use UFCS in `#[deriving(Hash)]`

expansion now uses `::std::hash::Hash::hash(&*__self_0_0, __arg_0)` instead of
`(*__self_0_0).hash(__arg_0)`

closes #21160

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libcollections/btree/set.rs b/src/libcollections/btree/set.rs
index 812cff6fab7..6e048e0e83c 100644
--- a/src/libcollections/btree/set.rs
+++ b/src/libcollections/btree/set.rs
@@ -18,6 +18,8 @@ use core::cmp::Ordering::{self, Less, Greater, Equal};
 use core::default::Default;
 use core::fmt::Show;
 use core::fmt;
+// NOTE(stage0) remove import after a snapshot
+#[cfg(stage0)]
 use core::hash::Hash;
 use core::iter::{Peekable, Map, FromIterator};
 use core::ops::{BitOr, BitAnd, BitXor, Sub};