Michael Park 215f55f526 Fix std::visit for the zero variants case.
Summary:
The following code is broken:

```
    std::visit([]{});
```

Reviewers: EricWF

Reviewed By: EricWF

Differential Revision: https://reviews.llvm.org/D33090

llvm-svn: 302773
2017-05-11 07:17:12 +00:00
..
2017-05-04 06:28:34 +00:00