Auto merge of #46130 - kennytm:rollup, r=kennytm

Rollup of 9 pull requests

- Successful merges: #46082, #46088, #46092, #46107, #46119, #46121, #46122, #46124, #46128
- Failed merges:

9 files changed, 70 insertions, 12 deletions

diff --git a/src/libstd/f32.rs b/src/libstd/f32.rs
index 14f0edc3690..645a4c21150 100644
--- a/src/libstd/f32.rs
+++ b/src/libstd/f32.rs
@@ -9,8 +9,9 @@
 // except according to those terms.
 
 //! This module provides constants which are specific to the implementation
-//! of the `f32` floating point data type. Mathematically significant
-//! numbers are provided in the `consts` sub-module.
+//! of the `f32` floating point data type.
+//!
+//! Mathematically significant numbers are provided in the `consts` sub-module.
 //!
 //! *[See also the `f32` primitive type](../primitive.f32.html).*
 
diff --git a/src/libstd/f64.rs b/src/libstd/f64.rs
index e0f0acc6ac4..7fd798155bd 100644
--- a/src/libstd/f64.rs
+++ b/src/libstd/f64.rs
@@ -9,8 +9,9 @@
 // except according to those terms.
 
 //! This module provides constants which are specific to the implementation
-//! of the `f64` floating point data type. Mathematically significant
-//! numbers are provided in the `consts` sub-module.
+//! of the `f64` floating point data type.
+//!
+//! Mathematically significant numbers are provided in the `consts` sub-module.
 //!
 //! *[See also the `f64` primitive type](../primitive.f64.html).*
 
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 57f8c39756e..62313d7d3a6 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -419,14 +419,8 @@ fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize>
 ///
 /// [`File`]s implement `Read`:
 ///
-/// [`read()`]: trait.Read.html#tymethod.read
-/// [`std::io`]: ../../std/io/index.html
-/// [`File`]: ../fs/struct.File.html
-/// [`BufRead`]: trait.BufRead.html
-/// [`BufReader`]: struct.BufReader.html
-///
 /// ```
-/// use std::io;
+/// # use std::io;
 /// use std::io::prelude::*;
 /// use std::fs::File;
 ///
@@ -449,6 +443,32 @@ fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize>
 /// # Ok(())
 /// # }
 /// ```
+///
+/// Read from `&str` because [`&[u8]`] implements [`Read`]:
+///
+/// ```
+/// # use std::io;
+/// use std::io::prelude::*;
+///
+/// # fn foo() -> io::Result<()> {
+/// let mut b = "This string will be read".as_bytes();
+/// let mut buffer = [0; 10];
+///
+/// // read up to 10 bytes
+/// b.read(&mut buffer)?;
+///
+/// // etc... it works exactly as a File does!
+/// # Ok(())
+/// # }
+/// ```
+///
+/// [`read()`]: trait.Read.html#tymethod.read
+/// [`std::io`]: ../../std/io/index.html
+/// [`File`]: ../fs/struct.File.html
+/// [`BufRead`]: trait.BufRead.html
+/// [`BufReader`]: struct.BufReader.html
+/// [`&[u8]`]: primitive.slice.html
+///
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait Read {
     /// Pull some bytes from this source into the specified buffer, returning
diff --git a/src/libstd/panic.rs b/src/libstd/panic.rs
index 385076e50dd..219e55d6c12 100644
--- a/src/libstd/panic.rs
+++ b/src/libstd/panic.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Panic support in the standard library
+//! Panic support in the standard library.
 
 #![stable(feature = "std_panic", since = "1.9.0")]
 
diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index eb507858b92..81f5594bc52 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -382,6 +382,17 @@ unsafe impl<#[may_dangle] T: ?Sized> Drop for Mutex<T> {
     }
 }
 
+#[stable(feature = "mutex_from", since = "1.22.0")]
+impl<T> From<T> for Mutex<T> {
+    /// Creates a new mutex in an unlocked state ready for use.
+    /// This is equivalent to [`Mutex::new`].
+    ///
+    /// [`Mutex::new`]: #method.new
+    fn from(t: T) -> Self {
+        Mutex::new(t)
+    }
+}
+
 #[stable(feature = "mutex_default", since = "1.10.0")]
 impl<T: ?Sized + Default> Default for Mutex<T> {
     /// Creates a `Mutex<T>`, with the `Default` value for T.
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index 6216d78528d..fd6cff6b69c 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -457,6 +457,17 @@ impl<T: Default> Default for RwLock<T> {
     }
 }
 
+#[stable(feature = "rw_lock_from", since = "1.22.0")]
+impl<T> From<T> for RwLock<T> {
+    /// Creates a new instance of an `RwLock<T>` which is unlocked.
+    /// This is equivalent to [`RwLock::new`].
+    ///
+    /// [`RwLock::new`]: #method.new
+    fn from(t: T) -> Self {
+        RwLock::new(t)
+    }
+}
+
 impl<'rwlock, T: ?Sized> RwLockReadGuard<'rwlock, T> {
     unsafe fn new(lock: &'rwlock RwLock<T>)
                   -> LockResult<RwLockReadGuard<'rwlock, T>> {
diff --git a/src/libstd/sys/redox/os.rs b/src/libstd/sys/redox/os.rs
index c27e2ee172c..480765b77a0 100644
--- a/src/libstd/sys/redox/os.rs
+++ b/src/libstd/sys/redox/os.rs
@@ -213,3 +213,7 @@ pub fn exit(code: i32) -> ! {
 pub fn getpid() -> u32 {
     syscall::getpid().unwrap() as u32
 }
+
+pub fn getppid() -> u32 {
+    syscall::getppid().unwrap() as u32
+}
diff --git a/src/libstd/sys/unix/ext/process.rs b/src/libstd/sys/unix/ext/process.rs
index cde21b089a2..60309bec6d4 100644
--- a/src/libstd/sys/unix/ext/process.rs
+++ b/src/libstd/sys/unix/ext/process.rs
@@ -191,3 +191,9 @@ impl IntoRawFd for process::ChildStderr {
         self.into_inner().into_fd().into_raw()
     }
 }
+
+/// Returns the OS-assigned process identifier associated with this process's parent.
+#[unstable(feature = "unix_ppid", issue = "46104")]
+pub fn parent_id() -> u32 {
+    ::sys::os::getppid()
+}
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 40b73f1b307..7e965b4b4c5 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -515,3 +515,7 @@ pub fn exit(code: i32) -> ! {
 pub fn getpid() -> u32 {
     unsafe { libc::getpid() as u32 }
 }
+
+pub fn getppid() -> u32 {
+    unsafe { libc::getppid() as u32 }
+}