Auto merge of #49939 - kennytm:rollup, r=kennytm

Rollup of 14 pull requests

Successful merges: #49908, #49876, #49916, #49951, #49465, #49922, #49866, #49915, #49886, #49913, #49852, #49958, #49871, #49864

Failed merges:

3 files changed, 103 insertions, 4 deletions

diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 35d70609c19..f2e8caaad14 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -15,6 +15,7 @@
 use convert::TryFrom;
 use fmt;
 use intrinsics;
+use mem;
 #[allow(deprecated)] use nonzero::NonZero;
 use ops;
 use str::FromStr;
@@ -1868,6 +1869,50 @@ $EndFeature, "
             #[inline]
             pub fn is_negative(self) -> bool { self < 0 }
         }
+
+        /// Return the memory representation of this integer as a byte array.
+        ///
+        /// The target platform’s native endianness is used.
+        /// Portable code likely wants to use this after [`to_be`] or [`to_le`].
+        ///
+        /// [`to_be`]: #method.to_be
+        /// [`to_le`]: #method.to_le
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// #![feature(int_to_from_bytes)]
+        ///
+        /// let bytes = i32::min_value().to_be().to_bytes();
+        /// assert_eq!(bytes, [0x80, 0, 0, 0]);
+        /// ```
+        #[unstable(feature = "int_to_from_bytes", issue = "49792")]
+        #[inline]
+        pub fn to_bytes(self) -> [u8; mem::size_of::<Self>()] {
+            unsafe { mem::transmute(self) }
+        }
+
+        /// Create an integer value from its memory representation as a byte array.
+        ///
+        /// The target platform’s native endianness is used.
+        /// Portable code likely wants to use [`from_be`] or [`from_le`] after this.
+        ///
+        /// [`from_be`]: #method.from_be
+        /// [`from_le`]: #method.from_le
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// #![feature(int_to_from_bytes)]
+        ///
+        /// let int = i32::from_be(i32::from_bytes([0x80, 0, 0, 0]));
+        /// assert_eq!(int, i32::min_value());
+        /// ```
+        #[unstable(feature = "int_to_from_bytes", issue = "49792")]
+        #[inline]
+        pub fn from_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
+            unsafe { mem::transmute(bytes) }
+        }
     }
 }
 
@@ -3373,6 +3418,50 @@ $EndFeature, "
                 self.one_less_than_next_power_of_two().checked_add(1)
             }
         }
+
+        /// Return the memory representation of this integer as a byte array.
+        ///
+        /// The target platform’s native endianness is used.
+        /// Portable code likely wants to use this after [`to_be`] or [`to_le`].
+        ///
+        /// [`to_be`]: #method.to_be
+        /// [`to_le`]: #method.to_le
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// #![feature(int_to_from_bytes)]
+        ///
+        /// let bytes = 0x1234_5678_u32.to_be().to_bytes();
+        /// assert_eq!(bytes, [0x12, 0x34, 0x56, 0x78]);
+        /// ```
+        #[unstable(feature = "int_to_from_bytes", issue = "49792")]
+        #[inline]
+        pub fn to_bytes(self) -> [u8; mem::size_of::<Self>()] {
+            unsafe { mem::transmute(self) }
+        }
+
+        /// Create an integer value from its memory representation as a byte array.
+        ///
+        /// The target platform’s native endianness is used.
+        /// Portable code likely wants to use [`to_be`] or [`to_le`] after this.
+        ///
+        /// [`to_be`]: #method.to_be
+        /// [`to_le`]: #method.to_le
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// #![feature(int_to_from_bytes)]
+        ///
+        /// let int = u32::from_be(u32::from_bytes([0x12, 0x34, 0x56, 0x78]));
+        /// assert_eq!(int, 0x1234_5678_u32);
+        /// ```
+        #[unstable(feature = "int_to_from_bytes", issue = "49792")]
+        #[inline]
+        pub fn from_bytes(bytes: [u8; mem::size_of::<Self>()]) -> Self {
+            unsafe { mem::transmute(bytes) }
+        }
     }
 }
 
diff --git a/src/libcore/ops/bit.rs b/src/libcore/ops/bit.rs
index a0ecd6cf75c..ec1e65be774 100644
--- a/src/libcore/ops/bit.rs
+++ b/src/libcore/ops/bit.rs
@@ -315,7 +315,12 @@ macro_rules! bitxor_impl {
 
 bitxor_impl! { bool usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 
-/// The left shift operator `<<`.
+/// The left shift operator `<<`. Note that because this trait is implemented
+/// for all integer types with multiple right-hand-side types, Rust's type
+/// checker has special handling for `_ << _`, setting the result type for
+/// integer operations to the type of the left-hand-side operand. This means
+/// that though `a << b` and `a.shl(b)` are one and the same from an evaluation
+/// standpoint, they are different when it comes to type inference.
 ///
 /// # Examples
 ///
@@ -417,7 +422,12 @@ macro_rules! shl_impl_all {
 
 shl_impl_all! { u8 u16 u32 u64 u128 usize i8 i16 i32 i64 isize i128 }
 
-/// The right shift operator `>>`.
+/// The right shift operator `>>`. Note that because this trait is implemented
+/// for all integer types with multiple right-hand-side types, Rust's type
+/// checker has special handling for `_ >> _`, setting the result type for
+/// integer operations to the type of the left-hand-side operand. This means
+/// that though `a >> b` and `a.shr(b)` are one and the same from an evaluation
+/// standpoint, they are different when it comes to type inference.
 ///
 /// # Examples
 ///
diff --git a/src/libcore/sync/atomic.rs b/src/libcore/sync/atomic.rs
index d336934ec72..62e0979c5fe 100644
--- a/src/libcore/sync/atomic.rs
+++ b/src/libcore/sync/atomic.rs
@@ -1425,8 +1425,8 @@ assert_eq!(foo.load(Ordering::SeqCst), 0b011110);
 
             doc_comment! {
                 concat!("Fetches the value, and applies a function to it that returns an optional
-new value. Returns a `Result` (`Ok(_)` if the function returned `Some(_)`, else `Err(_)`) of the
-previous value.
+new value. Returns a `Result` of `Ok(previous_value)` if the function returned `Some(_)`, else
+`Err(previous_value)`.
 
 Note: This may call the function multiple times if the value has been changed from other threads in
 the meantime, as long as the function returns `Some(_)`, but the function will have been applied