Throw better errors for non-iterables when Symbol doesn't exist (#11264)

packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/exec.js

@@ -0,0 +1,10 @@
+var a = (() => [2, 3])();
+
+// Simulate old environment
+let _Symbol = Symbol;
+Symbol = void 0;
+try {
+  expect([1, ...a]).toEqual([1, 2, 3]);
+} finally {
+  Symbol = _Symbol;
+}

packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/input.js

@@ -0,0 +1,6 @@
+var a = (() => [2, 3])();
+
+// !!! In order to run this test, this shouldn't be optimized using type inference
+// If it's optimized and doesn't call toConsumableArray, please modify this test
+// and exec.js
+[1, ...a];

packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/output.js

@@ -0,0 +1,6 @@
+var a = (() => [2, 3])(); // !!! In order to run this test, this shouldn't be optimized using type inference
+// If it's optimized and doesn't call toConsumableArray, please modify this test
+// and exec.js
+
+
+[1].concat(babelHelpers.toConsumableArray(a));

packages/babel-plugin-transform-spread/test/fixtures/spread/non-iterable/exec.js

@@ -0,0 +1,10 @@
+var o = {};
+
+expect(() => [...undefined]).toThrow(/spread non-iterable/);
+
+expect(() => [...o]).toThrow(/spread non-iterable/);
+
+// Simulate old browser
+Symbol = void 0;
+
+expect(() => [...o]).toThrow(/spread non-iterable/);