Rollup of 6 pull requests

compiler/rustc_data_structures/src/functor.rs

@@ -34,38 +34,43 @@ impl<T> IdFunctor for Vec<T> {
     type Inner = T;
 
     #[inline]
-    fn try_map_id<F, E>(mut self, mut f: F) -> Result<Self, E>
+    fn try_map_id<F, E>(self, mut f: F) -> Result<Self, E>
     where
         F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
     {
-        // FIXME: We don't really care about panics here and leak
-        // far more than we should, but that should be fine for now.
-        let len = self.len();
-        unsafe {
-            self.set_len(0);
-            let start = self.as_mut_ptr();
-            for i in 0..len {
-                let p = start.add(i);
-                match f(p.read()) {
-                    Ok(val) => p.write(val),
-                    Err(err) => {
-                        // drop all other elements in self
-                        // (current element was "moved" into the call to f)
-                        for j in (0..i).chain(i + 1..len) {
-                            start.add(j).drop_in_place();
-                        }
+        struct HoleVec<T> {
+            vec: Vec<mem::ManuallyDrop<T>>,
+            hole: Option<usize>,
+        }
 
-                        // returning will drop self, releasing the allocation
-                        // (len is 0 so elements will not be re-dropped)
-                        return Err(err);
+        impl<T> Drop for HoleVec<T> {
+            fn drop(&mut self) {
+                unsafe {
+                    for (index, slot) in self.vec.iter_mut().enumerate() {
+                        if self.hole != Some(index) {
+                            mem::ManuallyDrop::drop(slot);
+                        }
                     }
                 }
             }
-            // Even if we encountered an error, set the len back
-            // so we don't leak memory.
-            self.set_len(len);
         }
-        Ok(self)
+
+        unsafe {
+            let (ptr, length, capacity) = self.into_raw_parts();
+            let vec = Vec::from_raw_parts(ptr.cast(), length, capacity);
+            let mut hole_vec = HoleVec { vec, hole: None };
+
+            for (index, slot) in hole_vec.vec.iter_mut().enumerate() {
+                hole_vec.hole = Some(index);
+                let original = mem::ManuallyDrop::take(slot);
+                let mapped = f(original)?;
+                *slot = mem::ManuallyDrop::new(mapped);
+                hole_vec.hole = None;
+            }
+
+            mem::forget(hole_vec);
+            Ok(Vec::from_raw_parts(ptr, length, capacity))
+        }
     }
 }
 

compiler/rustc_data_structures/src/lib.rs

@@ -23,6 +23,7 @@
 #![feature(once_cell)]
 #![feature(test)]
 #![feature(thread_id_value)]
+#![feature(vec_into_raw_parts)]
 #![allow(rustc::default_hash_types)]
 #![deny(unaligned_references)]
 

library/core/src/array/mod.rs

@@ -645,6 +645,84 @@ impl<T, const N: usize> [T; N] {
     pub fn split_array_mut<const M: usize>(&mut self) -> (&mut [T; M], &mut [T]) {
         (&mut self[..]).split_array_mut::<M>()
     }
+
+    /// Divides one array reference into two at an index from the end.
+    ///
+    /// The first will contain all indices from `[0, N - M)` (excluding
+    /// the index `N - M` itself) and the second will contain all
+    /// indices from `[N - M, N)` (excluding the index `N` itself).
+    ///
+    /// # Panics
+    ///
+    /// Panics if `M > N`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(split_array)]
+    ///
+    /// let v = [1, 2, 3, 4, 5, 6];
+    ///
+    /// {
+    ///    let (left, right) = v.rsplit_array_ref::<0>();
+    ///    assert_eq!(left, &[1, 2, 3, 4, 5, 6]);
+    ///    assert_eq!(right, &[]);
+    /// }
+    ///
+    /// {
+    ///     let (left, right) = v.rsplit_array_ref::<2>();
+    ///     assert_eq!(left, &[1, 2, 3, 4]);
+    ///     assert_eq!(right, &[5, 6]);
+    /// }
+    ///
+    /// {
+    ///     let (left, right) = v.rsplit_array_ref::<6>();
+    ///     assert_eq!(left, &[]);
+    ///     assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
+    /// }
+    /// ```
+    #[unstable(
+        feature = "split_array",
+        reason = "return type should have array as 2nd element",
+        issue = "90091"
+    )]
+    #[inline]
+    pub fn rsplit_array_ref<const M: usize>(&self) -> (&[T], &[T; M]) {
+        (&self[..]).rsplit_array_ref::<M>()
+    }
+
+    /// Divides one mutable array reference into two at an index from the end.
+    ///
+    /// The first will contain all indices from `[0, N - M)` (excluding
+    /// the index `N - M` itself) and the second will contain all
+    /// indices from `[N - M, N)` (excluding the index `N` itself).
+    ///
+    /// # Panics
+    ///
+    /// Panics if `M > N`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(split_array)]
+    ///
+    /// let mut v = [1, 0, 3, 0, 5, 6];
+    /// let (left, right) = v.rsplit_array_mut::<4>();
+    /// assert_eq!(left, &mut [1, 0]);
+    /// assert_eq!(right, &mut [3, 0, 5, 6][..]);
+    /// left[1] = 2;
+    /// right[1] = 4;
+    /// assert_eq!(v, [1, 2, 3, 4, 5, 6]);
+    /// ```
+    #[unstable(
+        feature = "split_array",
+        reason = "return type should have array as 2nd element",
+        issue = "90091"
+    )]
+    #[inline]
+    pub fn rsplit_array_mut<const M: usize>(&mut self) -> (&mut [T], &mut [T; M]) {
+        (&mut self[..]).rsplit_array_mut::<M>()
+    }
 }
 
 /// Pulls `N` items from `iter` and returns them as an array. If the iterator

library/core/src/ptr/const_ptr.rs

@@ -48,6 +48,54 @@ impl<T: ?Sized> *const T {
         self as _
     }
 
+    /// Casts a pointer to its raw bits.
+    ///
+    /// This is equivalent to `as usize`, but is more specific to enhance readability.
+    /// The inverse method is [`from_bits`](#method.from_bits).
+    ///
+    /// In particular, `*p as usize` and `p as usize` will both compile for
+    /// pointers to numeric types but do very different things, so using this
+    /// helps emphasize that reading the bits was intentional.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ptr_to_from_bits)]
+    /// let array = [13, 42];
+    /// let p0: *const i32 = &array[0];
+    /// assert_eq!(<*const _>::from_bits(p0.to_bits()), p0);
+    /// let p1: *const i32 = &array[1];
+    /// assert_eq!(p1.to_bits() - p0.to_bits(), 4);
+    /// ```
+    #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
+    pub fn to_bits(self) -> usize
+    where
+        T: Sized,
+    {
+        self as usize
+    }
+
+    /// Creates a pointer from its raw bits.
+    ///
+    /// This is equivalent to `as *const T`, but is more specific to enhance readability.
+    /// The inverse method is [`to_bits`](#method.to_bits).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ptr_to_from_bits)]
+    /// use std::ptr::NonNull;
+    /// let dangling: *const u8 = NonNull::dangling().as_ptr();
+    /// assert_eq!(<*const u8>::from_bits(1), dangling);
+    /// ```
+    #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
+    pub fn from_bits(bits: usize) -> Self
+    where
+        T: Sized,
+    {
+        bits as Self
+    }
+
     /// Decompose a (possibly wide) pointer into its address and metadata components.
     ///
     /// The pointer can be later reconstructed with [`from_raw_parts`].

library/core/src/ptr/mut_ptr.rs

@@ -47,6 +47,55 @@ impl<T: ?Sized> *mut T {
         self as _
     }
 
+    /// Casts a pointer to its raw bits.
+    ///
+    /// This is equivalent to `as usize`, but is more specific to enhance readability.
+    /// The inverse method is [`from_bits`](#method.from_bits-1).
+    ///
+    /// In particular, `*p as usize` and `p as usize` will both compile for
+    /// pointers to numeric types but do very different things, so using this
+    /// helps emphasize that reading the bits was intentional.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ptr_to_from_bits)]
+    /// let mut array = [13, 42];
+    /// let mut it = array.iter_mut();
+    /// let p0: *mut i32 = it.next().unwrap();
+    /// assert_eq!(<*mut _>::from_bits(p0.to_bits()), p0);
+    /// let p1: *mut i32 = it.next().unwrap();
+    /// assert_eq!(p1.to_bits() - p0.to_bits(), 4);
+    /// ```
+    #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
+    pub fn to_bits(self) -> usize
+    where
+        T: Sized,
+    {
+        self as usize
+    }
+
+    /// Creates a pointer from its raw bits.
+    ///
+    /// This is equivalent to `as *mut T`, but is more specific to enhance readability.
+    /// The inverse method is [`to_bits`](#method.to_bits-1).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ptr_to_from_bits)]
+    /// use std::ptr::NonNull;
+    /// let dangling: *mut u8 = NonNull::dangling().as_ptr();
+    /// assert_eq!(<*mut u8>::from_bits(1), dangling);
+    /// ```
+    #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
+    pub fn from_bits(bits: usize) -> Self
+    where
+        T: Sized,
+    {
+        bits as Self
+    }
+
     /// Decompose a (possibly wide) pointer into its address and metadata components.
     ///
     /// The pointer can be later reconstructed with [`from_raw_parts_mut`].

library/core/src/slice/mod.rs

@@ -1705,6 +1705,84 @@ impl<T> [T] {
         unsafe { (&mut *(a.as_mut_ptr() as *mut [T; N]), b) }
     }
 
+    /// Divides one slice into an array and a remainder slice at an index from
+    /// the end.
+    ///
+    /// The slice will contain all indices from `[0, len - N)` (excluding
+    /// the index `len - N` itself) and the array will contain all
+    /// indices from `[len - N, len)` (excluding the index `len` itself).
+    ///
+    /// # Panics
+    ///
+    /// Panics if `N > len`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(split_array)]
+    ///
+    /// let v = &[1, 2, 3, 4, 5, 6][..];
+    ///
+    /// {
+    ///    let (left, right) = v.rsplit_array_ref::<0>();
+    ///    assert_eq!(left, [1, 2, 3, 4, 5, 6]);
+    ///    assert_eq!(right, &[]);
+    /// }
+    ///
+    /// {
+    ///     let (left, right) = v.rsplit_array_ref::<2>();
+    ///     assert_eq!(left, [1, 2, 3, 4]);
+    ///     assert_eq!(right, &[5, 6]);
+    /// }
+    ///
+    /// {
+    ///     let (left, right) = v.rsplit_array_ref::<6>();
+    ///     assert_eq!(left, []);
+    ///     assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
+    /// }
+    /// ```
+    #[unstable(feature = "split_array", reason = "new API", issue = "90091")]
+    #[inline]
+    pub fn rsplit_array_ref<const N: usize>(&self) -> (&[T], &[T; N]) {
+        assert!(N <= self.len());
+        let (a, b) = self.split_at(self.len() - N);
+        // SAFETY: b points to [T; N]? Yes it's [T] of length N (checked by split_at)
+        unsafe { (a, &*(b.as_ptr() as *const [T; N])) }
+    }
+
+    /// Divides one mutable slice into an array and a remainder slice at an
+    /// index from the end.
+    ///
+    /// The slice will contain all indices from `[0, len - N)` (excluding
+    /// the index `N` itself) and the array will contain all
+    /// indices from `[len - N, len)` (excluding the index `len` itself).
+    ///
+    /// # Panics
+    ///
+    /// Panics if `N > len`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(split_array)]
+    ///
+    /// let mut v = &mut [1, 0, 3, 0, 5, 6][..];
+    /// let (left, right) = v.rsplit_array_mut::<4>();
+    /// assert_eq!(left, [1, 0]);
+    /// assert_eq!(right, &mut [3, 0, 5, 6]);
+    /// left[1] = 2;
+    /// right[1] = 4;
+    /// assert_eq!(v, [1, 2, 3, 4, 5, 6]);
+    /// ```
+    #[unstable(feature = "split_array", reason = "new API", issue = "90091")]
+    #[inline]
+    pub fn rsplit_array_mut<const N: usize>(&mut self) -> (&mut [T], &mut [T; N]) {
+        assert!(N <= self.len());
+        let (a, b) = self.split_at_mut(self.len() - N);
+        // SAFETY: b points to [T; N]? Yes it's [T] of length N (checked by split_at_mut)
+        unsafe { (a, &mut *(b.as_mut_ptr() as *mut [T; N])) }
+    }
+
     /// Returns an iterator over subslices separated by elements that match
     /// `pred`. The matched element is not contained in the subslices.
     ///