---

yaml
---
r: 186341
b: refs/heads/try
c: 310ada0
h: refs/heads/master
i:
  186339: a74d28a
v: v3

Author: Junseok Lee

[refs]

@@ -2,7 +2,7 @@
 refs/heads/master: b4c965ee803a4521d8b4575f634e036f93e408f3
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 3a96d6a9818fe2affc98a187fb1065120458cee9
-refs/heads/try: b6544fd3520d5eed05aafeb6b78737e32bf2c435
+refs/heads/try: 310ada06f2d632340845ccd4d7e68a1b54d2f28a
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/dist-snap: ba4081a5a8573875fed17545846f6f6902c8ba8d
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596

branches/try/src/libcore/marker.rs

@@ -308,6 +308,20 @@ impl<T: ?Sized> Clone for ContravariantType<T> {
 ///
 /// For more information about variance, refer to this Uncyclopedia
 /// article <http://en.wikipedia.org/wiki/Variance_%28computer_science%29>.
+///
+/// # Example
+///
+/// The Cell type is an example of an `InvariantType` which uses unsafe
+/// code to achieve "interior" mutability:
+///
+/// ```
+/// struct Cell<T> { value: T }
+/// ```
+///
+/// The type system would infer that `value` is only read here
+/// and never written, but in fact `Cell` uses unsafe code to achieve
+/// interior mutability. In order to get correct behavior, the
+/// `InvariantType` marker must be applied.
 #[unstable(feature = "core",
            reason = "likely to change with new variance strategy")]
 #[lang="invariant_type"]