swift234

IRGen: Implement the dealloc_box instruction.

Failable initializers will need to clean up an uninitialized 'self' box in the case where a class initializer calls out to a 'super.init' or 'self.init' fails. Because some framework classes assume that they have a refcount of exactly one during initialization, we have to take 'self' from the box during the delegation, and reinitialize the box with the result of the delegation on success. This means we actually have to implement lowering for dealloc_box.

Swift SVN r21493