dart2js-kernel: implement rethrow

pkg/compiler/lib/src/ssa/nodes.dart

 // Copyright (c) 2012, 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.
 
 import '../closure.dart';
 import '../common.dart';
 import '../common/backend_api.dart' show BackendClasses;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
@@ skipping 253 matching lines @@
 
   HConstant addConstantBool(bool value, ClosedWorld closedWorld) {
     return addConstant(
         closedWorld.constantSystem.createBool(value), closedWorld);
   }
 
   HConstant addConstantNull(ClosedWorld closedWorld) {
     return addConstant(closedWorld.constantSystem.createNull(), closedWorld);
   }
 
+  HConstant addConstantUnreachable(ClosedWorld closedWorld) {
+    // A constant with an empty type used as the HInstruction of an expression
+    // in an unreachable context.
+    return addConstant(
+        new SyntheticConstantValue(
+            SyntheticConstantKind.EMPTY_VALUE, const TypeMask.nonNullEmpty()),
+        closedWorld);
+  }
+
   void finalize() {
     addBlock(exit);
     exit.open();
     exit.close(new HExit());
     assignDominators();
   }
 
   void assignDominators() {
     // Run through the blocks in order of increasing ids so we are
     // guaranteed that we have computed dominators for all blocks
@@ skipping 3180 matching lines @@
 class HDynamicType extends HRuntimeType {
   HDynamicType(DynamicType dartType, TypeMask instructionType)
       : super(const <HInstruction>[], dartType, instructionType);
 
   accept(HVisitor visitor) => visitor.visitDynamicType(this);
 
   int typeCode() => HInstruction.DYNAMIC_TYPE_TYPECODE;
 
   bool typeEquals(HInstruction other) => other is HDynamicType;
 }