1 files changed, 41 insertions, 0 deletions
diff --git a/src/test/run-pass/issue-42463.rs b/src/test/run-pass/issue-42463.rs
new file mode 100644
index 00000000000..7182fc213f7
--- /dev/null
+++ b/src/test/run-pass/issue-42463.rs
@@ -0,0 +1,41 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::ops::{Deref, DerefMut};
+
+struct CheckedDeref<T, F> {
+    value: T,
+    check: F
+}
+
+impl<F: Fn(&T) -> bool, T> Deref for CheckedDeref<T, F> {
+    type Target = T;
+    fn deref(&self) -> &T {
+        assert!((self.check)(&self.value));
+        &self.value
+    }
+}
+
+impl<F: Fn(&T) -> bool, T> DerefMut for CheckedDeref<T, F> {
+    fn deref_mut(&mut self) -> &mut T {
+        assert!((self.check)(&self.value));
+        &mut self.value
+    }
+}
+
+
+fn main() {
+    let mut v = CheckedDeref {
+        value: vec![0],
+        check: |v: &Vec<_>| !v.is_empty()
+    };
+    v.push(1);
+    assert_eq!(*v, vec![0, 1]);
+}