michael@0: // The argument to Map may be a generator-iterator that produces no values.
michael@0: 
michael@0: assertEq(Map(x for (x of [])).size, 0);
michael@0: 
michael@0: function none() {
michael@0:     if (0) yield 0;
michael@0: }
michael@0: assertEq(Map(none()).size, 0);