anchor.diff:      );
     }
   
  +  @useResult
     CheckTarget<String?> get returnType {
       return nest(
         value.suggestion.returnType,
  
positive.code:   }
  }
  
  extension CompletionSuggestionListExtension
      on CheckTarget<List<CompletionSuggestionForTesting>> {
    CheckTarget<Iterable<String>> get completions {
      return nest(
        value.map((e) => e.suggestion.completion).toList(),
        (selected) => 'has completions ${valueStr(selected)}',
      );
    }
  
    CheckTarget<Iterable<CompletionSuggestionForTesting>> get withElementClass {
      return nest(
        value.where((e) {
          return e.suggestion.element?.kind == ElementKind.CLASS;
        }).toList(),
        (selected) => 'withElementClass ${valueStr(selected)}',
      );
    }
  }
  
  extension CompletionSuggestionsExtension
      on CheckTarget<Iterable<CompletionSuggestionForTesting>> {
    CheckTarget<List<String>> get completions {
      return nest(
        value.map((e) => e.suggestion.completion).toList(),
  
negative.code:     );
    }
  
    @useResult
    CheckTarget<List<int>?> get defaultArgumentListTextRanges {
      return nest(
        value.suggestion.defaultArgumentListTextRanges,
  