Auto merge of rust-lang#83360 - Dylan-DPC:rollup-17xulpv, r=Dylan-DPC

Rollup of 9 pull requests

Successful merges:

 - rust-lang#80193 (stabilize `feature(osstring_ascii)`)
 - rust-lang#80771 (Make NonNull::as_ref (and friends) return refs with unbound lifetimes)
 - rust-lang#81607 (Implement TrustedLen and TrustedRandomAccess for Range<integer>, array::IntoIter, VecDequeue's iterators)
 - rust-lang#82554 (Fix invalid slice access in String::retain)
 - rust-lang#82686 (Move `std::sys::unix::platform` to `std::sys::unix::ext`)
 - rust-lang#82771 (slice: Stabilize IterMut::as_slice.)
 - rust-lang#83329 (Cleanup LLVM debuginfo module docs)
 - rust-lang#83336 (Fix ICE with `use clippy::a::b;`)
 - rust-lang#83350 (Download a more recent LLVM version if `src/version` is modified)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

alloc/src/collections/vec_deque/into_iter.rs

@@ -1,5 +1,5 @@
 use core::fmt;
-use core::iter::FusedIterator;
+use core::iter::{FusedIterator, TrustedLen, TrustedRandomAccess};
 
 use super::VecDeque;
 
@@ -36,6 +36,22 @@ impl<T> Iterator for IntoIter<T> {
         let len = self.inner.len();
         (len, Some(len))
     }
+
+    #[inline]
+    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item
+    where
+        Self: TrustedRandomAccess,
+    {
+        // Safety: The TrustedRandomAccess contract requires that callers only pass an index
+        // that is in bounds.
+        // Additionally Self: TrustedRandomAccess is only implemented for T: Copy which means even
+        // multiple repeated reads of the same index would be safe and the
+        // values are !Drop, thus won't suffer from double drops.
+        unsafe {
+            let idx = self.inner.wrap_add(self.inner.tail, idx);
+            self.inner.buffer_read(idx)
+        }
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -55,3 +71,17 @@ impl<T> ExactSizeIterator for IntoIter<T> {
 
 #[stable(feature = "fused", since = "1.26.0")]
 impl<T> FusedIterator for IntoIter<T> {}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T> TrustedLen for IntoIter<T> {}
+
+#[doc(hidden)]
+#[unstable(feature = "trusted_random_access", issue = "none")]
+// T: Copy as approximation for !Drop since get_unchecked does not update the pointers
+// and thus we can't implement drop-handling
+unsafe impl<T> TrustedRandomAccess for IntoIter<T>
+where
+    T: Copy,
+{
+    const MAY_HAVE_SIDE_EFFECT: bool = false;
+}

alloc/src/collections/vec_deque/iter.rs

@@ -1,5 +1,5 @@
 use core::fmt;
-use core::iter::FusedIterator;
+use core::iter::{FusedIterator, TrustedLen, TrustedRandomAccess};
 use core::ops::Try;
 
 use super::{count, wrap_index, RingSlices};
@@ -101,6 +101,19 @@ impl<'a, T> Iterator for Iter<'a, T> {
     fn last(mut self) -> Option<&'a T> {
         self.next_back()
     }
+
+    #[inline]
+    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item
+    where
+        Self: TrustedRandomAccess,
+    {
+        // Safety: The TrustedRandomAccess contract requires that callers only  pass an index
+        // that is in bounds.
+        unsafe {
+            let idx = wrap_index(self.tail.wrapping_add(idx), self.ring.len());
+            self.ring.get_unchecked(idx)
+        }
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -157,3 +170,12 @@ impl<T> ExactSizeIterator for Iter<'_, T> {
 
 #[stable(feature = "fused", since = "1.26.0")]
 impl<T> FusedIterator for Iter<'_, T> {}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T> TrustedLen for Iter<'_, T> {}
+
+#[doc(hidden)]
+#[unstable(feature = "trusted_random_access", issue = "none")]
+unsafe impl<T> TrustedRandomAccess for Iter<'_, T> {
+    const MAY_HAVE_SIDE_EFFECT: bool = false;
+}

alloc/src/collections/vec_deque/iter_mut.rs

@@ -1,5 +1,5 @@
 use core::fmt;
-use core::iter::FusedIterator;
+use core::iter::{FusedIterator, TrustedLen, TrustedRandomAccess};
 use core::marker::PhantomData;
 
 use super::{count, wrap_index, RingSlices};
@@ -87,6 +87,19 @@ impl<'a, T> Iterator for IterMut<'a, T> {
     fn last(mut self) -> Option<&'a mut T> {
         self.next_back()
     }
+
+    #[inline]
+    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item
+    where
+        Self: TrustedRandomAccess,
+    {
+        // Safety: The TrustedRandomAccess contract requires that callers only  pass an index
+        // that is in bounds.
+        unsafe {
+            let idx = wrap_index(self.tail.wrapping_add(idx), self.ring.len());
+            &mut *self.ring.get_unchecked_mut(idx)
+        }
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -126,3 +139,12 @@ impl<T> ExactSizeIterator for IterMut<'_, T> {
 
 #[stable(feature = "fused", since = "1.26.0")]
 impl<T> FusedIterator for IterMut<'_, T> {}
+
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T> TrustedLen for IterMut<'_, T> {}
+
+#[doc(hidden)]
+#[unstable(feature = "trusted_random_access", issue = "none")]
+unsafe impl<T> TrustedRandomAccess for IterMut<'_, T> {
+    const MAY_HAVE_SIDE_EFFECT: bool = false;
+}

alloc/src/collections/vec_deque/mod.rs

@@ -58,7 +58,7 @@ mod tests;
 const INITIAL_CAPACITY: usize = 7; // 2^3 - 1
 const MINIMUM_CAPACITY: usize = 1; // 2 - 1
 
-const MAXIMUM_ZST_CAPACITY: usize = 1 << (core::mem::size_of::<usize>() * 8 - 1); // Largest possible power of two
+const MAXIMUM_ZST_CAPACITY: usize = 1 << (usize::BITS - 1); // Largest possible power of two
 
 /// A double-ended queue implemented with a growable ring buffer.
 ///

alloc/src/string.rs

@@ -1289,37 +1289,44 @@ impl String {
     where
         F: FnMut(char) -> bool,
     {
-        let len = self.len();
-        let mut del_bytes = 0;
-        let mut idx = 0;
+        struct SetLenOnDrop<'a> {
+            s: &'a mut String,
+            idx: usize,
+            del_bytes: usize,
+        }
 
-        unsafe {
-            self.vec.set_len(0);
+        impl<'a> Drop for SetLenOnDrop<'a> {
+            fn drop(&mut self) {
+                let new_len = self.idx - self.del_bytes;
+                debug_assert!(new_len <= self.s.len());
+                unsafe { self.s.vec.set_len(new_len) };
+            }
         }
 
-        while idx < len {
-            let ch = unsafe { self.get_unchecked(idx..len).chars().next().unwrap() };
+        let len = self.len();
+        let mut guard = SetLenOnDrop { s: self, idx: 0, del_bytes: 0 };
+
+        while guard.idx < len {
+            let ch = unsafe { guard.s.get_unchecked(guard.idx..len).chars().next().unwrap() };
             let ch_len = ch.len_utf8();
 
             if !f(ch) {
-                del_bytes += ch_len;
-            } else if del_bytes > 0 {
+                guard.del_bytes += ch_len;
+            } else if guard.del_bytes > 0 {
                 unsafe {
                     ptr::copy(
-                        self.vec.as_ptr().add(idx),
-                        self.vec.as_mut_ptr().add(idx - del_bytes),
+                        guard.s.vec.as_ptr().add(guard.idx),
+                        guard.s.vec.as_mut_ptr().add(guard.idx - guard.del_bytes),
                         ch_len,
                     );
                 }
             }
 
             // Point idx to the next char
-            idx += ch_len;
+            guard.idx += ch_len;
         }
 
-        unsafe {
-            self.vec.set_len(len - del_bytes);
-        }
+        drop(guard);
     }
 
     /// Inserts a character into this `String` at a byte position.

core/src/array/iter.rs

@@ -2,7 +2,7 @@
 
 use crate::{
     fmt,
-    iter::{ExactSizeIterator, FusedIterator, TrustedLen},
+    iter::{ExactSizeIterator, FusedIterator, TrustedLen, TrustedRandomAccess},
     mem::{self, MaybeUninit},
     ops::Range,
     ptr,
@@ -130,6 +130,18 @@ impl<T, const N: usize> Iterator for IntoIter<T, N> {
     fn last(mut self) -> Option<Self::Item> {
         self.next_back()
     }
+
+    #[inline]
+    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item
+    where
+        Self: TrustedRandomAccess,
+    {
+        // SAFETY: Callers are only allowed to pass an index that is in bounds
+        // Additionally Self: TrustedRandomAccess is only implemented for T: Copy which means even
+        // multiple repeated reads of the same index would be safe and the
+        // values aree !Drop, thus won't suffer from double drops.
+        unsafe { self.data.get_unchecked(self.alive.start + idx).assume_init_read() }
+    }
 }
 
 #[stable(feature = "array_value_iter_impls", since = "1.40.0")]
@@ -184,6 +196,17 @@ impl<T, const N: usize> FusedIterator for IntoIter<T, N> {}
 #[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 unsafe impl<T, const N: usize> TrustedLen for IntoIter<T, N> {}
 
+#[doc(hidden)]
+#[unstable(feature = "trusted_random_access", issue = "none")]
+// T: Copy as approximation for !Drop since get_unchecked does not update the pointers
+// and thus we can't implement drop-handling
+unsafe impl<T, const N: usize> TrustedRandomAccess for IntoIter<T, N>
+where
+    T: Copy,
+{
+    const MAY_HAVE_SIDE_EFFECT: bool = false;
+}
+
 #[stable(feature = "array_value_iter_impls", since = "1.40.0")]
 impl<T: Clone, const N: usize> Clone for IntoIter<T, N> {
     fn clone(&self) -> Self {

core/src/iter/range.rs

@@ -3,7 +3,7 @@ use crate::convert::TryFrom;
 use crate::mem;
 use crate::ops::{self, Try};
 
-use super::{FusedIterator, TrustedLen};
+use super::{FusedIterator, TrustedLen, TrustedRandomAccess};
 
 /// Objects that have a notion of *successor* and *predecessor* operations.
 ///
@@ -493,6 +493,18 @@ macro_rules! range_exact_iter_impl {
     )*)
 }
 
+/// Safety: This macro must only be used on types that are `Copy` and result in ranges
+/// which have an exact `size_hint()` where the upper bound must not be `None`.
+macro_rules! unsafe_range_trusted_random_access_impl {
+    ($($t:ty)*) => ($(
+        #[doc(hidden)]
+        #[unstable(feature = "trusted_random_access", issue = "none")]
+        unsafe impl TrustedRandomAccess for ops::Range<$t> {
+            const MAY_HAVE_SIDE_EFFECT: bool = false;
+        }
+    )*)
+}
+
 macro_rules! range_incl_exact_iter_impl {
     ($($t:ty)*) => ($(
         #[stable(feature = "inclusive_range", since = "1.26.0")]
@@ -553,6 +565,18 @@ impl<A: Step> Iterator for ops::Range<A> {
     fn max(mut self) -> Option<A> {
         self.next_back()
     }
+
+    #[inline]
+    unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> Self::Item
+    where
+        Self: TrustedRandomAccess,
+    {
+        // SAFETY: The TrustedRandomAccess contract requires that callers only  pass an index
+        // that is in bounds.
+        // Additionally Self: TrustedRandomAccess is only implemented for Copy types
+        // which means even repeated reads of the same index would be safe.
+        unsafe { Step::forward_unchecked(self.start.clone(), idx) }
+    }
 }
 
 // These macros generate `ExactSizeIterator` impls for various range types.
@@ -574,6 +598,23 @@ range_exact_iter_impl! {
     u32
     i32
 }
+
+unsafe_range_trusted_random_access_impl! {
+    usize u8 u16
+    isize i8 i16
+}
+
+#[cfg(target_pointer_width = "32")]
+unsafe_range_trusted_random_access_impl! {
+    u32 i32
+}
+
+#[cfg(target_pointer_width = "64")]
+unsafe_range_trusted_random_access_impl! {
+    u32 i32
+    u64 i64
+}
+
 range_incl_exact_iter_impl! {
     u8
     i8

core/src/ptr/non_null.rs

@@ -110,7 +110,7 @@ impl<T: Sized> NonNull<T> {
     /// [the module documentation]: crate::ptr#safety
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    pub unsafe fn as_uninit_ref(&self) -> &MaybeUninit<T> {
+    pub unsafe fn as_uninit_ref<'a>(&self) -> &'a MaybeUninit<T> {
         // SAFETY: the caller must guarantee that `self` meets all the
         // requirements for a reference.
         unsafe { &*self.cast().as_ptr() }
@@ -142,7 +142,7 @@ impl<T: Sized> NonNull<T> {
     /// [the module documentation]: crate::ptr#safety
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    pub unsafe fn as_uninit_mut(&mut self) -> &mut MaybeUninit<T> {
+    pub unsafe fn as_uninit_mut<'a>(&mut self) -> &'a mut MaybeUninit<T> {
         // SAFETY: the caller must guarantee that `self` meets all the
         // requirements for a reference.
         unsafe { &mut *self.cast().as_ptr() }
@@ -244,7 +244,7 @@ impl<T: ?Sized> NonNull<T> {
     /// [the module documentation]: crate::ptr#safety
     #[stable(feature = "nonnull", since = "1.25.0")]
     #[inline]
-    pub unsafe fn as_ref(&self) -> &T {
+    pub unsafe fn as_ref<'a>(&self) -> &'a T {
         // SAFETY: the caller must guarantee that `self` meets all the
         // requirements for a reference.
         unsafe { &*self.as_ptr() }
@@ -280,7 +280,7 @@ impl<T: ?Sized> NonNull<T> {
     /// [the module documentation]: crate::ptr#safety
     #[stable(feature = "nonnull", since = "1.25.0")]
     #[inline]
-    pub unsafe fn as_mut(&mut self) -> &mut T {
+    pub unsafe fn as_mut<'a>(&mut self) -> &'a mut T {
         // SAFETY: the caller must guarantee that `self` meets all the
         // requirements for a mutable reference.
         unsafe { &mut *self.as_ptr() }
@@ -427,7 +427,7 @@ impl<T> NonNull<[T]> {
     /// [valid]: crate::ptr#safety
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    pub unsafe fn as_uninit_slice(&self) -> &[MaybeUninit<T>] {
+    pub unsafe fn as_uninit_slice<'a>(&self) -> &'a [MaybeUninit<T>] {
         // SAFETY: the caller must uphold the safety contract for `as_uninit_slice`.
         unsafe { slice::from_raw_parts(self.cast().as_ptr(), self.len()) }
     }
@@ -488,7 +488,7 @@ impl<T> NonNull<[T]> {
     /// ```
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
-    pub unsafe fn as_uninit_slice_mut(&self) -> &mut [MaybeUninit<T>] {
+    pub unsafe fn as_uninit_slice_mut<'a>(&self) -> &'a mut [MaybeUninit<T>] {
         // SAFETY: the caller must uphold the safety contract for `as_uninit_slice_mut`.
         unsafe { slice::from_raw_parts_mut(self.cast().as_ptr(), self.len()) }
     }

core/src/slice/iter.rs

@@ -286,7 +286,6 @@ impl<'a, T> IterMut<'a, T> {
     /// Basic usage:
     ///
     /// ```
-    /// # #![feature(slice_iter_mut_as_slice)]
     /// let mut slice: &mut [usize] = &mut [1, 2, 3];
     ///
     /// // First, we get the iterator:
@@ -299,12 +298,19 @@ impl<'a, T> IterMut<'a, T> {
     /// // Now `as_slice` returns "[2, 3]":
     /// assert_eq!(iter.as_slice(), &[2, 3]);
     /// ```
-    #[unstable(feature = "slice_iter_mut_as_slice", reason = "recently added", issue = "58957")]
+    #[stable(feature = "slice_iter_mut_as_slice", since = "1.53.0")]
     pub fn as_slice(&self) -> &[T] {
         self.make_slice()
     }
 }
 
+#[stable(feature = "slice_iter_mut_as_slice", since = "1.53.0")]
+impl<T> AsRef<[T]> for IterMut<'_, T> {
+    fn as_ref(&self) -> &[T] {
+        self.as_slice()
+    }
+}
+
 iterator! {struct IterMut -> *mut T, &'a mut T, mut, {mut}, {}}
 
 /// An internal abstraction over the splitting iterators, so that