semantics-09.js - mozsearch

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// The LHS of a for-of loop is not evaluated until after the .next() method returns.

var s;

function f() {

    s += 'f';

    return {};

// Test 1: .next() throws StopIteration right away. f is never called.

s = '';

for (f().x of [])

    s += '.';

assertEq(s, '');

// Test 2: check proper interleaving of f calls, iterator.next() calls, and the loop body.

function* g() {

    s += 'g';

    yield 0;

    s += 'g';

    yield 1;

    s += 'g';

for (f().x of g())

    s += '.';

assertEq(s, 'gf.gf.g');