Handle null literal in compile_from_dill

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

 // Copyright (c) 2017, 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.kernel.element_map;
 
 import 'package:kernel/ast.dart' as ir;
 import 'package:kernel/clone.dart';
 import 'package:kernel/type_algebra.dart';
 
@@ skipping 1304 matching lines @@
     return const VoidType();
   }
 
   @override
   DartType visitDynamicType(ir.DynamicType node) {
     return const DynamicType();
   }
 
   @override
   DartType visitInvalidType(ir.InvalidType node) {
-    if (topLevel) {
-      throw new UnimplementedError(
-          "Outermost invalid types not currently supported");
-    }
-    // Nested invalid types are treated as `dynamic`.
+    // Root uses such a `o is Unresolved` and `o as Unresolved` must be special
+    // cased in the builder, nested invalid types are treated as `dynamic`.
     return const DynamicType();
   }
 }
 
 /// [native.BehaviorBuilder] for kernel based elements.
 class KernelBehaviorBuilder extends native.BehaviorBuilder {
   final CommonElements commonElements;
 
   KernelBehaviorBuilder(this.commonElements);
 
@@ skipping 88 matching lines @@
   KernelResolutionWorldBuilder(
       this.elementMap,
       NativeBasicData nativeBasicData,
       NativeDataBuilder nativeDataBuilder,
       InterceptorDataBuilder interceptorDataBuilder,
       BackendUsageBuilder backendUsageBuilder,
       SelectorConstraintsStrategy selectorConstraintsStrategy)
       : super(
             elementMap.elementEnvironment,
             elementMap.commonElements,
+            elementMap._constantEnvironment.constantSystem,
             nativeBasicData,
             nativeDataBuilder,
             interceptorDataBuilder,
             backendUsageBuilder,
             selectorConstraintsStrategy);
 
   @override
   Iterable<InterfaceType> getSupertypes(ClassEntity cls) {
     return elementMap._getOrderedTypeSet(cls).supertypes;
   }
@@ skipping 96 matching lines @@
     return node.isExternal &&
         !elementMap.isForeignLibrary(node.enclosingLibrary);
   }
 
   @override
   bool isJsInteropMember(MemberEntity element) {
     // TODO(johnniwinther): Compute this.
     return false;
   }
 }