Make super.foo= erroneous if they are not assignable.

pkg/compiler/lib/src/tree/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 tree;
 
 abstract class Visitor<R> {
   const Visitor();
 
   R visitNode(Node node);
@@ skipping 365 matching lines @@
   visitChildren(Visitor visitor) {
     if (receiver != null) receiver.accept(visitor);
     if (selector != null) selector.accept(visitor);
     if (argumentsNode != null) argumentsNode.accept(visitor);
   }
 
   int argumentCount() {
     return (argumentsNode == null) ? -1 : argumentsNode.slowLength();
   }
 
-  bool get isSuperCall {
-    return receiver != null && receiver.isSuper();
-  }
+  bool get isSuperCall => receiver != null && receiver.isSuper();
+  bool get isThisCall => receiver != null && receiver.isThis();
   bool get isOperator => selector is Operator;
   bool get isPropertyAccess => argumentsNode == null;
   bool get isFunctionObjectInvocation => selector == null;
   bool get isPrefix => argumentsNode is Prefix;
   bool get isPostfix => argumentsNode is Postfix;
   bool get isCall => !isOperator && !isPropertyAccess;
   bool get isIndex =>
       isOperator && identical(selector.asOperator().source, '[]');
   bool get isLogicalAnd =>
       isOperator && identical(selector.asOperator().source, '&&');
@@ skipping 1925 matching lines @@
 
   // VariableDefinitions.
   get metadata => null;
   get type => null;
 
   // Typedef.
   get typeParameters => null;
   get formals => null;
   get typedefKeyword => null;
 }