core: Remove the cast module

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]

[breaking-change]

5 files changed, 32 insertions, 33 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);
             }
         }
     }
diff --git a/src/libstd/sync/atomics.rs b/src/libstd/sync/atomics.rs
index 2fba59c3233..6ddae97e901 100644
--- a/src/libstd/sync/atomics.rs
+++ b/src/libstd/sync/atomics.rs
@@ -108,11 +108,11 @@
 #![allow(missing_doc)]
 
 use intrinsics;
-use cast;
-use std::kinds::marker;
-use option::{Option,Some,None};
+use mem;
 use ops::Drop;
+use option::{Option,Some,None};
 use owned::Box;
+use std::kinds::marker;
 use ty::Unsafe;
 
 /// An atomic boolean type.
@@ -665,7 +665,7 @@ impl<T> AtomicPtr<T> {
 impl<T> AtomicOption<T> {
     /// Create a new `AtomicOption`
     pub fn new(p: Box<T>) -> AtomicOption<T> {
-        unsafe { AtomicOption { p: Unsafe::new(cast::transmute(p)) } }
+        unsafe { AtomicOption { p: Unsafe::new(mem::transmute(p)) } }
     }
 
     /// Create a new `AtomicOption` that doesn't contain a value
@@ -675,13 +675,13 @@ impl<T> AtomicOption<T> {
     #[inline]
     pub fn swap(&self, val: Box<T>, order: Ordering) -> Option<Box<T>> {
         unsafe {
-            let val = cast::transmute(val);
+            let val = mem::transmute(val);
 
             let p = atomic_swap(self.p.get(), val, order);
             if p as uint == 0 {
                 None
             } else {
-                Some(cast::transmute(p))
+                Some(mem::transmute(p))
             }
         }
     }
@@ -689,7 +689,7 @@ impl<T> AtomicOption<T> {
     /// Remove the value, leaving the `AtomicOption` empty.
     #[inline]
     pub fn take(&self, order: Ordering) -> Option<Box<T>> {
-        unsafe { self.swap(cast::transmute(0), order) }
+        unsafe { self.swap(mem::transmute(0), order) }
     }
 
     /// Replace an empty value with a non-empty value.
@@ -700,13 +700,13 @@ impl<T> AtomicOption<T> {
     #[inline]
     pub fn fill(&self, val: Box<T>, order: Ordering) -> Option<Box<T>> {
         unsafe {
-            let val = cast::transmute(val);
-            let expected = cast::transmute(0);
+            let val = mem::transmute(val);
+            let expected = mem::transmute(0);
             let oldval = atomic_compare_and_swap(self.p.get(), expected, val, order);
             if oldval == expected {
                 None
             } else {
-                Some(cast::transmute(val))
+                Some(mem::transmute(val))
             }
         }
     }
diff --git a/src/libstd/sync/deque.rs b/src/libstd/sync/deque.rs
index 8dfd691e6ff..175bb03d262 100644
--- a/src/libstd/sync/deque.rs
+++ b/src/libstd/sync/deque.rs
@@ -48,7 +48,6 @@
 // FIXME: all atomic operations in this module use a SeqCst ordering. That is
 //      probably overkill
 
-use cast;
 use clone::Clone;
 use iter::{range, Iterator};
 use kinds::Send;
@@ -57,12 +56,12 @@ use mem;
 use ops::Drop;
 use option::{Option, Some, None};
 use owned::Box;
-use ptr;
 use ptr::RawPtr;
+use ptr;
+use slice::ImmutableVector;
 use sync::arc::UnsafeArc;
 use sync::atomics::{AtomicInt, AtomicPtr, SeqCst};
 use unstable::sync::Exclusive;
-use slice::ImmutableVector;
 use vec::Vec;
 
 // Once the queue is less than 1/K full, then it will be downsized. Note that
@@ -230,7 +229,7 @@ impl<T: Send> Deque<T> {
         Deque {
             bottom: AtomicInt::new(0),
             top: AtomicInt::new(0),
-            array: AtomicPtr::new(unsafe { cast::transmute(buf) }),
+            array: AtomicPtr::new(unsafe { mem::transmute(buf) }),
             pool: pool,
         }
     }
@@ -272,7 +271,7 @@ impl<T: Send> Deque<T> {
             return Some(data);
         } else {
             self.bottom.store(t + 1, SeqCst);
-            cast::forget(data); // someone else stole this value
+            mem::forget(data); // someone else stole this value
             return None;
         }
     }
@@ -294,7 +293,7 @@ impl<T: Send> Deque<T> {
         if self.top.compare_and_swap(t, t + 1, SeqCst) == t {
             Data(data)
         } else {
-            cast::forget(data); // someone else stole this value
+            mem::forget(data); // someone else stole this value
             Abort
         }
     }
@@ -315,7 +314,7 @@ impl<T: Send> Deque<T> {
     // continue to be read after we flag this buffer for reclamation.
     unsafe fn swap_buffer(&mut self, b: int, old: *mut Buffer<T>,
                           buf: Buffer<T>) -> *mut Buffer<T> {
-        let newbuf: *mut Buffer<T> = cast::transmute(box buf);
+        let newbuf: *mut Buffer<T> = mem::transmute(box buf);
         self.array.store(newbuf, SeqCst);
         let ss = (*newbuf).size();
         self.bottom.store(b + ss, SeqCst);
@@ -323,7 +322,7 @@ impl<T: Send> Deque<T> {
         if self.top.compare_and_swap(t, t + ss, SeqCst) != t {
             self.bottom.store(b, SeqCst);
         }
-        self.pool.free(cast::transmute(old));
+        self.pool.free(mem::transmute(old));
         return newbuf;
     }
 }
@@ -340,7 +339,7 @@ impl<T: Send> Drop for Deque<T> {
         for i in range(t, b) {
             let _: T = unsafe { (*a).get(i) };
         }
-        self.pool.free(unsafe { cast::transmute(a) });
+        self.pool.free(unsafe { mem::transmute(a) });
     }
 }
 
@@ -373,7 +372,7 @@ impl<T: Send> Buffer<T> {
     unsafe fn put(&mut self, i: int, t: T) {
         let ptr = self.storage.offset(i & self.mask());
         ptr::copy_nonoverlapping_memory(ptr as *mut T, &t as *T, 1);
-        cast::forget(t);
+        mem::forget(t);
     }
 
     // Again, unsafe because this has incredibly dubious ownership violations.
@@ -400,7 +399,7 @@ mod tests {
     use prelude::*;
     use super::{Data, BufferPool, Abort, Empty, Worker, Stealer};
 
-    use cast;
+    use mem;
     use owned::Box;
     use rt::thread::Thread;
     use rand;
@@ -607,7 +606,7 @@ mod tests {
             let s = s.clone();
             let unique_box = box AtomicUint::new(0);
             let thread_box = unsafe {
-                *cast::transmute::<&Box<AtomicUint>,
+                *mem::transmute::<&Box<AtomicUint>,
                                    **mut AtomicUint>(&unique_box)
             };
             (Thread::start(proc() {
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;
             }
         }
diff --git a/src/libstd/sync/spsc_queue.rs b/src/libstd/sync/spsc_queue.rs
index 7854a0e168e..ed6d690def0 100644
--- a/src/libstd/sync/spsc_queue.rs
+++ b/src/libstd/sync/spsc_queue.rs
@@ -33,8 +33,8 @@
 //! concurrently between two tasks. This data structure is safe to use and
 //! enforces the semantics that there is one pusher and one popper.
 
-use cast;
 use kinds::Send;
+use mem;
 use ops::Drop;
 use option::{Some, None, Option};
 use owned::Box;
@@ -74,7 +74,7 @@ pub struct Queue<T> {
 impl<T: Send> Node<T> {
     fn new() -> *mut Node<T> {
         unsafe {
-            cast::transmute(box Node {
+            mem::transmute(box Node {
                 value: None,
                 next: AtomicPtr::new(0 as *mut Node<T>),
             })
@@ -188,7 +188,7 @@ impl<T: Send> Queue<T> {
                     (*self.tail_prev.load(Relaxed)).next.store(next, Relaxed);
                     // We have successfully erased all references to 'tail', so
                     // now we can safely drop it.
-                    let _: Box<Node<T>> = cast::transmute(tail);
+                    let _: Box<Node<T>> = mem::transmute(tail);
                 }
             }
             return ret;
@@ -216,7 +216,7 @@ impl<T: Send> Drop for Queue<T> {
             let mut cur = self.first;
             while !cur.is_null() {
                 let next = (*cur).next.load(Relaxed);
-                let _n: Box<Node<T>> = cast::transmute(cur);
+                let _n: Box<Node<T>> = mem::transmute(cur);
                 cur = next;
             }
         }