auto merge of #14069 : alexcrichton/rust/cast-module, r=brson

This commit revisits the `cast` module in libcore and libstd, and scrutinizes
all functions inside of it. The result was to remove the `cast` module entirely,
folding all functionality into the `mem` module. Specifically, this is the fate
of each function in the `cast` module.

* transmute - This function was moved to `mem`, but it is now marked as
              #[unstable]. This is due to planned changes to the `transmute`
              function and how it can be invoked (see the #[unstable] comment).
              For more information, see RFC 5 and #12898

* transmute_copy - This function was moved to `mem`, with clarification that is
                   is not an error to invoke it with T/U that are different
                   sizes, but rather that it is strongly discouraged. This
                   function is now #[stable]

* forget - This function was moved to `mem` and marked #[stable]

* bump_box_refcount - This function was removed due to the deprecation of
                      managed boxes as well as its questionable utility.

* transmute_mut - This function was previously deprecated, and removed as part
                  of this commit.

* transmute_mut_unsafe - This function doesn't serve much of a purpose when it
                         can be achieved with an `as` in safe code, so it was
                         removed.

* transmute_lifetime - This function was removed because it is likely a strong
                       indication that code is incorrect in the first place.

* transmute_mut_lifetime - This function was removed for the same reasons as
                           `transmute_lifetime`

* copy_lifetime - This function was moved to `mem`, but it is marked
                  `#[unstable]` now due to the likelihood of being removed in
                  the future if it is found to not be very useful.

* copy_mut_lifetime - This function was also moved to `mem`, but had the same
                      treatment as `copy_lifetime`.

* copy_lifetime_vec - This function was removed because it is not used today,
                      and its existence is not necessary with DST
                      (copy_lifetime will suffice).

In summary, the cast module was stripped down to these functions, and then the
functions were moved to the `mem` module.

    transmute - #[unstable]
    transmute_copy - #[stable]
    forget - #[stable]
    copy_lifetime - #[unstable]
    copy_mut_lifetime - #[unstable]

1 files changed, 2 insertions, 2 deletions

diff --git a/src/libstd/rt/backtrace.rs b/src/libstd/rt/backtrace.rs
index ee8041f6880..f4cb770544c 100644
--- a/src/libstd/rt/backtrace.rs
+++ b/src/libstd/rt/backtrace.rs
@@ -237,9 +237,9 @@ fn demangle(writer: &mut Writer, s: &str) -> IoResult<()> {
 #[cfg(unix)]
 mod imp {
     use c_str::CString;
-    use cast;
     use io::{IoResult, IoError, Writer};
     use libc;
+    use mem;
     use option::{Some, None, Option};
     use result::{Ok, Err};
     use unstable::mutex::{StaticNativeMutex, NATIVE_MUTEX_INIT};
@@ -280,7 +280,7 @@ mod imp {
 
         extern fn trace_fn(ctx: *uw::_Unwind_Context,
                            arg: *libc::c_void) -> uw::_Unwind_Reason_Code {
-            let cx: &mut Context = unsafe { cast::transmute(arg) };
+            let cx: &mut Context = unsafe { mem::transmute(arg) };
             let ip = unsafe { uw::_Unwind_GetIP(ctx) as *libc::c_void };
             // dladdr() on osx gets whiny when we use FindEnclosingFunction, and
             // it appears to work fine without it, so we only use