Implementation of async-await transformation on js ast.

pkg/compiler/lib/src/js_backend/backend.dart

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index edb9c57c8bbeb0f564827b137a4ab4a23dd48123..3dc61a43d9c8d4ca078e0aae8fc5932348d27c33 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -63,6 +63,7 @@ class FunctionInlineCache {
 
 class JavaScriptBackend extends Backend {
   static final Uri DART_JS_HELPER = new Uri(scheme: 'dart', path: '_js_helper');
+  static final Uri DART_ASYNC = new Uri(scheme: 'dart', path: 'async');

[Johnni Winther, 2015/02/02 10:45:10]

Not needed (exists on [Compiler]).

[sigurdm, 2015/02/03 16:59:27]

Done

   static final Uri DART_INTERCEPTORS =
       new Uri(scheme: 'dart', path: '_interceptors');
   static final Uri DART_INTERNAL =
@@ -122,6 +123,7 @@ class JavaScriptBackend extends Backend {
   FunctionInlineCache inlineCache = new FunctionInlineCache();
 
   LibraryElement jsHelperLibrary;
+  LibraryElement asyncLibrary;
   LibraryElement interceptorsLibrary;
   LibraryElement foreignLibrary;
   LibraryElement isolateHelperLibrary;
@@ -941,6 +943,7 @@ class JavaScriptBackend extends Backend {
       Element e = findHelper('boolConversionCheck');
       if (e != null) enqueue(world, e, registry);
     }
+
     if (TRACE_CALLS) {
       traceHelper = findHelper('traceHelper');
       assert(traceHelper != null);
@@ -1597,6 +1600,66 @@ class JavaScriptBackend extends Backend {
     return findHelper("throwCyclicInit");
   }
 
+  Element getFuture() {

[Johnni Winther, 2015/02/02 10:45:10]

This is [Compiler.futureClass].

[sigurdm, 2015/02/03 16:59:27]

And was not used anymore.
Thanks.

+    return asyncLibrary.find("Future");
+  }
+
+  Element getThenHelper() {
+    return findHelper("thenHelper");
+  }
+
+  Element getSyncStarYieldStar() {
+    ClassElement classElement = findHelper("IterationMarker");
+    classElement.ensureResolved(compiler);
+    return classElement.lookupLocalMember("yieldStar");
+  }
+
+  Element getYieldSingle() {
+    ClassElement classElement = findHelper("IterationMarker");
+    classElement.ensureResolved(compiler);
+    return classElement.lookupLocalMember("yieldSingle");
+  }
+
+  Element getStreamHelper() {
+    return findHelper("streamHelper");
+  }
+
+  Element getEndOfIteration() {
+    ClassElement classElement = findHelper("IterationMarker");
+    classElement.ensureResolved(compiler);
+    return classElement.lookupLocalMember("endOfIteration");
+  }
+
+  Element getSyncStarIterable() {
+    ClassElement classElement = findHelper("SyncStarIterable");
+    classElement.ensureResolved(compiler);
+    return classElement;
+  }
+
+  Element getSyncStarIterableConstructor() {
+    ClassElement classElement = getSyncStarIterable();
+    classElement.ensureResolved(compiler);
+    return classElement.lookupConstructor("");
+  }
+
+  Element getCompleterConstructor() {
+    ClassElement classElement = find(asyncLibrary, "Completer");
+    classElement.ensureResolved(compiler);
+    return classElement
+        .lookupConstructor("");
+  }
+
+  Element getMakeController() {
+    return findHelper("makeAsyncStarController");
+  }
+
+  Element getStreamIteratorConstructor() {
+    ClassElement classElement = find(asyncLibrary, "StreamIterator");
+    classElement.ensureResolved(compiler);
+    return classElement
+        .lookupConstructor("");
+  }
+
   bool isNullImplementation(ClassElement cls) {
     return cls == jsNullClass;
   }
@@ -1696,6 +1759,8 @@ class JavaScriptBackend extends Backend {
     Uri uri = library.canonicalUri;
     if (uri == DART_JS_HELPER) {
       jsHelperLibrary = library;
+    } else if (uri == DART_ASYNC) {
+      asyncLibrary = library;

[Johnni Winther, 2015/02/02 10:45:10]

Not needed.

[sigurdm, 2015/02/03 16:59:27]

Done

     } else if (uri == DART_INTERNAL) {
       internalLibrary = library;
     } else if (uri ==  DART_INTERCEPTORS) {
@@ -2331,6 +2396,26 @@ class JavaScriptBackend extends Backend {
     String extension = addExtension ? ".part.js" : "";
     return "${outName}_$name$extension";
   }
+
+  void registerAsyncMarker(FunctionElement element,
+                           Enqueuer enqueuer,
+                           Registry registry) {
+    if (element.asyncMarker == AsyncMarker.ASYNC) {
+      enqueue(enqueuer, getThenHelper(), registry);
+      enqueue(enqueuer, getCompleterConstructor(), registry);
+      enqueue(enqueuer, getStreamIteratorConstructor(), registry);
+    } else if (element.asyncMarker == AsyncMarker.SYNC_STAR) {
+      enqueuer.registerInstantiatedClass(getSyncStarIterable(), registry);
+      enqueue(enqueuer, getSyncStarIterableConstructor(), registry);
+      enqueue(enqueuer, getEndOfIteration(), registry);
+      enqueue(enqueuer, getSyncStarYieldStar(), registry);
+    } else if (element.asyncMarker == AsyncMarker.ASYNC_STAR) {
+      enqueue(enqueuer, getStreamHelper(), registry);
+      enqueue(enqueuer, getYieldSingle(), registry);
+      enqueue(enqueuer, getMakeController(), registry);
+      enqueue(enqueuer, getStreamIteratorConstructor(), registry);
+    }
+  }
 }
 
 class JavaScriptResolutionCallbacks extends ResolutionCallbacks {