Auto merge of #50191 - kennytm:rollup, r=kennytm

Rollup of 11 pull requests

Successful merges:

 - #49461 (std: Child::kill() returns error if process has already exited)
 - #49727 (Add Cell::update)
 - #49812 (Fix revision support for UI tests.)
 - #49829 (Add doc links to `std::os` extension traits)
 - #49906 (Stabilize `std::hint::unreachable_unchecked`.)
 - #49970 (Deprecate Read::chars and char::decode_utf8)
 - #49985 (don't see issue #0)
 - #50118 (fix search bar bug)
 - #50139 (encourage descriptive issue titles)
 - #50174 (Use FxHashMap in syntax_pos::symbol::Interner::intern.)
 - #50185 (core: Fix overflow in `int::mod_euc` when `self < 0 && rhs == MIN`)

Failed merges:

29 files changed, 165 insertions, 63 deletions

diff --git a/src/libstd/io/buffered.rs b/src/libstd/io/buffered.rs
index d6eac748334..ee297d3783e 100644
--- a/src/libstd/io/buffered.rs
+++ b/src/libstd/io/buffered.rs
@@ -1251,6 +1251,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(deprecated)]
     fn read_char_buffered() {
         let buf = [195, 159];
         let reader = BufReader::with_capacity(1, &buf[..]);
@@ -1258,6 +1259,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(deprecated)]
     fn test_chars() {
         let buf = [195, 159, b'a'];
         let reader = BufReader::with_capacity(1, &buf[..]);
diff --git a/src/libstd/io/cursor.rs b/src/libstd/io/cursor.rs
index 2673f3ccfa3..8ac52572810 100644
--- a/src/libstd/io/cursor.rs
+++ b/src/libstd/io/cursor.rs
@@ -566,6 +566,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(deprecated)]
     fn test_read_char() {
         let b = &b"Vi\xE1\xBB\x87t"[..];
         let mut c = Cursor::new(b).chars();
@@ -577,6 +578,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(deprecated)]
     fn test_read_bad_char() {
         let b = &b"\x80"[..];
         let mut c = Cursor::new(b).chars();
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index b02e133ee4d..eba4e9fe703 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -840,6 +840,9 @@ pub trait Read {
                                          of where errors happen is currently \
                                          unclear and may change",
                issue = "27802")]
+    #[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
+        https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
+    #[allow(deprecated)]
     fn chars(self) -> Chars<Self> where Self: Sized {
         Chars { inner: self }
     }
@@ -2010,16 +2013,22 @@ impl<R: Read> Iterator for Bytes<R> {
 /// [chars]: trait.Read.html#method.chars
 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
            issue = "27802")]
+#[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
+    https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
 #[derive(Debug)]
+#[allow(deprecated)]
 pub struct Chars<R> {
     inner: R,
 }
 
 /// An enumeration of possible errors that can be generated from the `Chars`
 /// adapter.
-#[derive(Debug)]
 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
            issue = "27802")]
+#[rustc_deprecated(since = "1.27.0", reason = "Use str::from_utf8 instead:
+    https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples")]
+#[derive(Debug)]
+#[allow(deprecated)]
 pub enum CharsError {
     /// Variant representing that the underlying stream was read successfully
     /// but it did not contain valid utf8 data.
@@ -2031,6 +2040,7 @@ pub enum CharsError {
 
 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
            issue = "27802")]
+#[allow(deprecated)]
 impl<R: Read> Iterator for Chars<R> {
     type Item = result::Result<char, CharsError>;
 
@@ -2063,6 +2073,7 @@ impl<R: Read> Iterator for Chars<R> {
 
 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
            issue = "27802")]
+#[allow(deprecated)]
 impl std_error::Error for CharsError {
     fn description(&self) -> &str {
         match *self {
@@ -2080,6 +2091,7 @@ impl std_error::Error for CharsError {
 
 #[unstable(feature = "io", reason = "awaiting stability of Read::chars",
            issue = "27802")]
+#[allow(deprecated)]
 impl fmt::Display for CharsError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 1df7bc777d1..41992193135 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -461,6 +461,8 @@ pub use alloc_crate::vec;
 pub use core::char;
 #[stable(feature = "i128", since = "1.26.0")]
 pub use core::u128;
+#[stable(feature = "core_hint", since = "1.27.0")]
+pub use core::hint;
 
 pub mod f32;
 pub mod f64;
diff --git a/src/libstd/os/android/fs.rs b/src/libstd/os/android/fs.rs
index a51b4655985..5899dc688e2 100644
--- a/src/libstd/os/android/fs.rs
+++ b/src/libstd/os/android/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::android::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/bitrig/fs.rs b/src/libstd/os/bitrig/fs.rs
index e4f1c9432f3..24caf326ab0 100644
--- a/src/libstd/os/bitrig/fs.rs
+++ b/src/libstd/os/bitrig/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::bitrig::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/dragonfly/fs.rs b/src/libstd/os/dragonfly/fs.rs
index db672e56435..6aea450774f 100644
--- a/src/libstd/os/dragonfly/fs.rs
+++ b/src/libstd/os/dragonfly/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::dragonfly::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/emscripten/fs.rs b/src/libstd/os/emscripten/fs.rs
index 8056ce4fdc4..e0e197dc122 100644
--- a/src/libstd/os/emscripten/fs.rs
+++ b/src/libstd/os/emscripten/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::emscripten::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/freebsd/fs.rs b/src/libstd/os/freebsd/fs.rs
index 2f17d2f7409..5f24cd636d5 100644
--- a/src/libstd/os/freebsd/fs.rs
+++ b/src/libstd/os/freebsd/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::freebsd::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/fuchsia/fs.rs b/src/libstd/os/fuchsia/fs.rs
index d22f9a628bd..16802576356 100644
--- a/src/libstd/os/fuchsia/fs.rs
+++ b/src/libstd/os/fuchsia/fs.rs
@@ -13,7 +13,9 @@
 use fs::Metadata;
 use sys_common::AsInner;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     #[stable(feature = "metadata_ext2", since = "1.8.0")]
diff --git a/src/libstd/os/haiku/fs.rs b/src/libstd/os/haiku/fs.rs
index 54f8ea1b71b..453136e0ac8 100644
--- a/src/libstd/os/haiku/fs.rs
+++ b/src/libstd/os/haiku/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::haiku::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/ios/fs.rs b/src/libstd/os/ios/fs.rs
index 275daf3d3a0..296ce69ff43 100644
--- a/src/libstd/os/ios/fs.rs
+++ b/src/libstd/os/ios/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::ios::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/linux/fs.rs b/src/libstd/os/linux/fs.rs
index 2be2fbcb2db..76fb10da850 100644
--- a/src/libstd/os/linux/fs.rs
+++ b/src/libstd/os/linux/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::linux::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/macos/fs.rs b/src/libstd/os/macos/fs.rs
index 12b44901d03..0b14c05cb55 100644
--- a/src/libstd/os/macos/fs.rs
+++ b/src/libstd/os/macos/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::macos::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/netbsd/fs.rs b/src/libstd/os/netbsd/fs.rs
index cd7d5fafd1c..e9cad33fee6 100644
--- a/src/libstd/os/netbsd/fs.rs
+++ b/src/libstd/os/netbsd/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::netbsd::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/openbsd/fs.rs b/src/libstd/os/openbsd/fs.rs
index cc812fcf12c..0f6b83b6e32 100644
--- a/src/libstd/os/openbsd/fs.rs
+++ b/src/libstd/os/openbsd/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::openbsd::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/os/solaris/fs.rs b/src/libstd/os/solaris/fs.rs
index 5dc43d03a86..19dce1ba34c 100644
--- a/src/libstd/os/solaris/fs.rs
+++ b/src/libstd/os/solaris/fs.rs
@@ -18,7 +18,9 @@ use sys_common::AsInner;
 #[allow(deprecated)]
 use os::solaris::raw;
 
-/// OS-specific extension methods for `fs::Metadata`
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Gain a reference to the underlying `stat` structure which contains
diff --git a/src/libstd/process.rs b/src/libstd/process.rs
index 92f0406c09b..00051d4487a 100644
--- a/src/libstd/process.rs
+++ b/src/libstd/process.rs
@@ -1121,8 +1121,13 @@ impl ExitCode {
 }
 
 impl Child {
-    /// Forces the child to exit. This is equivalent to sending a
-    /// SIGKILL on unix platforms.
+    /// Forces the child process to exit. If the child has already exited, an [`InvalidInput`]
+    /// error is returned.
+    ///
+    /// The mapping to [`ErrorKind`]s is not part of the compatibility contract of the function,
+    /// especially the [`Other`] kind might change to more specific kinds in the future.
+    ///
+    /// This is equivalent to sending a SIGKILL on Unix platforms.
     ///
     /// # Examples
     ///
@@ -1138,6 +1143,10 @@ impl Child {
     ///     println!("yes command didn't start");
     /// }
     /// ```
+    ///
+    /// [`ErrorKind`]: ../io/enum.ErrorKind.html
+    /// [`InvalidInput`]: ../io/enum.ErrorKind.html#variant.InvalidInput
+    /// [`Other`]: ../io/enum.ErrorKind.html#variant.Other
     #[stable(feature = "process", since = "1.0.0")]
     pub fn kill(&mut self) -> io::Result<()> {
         self.handle.kill()
diff --git a/src/libstd/sys/redox/ext/ffi.rs b/src/libstd/sys/redox/ext/ffi.rs
index d59b4fc0b70..cd88c8f46b3 100644
--- a/src/libstd/sys/redox/ext/ffi.rs
+++ b/src/libstd/sys/redox/ext/ffi.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Unix-specific extension to the primitives in the `std::ffi` module
+//! Redox-specific extension to the primitives in the `std::ffi` module.
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
@@ -17,7 +17,9 @@ use mem;
 use sys::os_str::Buf;
 use sys_common::{FromInner, IntoInner, AsInner};
 
-/// Unix-specific extensions to `OsString`.
+/// Redox-specific extensions to [`OsString`].
+///
+/// [`OsString`]: ../../../../std/ffi/struct.OsString.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStringExt {
     /// Creates an `OsString` from a byte vector.
@@ -39,7 +41,9 @@ impl OsStringExt for OsString {
     }
 }
 
-/// Unix-specific extensions to `OsStr`.
+/// Redox-specific extensions to [`OsStr`].
+///
+/// [`OsStr`]: ../../../../std/ffi/struct.OsStr.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStrExt {
     #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/libstd/sys/redox/ext/fs.rs b/src/libstd/sys/redox/ext/fs.rs
index 0f4762aa881..c1dba6edda4 100644
--- a/src/libstd/sys/redox/ext/fs.rs
+++ b/src/libstd/sys/redox/ext/fs.rs
@@ -18,7 +18,9 @@ use path::Path;
 use sys;
 use sys_common::{FromInner, AsInner, AsInnerMut};
 
-/// Redox-specific extensions to `Permissions`
+/// Redox-specific extensions to [`fs::Permissions`].
+///
+/// [`fs::Permissions`]: ../../../../std/fs/struct.Permissions.html
 #[stable(feature = "fs_ext", since = "1.1.0")]
 pub trait PermissionsExt {
     /// Returns the underlying raw `mode_t` bits that are the standard Redox
@@ -95,7 +97,9 @@ impl PermissionsExt for Permissions {
     }
 }
 
-/// Redox-specific extensions to `OpenOptions`
+/// Redox-specific extensions to [`fs::OpenOptions`].
+///
+/// [`fs::OpenOptions`]: ../../../../std/fs/struct.OpenOptions.html
 #[stable(feature = "fs_ext", since = "1.1.0")]
 pub trait OpenOptionsExt {
     /// Sets the mode bits that a new file will be created with.
@@ -163,13 +167,9 @@ impl OpenOptionsExt for OpenOptions {
     }
 }
 
-// Hm, why are there casts here to the returned type, shouldn't the types always
-// be the same? Right you are! Turns out, however, on android at least the types
-// in the raw `stat` structure are not the same as the types being returned. Who
-// knew!
-//
-// As a result to make sure this compiles for all platforms we do the manual
-// casts and rely on manual lowering to `stat` if the raw type is desired.
+/// Redox-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     #[stable(feature = "metadata_ext", since = "1.1.0")]
@@ -204,6 +204,13 @@ pub trait MetadataExt {
     fn blocks(&self) -> u64;
 }
 
+// Hm, why are there casts here to the returned type, shouldn't the types always
+// be the same? Right you are! Turns out, however, on android at least the types
+// in the raw `stat` structure are not the same as the types being returned. Who
+// knew!
+//
+// As a result to make sure this compiles for all platforms we do the manual
+// casts and rely on manual lowering to `stat` if the raw type is desired.
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 impl MetadataExt for fs::Metadata {
     fn dev(&self) -> u64 {
@@ -253,7 +260,12 @@ impl MetadataExt for fs::Metadata {
     }
 }
 
-/// Add special Redox types (block/char device, fifo and socket)
+/// Redox-specific extensions for [`FileType`].
+///
+/// Adds support for special Unix file types such as block/character devices,
+/// pipes, and sockets.
+///
+/// [`FileType`]: ../../../../std/fs/struct.FileType.html
 #[stable(feature = "file_type_ext", since = "1.5.0")]
 pub trait FileTypeExt {
     /// Returns whether this file type is a block device.
@@ -307,8 +319,10 @@ pub fn symlink<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> io::Result<()>
     sys::fs::symlink(src.as_ref(), dst.as_ref())
 }
 
+/// Redox-specific extensions to [`fs::DirBuilder`].
+///
+/// [`fs::DirBuilder`]: ../../../../std/fs/struct.DirBuilder.html
 #[stable(feature = "dir_builder", since = "1.6.0")]
-/// An extension trait for `fs::DirBuilder` for Redox-specific options.
 pub trait DirBuilderExt {
     /// Sets the mode to create new directories with. This option defaults to
     /// 0o777.
diff --git a/src/libstd/sys/redox/ext/process.rs b/src/libstd/sys/redox/ext/process.rs
index e68e180acf1..cfb6d5fc703 100644
--- a/src/libstd/sys/redox/ext/process.rs
+++ b/src/libstd/sys/redox/ext/process.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Unix-specific extensions to primitives in the `std::process` module.
+//! Redox-specific extensions to primitives in the `std::process` module.
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
@@ -18,7 +18,9 @@ use process;
 use sys;
 use sys_common::{AsInnerMut, AsInner, FromInner, IntoInner};
 
-/// Unix-specific extensions to the `std::process::Command` builder
+/// Redox-specific extensions to the [`process::Command`] builder,
+///
+/// [`process::Command`]: ../../../../std/process/struct.Command.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait CommandExt {
     /// Sets the child process's user id. This translates to a
@@ -107,7 +109,9 @@ impl CommandExt for process::Command {
     }
 }
 
-/// Unix-specific extensions to `std::process::ExitStatus`
+/// Redox-specific extensions to [`process::ExitStatus`].
+///
+/// [`process::ExitStatus`]: ../../../../std/process/struct.ExitStatus.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait ExitStatusExt {
     /// Creates a new `ExitStatus` from the raw underlying `i32` return value of
diff --git a/src/libstd/sys/redox/ext/thread.rs b/src/libstd/sys/redox/ext/thread.rs
index 52be2ccd9f9..71ff0d46b91 100644
--- a/src/libstd/sys/redox/ext/thread.rs
+++ b/src/libstd/sys/redox/ext/thread.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Unix-specific extensions to primitives in the `std::thread` module.
+//! Redox-specific extensions to primitives in the `std::thread` module.
 
 #![stable(feature = "thread_extensions", since = "1.9.0")]
 
@@ -19,7 +19,9 @@ use thread::JoinHandle;
 #[allow(deprecated)]
 pub type RawPthread = usize;
 
-/// Unix-specific extensions to `std::thread::JoinHandle`
+/// Redox-specific extensions to [`thread::JoinHandle`].
+///
+/// [`thread::JoinHandle`]: ../../../../std/thread/struct.JoinHandle.html
 #[stable(feature = "thread_extensions", since = "1.9.0")]
 pub trait JoinHandleExt {
     /// Extracts the raw pthread_t without taking ownership
diff --git a/src/libstd/sys/unix/ext/ffi.rs b/src/libstd/sys/unix/ext/ffi.rs
index fb9984ccbdd..8347145db5a 100644
--- a/src/libstd/sys/unix/ext/ffi.rs
+++ b/src/libstd/sys/unix/ext/ffi.rs
@@ -17,7 +17,9 @@ use mem;
 use sys::os_str::Buf;
 use sys_common::{FromInner, IntoInner, AsInner};
 
-/// Unix-specific extensions to `OsString`.
+/// Unix-specific extensions to [`OsString`].
+///
+/// [`OsString`]: ../../../../std/ffi/struct.OsString.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStringExt {
     /// Creates an [`OsString`] from a byte vector.
@@ -66,7 +68,9 @@ impl OsStringExt for OsString {
     }
 }
 
-/// Unix-specific extensions to `OsStr`.
+/// Unix-specific extensions to [`OsStr`].
+///
+/// [`OsStr`]: ../../../../std/ffi/struct.OsStr.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStrExt {
     #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/libstd/sys/unix/ext/fs.rs b/src/libstd/sys/unix/ext/fs.rs
index 3c5b9424fb0..4e981012669 100644
--- a/src/libstd/sys/unix/ext/fs.rs
+++ b/src/libstd/sys/unix/ext/fs.rs
@@ -105,7 +105,9 @@ impl FileExt for fs::File {
     }
 }
 
-/// Unix-specific extensions to `Permissions`
+/// Unix-specific extensions to [`fs::Permissions`].
+///
+/// [`fs::Permissions`]: ../../../../std/fs/struct.Permissions.html
 #[stable(feature = "fs_ext", since = "1.1.0")]
 pub trait PermissionsExt {
     /// Returns the underlying raw `st_mode` bits that contain the standard
@@ -180,7 +182,9 @@ impl PermissionsExt for Permissions {
     }
 }
 
-/// Unix-specific extensions to `OpenOptions`
+/// Unix-specific extensions to [`fs::OpenOptions`].
+///
+/// [`fs::OpenOptions`]: ../../../../std/fs/struct.OpenOptions.html
 #[stable(feature = "fs_ext", since = "1.1.0")]
 pub trait OpenOptionsExt {
     /// Sets the mode bits that a new file will be created with.
@@ -246,13 +250,9 @@ impl OpenOptionsExt for OpenOptions {
     }
 }
 
-// Hm, why are there casts here to the returned type, shouldn't the types always
-// be the same? Right you are! Turns out, however, on android at least the types
-// in the raw `stat` structure are not the same as the types being returned. Who
-// knew!
-//
-// As a result to make sure this compiles for all platforms we do the manual
-// casts and rely on manual lowering to `stat` if the raw type is desired.
+/// Unix-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 #[stable(feature = "metadata_ext", since = "1.1.0")]
 pub trait MetadataExt {
     /// Returns the ID of the device containing the file.
@@ -555,7 +555,12 @@ impl MetadataExt for fs::Metadata {
     fn blocks(&self) -> u64 { self.st_blocks() }
 }
 
-/// Add support for special unix types (block/char device, fifo and socket).
+/// Unix-specific extensions for [`FileType`].
+///
+/// Adds support for special Unix file types such as block/character devices,
+/// pipes, and sockets.
+///
+/// [`FileType`]: ../../../../std/fs/struct.FileType.html
 #[stable(feature = "file_type_ext", since = "1.5.0")]
 pub trait FileTypeExt {
     /// Returns whether this file type is a block device.
@@ -701,10 +706,10 @@ pub fn symlink<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> io::Result<()>
     sys::fs::symlink(src.as_ref(), dst.as_ref())
 }
 
-#[stable(feature = "dir_builder", since = "1.6.0")]
-/// An extension trait for [`fs::DirBuilder`] for unix-specific options.
+/// Unix-specific extensions to [`fs::DirBuilder`].
 ///
 /// [`fs::DirBuilder`]: ../../../../std/fs/struct.DirBuilder.html
+#[stable(feature = "dir_builder", since = "1.6.0")]
 pub trait DirBuilderExt {
     /// Sets the mode to create new directories with. This option defaults to
     /// 0o777.
diff --git a/src/libstd/sys/unix/ext/process.rs b/src/libstd/sys/unix/ext/process.rs
index 7b4ec20d91f..21630ae9746 100644
--- a/src/libstd/sys/unix/ext/process.rs
+++ b/src/libstd/sys/unix/ext/process.rs
@@ -18,7 +18,9 @@ use process;
 use sys;
 use sys_common::{AsInnerMut, AsInner, FromInner, IntoInner};
 
-/// Unix-specific extensions to the `std::process::Command` builder
+/// Unix-specific extensions to the [`process::Command`] builder.
+///
+/// [`process::Command`]: ../../../../std/process/struct.Command.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait CommandExt {
     /// Sets the child process's user id. This translates to a
@@ -117,7 +119,9 @@ impl CommandExt for process::Command {
     }
 }
 
-/// Unix-specific extensions to `std::process::ExitStatus`
+/// Unix-specific extensions to [`process::ExitStatus`].
+///
+/// [`process::ExitStatus`]: ../../../../std/process/struct.ExitStatus.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait ExitStatusExt {
     /// Creates a new `ExitStatus` from the raw underlying `i32` return value of
diff --git a/src/libstd/sys/unix/ext/thread.rs b/src/libstd/sys/unix/ext/thread.rs
index fe2a48764dc..8dadf29945c 100644
--- a/src/libstd/sys/unix/ext/thread.rs
+++ b/src/libstd/sys/unix/ext/thread.rs
@@ -21,7 +21,9 @@ use thread::JoinHandle;
 #[allow(deprecated)]
 pub type RawPthread = pthread_t;
 
-/// Unix-specific extensions to `std::thread::JoinHandle`
+/// Unix-specific extensions to [`thread::JoinHandle`].
+///
+/// [`thread::JoinHandle`]: ../../../../std/thread/struct.JoinHandle.html
 #[stable(feature = "thread_extensions", since = "1.9.0")]
 pub trait JoinHandleExt {
     /// Extracts the raw pthread_t without taking ownership
diff --git a/src/libstd/sys/windows/ext/ffi.rs b/src/libstd/sys/windows/ext/ffi.rs
index d6b8896ac09..98d43552489 100644
--- a/src/libstd/sys/windows/ext/ffi.rs
+++ b/src/libstd/sys/windows/ext/ffi.rs
@@ -76,7 +76,9 @@ use sys_common::{FromInner, AsInner};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use sys_common::wtf8::EncodeWide;
 
-/// Windows-specific extensions to `OsString`.
+/// Windows-specific extensions to [`OsString`].
+///
+/// [`OsString`]: ../../../../std/ffi/struct.OsString.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStringExt {
     /// Creates an `OsString` from a potentially ill-formed UTF-16 slice of
@@ -109,7 +111,9 @@ impl OsStringExt for OsString {
     }
 }
 
-/// Windows-specific extensions to `OsStr`.
+/// Windows-specific extensions to [`OsStr`].
+///
+/// [`OsStr`]: ../../../../std/ffi/struct.OsStr.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait OsStrExt {
     /// Re-encodes an `OsStr` as a wide character sequence, i.e. potentially
diff --git a/src/libstd/sys/windows/ext/fs.rs b/src/libstd/sys/windows/ext/fs.rs
index e5cd51b6550..78c9e95a055 100644
--- a/src/libstd/sys/windows/ext/fs.rs
+++ b/src/libstd/sys/windows/ext/fs.rs
@@ -103,9 +103,9 @@ impl FileExt for fs::File {
     }
 }
 
-/// Windows-specific extensions to [`OpenOptions`].
+/// Windows-specific extensions to [`fs::OpenOptions`].
 ///
-/// [`OpenOptions`]: ../../../fs/struct.OpenOptions.html
+/// [`fs::OpenOptions`]: ../../../../std/fs/struct.OpenOptions.html
 #[stable(feature = "open_options_ext", since = "1.10.0")]
 pub trait OpenOptionsExt {
     /// Overrides the `dwDesiredAccess` argument to the call to [`CreateFile`]
@@ -281,13 +281,12 @@ impl OpenOptionsExt for OpenOptions {
     }
 }
 
-/// Extension methods for [`fs::Metadata`] to access the raw fields contained
-/// within.
+/// Windows-specific extensions to [`fs::Metadata`].
 ///
 /// The data members that this trait exposes correspond to the members
 /// of the [`BY_HANDLE_FILE_INFORMATION`] structure.
 ///
-/// [`fs::Metadata`]: ../../../fs/struct.Metadata.html
+/// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
 /// [`BY_HANDLE_FILE_INFORMATION`]:
 ///     https://msdn.microsoft.com/en-us/library/windows/desktop/aa363788.aspx
 #[stable(feature = "metadata_ext", since = "1.1.0")]
@@ -445,8 +444,11 @@ impl MetadataExt for Metadata {
     fn file_size(&self) -> u64 { self.as_inner().size() }
 }
 
-/// Add support for the Windows specific fact that a symbolic link knows whether it is a file
-/// or directory.
+/// Windows-specific extensions to [`FileType`].
+///
+/// On Windows, a symbolic link knows whether it is a file or directory.
+///
+/// [`FileType`]: ../../../../std/fs/struct.FileType.html
 #[unstable(feature = "windows_file_type_ext", issue = "0")]
 pub trait FileTypeExt {
     /// Returns whether this file type is a symbolic link that is also a directory.
diff --git a/src/libstd/sys/windows/ext/process.rs b/src/libstd/sys/windows/ext/process.rs
index 759f055c4b1..a02bcbe0c87 100644
--- a/src/libstd/sys/windows/ext/process.rs
+++ b/src/libstd/sys/windows/ext/process.rs
@@ -82,7 +82,9 @@ impl IntoRawHandle for process::ChildStderr {
     }
 }
 
-/// Windows-specific extensions to `std::process::ExitStatus`
+/// Windows-specific extensions to [`process::ExitStatus`].
+///
+/// [`process::ExitStatus`]: ../../../../std/process/struct.ExitStatus.html
 #[stable(feature = "exit_status_from", since = "1.12.0")]
 pub trait ExitStatusExt {
     /// Creates a new `ExitStatus` from the raw underlying `u32` return value of
@@ -98,7 +100,9 @@ impl ExitStatusExt for process::ExitStatus {
     }
 }
 
-/// Windows-specific extensions to the `std::process::Command` builder
+/// Windows-specific extensions to the [`process::Command`] builder.
+///
+/// [`process::Command`]: ../../../../std/process/struct.Command.html
 #[stable(feature = "windows_process_extensions", since = "1.16.0")]
 pub trait CommandExt {
     /// Sets the [process creation flags][1] to be passed to `CreateProcess`.