Set correct async/generator in IIFE for params (#11346)

* Set correct async/generator in IIFE for params

* Reject in async params

* Skip async test on node 6 (it doesn't support async fns)

packages/babel-plugin-transform-parameters/test/fixtures/regression/scope-async-param-error-async/exec.js

@@ -0,0 +1,13 @@
+const err = new Error();
+
+async function f(a = (() => { throw err })()) {
+  throw 1;
+  var a = await a;
+  return a;
+}
+
+return (async () => {
+  let p;
+  expect(() => { p = f() }).not.toThrow();
+  await expect(p).rejects.toThrow(err);
+})();

packages/babel-plugin-transform-parameters/test/fixtures/regression/scope-async-param-error-async/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    "transform-parameters"
+  ],
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  },
+  "minNodeVersion": "8.0.0"
+}