anchor.diff:          continue;
         }
         if (includePlainAttributes && typeProvider != null) {
  -        if (typeProvider.stringType.isAssignableTo(input.setterType)) {
  +        if (typeSystem.isAssignableTo(
  +            typeProvider.stringType, input.setterType)) {
             final relevance = input.setterType.displayName == 'String'
                 ? DART_RELEVANCE_DEFAULT - 2
                 : DART_RELEVANCE_DEFAULT - 3;
  
positive.code:             collector,
              standardHtmlAttributes,
              target.parent.boundStandardInputs,
              typeProvider,
              includePlainAttributes: true);
          suggestOutputs(target.parent.boundDirectives, collector,
  
negative.code: import 'dart:async';
  
  import 'package:analyzer/dart/element/type_system.dart' show TypeSystem;
  import 'package:analyzer/src/generated/resolver.dart' show TypeProvider;
  import 'package:analyzer_plugin/protocol/protocol_common.dart'
      hide AnalysisError;
  