anchor.diff:      mRRComputer.clear();
     }
   
  +  /// Given some [ResolvedUnitResult] return the first error of high severity
  +  /// if such an error exists, null otherwise.
  +  err.AnalysisError _getFirstErrorOrNull(
  +      ResolvedUnitResult resolvedUnitResult) {
  +    for (var error in resolvedUnitResult.errors) {
  +      if (error.severity == Severity.error) {
  +        return error;
  +      }
  +    }
  +    return null;
  +  }
  +
     Future<List<CompletionSuggestion>> _computeCompletionSuggestions(
         ResolvedUnitResult resolvedUnitResult, int offset,
         [DeclarationsTracker declarationsTracker]) async {
  
positive.code:           try {
              final resolvedUnitResult =
                  await context.currentSession.getResolvedUnit(filePath);
              final visitor = ExpectedCompletionsVisitor();
  
              resolvedUnitResult.unit.accept(visitor);
  
              for (var expectedCompletion in visitor.expectedCompletions) {
  
negative.code: import 'package:analysis_server/src/status/pages.dart';
  import 'package:analyzer/dart/analysis/analysis_context_collection.dart';
  import 'package:analyzer/dart/analysis/results.dart';
  import 'package:analyzer/diagnostic/diagnostic.dart';
  import 'package:analyzer/error/error.dart' as err;
  import 'package:analyzer/file_system/physical_file_system.dart';
  import 'package:analyzer/src/dart/analysis/byte_store.dart';
  import 'package:analyzer/src/generated/engine.dart';
  