dart2js cps_ir: Use interceptors for is-checks.

pkg/compiler/lib/src/cps_ir/cps_ir_builder.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;
 
 import '../common/names.dart' show
     Names,
     Selectors;
 import '../compile_time_constants.dart' show
@@ skipping 2735 matching lines @@
       // This is not an optimization: the TypeOperator assumes that `null`
       // cannot satisfy the type test unless the type is a type variable.
       if (type.isObject || type.isDynamic) {
         // `x is Object` and `x is dynamic` are always true, even if x is null.
         return buildBooleanConstant(true);
       }
       if (type is InterfaceType && type.element == program.nullClass) {
         // `x is Null` is true if and only if x is null.
         return _buildCheckNull(value);
       }
-      return addPrimitive(new ir.TypeTest(value, type, typeArguments));
+      if (type.isInterfaceType && type.isRaw) {

[sra1, 2015/10/06 06:47:58]

I think this could me moved to type_propagation.

[sra1, 2015/10/07 04:01:06]

Done.

+        return addPrimitive(new ir.TypeTestRaw(value, type));
+      } else {
+        return addPrimitive(new ir.TypeTest(value, type, typeArguments));
+      }
     } else {
       if (type.isObject || type.isDynamic) {
         // `x as Object` and `x as dynamic` are the same as `x`.
         return value;
       }
       return _continueWithExpression(
               (k) => new ir.TypeCast(value, type, typeArguments, k));
     }
   }
 
@@ skipping 118 matching lines @@
 }
 
 class SwitchCaseInfo {
   final List<ir.Primitive> constants = <ir.Primitive>[];
   final SubbuildFunction buildBody;
 
   SwitchCaseInfo(this.buildBody);
 
   void addConstant(ir.Primitive constant) => constants.add(constant);
 }