Auto merge of #68067 - JohnTitor:rollup-vsj5won, r=JohnTitor

Rollup of 10 pull requests

Successful merges:

 - #66254 (Make Layout::new const)
 - #67122 (Do not deduplicate diagnostics in UI tests)
 - #67358 (Add HashSet::get_or_insert_owned)
 - #67725 (Simplify into_key_slice_mut)
 - #67935 (Relax the Sized bounds on Pin::map_unchecked(_mut))
 - #67967 (Delay bug to prevent ICE in MIR borrowck)
 - #67975 (Export public scalar statics in wasm)
 - #68006 (Recognise riscv64 in compiletest)
 - #68040 (Cleanup)
 - #68054 (doc: add Null-unchecked version section to mut pointer as_mut method)

Failed merges:

 - #67258 (Introduce `X..`, `..X`, and `..=X` range patterns)

r? @ghost

3 files changed, 19 insertions, 3 deletions

diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index b2d4b1b5fb9..163f9170b8b 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -17,7 +17,7 @@ use crate::usize;
 #[derive(Debug)]
 pub struct Excess(pub NonNull<u8>, pub usize);
 
-fn size_align<T>() -> (usize, usize) {
+const fn size_align<T>() -> (usize, usize) {
     (mem::size_of::<T>(), mem::align_of::<T>())
 }
 
@@ -120,14 +120,14 @@ impl Layout {
 
     /// Constructs a `Layout` suitable for holding a value of type `T`.
     #[stable(feature = "alloc_layout", since = "1.28.0")]
+    #[rustc_const_stable(feature = "alloc_layout_const_new", since = "1.42.0")]
     #[inline]
-    pub fn new<T>() -> Self {
+    pub const fn new<T>() -> Self {
         let (size, align) = size_align::<T>();
         // Note that the align is guaranteed by rustc to be a power of two and
         // the size+align combo is guaranteed to fit in our address space. As a
         // result use the unchecked constructor here to avoid inserting code
         // that panics if it isn't optimized well enough.
-        debug_assert!(Layout::from_size_align(size, align).is_ok());
         unsafe { Layout::from_size_align_unchecked(size, align) }
     }
 
diff --git a/src/libcore/pin.rs b/src/libcore/pin.rs
index aca6fb20138..676d2c784ac 100644
--- a/src/libcore/pin.rs
+++ b/src/libcore/pin.rs
@@ -672,6 +672,7 @@ impl<'a, T: ?Sized> Pin<&'a T> {
     #[stable(feature = "pin", since = "1.33.0")]
     pub unsafe fn map_unchecked<U, F>(self, func: F) -> Pin<&'a U>
     where
+        U: ?Sized,
         F: FnOnce(&T) -> &U,
     {
         let pointer = &*self.pointer;
@@ -763,6 +764,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
     #[stable(feature = "pin", since = "1.33.0")]
     pub unsafe fn map_unchecked_mut<U, F>(self, func: F) -> Pin<&'a mut U>
     where
+        U: ?Sized,
         F: FnOnce(&mut T) -> &mut U,
     {
         let pointer = Pin::get_unchecked_mut(self);
diff --git a/src/libcore/ptr/mut_ptr.rs b/src/libcore/ptr/mut_ptr.rs
index b3bb2f179b1..4bc0a3e9faa 100644
--- a/src/libcore/ptr/mut_ptr.rs
+++ b/src/libcore/ptr/mut_ptr.rs
@@ -250,6 +250,20 @@ impl<T: ?Sized> *mut T {
     /// *first_value = 4;
     /// println!("{:?}", s); // It'll print: "[4, 2, 3]".
     /// ```
+    ///
+    /// # Null-unchecked version
+    ///
+    /// If you are sure the pointer can never be null and are looking for some kind of
+    /// `as_mut_unchecked` that returns the `&mut T` instead of `Option<&mut T>`, know that
+    /// you can dereference the pointer directly.
+    ///
+    /// ```
+    /// let mut s = [1, 2, 3];
+    /// let ptr: *mut u32 = s.as_mut_ptr();
+    /// let first_value = unsafe { &mut *ptr };
+    /// *first_value = 4;
+    /// println!("{:?}", s); // It'll print: "[4, 2, 3]".
+    /// ```
     #[stable(feature = "ptr_as_ref", since = "1.9.0")]
     #[inline]
     pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {