rust-lang · bors · Jul 24, 2024 · Jun 4, 2024 · Jul 8, 2024 · Jul 21, 2024
diff --git a/library/alloc/src/collections/binary_heap/mod.rs b/library/alloc/src/collections/binary_heap/mod.rs
@@ -484,7 +484,7 @@ impl<T: Ord, A: Allocator> BinaryHeap<T, A> {
     /// heap.push(4);
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_binary_heap_new_in", issue = "112353")]
+    #[rustc_const_unstable(feature = "const_binary_heap_new_in", issue = "125961")]
     #[must_use]
     pub const fn new_in(alloc: A) -> BinaryHeap<T, A> {
         BinaryHeap { data: Vec::new_in(alloc) }

diff --git a/library/alloc/src/str.rs b/library/alloc/src/str.rs
@@ -269,7 +269,7 @@ impl str {
                   without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn replace<'a, P: Pattern<'a>>(&'a self, from: P, to: &str) -> String {
+    pub fn replace<P: Pattern>(&self, from: P, to: &str) -> String {
         let mut result = String::new();
         let mut last_end = 0;
         for (start, part) in self.match_indices(from) {
@@ -309,7 +309,7 @@ impl str {
     #[must_use = "this returns the replaced string as a new allocation, \
                   without modifying the original"]
     #[stable(feature = "str_replacen", since = "1.16.0")]
-    pub fn replacen<'a, P: Pattern<'a>>(&'a self, pat: P, to: &str, count: usize) -> String {
+    pub fn replacen<P: Pattern>(&self, pat: P, to: &str, count: usize) -> String {
         // Hope to reduce the times of re-allocation
         let mut result = String::with_capacity(32);
         let mut last_end = 0;

diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
@@ -1497,10 +1497,7 @@ impl String {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "string_remove_matches", reason = "new API", issue = "72826")]
-    pub fn remove_matches<'a, P>(&'a mut self, pat: P)
-    where
-        P: for<'x> Pattern<'x>,
-    {
+    pub fn remove_matches<P: Pattern>(&mut self, pat: P) {
         use core::str::pattern::Searcher;
 
         let rejections = {
@@ -2288,35 +2285,41 @@ impl<'a> Extend<Cow<'a, str>> for String {
     reason = "API not fully fleshed out and ready to be stabilized",
     issue = "27721"
 )]
-impl<'a, 'b> Pattern<'a> for &'b String {
-    type Searcher = <&'b str as Pattern<'a>>::Searcher;
+impl<'b> Pattern for &'b String {
+    type Searcher<'a> = <&'b str as Pattern>::Searcher<'a>;
 
-    fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher {
+    fn into_searcher(self, haystack: &str) -> <&'b str as Pattern>::Searcher<'_> {
         self[..].into_searcher(haystack)
     }
 
     #[inline]
-    fn is_contained_in(self, haystack: &'a str) -> bool {
+    fn is_contained_in(self, haystack: &str) -> bool {
         self[..].is_contained_in(haystack)
     }
 
     #[inline]
-    fn is_prefix_of(self, haystack: &'a str) -> bool {
+    fn is_prefix_of(self, haystack: &str) -> bool {
         self[..].is_prefix_of(haystack)
     }
 
     #[inline]
-    fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> {
+    fn strip_prefix_of(self, haystack: &str) -> Option<&str> {
         self[..].strip_prefix_of(haystack)
     }
 
     #[inline]
-    fn is_suffix_of(self, haystack: &'a str) -> bool {
+    fn is_suffix_of<'a>(self, haystack: &'a str) -> bool
+    where
+        Self::Searcher<'a>: core::str::pattern::ReverseSearcher<'a>,
+    {
         self[..].is_suffix_of(haystack)
     }
 
     #[inline]
-    fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> {
+    fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&str>
+    where
+        Self::Searcher<'a>: core::str::pattern::ReverseSearcher<'a>,
+    {
         self[..].strip_suffix_of(haystack)
     }
 }

diff --git a/library/alloc/tests/str.rs b/library/alloc/tests/str.rs
@@ -1927,12 +1927,10 @@ mod pattern {
         }
     }
 
-    fn cmp_search_to_vec<'a>(
-        rev: bool,
-        pat: impl Pattern<'a, Searcher: ReverseSearcher<'a>>,
-        haystack: &'a str,
-        right: Vec<SearchStep>,
-    ) {
+    fn cmp_search_to_vec<P>(rev: bool, pat: P, haystack: &str, right: Vec<SearchStep>)
+    where
+        P: for<'a> Pattern<Searcher<'a>: ReverseSearcher<'a>>,
+    {
         let mut searcher = pat.into_searcher(haystack);
         let mut v = vec![];
         loop {
@@ -2191,9 +2189,9 @@ generate_iterator_test! {
 fn different_str_pattern_forwarding_lifetimes() {
     use std::str::pattern::Pattern;
 
-    fn foo<'a, P>(p: P)
+    fn foo<P>(p: P)
     where
-        for<'b> &'b P: Pattern<'a>,
+        for<'b> &'b P: Pattern,
     {
         for _ in 0..3 {
             "asdf".find(&p);

diff --git a/library/core/src/primitive.rs b/library/core/src/primitive.rs
@@ -12,7 +12,7 @@
 //!     const SOME_PROPERTY: bool = true;
 //! }
 //!
-//! # trait QueryId { const SOME_PROPERTY: core::primitive::bool; }
+//! # trait QueryId { const SOME_PROPERTY: ::core::primitive::bool; }
 //! ```
 //!
 //! Note that the `SOME_PROPERTY` associated constant would not compile, as its
@@ -25,11 +25,17 @@
 //! pub struct bool;
 //!
 //! impl QueryId for bool {
-//!     const SOME_PROPERTY: core::primitive::bool = true;
+//!     const SOME_PROPERTY: ::core::primitive::bool = true;
 //! }
 //!
-//! # trait QueryId { const SOME_PROPERTY: core::primitive::bool; }
+//! # trait QueryId { const SOME_PROPERTY: ::core::primitive::bool; }
 //! ```
+//!
+//! We also used `::core` instead of `core`, because `core` can be
+//! shadowed, too. Paths, starting with `::`, are searched in
+//! the [extern prelude] since Edition 2018.
+//!
+//! [extern prelude]: https://doc.rust-lang.org/nightly/reference/names/preludes.html#extern-prelude
 
 #[stable(feature = "core_primitive", since = "1.43.0")]
 pub use bool;

diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
@@ -4522,6 +4522,121 @@ impl<T> [T] {
         // are disjunct and in bounds.
         unsafe { Ok(self.get_many_unchecked_mut(indices)) }
     }
+
+    /// Returns the index that an element reference points to.
+    ///
+    /// Returns `None` if `element` does not point within the slice or if it points between elements.
+    ///
+    /// This method is useful for extending slice iterators like [`slice::split`].
+    ///
+    /// Note that this uses pointer arithmetic and **does not compare elements**.
+    /// To find the index of an element via comparison, use
+    /// [`.iter().position()`](crate::iter::Iterator::position) instead.
+    ///
+    /// # Panics
+    /// Panics if `T` is zero-sized.
+    ///
+    /// # Examples
+    /// Basic usage:
+    /// ```
+    /// #![feature(substr_range)]
+    ///
+    /// let nums: &[u32] = &[1, 7, 1, 1];
+    /// let num = &nums[2];
+    ///
+    /// assert_eq!(num, &1);
+    /// assert_eq!(nums.elem_offset(num), Some(2));
+    /// ```
+    /// Returning `None` with an in-between element:
+    /// ```
+    /// #![feature(substr_range)]
+    ///
+    /// let arr: &[[u32; 2]] = &[[0, 1], [2, 3]];
+    /// let flat_arr: &[u32] = arr.as_flattened();
+    ///
+    /// let ok_elm: &[u32; 2] = flat_arr[0..2].try_into().unwrap();
+    /// let weird_elm: &[u32; 2] = flat_arr[1..3].try_into().unwrap();
+    ///
+    /// assert_eq!(ok_elm, &[0, 1]);
+    /// assert_eq!(weird_elm, &[1, 2]);
+    ///
+    /// assert_eq!(arr.elem_offset(ok_elm), Some(0)); // Points to element 0
+    /// assert_eq!(arr.elem_offset(weird_elm), None); // Points between element 0 and 1
+    /// ```
+    #[must_use]
+    #[unstable(feature = "substr_range", issue = "126769")]
+    pub fn elem_offset(&self, element: &T) -> Option<usize> {
+        if T::IS_ZST {
+            panic!("elements are zero-sized");
+        }
+
+        let self_start = self.as_ptr() as usize;
+        let elem_start = element as *const T as usize;
+
+        let byte_offset = elem_start.wrapping_sub(self_start);
+
+        if byte_offset % mem::size_of::<T>() != 0 {
+            return None;
+        }
+
+        let offset = byte_offset / mem::size_of::<T>();
+
+        if offset < self.len() { Some(offset) } else { None }
+    }
+
+    /// Returns the range of indices that a subslice points to.
+    ///
+    /// Returns `None` if `subslice` does not point within the slice or if it points between elements.
+    ///
+    /// This method **does not compare elements**. Instead, this method finds the location in the slice that
+    /// `subslice` was obtained from. To find the index of a subslice via comparison, instead use
+    /// [`.windows()`](slice::windows)[`.position()`](crate::iter::Iterator::position).
+    ///
+    /// This method is useful for extending slice iterators like [`slice::split`].
+    ///
+    /// Note that this may return a false positive (either `Some(0..0)` or `Some(self.len()..self.len())`)
+    /// if `subslice` has a length of zero and points to the beginning or end of another, separate, slice.
+    ///
+    /// # Panics
+    /// Panics if `T` is zero-sized.
+    ///
+    /// # Examples
+    /// Basic usage:
+    /// ```
+    /// #![feature(substr_range)]
+    ///
+    /// let nums = &[0, 5, 10, 0, 0, 5];
+    ///
+    /// let mut iter = nums
+    ///     .split(|t| *t == 0)
+    ///     .map(|n| nums.subslice_range(n).unwrap());
+    ///
+    /// assert_eq!(iter.next(), Some(0..0));
+    /// assert_eq!(iter.next(), Some(1..3));
+    /// assert_eq!(iter.next(), Some(4..4));
+    /// assert_eq!(iter.next(), Some(5..6));
+    /// ```
+    #[must_use]
+    #[unstable(feature = "substr_range", issue = "126769")]
+    pub fn subslice_range(&self, subslice: &[T]) -> Option<Range<usize>> {
+        if T::IS_ZST {
+            panic!("elements are zero-sized");
+        }
+
+        let self_start = self.as_ptr() as usize;
+        let subslice_start = subslice.as_ptr() as usize;
+
+        let byte_start = subslice_start.wrapping_sub(self_start);
+
+        if byte_start % core::mem::size_of::<T>() != 0 {
+            return None;
+        }
+
+        let start = byte_start / core::mem::size_of::<T>();
+        let end = start.wrapping_add(subslice.len());
+
+        if start <= self.len() && end <= self.len() { Some(start..end) } else { None }
+    }
 }
 
 impl<T, const N: usize> [[T; N]] {