Avoid renaming this bindings in simple arrow function cases.

packages/babel-core/src/transformation/internal-plugins/shadow-functions.js

@@ -30,6 +30,7 @@ function remap(path, key, create) {
 
   let shadowFunction = path.node._shadowedFunctionLiteral;
   let currentFunction;
+  let passedShadowFunction = false;
 
   let fnPath = path.findParent(function (path) {
     if (path.isProgram() || path.isFunction()) {
@@ -38,13 +39,18 @@ function remap(path, key, create) {
     }
 
     if (path.isProgram()) {
+      passedShadowFunction = true;
+
       return true;
     } else if (path.isFunction() && !path.isArrowFunctionExpression()) {
       if (shadowFunction) {
-        return path === shadowFunction || path.node === shadowFunction.node;
+        if (path === shadowFunction || path.node === shadowFunction.node) return true;
       } else {
-        return !path.is("shadow");
+        if (!path.is("shadow")) return true;
       }
+
+      passedShadowFunction = true;
+      return false;
     }
 
     return false;
@@ -53,6 +59,10 @@ function remap(path, key, create) {
   // no point in realiasing if we're in this function
   if (fnPath === currentFunction) return;
 
+  // If the only functions that were encountered are arrow functions, skip remapping the
+  // binding since arrow function syntax already does that.
+  if (!passedShadowFunction) return;
+
   let cached = fnPath.getData(key);
   if (cached) return path.replaceWith(cached);
 

packages/babel-plugin-transform-async-to-generator/test/fixtures/async-to-generator/deeply-nested-asyncs/expected.js

@@ -1,17 +1,15 @@
 let s = function () {
   var ref = babelHelpers.asyncToGenerator(function* (x) {
-    let t = (() => {
-      var _this3 = this;
-
-      var ref = babelHelpers.asyncToGenerator(function* (y, a) {
-        let r = (() => {
     var _this2 = this;
 
+    let t = (() => {
+      var ref = babelHelpers.asyncToGenerator(function* (y, a) {
+        let r = (() => {
           var ref = babelHelpers.asyncToGenerator(function* (z, b) {
             yield z;
             return _this2.x;
           }),
-              _this = this;
+              _this = _this2;
 
           return function r(_x4, _x5) {
             return ref.apply(_this, arguments);
@@ -19,10 +17,9 @@ let s = function () {
         })();
         yield r();
 
-        return _this3.g(r);
+        return _this2.g(r);
       }),
           _this = this;
-
       return function t(_x2, _x3) {
         return ref.apply(_this, arguments);
       };