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]

src/test/run-pass/issue-11881.rs

@@ -13,16 +13,15 @@
 extern crate rbml;
 extern crate serialize;
 
-use std::old_io;
+use std::io::Cursor;
+use std::io::prelude::*;
 use std::fmt;
-use std::old_io::{IoResult, SeekStyle};
 use std::slice;
 
 use serialize::{Encodable, Encoder};
 use serialize::json;
 
 use rbml::writer;
-use rbml::io::SeekableMemWriter;
 
 #[derive(Encodable)]
 struct Foo {
@@ -40,17 +39,17 @@ enum WireProtocol {
     // ...
 }
 
-fn encode_json<T: Encodable>(val: &T, wr: &mut SeekableMemWriter) {
+fn encode_json<T: Encodable>(val: &T, wr: &mut Cursor<Vec<u8>>) {
     write!(wr, "{}", json::as_json(val));
 }
-fn encode_rbml<T: Encodable>(val: &T, wr: &mut SeekableMemWriter) {
+fn encode_rbml<T: Encodable>(val: &T, wr: &mut Cursor<Vec<u8>>) {
     let mut encoder = writer::Encoder::new(wr);
     val.encode(&mut encoder);
 }
 
 pub fn main() {
     let target = Foo{baz: false,};
-    let mut wr = SeekableMemWriter::new();
+    let mut wr = Cursor::new(Vec::new());
     let proto = WireProtocol::JSON;
     match proto {
         WireProtocol::JSON => encode_json(&target, &mut wr),

src/test/run-pass/task-stderr.rs

@@ -11,21 +11,30 @@
 #![allow(unknown_features)]
 #![feature(box_syntax)]
 
-use std::sync::mpsc::channel;
-use std::old_io::{ChanReader, ChanWriter};
+use std::io::prelude::*;
+use std::io;
+use std::str;
+use std::sync::{Arc, Mutex};
 use std::thread;
 
-fn main() {
-    let (tx, rx) = channel();
-    let mut reader = ChanReader::new(rx);
-    let stderr = ChanWriter::new(tx);
+struct Sink(Arc<Mutex<Vec<u8>>>);
+impl Write for Sink {
+    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
+        Write::write(&mut *self.0.lock().unwrap(), data)
+    }
+    fn flush(&mut self) -> io::Result<()> { Ok(()) }
+}
 
-    let res = thread::Builder::new().stderr(box stderr as Box<Writer + Send>)
-                                    .spawn(move|| -> () {
+fn main() {
+    let data = Arc::new(Mutex::new(Vec::new()));
+    let sink = Sink(data.clone());
+    let res = thread::Builder::new().spawn(move|| -> () {
+        io::set_panic(Box::new(sink));
         panic!("Hello, world!")
     }).unwrap().join();
     assert!(res.is_err());
 
-    let output = reader.read_to_string().unwrap();
+    let output = data.lock().unwrap();
+    let output = str::from_utf8(&output).unwrap();
     assert!(output.contains("Hello, world!"));
 }