removed weird example

Author: Junseok Lee

src/libcore/marker.rs

@@ -308,19 +308,6 @@ impl<T: ?Sized> Clone for ContravariantType<T> {
 ///
 /// For more information about variance, refer to this Wikipedia
 /// article <http://en.wikipedia.org/wiki/Variance_%28computer_science%29>.
-///
-/// # Example
-///
-/// The Cell type is an example 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.
 #[unstable(feature = "core",
            reason = "likely to change with new variance strategy")]
 #[lang="invariant_type"]