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/src/params.js

@@ -181,6 +181,13 @@ export default function convertFunctionParams(path, loose) {
     const bodyPath = path.get("body.body");
     const arrowPath = bodyPath[bodyPath.length - 1].get("argument.callee");
     arrowPath.arrowFunctionToExpression();
+
+    arrowPath.node.generator = path.node.generator;
+    arrowPath.node.async = path.node.async;
+
+    // We don't reset "async" because if the default value of a parameter
+    // throws, it must reject asynchronously.
+    path.node.generator = false;
   } else {
     path.get("body").unshiftContainer("body", body);
   }

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"
+}

packages/babel-plugin-transform-parameters/test/fixtures/regression/scope-gen-async/input.js

@@ -0,0 +1,14 @@
+function* f(a = 1) {
+  var a = yield a;
+  return a;
+}
+
+async function g(a = 1) {
+  var a = await a;
+  return a;
+}
+
+async function* h(a = 1) {
+  var a = await (yield a);
+  return a;
+}

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

@@ -0,0 +1,5 @@
+{
+  "plugins": [
+    "transform-parameters"
+  ]
+}

packages/babel-plugin-transform-parameters/test/fixtures/regression/scope-gen-async/output.js

@@ -0,0 +1,23 @@
+function f() {
+  let a = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
+  return function* (a) {
+    var a = yield a;
+    return a;
+  }(a);
+}
+
+async function g() {
+  let a = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
+  return async function (a) {
+    var a = await a;
+    return a;
+  }(a);
+}
+
+async function h() {
+  let a = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
+  return async function* (a) {
+    var a = await (yield a);
+    return a;
+  }(a);
+}