Auto merge of rust-lang#62561 - Centril:rollup-5pxj3bo, r=Centril

Rollup of 5 pull requests

Successful merges:

 - rust-lang#62275 (rustc_mir: treat DropAndReplace as Drop + Assign in qualify_consts.)
 - rust-lang#62465 (Sometimes generate storage statements for temporaries with type `!`)
 - rust-lang#62481 (Use `fold` in `Iterator::last` default implementation)
 - rust-lang#62493 (rust-lang#62357: doc(ptr): add example for {read,write}_unaligned)
 - rust-lang#62532 (Some more cleanups to syntax::print)

Failed merges:

r? @ghost

src/libcore/iter/traits/iterator.rs

@@ -263,9 +263,7 @@ pub trait Iterator {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn last(self) -> Option<Self::Item> where Self: Sized {
-        let mut last = None;
-        for x in self { last = Some(x); }
-        last
+        self.fold(None, |_, x| Some(x))
     }
 
     /// Returns the `n`th element of the iterator.

src/libcore/ptr/mod.rs

@@ -669,6 +669,22 @@ pub unsafe fn read<T>(src: *const T) -> T {
 ///
 /// Accessing unaligned fields directly with e.g. `packed.unaligned` is safe however.
 // FIXME: Update docs based on outcome of RFC #2582 and friends.
+///
+/// # Examples
+///
+/// Read an usize value from a byte buffer:
+///
+/// ```
+/// use std::mem;
+///
+/// fn read_usize(x: &[u8]) -> usize {
+///     assert!(x.len() >= mem::size_of::<usize>());
+///
+///     let ptr = x.as_ptr() as *const usize;
+///
+///     unsafe { ptr.read_unaligned() }
+/// }
+/// ```
 #[inline]
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
 pub unsafe fn read_unaligned<T>(src: *const T) -> T {
@@ -839,6 +855,22 @@ pub unsafe fn write<T>(dst: *mut T, src: T) {
 ///
 /// Accessing unaligned fields directly with e.g. `packed.unaligned` is safe however.
 // FIXME: Update docs based on outcome of RFC #2582 and friends.
+///
+/// # Examples
+///
+/// Write an usize value to a byte buffer:
+///
+/// ```
+/// use std::mem;
+///
+/// fn write_usize(x: &mut [u8], val: usize) {
+///     assert!(x.len() >= mem::size_of::<usize>());
+///
+///     let ptr = x.as_mut_ptr() as *mut usize;
+///
+///     unsafe { ptr.write_unaligned(val) }
+/// }
+/// ```
 #[inline]
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
 pub unsafe fn write_unaligned<T>(dst: *mut T, src: T) {

src/librustc/hir/map/mod.rs

@@ -1212,10 +1212,8 @@ impl<'a> print::State<'a> {
             Node::Pat(a)          => self.print_pat(&a),
             Node::Arm(a)          => self.print_arm(&a),
             Node::Block(a)        => {
-                use syntax::print::pprust::PrintState;
-
                 // containing cbox, will be closed by print-block at }
-                self.cbox(print::indent_unit);
+                self.cbox(print::INDENT_UNIT);
                 // head-ibox, will be closed by print-block after {
                 self.ibox(0);
                 self.print_block(&a)