---

yaml
---
r: 183255
b: refs/heads/beta
c: 310ada0
h: refs/heads/master
i:
  183253: 2bb6745
  183251: 77c8de1
  183247: 257c859
v: v3

Author: Junseok Lee

[refs]

@@ -31,7 +31,7 @@ refs/heads/automation-fail: 1bf06495443584539b958873e04cc2f864ab10e4
 refs/heads/issue-18208-method-dispatch-3-quick-reject: 2009f85b9f99dedcec4404418eda9ddba90258a2
 refs/heads/batch: b7fd822592a4fb577552d93010c4a4e14f314346
 refs/heads/building: 126db549b038c84269a1e4fe46f051b2c15d6970
-refs/heads/beta: b6544fd3520d5eed05aafeb6b78737e32bf2c435
+refs/heads/beta: 310ada06f2d632340845ccd4d7e68a1b54d2f28a
 refs/heads/windistfix: 7608dbad651f02e837ed05eef3d74a6662a6e928
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: eb836bf767aa1d8d4cba488a9091cde3c0ab4b2f

branches/beta/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"]