librustc: Remove cross borrowing from mutable `Box`es to `&mut`.

This will break code like:

    fn f(x: &mut int) {}

    let mut a = box 1i;
    f(a);

Change it to:

    fn f(x: &mut int) {}

    let mut a = box 1i;
    f(&mut *a);

RFC 33; issue #10504.

[breaking-change]

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libsync/raw.rs b/src/libsync/raw.rs
index 28a08a7fef2..35865e65612 100644
--- a/src/libsync/raw.rs
+++ b/src/libsync/raw.rs
@@ -899,7 +899,7 @@ mod tests {
             });
         }
         {
-            access_shared(sharedstate, &x, mode2, 10);
+            access_shared(&mut *sharedstate, &x, mode2, 10);
             let _ = rx.recv();
 
             assert_eq!(*sharedstate, 20);