dart2js cps: Support async/await by rewriting the JavaScript AST.

pkg/compiler/lib/src/tree_ir/tree_ir_nodes.dart

 // Copyright (c) 2014, 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.
 
 library tree_ir_nodes;
 
 import '../constants/values.dart' as values;
 import '../dart_types.dart' show DartType, InterfaceType, TypeVariableType;
 import '../elements/elements.dart';
 import '../io/source_information.dart' show SourceInformation;
@@ skipping 877 matching lines @@
 
   accept(ExpressionVisitor visitor) {
     return visitor.visitTypeExpression(this);
   }
 
   accept1(ExpressionVisitor1 visitor, arg) {
     return visitor.visitTypeExpression(this, arg);
   }
 }
 
+class Await extends Expression {
+  Expression input;
+
+  Await(this.input);
+
+  accept(ExpressionVisitor visitor) {
+    return visitor.visitAwait(this);
+  }
+
+  accept1(ExpressionVisitor1 visitor, arg) {
+    return visitor.visitAwait(this, arg);
+  }
+}
+
 abstract class ExpressionVisitor<E> {
   E visitExpression(Expression node) => node.accept(this);
   E visitVariableUse(VariableUse node);
   E visitAssign(Assign node);
   E visitInvokeStatic(InvokeStatic node);
   E visitInvokeMethod(InvokeMethod node);
   E visitInvokeMethodDirectly(InvokeMethodDirectly node);
   E visitInvokeConstructor(InvokeConstructor node);
   E visitConstant(Constant node);
   E visitThis(This node);
@@ skipping 13 matching lines @@
   E visitReifyRuntimeType(ReifyRuntimeType node);
   E visitReadTypeVariable(ReadTypeVariable node);
   E visitTypeExpression(TypeExpression node);
   E visitCreateInvocationMirror(CreateInvocationMirror node);
   E visitInterceptor(Interceptor node);
   E visitApplyBuiltinOperator(ApplyBuiltinOperator node);
   E visitForeignExpression(ForeignExpression node);
   E visitGetLength(GetLength node);
   E visitGetIndex(GetIndex node);
   E visitSetIndex(SetIndex node);
+  E visitAwait(Await node);
 }
 
 abstract class ExpressionVisitor1<E, A> {
   E visitExpression(Expression node, A arg) => node.accept1(this, arg);
   E visitVariableUse(VariableUse node, A arg);
   E visitAssign(Assign node, A arg);
   E visitInvokeStatic(InvokeStatic node, A arg);
   E visitInvokeMethod(InvokeMethod node, A arg);
   E visitInvokeMethodDirectly(InvokeMethodDirectly node, A arg);
   E visitInvokeConstructor(InvokeConstructor node, A arg);
@@ skipping 15 matching lines @@
   E visitReifyRuntimeType(ReifyRuntimeType node, A arg);
   E visitReadTypeVariable(ReadTypeVariable node, A arg);
   E visitTypeExpression(TypeExpression node, A arg);
   E visitCreateInvocationMirror(CreateInvocationMirror node, A arg);
   E visitInterceptor(Interceptor node, A arg);
   E visitApplyBuiltinOperator(ApplyBuiltinOperator node, A arg);
   E visitForeignExpression(ForeignExpression node, A arg);
   E visitGetLength(GetLength node, A arg);
   E visitGetIndex(GetIndex node, A arg);
   E visitSetIndex(SetIndex node, A arg);
+  E visitAwait(Await node, A arg);
 }
 
 abstract class StatementVisitor<S> {
   S visitStatement(Statement node) => node.accept(this);
   S visitLabeledStatement(LabeledStatement node);
   S visitReturn(Return node);
   S visitThrow(Throw node);
   S visitRethrow(Rethrow node);
   S visitBreak(Break node);
   S visitContinue(Continue node);
@@ skipping 213 matching lines @@
   visitGetIndex(GetIndex node) {
     visitExpression(node.object);
     visitExpression(node.index);
   }
 
   visitSetIndex(SetIndex node) {
     visitExpression(node.object);
     visitExpression(node.index);
     visitExpression(node.value);
   }
+
+  visitAwait(Await node) {
+    visitExpression(node.input);
+  }
 }
 
 abstract class Transformer implements ExpressionVisitor<Expression>,
                                       StatementVisitor<Statement> {
    Expression visitExpression(Expression e) => e.accept(this);
    Statement visitStatement(Statement s) => s.accept(this);
 }
 
 class RecursiveTransformer extends Transformer {
   void visitInnerFunction(FunctionDefinition node) {
@@ skipping 222 matching lines @@
     node.index = visitExpression(node.index);
     return node;
   }
 
   visitSetIndex(SetIndex node) {
     node.object = visitExpression(node.object);
     node.index = visitExpression(node.index);
     node.value = visitExpression(node.value);
     return node;
   }
+
+  visitAwait(Await node) {
+    node.input = visitExpression(node.input);
+    return node;
+  }
 }
 
 class FallthroughTarget {
   final Statement target;
   int useCount = 0;
 
   FallthroughTarget(this.target);
 }
 
 /// A stack machine for tracking fallthrough while traversing the Tree IR.
@@ skipping 17 matching lines @@
 
   /// Number of uses of the current fallthrough target.
   int get useCount => _stack.last.useCount;
 
   /// Indicate that a statement will fall through to the current fallthrough
   /// target.
   void use() {
     ++_stack.last.useCount;
   }
 }