function shouldBe(actual, expected) { if (actual !== expected) throw new Error('bad value: ' + actual); } function shouldThrow(func, errorMessage) { var errorThrown = false; var error = null; try { func(); } catch (e) { errorThrown = true; error = e; } if (!errorThrown) throw new Error('not thrown'); if (String(error) !== errorMessage) throw new Error(`bad error: ${String(error)}`); } var func = Set.prototype.add; function target(set) { return func.call(set, 42); } noInline(target); for (var i = 0; i < 1e6; ++i) { var set = new Set(); shouldBe(target(set), set); shouldBe(set.has(42), true); } shouldThrow(() => { target(new Map()); }, `TypeError: Set operation called on non-Set object`);