### HHVM Version

> Please include the output of `hhvm --version` and `hh_client --version`

### Operating System and Version

> For example, 'Debian Squeeze', 'Ubuntu 16.04', 'MacOS High Sierra'. Please
> also mention if you are using Docker or similar images.

### Standalone code, or other way to reproduce the problem

> This should not depend on installing any libraries or frameworks. Ideally, it
> should be possible to copy-paste this into a single file and reproduce the
> problem by running `hhvm` and/or `hh_client`

### Actual result

> If applicable, please copy-paste output from `hhvm` or `hh_client`

### Expected result
