Fix for deeply nested async arrows

packages/babel-helper-remap-async-to-generator/src/index.js

@@ -27,7 +27,9 @@ let awaitVisitor = {
   },
 
   ArrowFunctionExpression(path) {
+    if (!path.node.async) {
       path.arrowFunctionToShadowed();
+    }
   },
 
   AwaitExpression({ node }) {

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

@@ -0,0 +1,13 @@
+async function s(x) {
+  let t = async (y) => {
+    let r = async (z) =>  {
+      await z;
+      return this.x;
+    }
+    await r;
+
+    return this.g(r);
+  }
+  await t;
+  return this.h(t);
+}

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

@@ -0,0 +1,28 @@
+let s = function () {
+  var ref = babelHelpers.asyncToGenerator(function* (x) {
+    let t = (() => {
+      var _this2 = this;
+
+      var ref = babelHelpers.asyncToGenerator(function* (y) {
+        let r = (() => {
+          var _this = this;
+
+          var ref = babelHelpers.asyncToGenerator(function* (z) {
+            yield z;
+            return _this.x;
+          });
+          return _x3 => ref.apply(this, arguments);
+        })();
+        yield r;
+
+        return _this2.g(r);
+      });
+      return _x2 => ref.apply(this, arguments);
+    })();
+    yield t;
+    return this.h(t);
+  });
+  return function s(_x) {
+    return ref.apply(this, arguments);
+  };
+}();