diff --git a/pkg/compiler/lib/src/inferrer/type_graph_inferrer.dart b/pkg/compiler/lib/src/inferrer/type_graph_inferrer.dart
index 2daea5b5b45..f530c3c05e6 100644
--- a/pkg/compiler/lib/src/inferrer/type_graph_inferrer.dart
+++ b/pkg/compiler/lib/src/inferrer/type_graph_inferrer.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.10
-
 library type_graph_inferrer;
 
 import 'package:kernel/ast.dart' as ir;
@@ -13,8 +11,8 @@ import '../compiler_interfaces.dart';
 import '../elements/entities.dart';
 import '../js_backend/inferred_data.dart';
 import '../js_model/elements.dart' show JClosureCallMethod;
+import '../js_model/js_world.dart';
 import '../js_model/locals.dart';
-import '../world.dart';
 import 'abstract_value_domain.dart';
 import 'engine.dart';
 import 'engine.dart' as engine;
@@ -22,8 +20,8 @@ import 'type_graph_nodes.dart';
 import 'types.dart';
 
 class TypeGraphInferrer implements TypesInferrer {
-  InferrerEngine inferrer;
-  final JClosedWorld closedWorld;
+  late InferrerEngine inferrer;
+  final JsClosedWorld closedWorld;
 
   final CompilerInferrerFacade _compiler;
   final GlobalLocalsMap _globalLocalsMap;
@@ -61,7 +59,7 @@ class TypeGraphInferrer implements TypesInferrer {
         _inferredDataBuilder);
   }
 
-  Iterable<MemberEntity> /*?*/ getCallersOfForTesting(MemberEntity element) {
+  Iterable<MemberEntity>? getCallersOfForTesting(MemberEntity element) {
     return inferrer.getCallersOfForTesting(element);
   }
 
@@ -74,12 +72,11 @@ class TypeGraphInferrer implements TypesInferrer {
 
     void createMemberResults(
         MemberEntity member, MemberTypeInformation typeInformation) {
-      GlobalTypeInferenceElementData data =
-          inferrer.dataOfMember(member).compress();
+      final data = inferrer.dataOfMember(member).compress();
       bool isJsInterop = closedWorld.nativeData.isJsInteropMember(member);
 
-      AbstractValue returnType;
-      AbstractValue type;
+      late AbstractValue returnType;
+      AbstractValue? type;
 
       if (isJsInterop) {
         returnType = type = abstractValueDomain.dynamicType;
@@ -93,8 +90,7 @@ class TypeGraphInferrer implements TypesInferrer {
 
       bool throwsAlways =
           // Always throws if the return type was inferred to be non-null empty.
-          returnType != null &&
-              abstractValueDomain.isEmpty(returnType).isDefinitelyTrue;
+          abstractValueDomain.isEmpty(returnType).isDefinitelyTrue;
 
       bool isCalledOnce = typeInformation.isCalledOnce();
 
@@ -108,8 +104,8 @@ class TypeGraphInferrer implements TypesInferrer {
         (MemberEntity member, MemberTypeInformation typeInformation) {
       createMemberResults(member, typeInformation);
       if (member is JClosureCallMethod) {
-        ClosureRepresentationInfo info =
-            closedWorld.closureDataLookup.getScopeInfo(member);
+        final info = closedWorld.closureDataLookup.getScopeInfo(member)
+            as ClosureRepresentationInfo;
         info.forEachFreeVariable(_globalLocalsMap.getLocalsMap(member),
             (Local from, FieldEntity to) {
           freeVariables.add(to);
diff --git a/pkg/compiler/lib/src/inferrer_experimental/type_graph_inferrer.dart b/pkg/compiler/lib/src/inferrer_experimental/type_graph_inferrer.dart
index 53f2d16691f..4adf28c418d 100644
--- a/pkg/compiler/lib/src/inferrer_experimental/type_graph_inferrer.dart
+++ b/pkg/compiler/lib/src/inferrer_experimental/type_graph_inferrer.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.10
-
 library type_graph_inferrer;
 
 import 'package:kernel/ast.dart' as ir;
@@ -13,8 +11,8 @@ import '../compiler_interfaces.dart';
 import '../elements/entities.dart';
 import '../js_backend/inferred_data.dart';
 import '../js_model/elements.dart' show JClosureCallMethod;
+import '../js_model/js_world.dart';
 import '../js_model/locals.dart';
-import '../world.dart';
 import '../inferrer/abstract_value_domain.dart';
 import 'engine.dart';
 import 'engine.dart' as engine;
@@ -22,8 +20,8 @@ import 'type_graph_nodes.dart';
 import 'types.dart';
 
 class TypeGraphInferrer implements TypesInferrer {
-  InferrerEngine inferrer;
-  final JClosedWorld closedWorld;
+  late InferrerEngine inferrer;
+  final JsClosedWorld closedWorld;
 
   final CompilerInferrerFacade _compiler;
   final GlobalLocalsMap _globalLocalsMap;
@@ -61,7 +59,7 @@ class TypeGraphInferrer implements TypesInferrer {
         _inferredDataBuilder);
   }
 
-  Iterable<MemberEntity> /*?*/ getCallersOfForTesting(MemberEntity element) {
+  Iterable<MemberEntity>? getCallersOfForTesting(MemberEntity element) {
     return inferrer.getCallersOfForTesting(element);
   }
 
@@ -74,12 +72,11 @@ class TypeGraphInferrer implements TypesInferrer {
 
     void createMemberResults(
         MemberEntity member, MemberTypeInformation typeInformation) {
-      GlobalTypeInferenceElementData data =
-          inferrer.dataOfMember(member).compress();
+      final data = inferrer.dataOfMember(member).compress();
       bool isJsInterop = closedWorld.nativeData.isJsInteropMember(member);
 
-      AbstractValue returnType;
-      AbstractValue type;
+      late AbstractValue returnType;
+      AbstractValue? type;
 
       if (isJsInterop) {
         returnType = type = abstractValueDomain.dynamicType;
@@ -93,8 +90,7 @@ class TypeGraphInferrer implements TypesInferrer {
 
       bool throwsAlways =
           // Always throws if the return type was inferred to be non-null empty.
-          returnType != null &&
-              abstractValueDomain.isEmpty(returnType).isDefinitelyTrue;
+          abstractValueDomain.isEmpty(returnType).isDefinitelyTrue;
 
       bool isCalledOnce = typeInformation.isCalledOnce();
 
@@ -108,8 +104,8 @@ class TypeGraphInferrer implements TypesInferrer {
         (MemberEntity member, MemberTypeInformation typeInformation) {
       createMemberResults(member, typeInformation);
       if (member is JClosureCallMethod) {
-        ClosureRepresentationInfo info =
-            closedWorld.closureDataLookup.getScopeInfo(member);
+        final info = closedWorld.closureDataLookup.getScopeInfo(member)
+            as ClosureRepresentationInfo;
         info.forEachFreeVariable(_globalLocalsMap.getLocalsMap(member),
             (Local from, FieldEntity to) {
           freeVariables.add(to);