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, 7 insertions, 7 deletions

diff --git a/src/libstd/failure.rs b/src/libstd/failure.rs
index a7de84184ff..07759974356 100644
--- a/src/libstd/failure.rs
+++ b/src/libstd/failure.rs
@@ -51,11 +51,11 @@ pub fn on_fail(obj: &Any + Send, file: &'static str, line: uint) {
     // all times. This means that this `exists` will return true almost all of
     // the time. There are border cases, however, when the runtime has
     // *almost* set up the local task, but hasn't quite gotten there yet. In
-    // order to get some better diagnostics, we print on failure and
+    // order to get some better diagnostics, we print on panic and
     // immediately abort the whole process if there is no local task
     // available.
     if !Local::exists(None::<Task>) {
-        let _ = writeln!(&mut err, "failed at '{}', {}:{}", msg, file, line);
+        let _ = writeln!(&mut err, "panicked at '{}', {}:{}", msg, file, line);
         if backtrace::log_enabled() {
             let _ = backtrace::write(&mut err);
         } else {
@@ -76,9 +76,9 @@ pub fn on_fail(obj: &Any + Send, file: &'static str, line: uint) {
 
         match local_stderr.replace(None) {
             Some(mut stderr) => {
-                // FIXME: what to do when the task printing fails?
+                // FIXME: what to do when the task printing panics?
                 let _ = writeln!(stderr,
-                                 "task '{}' failed at '{}', {}:{}\n",
+                                 "task '{}' panicked at '{}', {}:{}\n",
                                  n, msg, file, line);
                 if backtrace::log_enabled() {
                     let _ = backtrace::write(&mut *stderr);
@@ -86,7 +86,7 @@ pub fn on_fail(obj: &Any + Send, file: &'static str, line: uint) {
                 local_stderr.replace(Some(stderr));
             }
             None => {
-                let _ = writeln!(&mut err, "task '{}' failed at '{}', {}:{}",
+                let _ = writeln!(&mut err, "task '{}' panicked at '{}', {}:{}",
                                  n, msg, file, line);
                 if backtrace::log_enabled() {
                     let _ = backtrace::write(&mut err);
@@ -94,8 +94,8 @@ pub fn on_fail(obj: &Any + Send, file: &'static str, line: uint) {
             }
         }
 
-        // If this is a double failure, make sure that we printed a backtrace
-        // for this failure.
+        // If this is a double panic, make sure that we printed a backtrace
+        // for this panic.
         if unwinding && !backtrace::log_enabled() {
             let _ = backtrace::write(&mut err);
         }