refer to parent arguments inside arrow functions - fixes #39

lib/6to5/transformers/arrow-functions.js

@@ -24,3 +24,32 @@ exports.ArrowFunctionExpression = function (node) {
     return node;
   }
 };
+
+exports.FunctionDeclaration =
+exports.FunctionExpression = function (node, parent, opts, generateUid) {
+  var hasArguments = false;
+  var id;
+
+  // traverse the function and find all arrow functions
+  traverse(node, function (node) {
+    if (node.type !== "ArrowFunctionExpression") return;
+
+    traverse(node, function (node, parent) {
+      if (node.type === "Identifier" && node.name === "arguments" &&
+          parent.type !== "MemberExpression") {
+        hasArguments = true;
+        id = id || b.identifier(generateUid("arguments"));
+        return id;
+      }
+    }, ["FunctionDeclaration", "FunctionExpression", "ArrowFunctionExpression"]);
+
+    return false;
+  }, ["FunctionDeclaration", "FunctionExpression"]);
+
+  if (hasArguments) {
+    util.ensureBlock(node);
+    node.body.body.unshift(b.variableDeclaration("var", [
+      b.variableDeclarator(id, b.identifier("arguments"))
+    ]));
+  }
+};

test/fixtures/arrow-functions/arguments/actual.js

@@ -0,0 +1,16 @@
+function outer() {
+  var inner = () => arguments;
+  return [].slice.call(inner());
+}
+console.log(outer(1, 2));
+
+function outer() {
+  var inner = () => arguments;
+
+  var another = function () {
+    var inner2 = () => arguments;
+  };
+
+  return [].slice.call(inner());
+}
+console.log(outer(1, 2));

test/fixtures/arrow-functions/arguments/expected.js

@@ -0,0 +1,19 @@
+function outer() {
+  var _arguments = arguments;
+  var inner = function () { return _arguments; };
+  return [].slice.call(inner());
+}
+console.log(outer(1, 2));
+
+function outer() {
+  var _arguments2 = arguments;
+  var inner = function () { return _arguments2; };
+
+  var another = function () {
+    var _arguments3 = arguments;
+    var inner2 = function () { return _arguments3; };
+  };
+
+  return [].slice.call(inner());
+}
+console.log(outer(1, 2));