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, 5 deletions

diff --git a/src/libstd/slice.rs b/src/libstd/slice.rs
index b97c55ad701..b0868dd0daf 100644
--- a/src/libstd/slice.rs
+++ b/src/libstd/slice.rs
@@ -97,8 +97,7 @@ There are a number of free functions that create or take vectors, for example:
 
 */
 
-use cast::transmute;
-use cast;
+use mem::transmute;
 use clone::Clone;
 use cmp::{TotalOrd, Ordering, Less, Greater};
 use cmp;
@@ -333,7 +332,7 @@ impl<'a, T: Clone> CloneableVector<T> for &'a [T] {
                     // FIXME: #13994 (should pass align and size here)
                     exchange_free(ret as *mut u8, 0, 8);
                 });
-            cast::transmute(ret)
+            mem::transmute(ret)
         }
     }
 
@@ -380,7 +379,7 @@ impl<'a, T: Clone> CloneableVector<T> for &'a [T] {
                     // FIXME: #13994 (should pass align and size here)
                     exchange_free(ret as *mut u8, 0, 8);
                 });
-            cast::transmute(ret)
+            mem::transmute(ret)
         }
     }
 
@@ -531,7 +530,7 @@ fn insertion_sort<T>(v: &mut [T], compare: |&T, &T| -> Ordering) {
                 ptr::copy_nonoverlapping_memory(buf_v.offset(j),
                                                 &tmp as *T,
                                                 1);
-                cast::forget(tmp);
+                mem::forget(tmp);
             }
         }
     }