Fix hoisting of arguments

package.json

@@ -37,6 +37,8 @@
     "through": "^2.3.8"
   },
   "devDependencies": {
+    "babel-plugin-transform-es2015-parameters": "^6.23.0",
+    "babel-plugin-transform-es2015-spread": "^6.22.0",
     "babylon": "^6.14.1",
     "mocha": "^2.3.4",
     "promise": "^7.0.4",

packages/regenerator-transform/src/visit.js

@@ -96,8 +96,11 @@ exports.visitor = {
       let didRenameArguments = renameArguments(path, argsId);
       if (didRenameArguments) {
         vars = vars || t.variableDeclaration("var", []);
+        const argumentIdentifier = t.identifier("arguments");
+        // we need to do this as otherwise arguments in arrow functions gets hoisted
+        argumentIdentifier._shadowedFunctionLiteral = path;
         vars.declarations.push(t.variableDeclarator(
-          argsId, t.identifier("arguments")
+          argsId, argumentIdentifier
         ));
       }
 

test/regression.js

@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) 2017, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * https://raw.github.com/facebook/regenerator/master/LICENSE file. An
+ * additional grant of patent rights can be found in the PATENTS file in
+ * the same directory.
+ */
+
+var assert = require("assert");
+
+describe("regressions", function() {
+  it("should correctly hoist arguments", async function () {
+    function test(fn) {
+      return async (...args) => {
+        return fn(...args);
+      };
+    }
+    const result = [];
+    await test((arg1, arg2) => { result.push(arg1, arg2); })(1, "foo");
+
+    assert.deepEqual(result, [1, "foo"]);
+  });
+});

test/run.js

@@ -128,6 +128,31 @@ enqueue(convert, [
   "./test/async.es5.js"
 ]);
 
+function convertWithSpread(es6File, es5File, callback) {
+  var transformOptions = {
+    presets:[require("regenerator-preset")],
+    plugins: [
+      require("babel-plugin-transform-es2015-spread"),
+      require("babel-plugin-transform-es2015-parameters")
+    ]
+  };
+
+  fs.readFile(es6File, "utf-8", function(err, es6) {
+    if (err) {
+      return callback(err);
+    }
+
+    var es5 = require("babel-core").transform(es6, transformOptions).code;
+
+    fs.writeFile(es5File, es5, callback);
+  });
+}
+
+enqueue(convertWithSpread, [
+  "./test/regression.js",
+  "./test/regression.es5.js"
+]);
+
 enqueue(makeMochaCopyFunction("mocha.js"));
 enqueue(makeMochaCopyFunction("mocha.css"));
 
@@ -137,11 +162,14 @@ if (!semver.eq(process.version, "0.11.7")) {
   try {
     require.resolve("browserify"); // Throws if missing.
     enqueue(bundle, [
-      ["./test/runtime.js",
-       "./test/tests.es5.js",
-       "./test/tests-node4.es5.js",
-       "./test/non-native.es5.js",
-       "./test/async.es5.js"],
+      [
+        "./test/runtime.js",
+        "./test/tests.es5.js",
+        "./test/tests-node4.es5.js",
+        "./test/non-native.es5.js",
+        "./test/async.es5.js",
+        "./test/regression.es5.js"
+      ],
       "./test/tests.browser.js"
     ]);
   } catch (ignored) {
@@ -156,6 +184,7 @@ enqueue("mocha", [
   "./test/tests-node4.es5.js",
   "./test/non-native.es5.js",
   "./test/async.es5.js",
+  "./test/regression.es5.js",
   "./test/tests.transform.js"
 ]);