Fix the locals lookup of variables and partial implementation of boxing of variables.

pkg/compiler/lib/src/kernel/env.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.env;
 
 import 'package:kernel/ast.dart' as ir;
 import 'package:kernel/clone.dart';
 import 'package:kernel/type_algebra.dart';
 
@@ skipping 357 matching lines @@
   void addConstructorBody(ConstructorBodyEntity constructorBody) {
     _constructorBodyList ??= <ConstructorBodyEntity>[];
     _constructorBodyList.add(constructorBody);
   }
 
   void forEachConstructorBody(void f(ConstructorBodyEntity constructor)) {
     _constructorBodyList?.forEach(f);
   }
 }
 
-class ClosureClassEnv implements ClassEnv {
+class ClosureClassEnv extends RecordContainerEnv {
+  ClosureClassEnv(Map<String, MemberEntity> memberMap) : super(memberMap);
+
+  @override
+  MemberEntity lookupMember(KernelToElementMap elementMap, String name,
+      {bool setter: false}) {
+    if (setter) {
+      // All closure fields are final.
+      return null;
+    }
+    return super.lookupMember(elementMap, name, setter: setter);
+  }
+}
+
+class RecordContainerEnv implements ClassEnv {
   final Map<String, MemberEntity> _memberMap;
 
-  ClosureClassEnv(this._memberMap);
+  RecordContainerEnv(this._memberMap);
 
   @override
   void forEachConstructorBody(void f(ConstructorBodyEntity constructor)) {
-    // We do not create constructor bodies for closure classes.
+    // We do not create constructor bodies for containers.
   }
 
   @override
   void forEachConstructor(
       KernelToElementMap elementMap, void f(ConstructorEntity constructor)) {
-    // We do not create constructors for closure classes.
+    // We do not create constructors for containers.
   }
 
   @override
   ConstructorEntity lookupConstructor(
       KernelToElementMap elementMap, String name) {
-    // We do not create constructors for closure classes.
+    // We do not create constructors for containers.
     return null;
   }
 
   @override
   void forEachMember(
       KernelToElementMap elementMap, void f(MemberEntity member)) {
     _memberMap.values.forEach(f);
   }
 
   @override
   MemberEntity lookupMember(KernelToElementMap elementMap, String name,
       {bool setter: false}) {
-    if (setter) {
-      // All closure fields are final.
-      return null;
-    }
     return _memberMap[name];
   }
 
   @override
   bool get isUnnamedMixinApplication => false;
 
   @override
   ir.Class get cls => null;
 }
 
@@ skipping 172 matching lines @@
   }
 }
 
 class TypedefData {
   final ir.Typedef node;
   final TypedefEntity element;
   final TypedefType rawType;
 
   TypedefData(this.node, this.element, this.rawType);
 }