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, 4 insertions, 4 deletions

diff --git a/src/libstd/sync/mpsc_queue.rs b/src/libstd/sync/mpsc_queue.rs
index e05959e2591..4cdcd05e9b4 100644
--- a/src/libstd/sync/mpsc_queue.rs
+++ b/src/libstd/sync/mpsc_queue.rs
@@ -38,8 +38,8 @@
 // http://www.1024cores.net/home/lock-free-algorithms
 //                         /queues/non-intrusive-mpsc-node-based-queue
 
-use cast;
 use kinds::Send;
+use mem;
 use ops::Drop;
 use option::{Option, None, Some};
 use owned::Box;
@@ -74,7 +74,7 @@ pub struct Queue<T> {
 
 impl<T> Node<T> {
     unsafe fn new(v: Option<T>) -> *mut Node<T> {
-        cast::transmute(box Node {
+        mem::transmute(box Node {
             next: AtomicPtr::new(0 as *mut Node<T>),
             value: v,
         })
@@ -121,7 +121,7 @@ impl<T: Send> Queue<T> {
                 assert!((*tail).value.is_none());
                 assert!((*next).value.is_some());
                 let ret = (*next).value.take_unwrap();
-                let _: Box<Node<T>> = cast::transmute(tail);
+                let _: Box<Node<T>> = mem::transmute(tail);
                 return Data(ret);
             }
 
@@ -146,7 +146,7 @@ impl<T: Send> Drop for Queue<T> {
             let mut cur = self.tail;
             while !cur.is_null() {
                 let next = (*cur).next.load(Relaxed);
-                let _: Box<Node<T>> = cast::transmute(cur);
+                let _: Box<Node<T>> = mem::transmute(cur);
                 cur = next;
             }
         }