Don't rely on any speculative type in the bailout version.

lib/compiler/implementation/ssa/tracer.dart

 // Copyright (c) 2011, 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('tracer');
 
 #import('dart:io');
 #import('ssa.dart');
 #import('../leg.dart');
 
@@ skipping 385 matching lines @@
       finallyBlock = 'B${node.finallyBlock.id}';
     } else {
       catchBlocks.add('B${successors[successors.length - 1].id}');
       finallyBlock = 'none';
     }
     return "Try: $tryBlock, Catch: $catchBlocks, Finally: $finallyBlock";
   }
 
   String visitTypeGuard(HTypeGuard node) {
     String type;
-    switch (node.propagatedType) {
+    switch (node.guardedType) {
       case HType.MUTABLE_ARRAY: type = "mutable_array"; break;
       case HType.READABLE_ARRAY: type = "readable_array"; break;
       case HType.BOOLEAN: type = "bool"; break;
       case HType.INTEGER: type = "integer"; break;
       case HType.DOUBLE: type = "double"; break;
       case HType.NUMBER: type = "number"; break;
       case HType.STRING: type = "string"; break;
       case HType.STRING_OR_ARRAY: type = "string_or_array"; break;
       case HType.UNKNOWN: type = 'unknown'; break;
       default: unreachable();
     }
-    return "TypeGuard: ${temporaryId(node.inputs[0])} is $type";
+    String onString = node.isOn ? "on" : "off";
+    return "TypeGuard: ${temporaryId(node.inputs[0])} is $type ($onString)";
   }
 
   String visitIs(HIs node) {
     String type = node.typeName.toString();
     return "TypeTest: ${temporaryId(node.expression)} is $type";
   }
 }