Implement await and async for the js-ast.

pkg/compiler/lib/src/js/nodes.dart

 // Copyright (c) 2012, 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.
 
 part of js;
 
 abstract class NodeVisitor<T> {
   T visitProgram(Program node);
 
   T visitBlock(Block node);
@@ skipping 42 matching lines @@
   T visitLiteralString(LiteralString node);
   T visitLiteralNumber(LiteralNumber node);
   T visitLiteralNull(LiteralNull node);
 
   T visitArrayInitializer(ArrayInitializer node);
   T visitArrayHole(ArrayHole node);
   T visitObjectInitializer(ObjectInitializer node);
   T visitProperty(Property node);
   T visitRegExpLiteral(RegExpLiteral node);
 
+  T visitAwait(Await node);
+
   T visitComment(Comment node);
 
   T visitInterpolatedExpression(InterpolatedExpression node);
   T visitInterpolatedLiteral(InterpolatedLiteral node);
   T visitInterpolatedParameter(InterpolatedParameter node);
   T visitInterpolatedSelector(InterpolatedSelector node);
   T visitInterpolatedStatement(InterpolatedStatement node);
 }
 
 class BaseVisitor<T> implements NodeVisitor<T> {
@@ skipping 85 matching lines @@
       => visitInterpolatedNode(node);
   T visitInterpolatedParameter(InterpolatedParameter node)
       => visitInterpolatedNode(node);
   T visitInterpolatedSelector(InterpolatedSelector node)
       => visitInterpolatedNode(node);
   T visitInterpolatedStatement(InterpolatedStatement node)
       => visitInterpolatedNode(node);
 
   // Ignore comments by default.
   T visitComment(Comment node) => null;
+
+  T visitAwait(Await node) => visitExpression(node);
 }
 
 abstract class Node {
   get sourcePosition => _sourcePosition;
   get endSourcePosition => _endSourcePosition;
 
   var _sourcePosition;
   var _endSourcePosition;
 
   accept(NodeVisitor visitor);
@@ skipping 662 matching lines @@
     function.accept(visitor);
   }
   NamedFunction _clone() => new NamedFunction(name, function);
 
   int get precedenceLevel => CALL;
 }
 
 class Fun extends Expression {
   final List<Parameter> params;
   final Block body;
+  final AsyncModifier asyncModifier;
 
-  Fun(this.params, this.body);
+  Fun(this.params, this.body, {this.asyncModifier: const AsyncModifier.sync()});
 
   accept(NodeVisitor visitor) => visitor.visitFun(this);
 
   void visitChildren(NodeVisitor visitor) {
     for (Parameter param in params) param.accept(visitor);
     body.accept(visitor);
   }
 
   Fun _clone() => new Fun(params, body);
 
   int get precedenceLevel => CALL;
 }
 
+class AsyncModifier {
+  final bool isAsync;
+  final bool isYielding;
+
+  const AsyncModifier.sync() : isAsync = false, isYielding = false;
+  const AsyncModifier.async() : isAsync = true, isYielding = false;
+  const AsyncModifier.asyncStar() : isAsync = true, isYielding = true;
+  const AsyncModifier.syncStar() : isAsync = false, isYielding = true;
+}
+
 class PropertyAccess extends Expression {
   final Expression receiver;
   final Expression selector;
 
   PropertyAccess(this.receiver, this.selector);
   PropertyAccess.field(this.receiver, String fieldName)
       : selector = new LiteralString('"$fieldName"');
   PropertyAccess.indexed(this.receiver, int index)
       : selector = new LiteralNumber('$index');
 
@@ skipping 209 matching lines @@
   RegExpLiteral(this.pattern);
 
   accept(NodeVisitor visitor) => visitor.visitRegExpLiteral(this);
   void visitChildren(NodeVisitor visitor) {}
   RegExpLiteral _clone() => new RegExpLiteral(pattern);
 
   int get precedenceLevel => PRIMARY;
 }
 
 /**
+ * An asynchronous await.
+ *
+ * Not part of javascript. We desugar this expression before outputting.
+ * Should only occur in a [Fun] with `asyncModifier` async or asyncStar.
+ */
+class Await extends Expression {
+  /** The awaited expression. */
+  final Expression expression;
+
+  Await(this.expression);
+
+  int get precedenceLevel => UNARY;
+  accept(NodeVisitor visitor) => visitor.visitAwait(this);
+  void visitChildren(NodeVisitor visitor) => expression.accept(visitor);
+  Await _clone() => new Await(expression);
+
+}
+
+/**
  * A comment.
  *
  * Extends [Statement] so we can add comments before statements in
  * [Block] and [Program].
  */
 class Comment extends Statement {
   final String comment;
 
   Comment(this.comment);
 
   accept(NodeVisitor visitor) => visitor.visitComment(this);
   Comment _clone() => new Comment(comment);
 
   void visitChildren(NodeVisitor visitor) {}
 }