Fix some operator madness (see incr_op_test for more details.)

lib/compiler/implementation/tree/unparser.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.
 
 // Returns null if no need to rename a node.
 typedef String Renamer(Node node);
 
 class Unparser implements Visitor {
   Renamer rename;
   StringBuffer sb;
@@ skipping 282 matching lines @@
       add(node.assignmentOperator.token.value);
     }
     unparseNodeListFrom(node.argumentsNode, node.argumentsNode.nodes.tail);
   }
 
   visitSendSet(SendSet node) {
     if (node.isIndex) {
       unparseIndexedSet(node);
     } else {
       if (node.isPrefix) {
-        add(node.assignmentOperator.token.value);
+        sb.add(' ');
+        add(node.assignmentOperator.source);
       }
-      unparseSendPart(node);
+      if (node.receiver !== null && rename(node.receiver) != '') {
+        visit(node.receiver);
+        CascadeReceiver asCascadeReceiver = node.receiver.asCascadeReceiver();
+        if (asCascadeReceiver !== null) {
+          add(asCascadeReceiver.cascadeOperator.value);
+        } else {
+          sb.add('.');
+        }
+      }
+      visit(node.selector);
       if (!node.isPrefix) {
-        add(node.assignmentOperator.token.value);
+        SourceString source = node.assignmentOperator.source;
+        add(source);
+        if (source.slowToString() != '=') sb.add(' ');
       }
       visit(node.argumentsNode);
     }
   }
 
   visitThrow(Throw node) {
     add(node.throwToken.value);
     if (node.expression !== null) {
       sb.add(' ');
       visit(node.expression);
@@ skipping 188 matching lines @@
       sb.add(' ');
     }
     visit(node.name);
     if (node.typeParameters !== null) {
       visit(node.typeParameters);
     }
     visit(node.formals);
     add(node.endToken.value);
   }
 }