Implementation of async-await transformation on 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);
   T visitExpressionStatement(ExpressionStatement node);
   T visitEmptyStatement(EmptyStatement node);
   T visitIf(If node);
   T visitFor(For node);
   T visitForIn(ForIn node);
   T visitWhile(While node);
   T visitDo(Do node);
   T visitContinue(Continue node);
   T visitBreak(Break node);
   T visitReturn(Return node);
   T visitThrow(Throw node);
   T visitTry(Try node);
   T visitCatch(Catch node);
   T visitSwitch(Switch node);
   T visitCase(Case node);
   T visitDefault(Default node);
   T visitFunctionDeclaration(FunctionDeclaration node);
   T visitLabeledStatement(LabeledStatement node);
   T visitLiteralStatement(LiteralStatement node);
+  T visitDartYield(DartYield node);
 
   T visitBlob(Blob node);
   T visitLiteralExpression(LiteralExpression node);
   T visitVariableDeclarationList(VariableDeclarationList node);
   T visitAssignment(Assignment node);
   T visitVariableInitialization(VariableInitialization node);
   T visitConditional(Conditional cond);
   T visitNew(New node);
   T visitCall(Call node);
   T visitBinary(Binary node);
@@ skipping 122 matching lines @@
       => 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);
+  T visitDartYield(DartYield node) => visitStatement(node);
 }
 
 abstract class Node {
   get sourcePosition => _sourcePosition;
   get endSourcePosition => _endSourcePosition;
 
   var _sourcePosition;
   var _endSourcePosition;
 
   accept(NodeVisitor visitor);
@@ skipping 343 matching lines @@
   final String code;
 
   LiteralStatement(this.code);
 
   accept(NodeVisitor visitor) => visitor.visitLiteralStatement(this);
   void visitChildren(NodeVisitor visitor) { }
 
   LiteralStatement _clone() => new LiteralStatement(code);
 }
 
+// Not a real javascript node, but represents the yield statement from a dart
+// program translated to javascript.
+class DartYield extends Statement {
+  final Expression expression;
+
+  final bool hasStar;
+
+  DartYield(this.expression, this.hasStar);
+
+  accept(NodeVisitor visitor) => visitor.visitDartYield(this);
+
+  void visitChildren(NodeVisitor visitor) {
+    expression.accept(visitor);
+  }
+
+  DartYield _clone() => new DartYield(expression, hasStar);
+}
+
 abstract class Expression extends Node {
   int get precedenceLevel;
 
   Statement toStatement() => new ExpressionStatement(this);
 
   Expression withPosition(var sourcePosition, var endSourcePosition) =>
       super.withPosition(sourcePosition, endSourcePosition);
 }
 
 /// Wrap a CodeBuffer as an expression.
@@ skipping 310 matching lines @@
 
   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);
+  Fun _clone() => new Fun(params, body, asyncModifier: asyncModifier);
 
   int get precedenceLevel => CALL;
 }
 
 class AsyncModifier {
   final bool isAsync;
   final bool isYielding;
+  final String description;
 
-  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;
+  const AsyncModifier.sync()
+      : isAsync = false,
+        isYielding = false,
+        description = "sync";
+  const AsyncModifier.async()
+      : isAsync = true,
+        isYielding = false,
+        description = "async";
+  const AsyncModifier.asyncStar()
+      : isAsync = true,
+        isYielding = true,
+        description = "async*";
+  const AsyncModifier.syncStar()
+      : isAsync = false,
+        isYielding = true,
+        description = "sync*";
+  toString() => description;
 }
 
 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)
@@ skipping 245 matching lines @@
 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) {}
 }