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, 3 insertions, 3 deletions

diff --git a/src/libstd/sync/arc.rs b/src/libstd/sync/arc.rs
index 676c836c459..7dcfe62ffb8 100644
--- a/src/libstd/sync/arc.rs
+++ b/src/libstd/sync/arc.rs
@@ -21,10 +21,10 @@
 //! the underlying data will remain valid (not free'd) so long as the reference
 //! count is greater than one.
 
-use cast;
 use clone::Clone;
 use iter::Iterator;
 use kinds::Send;
+use mem;
 use ops::Drop;
 use owned::Box;
 use ptr::RawPtr;
@@ -50,7 +50,7 @@ unsafe fn new_inner<T: Send>(data: T, refcount: uint) -> *mut ArcData<T> {
                     count: AtomicUint::new(refcount),
                     data: Unsafe::new(data)
                  };
-    cast::transmute(data)
+    mem::transmute(data)
 }
 
 impl<T: Send> UnsafeArc<T> {
@@ -158,7 +158,7 @@ impl<T> Drop for UnsafeArc<T>{
                 //  happened before), and an "acquire" operation before deleting the object.
                 // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
                 fence(Acquire);
-                let _: Box<ArcData<T>> = cast::transmute(self.data);
+                let _: Box<ArcData<T>> = mem::transmute(self.data);
             }
         }
     }