fix #29753, use ES5 constructors for ddc

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/generators.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// This library adapts ES6 generators to implement Dart's async/await.
 /// It's designed to interact with Dart's Future/Stream and follow Dart
 /// async/await semantics.
 /// See https://github.com/dart-lang/sdk/issues/27315 for ideas on
 /// reconciling Dart's Future and ES6 Promise.
 /// Inspired by `co`: https://github.com/tj/co/blob/master/index.js, which is a
 /// stepping stone for proposed ES7 async/await, and uses ES6 Promises.
 part of dart._runtime;
 
 final _jsIterator = JS('', 'Symbol("_jsIterator")');
 final _current = JS('', 'Symbol("_current")');
 
-syncStar(gen, E, @rest args) => JS(
-    '',
-    '''(() => {
-  const SyncIterable_E = ${getGenericClass(SyncIterable)}($E);
-  return new SyncIterable_E($gen, $args);
-})()''');
+syncStar(gen, E, @rest args) =>
+    JS('', 'new (${getGenericClass(SyncIterable)}($E).new)($gen, $args)');
 
 @JSExportName('async')
 async_(gen, T, @rest args) => JS(
     '',
     '''(() => {
   let iter;
   const FutureT = ${getGenericClass(Future)}($T);
   let _FutureType;
   // Return the raw class type or null if not a class object.
   // This is streamlined to test for native futures.
@@ skipping 39 matching lines @@
       return result.then($T)((x) => x, {onError: onError});
     } else {
       return result;
     }
   });
   // TODO(jmesserly): optimize this further.
   _FutureType = _getRawClassType(result);
   return result;  
 })()''');
 
-// Implementation inspired by _AsyncStarStreamController in
-// dart-lang/sdk's runtime/lib/core_patch.dart
-//
-// Given input like:
-//
-//     foo() async* {
-//       yield 1;
-//       yield* bar();
-//       print(await baz());
-//     }
-//
-// This generates as:
-//
-//    function foo() {
-//      return dart.asyncStar(function*(stream) {
-//        if (stream.add(1)) return;
-//        yield;
-//        if (stream.addStream(bar()) return;
-//        yield;
-//        print(yield baz());
-//      });
-//    }
-//
-// TODO(ochafik): Port back to Dart (which it used to be in the past).
+/// Implementation inspired by _AsyncStarStreamController in
+/// dart-lang/sdk's runtime/lib/core_patch.dart
+///
+/// Given input like:
+///
+///     foo() async* {
+///       yield 1;
+///       yield* bar();
+///       print(await baz());
+///     }
+///
+/// This generates as:
+///
+///     function foo() {
+///       return dart.asyncStar(function*(stream) {
+///         if (stream.add(1)) return;
+///         yield;
+///         if (stream.addStream(bar()) return;
+///         yield;
+///         print(yield baz());
+///      });
+///     }
+///
+// TODO(jmesserly): port back to Dart, based on VM's equivalent class.
 final _AsyncStarStreamController = JS(
     '',
     '''
   class _AsyncStarStreamController {
     constructor(generator, T, args) {
       this.isAdding = false;
       this.isWaiting = false;
       this.isScheduled = false;
       this.isSuspendedAtYield = false;
       this.canceler = null;
@@ skipping 122 matching lines @@
         // with the error.
         this.canceler.completeError(error, stackTrace);
         return;
       }
       if (!this.controller.hasListener) return;
       this.controller.addError(error, stackTrace);
     }
   }
 ''');
 
-/// Returns a Stream of T implemented by an async* function. */
-///
-asyncStar(gen, T, @rest args) => JS(
-    '',
-    '''(() => {
-  return new $_AsyncStarStreamController($gen, $T, $args).controller.stream;
-})()''');
+/// Returns a Stream of T implemented by an async* function.
+asyncStar(gen, T, @rest args) => JS('', 'new #(#, #, #).controller.stream',

[vsm, 2017/06/12 19:39:31]

Do we need a '.new' here on the constructor?

[Jennifer Messerly, 2017/06/12 22:19:34]

we don't because it's a JavaScript class not a Dart class (see above).

I was messing around with it, but it turned out to be beyond the scope of this
change, that's why I just updated the TODO above. At one point while I was
messing around, I broke this, and it caused a bunch of test failures, so we
definitely do have test coverage :)

+    _AsyncStarStreamController, gen, T, args);