public MyError Merge__MemberOrExtensionMethod(MyError other) => this is Aggregated_ a
public static MyResult <IReadOnlyCollection <T> > Aggregate <T>(this IEnumerable <MyResult <T> > results)
{
var isError = false;
MyError aggregated = default !;
public static MyResult <T> Error <T>(MyError details) => new MyResult <T> .Error_(details);