Rollup of 10 pull requests

Cargo.lock

@@ -4624,6 +4624,10 @@ dependencies = [
  "walkdir",
 ]
 
+[[package]]
+name = "tier-check"
+version = "0.1.0"
+
 [[package]]
 name = "time"
 version = "0.1.42"

Cargo.toml

@@ -13,6 +13,7 @@ members = [
   "src/tools/rustbook",
   "src/tools/unstable-book-gen",
   "src/tools/tidy",
+  "src/tools/tier-check",
   "src/tools/build-manifest",
   "src/tools/remote-test-client",
   "src/tools/remote-test-server",

library/core/src/array/mod.rs

@@ -364,3 +364,66 @@ macro_rules! array_impl_default {
 }
 
 array_impl_default! {32, T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T}
+
+#[cfg(not(bootstrap))]
+#[lang = "array"]
+impl<T, const N: usize> [T; N] {
+    /// Returns an array of the same size as `self`, with function `f` applied to each element
+    /// in order.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(array_map)]
+    /// let x = [1, 2, 3];
+    /// let y = x.map(|v| v + 1);
+    /// assert_eq!(y, [2, 3, 4]);
+    ///
+    /// let x = [1, 2, 3];
+    /// let mut temp = 0;
+    /// let y = x.map(|v| { temp += 1; v * temp });
+    /// assert_eq!(y, [1, 4, 9]);
+    ///
+    /// let x = ["Ferris", "Bueller's", "Day", "Off"];
+    /// let y = x.map(|v| v.len());
+    /// assert_eq!(y, [6, 9, 3, 3]);
+    /// ```
+    #[unstable(feature = "array_map", issue = "75243")]
+    pub fn map<F, U>(self, mut f: F) -> [U; N]
+    where
+        F: FnMut(T) -> U,
+    {
+        use crate::mem::MaybeUninit;
+        struct Guard<T, const N: usize> {
+            dst: *mut T,
+            initialized: usize,
+        }
+
+        impl<T, const N: usize> Drop for Guard<T, N> {
+            fn drop(&mut self) {
+                debug_assert!(self.initialized <= N);
+
+                let initialized_part =
+                    crate::ptr::slice_from_raw_parts_mut(self.dst, self.initialized);
+                // SAFETY: this raw slice will contain only initialized objects
+                // that's why, it is allowed to drop it.
+                unsafe {
+                    crate::ptr::drop_in_place(initialized_part);
+                }
+            }
+        }
+        let mut dst = MaybeUninit::uninit_array::<N>();
+        let mut guard: Guard<U, N> =
+            Guard { dst: MaybeUninit::first_ptr_mut(&mut dst), initialized: 0 };
+        for (src, dst) in IntoIter::new(self).zip(&mut dst) {
+            dst.write(f(src));
+            guard.initialized += 1;
+        }
+        // FIXME: Convert to crate::mem::transmute once it works with generics.
+        // unsafe { crate::mem::transmute::<[MaybeUninit<U>; N], [U; N]>(dst) }
+        crate::mem::forget(guard);
+        // SAFETY: At this point we've properly initialized the whole array
+        // and we just need to cast it to the correct type.
+        unsafe { (&mut dst as *mut _ as *mut [U; N]).read() }
+    }
+}

library/core/src/lib.rs

@@ -145,6 +145,7 @@
 #![feature(abi_unadjusted)]
 #![feature(adx_target_feature)]
 #![feature(maybe_uninit_slice)]
+#![feature(maybe_uninit_extra)]
 #![feature(external_doc)]
 #![feature(associated_type_bounds)]
 #![feature(const_caller_location)]

library/core/tests/array.rs

@@ -290,3 +290,42 @@ fn empty_array_is_always_default() {
 
     let _arr = <[DoesNotImplDefault; 0]>::default();
 }
+
+#[test]
+fn array_map() {
+    let a = [1, 2, 3];
+    let b = a.map(|v| v + 1);
+    assert_eq!(b, [2, 3, 4]);
+
+    let a = [1u8, 2, 3];
+    let b = a.map(|v| v as u64);
+    assert_eq!(b, [1, 2, 3]);
+}
+
+#[test]
+fn array_map_drop_safety() {
+    use core::sync::atomic::AtomicUsize;
+    use core::sync::atomic::Ordering;
+    static DROPPED: AtomicUsize = AtomicUsize::new(0);
+    struct DropCounter;
+    impl Drop for DropCounter {
+        fn drop(&mut self) {
+            DROPPED.fetch_add(1, Ordering::SeqCst);
+        }
+    }
+
+    let num_to_create = 5;
+    let success = std::panic::catch_unwind(|| {
+        let items = [0; 10];
+        let mut nth = 0;
+        items.map(|_| {
+            if nth == num_to_create {
+                panic!("Oh no!");
+            }
+            nth += 1;
+            DropCounter
+        });
+    });
+    assert!(success.is_err());
+    assert_eq!(DROPPED.load(Ordering::SeqCst), num_to_create);
+}

library/core/tests/lib.rs

@@ -1,5 +1,6 @@
 #![feature(alloc_layout_extra)]
 #![feature(array_chunks)]
+#![feature(array_map)]
 #![feature(bool_to_option)]
 #![feature(bound_cloned)]
 #![feature(box_syntax)]

library/std/src/primitive_docs.rs

@@ -768,7 +768,8 @@ mod prim_tuple {}
 ///
 /// This type can represent a wide range of decimal numbers, like `3.5`, `27`,
 /// `-113.75`, `0.0078125`, `34359738368`, `0`, `-1`. So unlike integer types
-/// (like `i32`), floating point types can represent non-integer numbers, too.
+/// (such as `i32`), floating point types can represent non-integer numbers,
+/// too.
 ///
 /// However, being able to represent this wide range of numbers comes at the
 /// cost of precision: floats can only represent some of the real numbers and
@@ -779,15 +780,12 @@ mod prim_tuple {}
 /// often discard insignificant digits: `println!("{}", 1.0f32 / 5.0f32)` will
 /// print `0.2`.
 ///
-/// The precision is better for numbers near 0 and worse for large numbers. For
-/// example, above 2<sup>24</sup>, not even all integers are representable.
-///
 /// Additionally, `f32` can represent a couple of special values:
 ///
 /// - `-0`: this is just due to how floats are encoded. It is semantically
 ///   equivalent to `0` and `-0.0 == 0.0` results in `true`.
 /// - [∞](#associatedconstant.INFINITY) and
-///   [-∞](#associatedconstant.NEG_INFINITY): these result from calculations
+///   [−∞](#associatedconstant.NEG_INFINITY): these result from calculations
 ///   like `1.0 / 0.0`.
 /// - [NaN (not a number)](#associatedconstant.NAN): this value results from
 ///   calculations like `(-1.0).sqrt()`. NaN has some potentially unexpected