} else if (IndexDescriptor::kIndexNameFieldName == indexSpecElemFieldName) {
            if (indexSpecElem.type() != BSONType::String) {
                return {ErrorCodes::TypeMismatch,
                        str::stream()
                            << "The field '" << IndexDescriptor::kIndexNameFieldName
                            << "' must be a string, but got " << typeName(indexSpecElem.type())};
            }

            hasIndexNameField = true;
        } else if (IndexDescriptor::kHiddenFieldName == indexSpecElemFieldName) {
            if (indexSpecElem.type() != BSONType::Bool) {
                return {ErrorCodes::TypeMismatch,
                        str::stream()
                       // HERE - I think this message should refer to kHiddenFieldName
                            << "The field '" << IndexDescriptor::kIndexNameFieldName
                            << "' must be a bool, but got " << typeName(indexSpecElem.type())};
            }