lazy statics design notes

[Brian Goetz]

> The limitation against T.default can be spun, to many users, as a common sense
> error check, against uninitialized variables.  To more curious users, it can be spun
> as a conscious reservation for efficient implementations.

This is justifiable for (most) ref types, but what about numeric 
types?   I can imagine many potentially-expensive computations that 
could reasonably sum to zero.  (And as you point out, the smaller the 
range, the more silly this gets, ending with boolean.)  So if we're 
going to have this restriction, it should be restricted to class types, 
and the recommended workaround be some sort of Optional or box.  And 
given that not all values will be null-default, it rules out any value 
types for which the zero answer is a reasonable answer.  I think this 
edge is sharper than it looks.