Void-safety (and related things)

[Ary Borenszweig]

Michiel Helvensteijn wrote:
> bearophile wrote:
> 
>> You can't ask a single person to be able to do everything. Are you able to
>> implement that thing? Probably I am not able. If someone here is able and
>> willing to do it then I suggest such person to ask Walter permission to
>> implement it.
> 
> I doubt it's the direction D wants to go. Because proving correctness at
> compile-time requires the holy grail, and testing correctness at runtime
> requires extra space for each variable and extra time for each access.

What do you mean by "holy grail"?