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]

1 files changed, 6 insertions, 6 deletions

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),
         }
     }