Auto merge of #35425 - apasel422:refcell, r=alexcrichton

Implement `RefCell::{try_borrow, try_borrow_mut}`

CC #35070

r? @alexcrichton

1 files changed, 15 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`