Auto merge of #41086 - frewsxcv:rollup, r=frewsxcv

Rollup of 19 pull requests

- Successful merges: #40608, #40870, #40949, #40977, #40981, #40988, #40992, #40997, #40999, #41007, #41014, #41019, #41035, #41043, #41049, #41062, #41066, #41076, #41085
- Failed merges:

4 files changed, 108 insertions, 59 deletions

diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index 1ae8b6bb451..e0a4707ff66 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -61,16 +61,18 @@ extern "rust-intrinsic" {
     /// `std::sync::atomic` types via the `compare_exchange` method by passing
     /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
     /// as both the `success` and `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `compare_exchange` method by passing
     /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
     /// as both the `success` and `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -79,8 +81,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -89,16 +92,18 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `compare_exchange` method by passing
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as both the `success` and `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -107,8 +112,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -117,8 +123,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -127,8 +134,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -137,8 +145,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange).
+    /// [`AtomicBool::compare_exchange`][compare_exchange].
+    ///
+    /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
     pub fn atomic_cxchg_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
 
     /// Stores a value if the current value is the same as the `old` value.
@@ -146,16 +155,18 @@ extern "rust-intrinsic" {
     /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
     /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
     /// as both the `success` and `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
     /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
     /// as both the `success` and `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -164,8 +175,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -174,16 +186,18 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as both the `success` and `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -192,8 +206,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -202,8 +217,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -212,8 +228,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
     /// Stores a value if the current value is the same as the `old` value.
     /// The stabilized version of this intrinsic is available on the
@@ -222,8 +239,9 @@ extern "rust-intrinsic" {
     /// as the `success` and
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `failure` parameters. For example,
-    /// [`AtomicBool::compare_exchange_weak`]
-    /// (../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak).
+    /// [`AtomicBool::compare_exchange_weak`][cew].
+    ///
+    /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
     pub fn atomic_cxchgweak_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
 
     /// Loads the current value of the pointer.
@@ -1253,17 +1271,17 @@ extern "rust-intrinsic" {
     #[cfg(not(stage0))]
     pub fn unchecked_shr<T>(x: T, y: T) -> T;
 
-    /// Returns (a + b) mod 2^N, where N is the width of T in bits.
+    /// Returns (a + b) mod 2<sup>N</sup>, where N is the width of T in bits.
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `wrapping_add` method. For example,
     /// [`std::u32::wrapping_add`](../../std/primitive.u32.html#method.wrapping_add)
     pub fn overflowing_add<T>(a: T, b: T) -> T;
-    /// Returns (a - b) mod 2^N, where N is the width of T in bits.
+    /// Returns (a - b) mod 2<sup>N</sup>, where N is the width of T in bits.
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `wrapping_sub` method. For example,
     /// [`std::u32::wrapping_sub`](../../std/primitive.u32.html#method.wrapping_sub)
     pub fn overflowing_sub<T>(a: T, b: T) -> T;
-    /// Returns (a * b) mod 2^N, where N is the width of T in bits.
+    /// Returns (a * b) mod 2<sup>N</sup>, where N is the width of T in bits.
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `wrapping_mul` method. For example,
     /// [`std::u32::wrapping_mul`](../../std/primitive.u32.html#method.wrapping_mul)
diff --git a/src/libcore/num/dec2flt/rawfp.rs b/src/libcore/num/dec2flt/rawfp.rs
index e3b58b6cc7c..45fa721a5a3 100644
--- a/src/libcore/num/dec2flt/rawfp.rs
+++ b/src/libcore/num/dec2flt/rawfp.rs
@@ -10,12 +10,12 @@
 
 //! Bit fiddling on positive IEEE 754 floats. Negative numbers aren't and needn't be handled.
 //! Normal floating point numbers have a canonical representation as (frac, exp) such that the
-//! value is 2^exp * (1 + sum(frac[N-i] / 2^i)) where N is the number of bits. Subnormals are
-//! slightly different and weird, but the same principle applies.
+//! value is 2<sup>exp</sup> * (1 + sum(frac[N-i] / 2<sup>i</sup>)) where N is the number of bits.
+//! Subnormals are slightly different and weird, but the same principle applies.
 //!
-//! Here, however, we represent them as (sig, k) with f positive, such that the value is f * 2^e.
-//! Besides making the "hidden bit" explicit, this changes the exponent by the so-called
-//! mantissa shift.
+//! Here, however, we represent them as (sig, k) with f positive, such that the value is f *
+//! 2<sup>e</sup>. Besides making the "hidden bit" explicit, this changes the exponent by the
+//! so-called mantissa shift.
 //!
 //! Put another way, normally floats are written as (1) but here they are written as (2):
 //!
@@ -94,7 +94,8 @@ pub trait RawFloat : Float + Copy + Debug + LowerExp
     /// represented, the other code in this module makes sure to never let that happen.
     fn from_int(x: u64) -> Self;
 
-    /// Get the value 10^e from a pre-computed table. Panics for e >= ceil_log5_of_max_sig().
+    /// Get the value 10<sup>e</sup> from a pre-computed table. Panics for e >=
+    /// ceil_log5_of_max_sig().
     fn short_fast_pow10(e: usize) -> Self;
 
     // FIXME Everything that follows should be associated constants, but taking the value of an
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index d997f3592fd..1a48f277625 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -894,9 +894,15 @@ impl<A> ExactSizeIterator for Item<A> {}
 impl<A> FusedIterator for Item<A> {}
 unsafe impl<A> TrustedLen for Item<A> {}
 
-/// An iterator over a reference of the contained item in an [`Option`].
+/// An iterator over a reference to the [`Some`] variant of an [`Option`].
+///
+/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
+///
+/// This `struct` is created by the [`Option::iter`] function.
 ///
 /// [`Option`]: enum.Option.html
+/// [`Some`]: enum.Option.html#variant.Some
+/// [`Option::iter`]: enum.Option.html#method.iter
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
 pub struct Iter<'a, A: 'a> { inner: Item<&'a A> }
@@ -933,9 +939,15 @@ impl<'a, A> Clone for Iter<'a, A> {
     }
 }
 
-/// An iterator over a mutable reference of the contained item in an [`Option`].
+/// An iterator over a mutable reference to the [`Some`] variant of an [`Option`].
+///
+/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
+///
+/// This `struct` is created by the [`Option::iter_mut`] function.
 ///
 /// [`Option`]: enum.Option.html
+/// [`Some`]: enum.Option.html#variant.Some
+/// [`Option::iter_mut`]: enum.Option.html#method.iter_mut
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
 pub struct IterMut<'a, A: 'a> { inner: Item<&'a mut A> }
@@ -964,9 +976,15 @@ impl<'a, A> FusedIterator for IterMut<'a, A> {}
 #[unstable(feature = "trusted_len", issue = "37572")]
 unsafe impl<'a, A> TrustedLen for IterMut<'a, A> {}
 
-/// An iterator over the item contained inside an [`Option`].
+/// An iterator over the value in [`Some`] variant of an [`Option`].
+///
+/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
+///
+/// This `struct` is created by the [`Option::into_iter`] function.
 ///
 /// [`Option`]: enum.Option.html
+/// [`Some`]: enum.Option.html#variant.Some
+/// [`Option::into_iter`]: enum.Option.html#method.into_iter
 #[derive(Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<A> { inner: Item<A> }
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index f75a1f7ab6e..352cc926994 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -152,11 +152,16 @@ impl fmt::Display for ParseBoolError {
 Section: Creating a string
 */
 
-/// Errors which can occur when attempting to interpret a sequence of `u8`
+/// Errors which can occur when attempting to interpret a sequence of [`u8`]
 /// as a string.
 ///
-/// As such, the `from_utf8` family of functions and methods for both `String`s
-/// and `&str`s make use of this error, for example.
+/// [`u8`]: ../../std/primitive.u8.html
+///
+/// As such, the `from_utf8` family of functions and methods for both [`String`]s
+/// and [`&str`]s make use of this error, for example.
+///
+/// [`String`]: ../../std/string/struct.String.html#method.from_utf8
+/// [`&str`]: ../../std/str/fn.from_utf8.html
 #[derive(Copy, Eq, PartialEq, Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Utf8Error {
@@ -210,11 +215,15 @@ impl Utf8Error {
 
 /// Converts a slice of bytes to a string slice.
 ///
-/// A string slice (`&str`) is made of bytes (`u8`), and a byte slice (`&[u8]`)
-/// is made of bytes, so this function converts between the two. Not all byte
-/// slices are valid string slices, however: `&str` requires that it is valid
-/// UTF-8. `from_utf8()` checks to ensure that the bytes are valid UTF-8, and
-/// then does the conversion.
+/// A string slice ([`&str`]) is made of bytes ([`u8`]), and a byte slice
+/// ([`&[u8]`][byteslice]) is made of bytes, so this function converts between
+/// the two. Not all byte slices are valid string slices, however: [`&str`] requires
+/// that it is valid UTF-8. `from_utf8()` checks to ensure that the bytes are valid
+/// UTF-8, and then does the conversion.
+///
+/// [`&str`]: ../../std/primitive.str.html
+/// [`u8`]: ../../std/primitive.u8.html
+/// [byteslice]: ../../std/primitive.slice.html
 ///
 /// If you are sure that the byte slice is valid UTF-8, and you don't want to
 /// incur the overhead of the validity check, there is an unsafe version of
@@ -228,9 +237,12 @@ impl Utf8Error {
 ///
 /// [string]: ../../std/string/struct.String.html#method.from_utf8
 ///
-/// Because you can stack-allocate a `[u8; N]`, and you can take a `&[u8]` of
-/// it, this function is one way to have a stack-allocated string. There is
-/// an example of this in the examples section below.
+/// Because you can stack-allocate a `[u8; N]`, and you can take a
+/// [`&[u8]`][byteslice] of it, this function is one way to have a
+/// stack-allocated string. There is an example of this in the
+/// examples section below.
+///
+/// [byteslice]: ../../std/primitive.slice.html
 ///
 /// # Errors
 ///