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, 4 insertions, 4 deletions

diff --git a/src/libgreen/stack.rs b/src/libgreen/stack.rs
index cccf0ec6987..7d6c82cb0c3 100644
--- a/src/libgreen/stack.rs
+++ b/src/libgreen/stack.rs
@@ -24,7 +24,7 @@ pub struct Stack {
 // Try to use MAP_STACK on platforms that support it (it's what we're doing
 // anyway), but some platforms don't support it at all. For example, it appears
 // that there's a bug in freebsd that MAP_STACK implies MAP_FIXED (so it always
-// fails): http://lists.freebsd.org/pipermail/freebsd-bugs/2011-July/044840.html
+// panics): http://lists.freebsd.org/pipermail/freebsd-bugs/2011-July/044840.html
 //
 // DragonFly BSD also seems to suffer from the same problem. When MAP_STACK is
 // used, it returns the same `ptr` multiple times.
@@ -37,7 +37,7 @@ static STACK_FLAGS: libc::c_int = libc::MAP_PRIVATE | libc::MAP_ANON;
 static STACK_FLAGS: libc::c_int = 0;
 
 impl Stack {
-    /// Allocate a new stack of `size`. If size = 0, this will fail. Use
+    /// Allocate a new stack of `size`. If size = 0, this will panic. Use
     /// `dummy_stack` if you want a zero-sized stack.
     pub fn new(size: uint) -> Stack {
         // Map in a stack. Eventually we might be able to handle stack
@@ -47,7 +47,7 @@ impl Stack {
         let stack = match MemoryMap::new(size, [MapReadable, MapWritable,
                                          MapNonStandardFlags(STACK_FLAGS)]) {
             Ok(map) => map,
-            Err(e) => fail!("mmap for stack of size {} failed: {}", size, e)
+            Err(e) => panic!("mmap for stack of size {} failed: {}", size, e)
         };
 
         // Change the last page to be inaccessible. This is to provide safety;
@@ -55,7 +55,7 @@ impl Stack {
         // page. It isn't guaranteed, but that's why FFI is unsafe. buf.data is
         // guaranteed to be aligned properly.
         if !protect_last_page(&stack) {
-            fail!("Could not memory-protect guard page. stack={}, errno={}",
+            panic!("Could not memory-protect guard page. stack={}, errno={}",
                   stack.data(), errno());
         }