Implement references to "this" in the new IR.

sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.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 dart_tree;
 
 import '../dart2jslib.dart' as dart2js;
 import '../elements/elements.dart'
     show Element, FunctionElement, FunctionSignature, ParameterElement,
          ClassElement;
@@ skipping 156 matching lines @@
  * A constant.
  */
 class Constant extends Expression {
   dart2js.Constant value;
 
   Constant(this.value);
 
   accept(ExpressionVisitor visitor) => visitor.visitConstant(this);
 }
 
+class This extends Expression {
+  accept(Visitor visitor) => visitor.visitThis(this);
+}
+
 class LiteralList extends Expression {
   final GenericType type;
   final List<Expression> values;
   final dart2js.Constant constant;
 
   LiteralList(this.type, this.values, [this.constant]);
 
   accept(ExpressionVisitor visitor) => visitor.visitLiteralList(this);
 }
 
@@ skipping 227 matching lines @@
 }
 
 abstract class ExpressionVisitor<E> {
   E visitExpression(Expression e) => e.accept(this);
   E visitVariable(Variable node);
   E visitInvokeStatic(InvokeStatic node);
   E visitInvokeMethod(InvokeMethod node);
   E visitInvokeConstructor(InvokeConstructor node);
   E visitConcatenateStrings(ConcatenateStrings node);
   E visitConstant(Constant node);
+  E visitThis(This node);
   E visitConditional(Conditional node);
   E visitLogicalOperator(LogicalOperator node);
   E visitNot(Not node);
   E visitLiteralList(LiteralList node);
   E visitLiteralMap(LiteralMap node);
 }
 
 abstract class StatementVisitor<S> {
   S visitStatement(Statement s) => s.accept(this);
   S visitLabeledStatement(LabeledStatement node);
@@ skipping 367 matching lines @@
         node.constructor,
         node.selector,
         translateArguments(node.arguments),
         node.constant);
   }
 
   Expression visitConstant(ir.Constant node) {
     return new Constant(node.value);
   }
 
+  Expression visitThis(ir.This node) {
+    return new This();
+  }
+
   Expression visitLiteralList(ir.LiteralList node) {
     return new LiteralList(
             node.type,
             translateArguments(node.values),
             node.constant);
   }
 
   Expression visitLiteralMap(ir.LiteralMap node) {
     return new LiteralMap(
         node.type,
@@ skipping 327 matching lines @@
 
   Statement visitWhileCondition(WhileCondition node) {
     // Not introduced yet
     throw "Unexpected WhileCondition in StatementRewriter";
   }
 
   Expression visitConstant(Constant node) {
     return node;
   }
 
+  Expression visitThis(This node) {
+    return node;
+  }
+
   Expression visitLiteralList(LiteralList node) {
     // Process values right-to-left, the opposite of evaluation order.
     for (int i = node.values.length - 1; i >= 0; --i) {
       node.values[i] = visitExpression(node.values[i]);
     }
     return node;
   }
 
   Expression visitLiteralMap(LiteralMap node) {
     // Process arguments right-to-left, the opposite of evaluation order.
@@ skipping 492 matching lines @@
   Expression visitLiteralMap(LiteralMap node) {
     _rewriteList(node.keys);
     _rewriteList(node.values);
     return node;
   }
 
   Expression visitConstant(Constant node) {
     return node;
   }
 
+  Expression visitThis(This node) {
+    return node;
+  }
+
   Expression visitNot(Not node) {
     return toBoolean(makeCondition(node.operand, false, liftNots: false));
   }
 
   Expression visitConditional(Conditional node) {
     // node.condition will be visited after the then and else parts, because its
     // polarity depends on what rewrite we use.
     node.thenExpression = visitExpression(node.thenExpression);
     node.elseExpression = visitExpression(node.elseExpression);
 
@@ skipping 197 matching lines @@
     }
   }
 
   /// Destructively updates each entry of [l] with the result of visiting it.
   void _rewriteList(List<Expression> l) {
     for (int i = 0; i < l.length; i++) {
       l[i] = visitExpression(l[i]);
     }
   }
 }