This syntax causes 1.8.6 to blow up.  (Its parser can't handle blocks accepting blocks).

We're planning on dropping 1.8.6 support in 3.0, and starting on 3.0 as soon as 2.14 ships, so we can just hold off on merging this until we get started on 3.0.  If you want to get this in 2.14 you'll have to change stuff so it's 1.8.6 compatible, but that would be a bunch of work that we would undo as soon as 3.0 starts, because we don't want to keep the 1.8.6 hacks in 3.0.

Thoughts?