auto merge of #11946 : alexcrichton/rust/no-io-error, r=brson

Turns out this was a little more far-reaching than I thought it was.

The first commit is the crux of this stack of commits. The `io::io_error` condition is completely removed and the `read` and `write` methods are altered to return `IoResult<T>`. This turned out to be an incredibly far-reaching change!

Overall, I'm very happy with how this turned out (in addition with the `unused_must_use` lint). I had to almost rewrite the pretty printer in `libsyntax` as well as the the formatting in `librustdoc` (as one would expect). These two modules do *tons* of I/O, and I believe that it's definitely improved.

This pull request also introduces the `if_ok!()` macro for returning-early from something that returns a result. I made quite liberal use of this in mostly the pretty printer and html renderer, and I found its usage generally quite pleasant and convenient to have. I didn't really feel like adding any other macro while I was using it, and I figured that pretty printing could be nicer, but it's nowhere near horrid today.

This may be a controversial issue closing, but I'm going to say it.

Closes #6163

1 files changed, 4 insertions, 3 deletions

diff --git a/src/libnative/io/timer_timerfd.rs b/src/libnative/io/timer_timerfd.rs
index ca20314997e..7c22e90bbff 100644
--- a/src/libnative/io/timer_timerfd.rs
+++ b/src/libnative/io/timer_timerfd.rs
@@ -96,7 +96,7 @@ fn helper(input: libc::c_int, messages: Port<Req>) {
             if fd == input {
                 let mut buf = [0, ..1];
                 // drain the input file descriptor of its input
-                FileDesc::new(fd, false).inner_read(buf).unwrap();
+                let _ = FileDesc::new(fd, false).inner_read(buf).unwrap();
                 incoming = true;
             } else {
                 let mut bits = [0, ..8];
@@ -104,7 +104,7 @@ fn helper(input: libc::c_int, messages: Port<Req>) {
                 //
                 // FIXME: should this perform a send() this number of
                 //      times?
-                FileDesc::new(fd, false).inner_read(bits).unwrap();
+                let _ = FileDesc::new(fd, false).inner_read(bits).unwrap();
                 let remove = {
                     match map.find(&fd).expect("fd unregistered") {
                         &(ref c, oneshot) => !c.try_send(()) || oneshot
@@ -166,7 +166,8 @@ impl Timer {
     }
 
     pub fn sleep(ms: u64) {
-        unsafe { libc::usleep((ms * 1000) as libc::c_uint); }
+        // FIXME: this can fail because of EINTR, what do do?
+        let _ = unsafe { libc::usleep((ms * 1000) as libc::c_uint) };
     }
 
     fn remove(&mut self) {