dart2js cps: Type casts and related changes to type propagation.

pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart

 // Copyright (c) 2014, 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 tree_ir_tracer;
 
 import 'dart:async' show EventSink;
 import '../tracer.dart';
 import 'tree_ir_nodes.dart';
 
@@ skipping 68 matching lines @@
   }
 
   visitThrow(Throw node) {
     _addStatement(node);
   }
 
   visitRethrow(Rethrow node) {
     _addStatement(node);
   }
 
+  visitUnreachable(Unreachable node) {
+    _addStatement(node);
+  }
+
   visitBreak(Break node) {
     _addStatement(node);
     blocks.last.addEdgeTo(breakTargets[node.target]);
   }
 
   visitContinue(Continue node) {
     _addStatement(node);
     blocks.last.addEdgeTo(continueTargets[node.target]);
   }
 
@@ skipping 155 matching lines @@
   }
 
   visitThrow(Throw node) {
     printStatement(null, "throw ${expr(node.value)}");
   }
 
   visitRethrow(Rethrow node) {
     printStatement(null, "rethrow");
   }
 
+  visitUnreachable(Unreachable node) {
+    printStatement(null, "unreachable");
+  }
+
   visitBreak(Break node) {
     printStatement(null, "break ${collector.breakTargets[node.target].name}");
   }
 
   visitContinue(Continue node) {
     printStatement(null,
         "continue ${collector.continueTargets[node.target].name}");
   }
 
   visitIf(If node) {
@@ skipping 247 matching lines @@
       String prefix = v.element == null ? 'v' : '${v.element.name}_';
       while (name == null || _usedNames.contains(name)) {
         name = "$prefix${_counter++}";
       }
       _names[v] = name;
       _usedNames.add(name);
     }
     return name;
   }
 }