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

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.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 dart2js.ir_builder_task;
 
 import '../closure.dart' as closurelib;
 import '../closure.dart' hide ClosureScope;
 import '../constants/expressions.dart';
 import '../dart_types.dart';
@@ skipping 2792 matching lines @@
 /// Perform simple post-processing on the initial CPS-translated root term.
 ///
 /// This pass performs backend-independent post-processing on the translated
 /// term.  It is implemented separately from the optimization passes because
 /// it is required for correctness of the implementation.
 ///
 /// It performs the following translations:
 ///   - Replace [ir.LetPrim] binding a [ir.NonTailThrow] with a [ir.Throw]
 ///     expression.
 class CleanupPass extends ir.RecursiveVisitor {
-  RemovalVisitor _remover = new RemovalVisitor();
-
   ir.Expression replacementFor(ir.Expression expression) {
     if (expression != null && expression is ir.LetPrim) {
       ir.Primitive primitive = expression.primitive;
       if (primitive is ir.NonTailThrow) {
-        _remover.visit(expression);
+        ir.RemovalVisitor.remove(expression);
         return new ir.Throw(primitive.value.definition);
       }
     }
     return expression;
   }
 
   processFunctionDefinition(ir.FunctionDefinition node) {
     node.body = replacementFor(node.body);
   }
 
@@ skipping 22 matching lines @@
   }
 
   processSetStatic(ir.SetStatic node) {
     node.body = replacementFor(node.body);
   }
 
   processContinuation(ir.Continuation node) {
     node.body = replacementFor(node.body);
   }
 }
-
-/// Visit a just-deleted subterm and unlink all [Reference]s in it.
-class RemovalVisitor extends ir.RecursiveVisitor {
-  processReference(ir.Reference reference) {
-    reference.unlink();
-  }
-}