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]

2 files changed, 7 insertions, 8 deletions

diff --git a/src/libstd/comm/select.rs b/src/libstd/comm/select.rs
index cebfeb5399e..ed884647fb6 100644
--- a/src/libstd/comm/select.rs
+++ b/src/libstd/comm/select.rs
@@ -45,11 +45,11 @@
 
 #![allow(dead_code)]
 
-use cast;
 use cell::Cell;
 use iter::Iterator;
-use kinds::marker;
 use kinds::Send;
+use kinds::marker;
+use mem;
 use ops::Drop;
 use option::{Some, None, Option};
 use owned::Box;
@@ -247,8 +247,8 @@ impl<'rx, T: Send> Handle<'rx, T> {
     /// while it is added to the `Select` set.
     pub unsafe fn add(&mut self) {
         if self.added { return }
-        let selector: &mut Select = cast::transmute(&*self.selector);
-        let me: *mut Handle<'static, ()> = cast::transmute(&*self);
+        let selector: &mut Select = mem::transmute(&*self.selector);
+        let me: *mut Handle<'static, ()> = mem::transmute(&*self);
 
         if selector.head.is_null() {
             selector.head = me;
@@ -268,8 +268,8 @@ impl<'rx, T: Send> Handle<'rx, T> {
     pub unsafe fn remove(&mut self) {
         if !self.added { return }
 
-        let selector: &mut Select = cast::transmute(&*self.selector);
-        let me: *mut Handle<'static, ()> = cast::transmute(&*self);
+        let selector: &mut Select = mem::transmute(&*self.selector);
+        let me: *mut Handle<'static, ()> = mem::transmute(&*self);
 
         if self.prev.is_null() {
             assert_eq!(selector.head, me);
diff --git a/src/libstd/comm/sync.rs b/src/libstd/comm/sync.rs
index db3f90cad5a..819e885526c 100644
--- a/src/libstd/comm/sync.rs
+++ b/src/libstd/comm/sync.rs
@@ -33,7 +33,6 @@
 /// of a synchronous channel. There are a few branches for the unbuffered case,
 /// but they're mostly just relevant to blocking senders.
 
-use cast;
 use container::Container;
 use iter::Iterator;
 use kinds::Send;
@@ -187,7 +186,7 @@ impl<T: Send> Packet<T> {
             NoneBlocked if state.cap == 0 => {
                 let mut canceled = false;
                 assert!(state.canceled.is_none());
-                state.canceled = Some(unsafe { cast::transmute(&mut canceled) });
+                state.canceled = Some(unsafe { mem::transmute(&mut canceled) });
                 wait(&mut state.blocker, BlockedSender, &self.lock);
                 if canceled {Err(state.buf.dequeue())} else {Ok(())}
             }