in lib/src/core_matchers.dart [252:260]
Description describeMismatch(Object? item, Description mismatchDescription,
Map matchState, bool verbose) {
if (item is String || item is Iterable || item is Map) {
return super
.describeMismatch(item, mismatchDescription, matchState, verbose);
} else {
return mismatchDescription.add('is not a string, map or iterable');
}
}