Currently, the Handlebars language is defined by the behavior of this reference implementation and incompletely described by the documentation found at handlebarsjs.com. This makes it very difficult to reason about bugs like #1276. Should partials that use {{> @partial-block}} be invocable in the manner the bug reporter expects? Not clear.

I had a related discussion with @wycats and we came to the conclusion that we need to specify the language before we move forward with any new features.

This would be a non-trivial effort. Thoughts?