Rename fail! to panic!

https://github.com/rust-lang/rfcs/pull/221

The current terminology of "task failure" often causes problems when
writing or speaking about code. You often want to talk about the
possibility of an operation that returns a Result "failing", but cannot
because of the ambiguity with task failure. Instead, you have to speak
of "the failing case" or "when the operation does not succeed" or other
circumlocutions.

Likewise, we use a "Failure" header in rustdoc to describe when
operations may fail the task, but it would often be helpful to separate
out a section describing the "Err-producing" case.

We have been steadily moving away from task failure and toward Result as
an error-handling mechanism, so we should optimize our terminology
accordingly: Result-producing functions should be easy to describe.

To update your code, rename any call to `fail!` to `panic!` instead.
Assuming you have not created your own macro named `panic!`, this
will work on UNIX based systems:

    grep -lZR 'fail!' . | xargs -0 -l sed -i -e 's/fail!/panic!/g'

You can of course also do this by hand.

[breaking-change]

6 files changed, 17 insertions, 17 deletions

diff --git a/src/libnative/io/file_unix.rs b/src/libnative/io/file_unix.rs
index 88f5061bbef..f616295c73d 100644
--- a/src/libnative/io/file_unix.rs
+++ b/src/libnative/io/file_unix.rs
@@ -523,7 +523,7 @@ mod tests {
                 assert_eq!(buf[2], 's' as u8);
                 assert_eq!(buf[3], 't' as u8);
             }
-            r => fail!("invalid read: {}", r)
+            r => panic!("invalid read: {}", r),
         }
 
         assert!(writer.inner_read(buf).is_err());
@@ -547,7 +547,7 @@ mod tests {
                     assert_eq!(buf[2], 's' as u8);
                     assert_eq!(buf[3], 't' as u8);
                 }
-                r => fail!("invalid read: {}", r)
+                r => panic!("invalid read: {}", r)
             }
         }
     }
diff --git a/src/libnative/io/pipe_windows.rs b/src/libnative/io/pipe_windows.rs
index bc08ede39f7..f764470f37d 100644
--- a/src/libnative/io/pipe_windows.rs
+++ b/src/libnative/io/pipe_windows.rs
@@ -710,7 +710,7 @@ impl UnixAcceptor {
         if new_handle == libc::INVALID_HANDLE_VALUE {
             let ret = Err(super::last_error());
             // If our disconnection fails, then there's not really a whole lot
-            // that we can do, so fail the task.
+            // that we can do, so panic
             let err = unsafe { libc::DisconnectNamedPipe(handle) };
             assert!(err != 0);
             return ret;
diff --git a/src/libnative/io/process.rs b/src/libnative/io/process.rs
index d69042175f7..fed4a46b9df 100644
--- a/src/libnative/io/process.rs
+++ b/src/libnative/io/process.rs
@@ -600,7 +600,7 @@ fn spawn_process_os(cfg: ProcessConfig,
                             handle: ptr::null_mut()
                         })
                     }
-                    Ok(..) => fail!("short read on the cloexec pipe"),
+                    Ok(..) => panic!("short read on the cloexec pipe"),
                 };
             }
             // And at this point we've reached a special time in the life of the
@@ -944,7 +944,7 @@ fn waitpid(pid: pid_t, deadline: u64) -> IoResult<rtio::ProcessExit> {
     let mut status = 0 as c_int;
     if deadline == 0 {
         return match retry(|| unsafe { c::waitpid(pid, &mut status, 0) }) {
-            -1 => fail!("unknown waitpid error: {}", super::last_error().code),
+            -1 => panic!("unknown waitpid error: {}", super::last_error().code),
             _ => Ok(translate_status(status)),
         }
     }
@@ -1069,7 +1069,7 @@ fn waitpid(pid: pid_t, deadline: u64) -> IoResult<rtio::ProcessExit> {
                     continue
                 }
 
-                n => fail!("error in select {} ({})", os::errno(), n),
+                n => panic!("error in select {} ({})", os::errno(), n),
             }
 
             // Process any pending messages
@@ -1149,7 +1149,7 @@ fn waitpid(pid: pid_t, deadline: u64) -> IoResult<rtio::ProcessExit> {
                 n if n > 0 => { ret = true; }
                 0 => return true,
                 -1 if util::wouldblock() => return ret,
-                n => fail!("bad read {} ({})", os::last_os_error(), n),
+                n => panic!("bad read {} ({})", os::last_os_error(), n),
             }
         }
     }
@@ -1172,7 +1172,7 @@ fn waitpid(pid: pid_t, deadline: u64) -> IoResult<rtio::ProcessExit> {
         } {
             1 => {}
             -1 if util::wouldblock() => {} // see above comments
-            n => fail!("bad error on write fd: {} {}", n, os::errno()),
+            n => panic!("bad error on write fd: {} {}", n, os::errno()),
         }
     }
 }
@@ -1192,7 +1192,7 @@ fn waitpid_nowait(pid: pid_t) -> Option<rtio::ProcessExit> {
         }) {
             n if n == pid => Some(translate_status(status)),
             0 => None,
-            n => fail!("unknown waitpid error `{}`: {}", n,
+            n => panic!("unknown waitpid error `{}`: {}", n,
                        super::last_error().code),
         }
     }
diff --git a/src/libnative/io/timer_unix.rs b/src/libnative/io/timer_unix.rs
index 6f57a5e88ba..38895f2a8f9 100644
--- a/src/libnative/io/timer_unix.rs
+++ b/src/libnative/io/timer_unix.rs
@@ -194,7 +194,7 @@ fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
             }
 
             -1 if os::errno() == libc::EINTR as int => {}
-            n => fail!("helper thread failed in select() with error: {} ({})",
+            n => panic!("helper thread panicked in select() with error: {} ({})",
                        n, os::last_os_error())
         }
     }
@@ -227,7 +227,7 @@ impl Timer {
         };
         while unsafe { libc::nanosleep(&to_sleep, &mut to_sleep) } != 0 {
             if os::errno() as int != libc::EINTR as int {
-                fail!("failed to sleep, but not because of EINTR?");
+                panic!("failed to sleep, but not because of EINTR?");
             }
         }
     }
diff --git a/src/libnative/lib.rs b/src/libnative/lib.rs
index c99143f0a5d..4da088cccb3 100644
--- a/src/libnative/lib.rs
+++ b/src/libnative/lib.rs
@@ -142,7 +142,7 @@ pub fn start(argc: int, argv: *const *const u8, main: proc()) -> int {
         exit_code = Some(run(main.take().unwrap()));
     }).destroy());
     unsafe { rt::cleanup(); }
-    // If the exit code wasn't set, then the task block must have failed.
+    // If the exit code wasn't set, then the task block must have panicked.
     return exit_code.unwrap_or(rt::DEFAULT_ERROR_CODE);
 }
 
diff --git a/src/libnative/task.rs b/src/libnative/task.rs
index 455656c09d4..e702c12bdff 100644
--- a/src/libnative/task.rs
+++ b/src/libnative/task.rs
@@ -297,11 +297,11 @@ mod tests {
     }
 
     #[test]
-    fn smoke_fail() {
+    fn smoke_panic() {
         let (tx, rx) = channel::<()>();
         spawn(proc() {
             let _tx = tx;
-            fail!()
+            panic!()
         });
         assert_eq!(rx.recv_opt(), Err(()));
     }
@@ -318,11 +318,11 @@ mod tests {
     }
 
     #[test]
-    fn smoke_opts_fail() {
+    fn smoke_opts_panic() {
         let mut opts = TaskOpts::new();
         let (tx, rx) = channel();
         opts.on_exit = Some(proc(r) tx.send(r));
-        NativeSpawner.spawn(opts, proc() { fail!() });
+        NativeSpawner.spawn(opts, proc() { panic!() });
         assert!(rx.recv().is_err());
     }
 
@@ -365,7 +365,7 @@ mod tests {
                     Some(ops) => {
                         task.put_runtime(ops);
                     }
-                    None => fail!(),
+                    None => panic!(),
                 }
                 Local::put(task);
                 tx.send(());