Create closed world for hello world using .dill file

pkg/compiler/lib/src/kernel/kernel_visitor.dart

 // Copyright (c) 2016, 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.md file.
 
 import 'package:kernel/ast.dart' as ir;
 import 'package:kernel/frontend/accessors.dart'
     show
         Accessor,
         IndexAccessor,
         NullAwarePropertyAccessor,
@@ skipping 239 matching lines @@
     try {
       return node?.accept(this);
     } finally {
       isVoidContext = wasVoidContext;
     }
   }
 
   ir.TreeNode visitWithCurrentContext(Expression node) => node?.accept(this);
 
   withCurrentElement(AstElement element, f()) {
-    assert(element.library == kernel.compiler.currentElement.library);
+    assert(
+        element.library == (kernel.compiler.currentElement as Element).library);
     Element previousElement = currentElement;
     currentElement = element;
     try {
       return f();
     } finally {
       currentElement = previousElement;
     }
   }
 
   ir.DartType computeType(TypeAnnotation node) {
@@ skipping 2695 matching lines @@
       : this(null, true, node, initializers);
 
   accept(ir.Visitor v) => throw "unsupported";
 
   visitChildren(ir.Visitor v) => throw "unsupported";
 
   String toString() {
     return "IrFunction($kind, $isConstructor, $node, $initializers)";
   }
 }