Auto merge of #38369 - aturon:stab-1.15, r=alexcrichton

Library stabilizations/deprecations for 1.15 release

Stabilized:

- `std::iter::Iterator::{min_by, max_by}`
- `std::os::*::fs::FileExt`
- `std::sync::atomic::Atomic*::{get_mut, into_inner}`
- `std::vec::IntoIter::{as_slice, as_mut_slice}`
- `std::sync::mpsc::Receiver::try_iter`
- `std::os::unix::process::CommandExt::before_exec`
- `std::rc::Rc::{strong_count, weak_count}`
- `std::sync::Arc::{strong_count, weak_count}`
- `std::char::{encode_utf8, encode_utf16}`
- `std::cell::Ref::clone`
- `std::io::Take::into_inner`

Deprecated:

- `std::rc::Rc::{would_unwrap, is_unique}`
- `std::cell::RefCell::borrow_state`

Closes #23755
Closes #27733
Closes #27746
Closes #27784
Closes #28356
Closes #31398
Closes #34931
Closes #35601
Closes #35603
Closes #35918
Closes #36105

2 files changed, 4 insertions, 6 deletions

diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index b3b89213df1..b07da0dc268 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -1526,8 +1526,6 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(io_take_into_inner)]
-    ///
     /// use std::io;
     /// use std::io::prelude::*;
     /// use std::fs::File;
@@ -1543,7 +1541,7 @@ impl<T> Take<T> {
     /// # Ok(())
     /// # }
     /// ```
-    #[unstable(feature = "io_take_into_inner", issue = "23755")]
+    #[stable(feature = "io_take_into_inner", since = "1.15.0")]
     pub fn into_inner(self) -> T {
         self.inner
     }
diff --git a/src/libstd/io/stdio.rs b/src/libstd/io/stdio.rs
index 6419a9ff683..1a65bee13b8 100644
--- a/src/libstd/io/stdio.rs
+++ b/src/libstd/io/stdio.rs
@@ -10,7 +10,7 @@
 
 use io::prelude::*;
 
-use cell::{RefCell, BorrowState};
+use cell::RefCell;
 use fmt;
 use io::lazy::Lazy;
 use io::{self, BufReader, LineWriter};
@@ -638,8 +638,8 @@ pub fn _print(args: fmt::Arguments) {
         LocalKeyState::Destroyed => stdout().write_fmt(args),
         LocalKeyState::Valid => {
             LOCAL_STDOUT.with(|s| {
-                if s.borrow_state() == BorrowState::Unused {
-                    if let Some(w) = s.borrow_mut().as_mut() {
+                if let Ok(mut borrowed) = s.try_borrow_mut() {
+                    if let Some(w) = borrowed.as_mut() {
                         return w.write_fmt(args);
                     }
                 }