++/// # Examples
++///
++/// ```
++/// #![feature(slice_check_range)]
++/// use std::slice;
++///
++/// let v = [10, 40, 30];
++/// assert_eq!(1..2, slice::check_range(v.len(), 1..2));
++/// assert_eq!(0..2, slice::check_range(v.len(), ..2));
++/// assert_eq!(1..3, slice::check_range(v.len(), 1..));
++/// ```
++///
++/// Panics when [`Index::index`] would panic:
++///
++/// ```should_panic
++/// #![feature(slice_check_range)]
++///
++/// std::slice::check_range(3, 2..1);
++/// ```
++///
++/// ```should_panic
++/// #![feature(slice_check_range)]
++///
++/// std::slice::check_range(3, 1..4);
++/// ```
++///
++/// ```should_panic
++/// #![feature(slice_check_range)]
++///
++/// std::slice::check_range(3, 1..=usize::MAX);
++/// ```
++///
++/// [`Index::index`]: ops::Index::index
++#[track_caller]
++#[unstable(feature = "slice_check_range", issue = "76393")]
++pub fn check_range<R: RangeBounds<usize>>(len: usize, range: R) -> Range<usize> {
++    let start = match range.start_bound() {
++        Bound::Included(&start) => start,
++        Bound::Excluded(start) => {
++            start.checked_add(1).unwrap_or_else(|| slice_start_index_overflow_fail())
++        }
++        Bound::Unbounded => 0,
++    };
++
++    let end = match range.end_bound() {
++        Bound::Included(end) => {
++            end.checked_add(1).unwrap_or_else(|| slice_end_index_overflow_fail())
++        }
++        Bound::Excluded(&end) => end,
++        Bound::Unbounded => len,
++    };
++
++    if start > end {
++        slice_index_order_fail(start, end);
++    }
++    if end > len {
++        slice_end_index_len_fail(end, len);
++    }
++
++    Range { start, end }
++}
++
+ /// Forms a slice from a pointer and a length.
+ ///
+ /// The `len` argument is the number of **elements**, not the number of bytes.

rust-version

@@ -1 +1 @@
-nightly-2020-08-19
+nightly-2020-09-12