Implement `RefCell::{try_borrow, try_borrow_mut}`

2 files changed, 16 insertions, 0 deletions

diff --git a/src/libstd/error.rs b/src/libstd/error.rs
index 1459420cdc0..914599271ac 100644
--- a/src/libstd/error.rs
+++ b/src/libstd/error.rs
@@ -49,6 +49,7 @@
 
 use any::TypeId;
 use boxed::Box;
+use cell;
 use char;
 use fmt::{self, Debug, Display};
 use marker::{Send, Sync, Reflect};
@@ -289,6 +290,20 @@ impl Error for fmt::Error {
     }
 }
 
+#[unstable(feature = "try_borrow", issue = "35070")]
+impl<'a, T: ?Sized + Reflect> Error for cell::BorrowError<'a, T> {
+    fn description(&self) -> &str {
+        "already mutably borrowed"
+    }
+}
+
+#[unstable(feature = "try_borrow", issue = "35070")]
+impl<'a, T: ?Sized + Reflect> Error for cell::BorrowMutError<'a, T> {
+    fn description(&self) -> &str {
+        "already borrowed"
+    }
+}
+
 // copied from any.rs
 impl Error + 'static {
     /// Returns true if the boxed type is the same as `T`
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 865d067cdb6..c6272012d66 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -269,6 +269,7 @@
 #![feature(str_utf16)]
 #![feature(test, rustc_private)]
 #![feature(thread_local)]
+#![feature(try_borrow)]
 #![feature(try_from)]
 #![feature(unboxed_closures)]
 #![feature(unicode)]