Auto merge of #23292 - alexcrichton:stabilize-io, r=aturon

The new `std::io` module has had some time to bake now, and this commit
stabilizes its functionality. There are still portions of the module which
remain unstable, and below contains a summart of the actions taken.

This commit also deprecates the entire contents of the `old_io` module in a
blanket fashion. All APIs should now have a reasonable replacement in the
new I/O modules.

Stable APIs:

* `std::io` (the name)
* `std::io::prelude` (the name)
* `Read`
* `Read::read`
* `Read::{read_to_end, read_to_string}` after being modified to return a `usize`
  for the number of bytes read.
* `ReadExt`
* `Write`
* `Write::write`
* `Write::{write_all, write_fmt}`
* `WriteExt`
* `BufRead`
* `BufRead::{fill_buf, consume}`
* `BufRead::{read_line, read_until}` after being modified to return a `usize`
  for the number of bytes read.
* `BufReadExt`
* `BufReader`
* `BufReader::{new, with_capacity}`
* `BufReader::{get_ref, get_mut, into_inner}`
* `{Read,BufRead} for BufReader`
* `BufWriter`
* `BufWriter::{new, with_capacity}`
* `BufWriter::{get_ref, get_mut, into_inner}`
* `Write for BufWriter`
* `IntoInnerError`
* `IntoInnerError::{error, into_inner}`
* `{Error,Display} for IntoInnerError`
* `LineWriter`
* `LineWriter::{new, with_capacity}` - `with_capacity` was added
* `LineWriter::{get_ref, get_mut, into_inner}` - `get_mut` was added)
* `Write for LineWriter`
* `BufStream`
* `BufStream::{new, with_capacities}`
* `BufStream::{get_ref, get_mut, into_inner}`
* `{BufRead,Read,Write} for BufStream`
* `stdin`
* `Stdin`
* `Stdin::lock`
* `Stdin::read_line` - added method
* `StdinLock`
* `Read for Stdin`
* `{Read,BufRead} for StdinLock`
* `stdout`
* `Stdout`
* `Stdout::lock`
* `StdoutLock`
* `Write for Stdout`
* `Write for StdoutLock`
* `stderr`
* `Stderr`
* `Stderr::lock`
* `StderrLock`
* `Write for Stderr`
* `Write for StderrLock`
* `io::Result`
* `io::Error`
* `io::Error::last_os_error`
* `{Display, Error} for Error`

Unstable APIs:

(reasons can be found in the commit itself)

* `Write::flush`
* `Seek`
* `ErrorKind`
* `Error::new`
* `Error::from_os_error`
* `Error::kind`

Deprecated APIs

* `Error::description` - available via the `Error` trait
* `Error::detail` - available via the `Display` implementation
* `thread::Builder::{stdout, stderr}`

Changes in functionality:

* `old_io::stdio::set_stderr` is now a noop as the infrastructure for printing
  backtraces has migrated to `std::io`.

[breaking-change]

2 files changed, 8 insertions, 25 deletions

diff --git a/src/libstd/old_io/mod.rs b/src/libstd/old_io/mod.rs
index f71698fa725..9d438978f42 100644
--- a/src/libstd/old_io/mod.rs
+++ b/src/libstd/old_io/mod.rs
@@ -242,6 +242,9 @@
 #![deny(unused_must_use)]
 #![allow(deprecated)] // seriously this is all deprecated
 #![allow(unused_imports)]
+#![deprecated(since = "1.0.0",
+              reasons = "APIs have been replaced with new I/O modules such as \
+                         std::{io, fs, net, process}")]
 
 pub use self::SeekStyle::*;
 pub use self::FileMode::*;
diff --git a/src/libstd/old_io/stdio.rs b/src/libstd/old_io/stdio.rs
index 70e8a4ceff0..34b4ec94a44 100644
--- a/src/libstd/old_io/stdio.rs
+++ b/src/libstd/old_io/stdio.rs
@@ -31,10 +31,9 @@ use boxed;
 use boxed::Box;
 use cell::RefCell;
 use clone::Clone;
-use panicking::LOCAL_STDERR;
 use fmt;
 use old_io::{Reader, Writer, IoResult, IoError, OtherIoError, Buffer,
-         standard_error, EndOfFile, LineBufferedWriter, BufferedReader};
+             standard_error, EndOfFile, LineBufferedWriter, BufferedReader};
 use marker::{Sync, Send};
 use libc;
 use mem;
@@ -319,14 +318,10 @@ pub fn set_stdout(stdout: Box<Writer + Send>) -> Option<Box<Writer + Send>> {
 ///
 /// Note that this does not need to be called for all new tasks; the default
 /// output handle is to the process's stderr stream.
-pub fn set_stderr(stderr: Box<Writer + Send>) -> Option<Box<Writer + Send>> {
-    let mut new = Some(stderr);
-    LOCAL_STDERR.with(|slot| {
-        mem::replace(&mut *slot.borrow_mut(), new.take())
-    }).and_then(|mut s| {
-        let _ = s.flush();
-        Some(s)
-    })
+#[unstable(feature = "old_io")]
+#[deprecated(since = "1.0.0", reason = "replaced with std::io::set_panic")]
+pub fn set_stderr(_stderr: Box<Writer + Send>) -> Option<Box<Writer + Send>> {
+    None
 }
 
 // Helper to access the local task's stdout handle
@@ -554,19 +549,4 @@ mod tests {
         });
         assert_eq!(r.read_to_string().unwrap(), "hello!\n");
     }
-
-    #[test]
-    fn capture_stderr() {
-        use old_io::{ChanReader, ChanWriter, Reader};
-
-        let (tx, rx) = channel();
-        let (mut r, w) = (ChanReader::new(rx), ChanWriter::new(tx));
-        // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
-        let _t = thread::spawn(move || -> () {
-            set_stderr(Box::new(w));
-            panic!("my special message");
-        });
-        let s = r.read_to_string().unwrap();
-        assert!(s.contains("my special message"));
-    }
 }