Though a downside here is you can't require a check attribute to
be present on a class without modifying druntime. The class
attribute could go down and check its members, but there's no way
to error on an unchecked class without changing object.d, or at
least a runtime check to loop through the modules and check it
then.
It just checks ones that are there, and at that point, it isn't
really that much different than just writing static
assert(test.sizeof < 8); right there in the module.
so maybe not as awesome as i first thought, but still, this is an
exciting technique and I'm sure there's more we can do with it.
