A better assert() [was: Re: std.unittests [updated] for review]

[bearophile]

> So moving them into explicit little features makes the language more

The two little features I am talking about are:
- a halt() somewhere like in core.bitop or std.intrinsic or the default object module to replace assert(0);
- And to use class_instance.invariant() to replace assert(class_instance).

Bye,
bearophile