michael@0: // The LHS of a for-of loop is not evaluated until after the .next() method returns.
michael@0: 
michael@0: var s;
michael@0: function f() {
michael@0:     s += 'f';
michael@0:     return {};
michael@0: }
michael@0: 
michael@0: // Test 1: .next() throws StopIteration right away. f is never called.
michael@0: s = '';
michael@0: for (f().x of [])
michael@0:     s += '.';
michael@0: assertEq(s, '');
michael@0: 
michael@0: // Test 2: check proper interleaving of f calls, iterator.next() calls, and the loop body.
michael@0: function g() {
michael@0:     s += 'g';
michael@0:     yield 0;
michael@0:     s += 'g';
michael@0:     yield 1;
michael@0:     s += 'g';
michael@0: }
michael@0: for (f().x of g())
michael@0:     s += '.';
michael@0: assertEq(s, 'gf.gf.g');