Handle more unqualified SendSets

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 468 matching lines @@
   SendSet.prefix(receiver,
                  selector,
                  this.assignmentOperator,
                  [Node argument = null, bool isConditional = false])
       : super.prefix(receiver, selector, argument, isConditional);
 
   SendSet asSendSet() => this;
 
   accept(Visitor visitor) => visitor.visitSendSet(this);
 
+  /// `true` if this send is not a simple assignment.
+  bool get isComplex => !identical(assignmentOperator.source, '=');
+
   /// Whether this is an if-null assignment of the form `a ??= b`.
   bool get isIfNullAssignment =>
       identical(assignmentOperator.source, '??=');
 
   visitChildren(Visitor visitor) {
     super.visitChildren(visitor);
     if (assignmentOperator != null) assignmentOperator.accept(visitor);
   }
 
   Send copyWithReceiver(Node newReceiver, bool isConditional) {
@@ skipping 1841 matching lines @@
 
   // VariableDefinitions.
   get metadata => null;
   get type => null;
 
   // Typedef.
   get typeParameters => null;
   get formals => null;
   get typedefKeyword => null;
 }