Create closed world for hello world using .dill file

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

Index: pkg/compiler/lib/src/kernel/kernel_visitor.dart
diff --git a/pkg/compiler/lib/src/kernel/kernel_visitor.dart b/pkg/compiler/lib/src/kernel/kernel_visitor.dart
index c5841c61d47d6207be5c6da968ab0e8ad5402960..7621656afb88dcc983160106dfd0f059644bdb72 100644
--- a/pkg/compiler/lib/src/kernel/kernel_visitor.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_visitor.dart
@@ -257,7 +257,8 @@ class KernelVisitor extends Object
   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 {