Region.empty

alias R = Region!(int, int);
alias TI = R.TaggedInterval;

R emptyRegion1;
auto emptyRegion2 = R([TI(0, 0, 0), TI(0, 10, 10)]);
auto emptyRegion3 = R([TI(0, 0, 0), TI(1, 0, 0)]);
auto region1 = R(0, 0, 10);

assert(emptyRegion1.empty);
assert(emptyRegion2.empty);
assert(emptyRegion3.empty);
assert(!region1.empty);