Deprecate std::cell::RefCell::borrow_state

Author: aturon

src/libcore/cell.rs

@@ -393,6 +393,7 @@ pub struct RefCell<T: ?Sized> {
 /// An enumeration of values returned from the `state` method on a `RefCell<T>`.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 #[unstable(feature = "borrow_state", issue = "27733")]
+#[rustc_deprecated(since = "1.15.0", reason = "use `try_borrow` instead")]
 pub enum BorrowState {
     /// The cell is currently being read, there is at least one active `borrow`.
     Reading,
@@ -511,6 +512,7 @@ impl<T: ?Sized> RefCell<T> {
     /// }
     /// ```
     #[unstable(feature = "borrow_state", issue = "27733")]
+    #[rustc_deprecated(since = "1.15.0", reason = "use `try_borrow` instead")]
     #[inline]
     pub fn borrow_state(&self) -> BorrowState {
         match self.borrow.get() {