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]

1 files changed, 4 insertions, 4 deletions

diff --git a/src/libstd/path/windows.rs b/src/libstd/path/windows.rs
index f21fbe1b6e6..dfe7241d7af 100644
--- a/src/libstd/path/windows.rs
+++ b/src/libstd/path/windows.rs
@@ -12,13 +12,13 @@
 
 use ascii::AsciiCast;
 use c_str::{CString, ToCStr};
-use cast;
 use clone::Clone;
-use container::Container;
 use cmp::{Eq, TotalEq};
+use container::Container;
 use from_str::FromStr;
 use io::Writer;
 use iter::{AdditiveIterator, DoubleEndedIterator, Extendable, Rev, Iterator, Map};
+use mem;
 use option::{Option, Some, None};
 use slice::{Vector, OwnedVector, ImmutableVector};
 use str::{CharSplits, Str, StrAllocating, StrVector, StrSlice};
@@ -389,13 +389,13 @@ impl GenericPath for Path {
     #[inline]
     fn filestem_str<'a>(&'a self) -> Option<&'a str> {
         // filestem() returns a byte vector that's guaranteed valid UTF-8
-        self.filestem().map(|t| unsafe { cast::transmute(t) })
+        self.filestem().map(|t| unsafe { mem::transmute(t) })
     }
 
     #[inline]
     fn extension_str<'a>(&'a self) -> Option<&'a str> {
         // extension() returns a byte vector that's guaranteed valid UTF-8
-        self.extension().map(|t| unsafe { cast::transmute(t) })
+        self.extension().map(|t| unsafe { mem::transmute(t) })
     }
 
     fn dir_path(&self) -> Path {