Accept more labels per switch case.

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 163 matching lines @@
         case HType.READABLE_ARRAY: prefix = 'a'; break;
         case HType.EXTENDABLE_ARRAY: prefix = 'e'; break;
         case HType.BOOLEAN: prefix = 'b'; break;
         case HType.INTEGER: prefix = 'i'; break;
         case HType.DOUBLE: prefix = 'd'; break;
         case HType.NUMBER: prefix = 'n'; break;
         case HType.STRING: prefix = 's'; break;
         case HType.UNKNOWN: prefix = 'v'; break;
         case HType.CONFLICTING: prefix = 'c'; break;
         case HType.INDEXABLE_PRIMITIVE: prefix = 'r'; break;
+        case HType.NULL: prefix = 'u'; break;
         default: unreachable();
       }
     }
     return "$prefix${instruction.id}";
   }
 
   String visitBoolify(HBoolify node) {
     return "Boolify: ${temporaryId(node.inputs[0])}";
   }
 
@@ skipping 241 matching lines @@
   String visitIs(HIs node) {
     String type = node.typeExpression.toString();
     return "TypeTest: ${temporaryId(node.expression)} is $type";
   }
 
   String visitTypeConversion(HTypeConversion node) {
     String type = node.propagatedType.toString();
     return "TypeConversion: ${temporaryId(node.inputs[0])} to $type";
   }
 }