Detect total switches to prevent type pollution by default cases.

sdk/lib/_internal/compiler/implementation/ssa/tracer.dart

 // Copyright (c) 2013, 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:async' show EventSink;
 
 import 'ssa.dart';
 import '../js_backend/js_backend.dart';
@@ skipping 448 matching lines @@
     buf.write("Switch: (");
     buf.write(temporaryId(node.inputs[0]));
     buf.write(") ");
     for (int i = 1; i < node.inputs.length; i++) {
       buf.write(temporaryId(node.inputs[i]));
       buf.write(": B");
       buf.write(node.block.successors[i - 1].id);
       buf.write(", ");
     }
     buf.write("default: B");
-    buf.write(node.block.successors.last.id);
+    buf.write(node.defaultTarget.id);
     return buf.toString();
   }
 
   String visitThis(HThis node) => "this";
 
   String visitThrow(HThrow node) => "Throw ${temporaryId(node.inputs[0])}";
 
   String visitThrowExpression(HThrowExpression node) {
     return "ThrowExpression ${temporaryId(node.inputs[0])}";
   }
@@ skipping 59 matching lines @@
   }
 
   String visitInterfaceType(HInterfaceType node) {
     return "InterfaceType: ${node.dartType}";
   }
 
   String visitDynamicType(HDynamicType node) {
     return "DynamicType";
   }
 }