pub static DEPRECATED_IN_FUTURE: &'static Lint
deprecated_in_future lint is internal to rustc and should not be
used by user code.
This lint is only enabled in the standard library. It works with the
#[deprecated] with a
since field of a version in the future.
This allows something to be marked as deprecated in a future version,
and then this lint will ensure that the item is no longer used in the
standard library. See the stability documentation for more details.