anchor.diff:            .registerTypeUse(TypeUse.instantiation(_commonElements.typeType));
         // If the type is a web component, we need to ensure the constructors are
         // available to 'upgrade' the native object.
  -      if (constant.representedType is InterfaceType) {
  -        InterfaceType representedType = constant.representedType;
  +      final representedType = constant.representedType;
  +      if (representedType is InterfaceType) {
           _customElementsAnalysis.registerTypeConstant(representedType.element);
         }
       } else if (constant is InstantiationConstantValue) {
  
positive.code: // 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.
  
  // @dart = 2.10
  
  library js_backend.backend.codegen_listener;
  
  
negative.code:     _customElementsAnalysis.registerStaticUse(member);
  
      if (member.isFunction && member.isInstanceMember) {
        ClassEntity cls = member.enclosingClass!;
        if (member.name == Identifiers.call &&
            _elementEnvironment.isGenericClass(cls) &&
            _rtiNeed.methodNeedsSignature(member as FunctionEntity)) {
          worldImpact.addImpact(_registerComputeSignature());
        }
      }
  