5 files changed, 66 insertions, 4 deletions
diff --git a/src/liballoc/alloc.rs b/src/liballoc/alloc.rs
index 3bd0c243b39..1a8a081e16f 100644
--- a/src/liballoc/alloc.rs
+++ b/src/liballoc/alloc.rs
@@ -21,6 +21,10 @@ use core::usize;
 pub use core::alloc::*;
 
 extern "Rust" {
+    // These are the magic symbols to call the global allocator.  rustc generates
+    // them from the `#[global_allocator]` attribute if there is one, or uses the
+    // default implementations in libstd (`__rdl_alloc` etc in `src/libstd/alloc.rs`)
+    // otherwise.
     #[allocator]
     #[rustc_allocator_nounwind]
     fn __rust_alloc(size: usize, align: usize) -> *mut u8;
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 74354f605e5..63b262d1f3d 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -73,7 +73,7 @@ use core::convert::From;
 use core::fmt;
 use core::future::Future;
 use core::hash::{Hash, Hasher};
-use core::iter::FusedIterator;
+use core::iter::{Iterator, FromIterator, FusedIterator};
 use core::marker::{Unpin, Unsize};
 use core::mem;
 use core::pin::Pin;
@@ -81,6 +81,7 @@ use core::ops::{CoerceUnsized, DispatchFromDyn, Deref, DerefMut, Generator, Gene
 use core::ptr::{self, NonNull, Unique};
 use core::task::{LocalWaker, Poll};
 
+use vec::Vec;
 use raw_vec::RawVec;
 use str::from_boxed_utf8_unchecked;
 
@@ -699,6 +700,13 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Box<U>> for Box<T> {}
 #[unstable(feature = "dispatch_from_dyn", issue = "0")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U>> for Box<T> {}
 
+#[stable(feature = "boxed_slice_from_iter", since = "1.32.0")]
+impl<A> FromIterator<A> for Box<[A]> {
+    fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> Self {
+        iter.into_iter().collect::<Vec<_>>().into_boxed_slice()
+    }
+}
+
 #[stable(feature = "box_slice_clone", since = "1.3.0")]
 impl<T: Clone> Clone for Box<[T]> {
     fn clone(&self) -> Self {
diff --git a/src/liballoc/boxed_test.rs b/src/liballoc/boxed_test.rs
index 55995742a4a..f340ea01c5f 100644
--- a/src/liballoc/boxed_test.rs
+++ b/src/liballoc/boxed_test.rs
@@ -140,3 +140,11 @@ fn str_slice() {
     let boxed: Box<str> = Box::from(s);
     assert_eq!(&*boxed, s)
 }
+
+#[test]
+fn boxed_slice_from_iter() {
+    let iter = 0..100;
+    let boxed: Box<[u32]> = iter.collect();
+    assert_eq!(boxed.len(), 100);
+    assert_eq!(boxed[7], 7);
+}
diff --git a/src/liballoc/collections/btree/map.rs b/src/liballoc/collections/btree/map.rs
index 24c8fd3a969..49e488702b4 100644
--- a/src/liballoc/collections/btree/map.rs
+++ b/src/liballoc/collections/btree/map.rs
@@ -853,9 +853,10 @@ impl<K: Ord, V> BTreeMap<K, V> {
     /// ```
     /// use std::collections::BTreeMap;
     ///
-    /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"].iter()
-    ///                                                                       .map(|&s| (s, 0))
-    ///                                                                       .collect();
+    /// let mut map: BTreeMap<&str, i32> = ["Alice", "Bob", "Carol", "Cheryl"]
+    ///     .iter()
+    ///     .map(|&s| (s, 0))
+    ///     .collect();
     /// for (_, balance) in map.range_mut("B".."Cheryl") {
     ///     *balance += 100;
     /// }
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 5c776292f53..2beb3240aac 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -2206,6 +2206,20 @@ impl<'a> From<&'a str> for String {
 #[cfg(not(test))]
 #[stable(feature = "string_from_box", since = "1.18.0")]
 impl From<Box<str>> for String {
+    /// Converts the given boxed `str` slice to a `String`.
+    /// It is notable that the `str` slice is owned.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s1: String = String::from("hello world");
+    /// let s2: Box<str> = s1.into_boxed_str();
+    /// let s3: String = String::from(s2);
+    ///
+    /// assert_eq!("hello world", s3)
+    /// ```
     fn from(s: Box<str>) -> String {
         s.into_string()
     }
@@ -2213,6 +2227,19 @@ impl From<Box<str>> for String {
 
 #[stable(feature = "box_from_str", since = "1.20.0")]
 impl From<String> for Box<str> {
+    /// Converts the given `String` to a boxed `str` slice that is owned.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s1: String = String::from("hello world");
+    /// let s2: Box<str> = Box::from(s1);
+    /// let s3: String = String::from(s2);
+    ///
+    /// assert_eq!("hello world", s3)
+    /// ```
     fn from(s: String) -> Box<str> {
         s.into_boxed_str()
     }
@@ -2272,6 +2299,20 @@ impl<'a> FromIterator<String> for Cow<'a, str> {
 
 #[stable(feature = "from_string_for_vec_u8", since = "1.14.0")]
 impl From<String> for Vec<u8> {
+    /// Converts the given `String` to a vector `Vec` that holds values of type `u8`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s1 = String::from("hello world");
+    /// let v1 = Vec::from(s1);
+    ///
+    /// for b in v1 {
+    ///     println!("{}", b);
+    /// }
+    /// ```
     fn from(string: String) -> Vec<u8> {
         string.into_bytes()
     }