using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

namespace Test

{

​

    public class Program

    {

        private static T Invoke<T>(Func<T> primary, Func<T> alternative)

        {

            return alternative();

        }

        static DateTime? Nullable() { return default; }

        static DateTime Struct() { return default; }

        static Type GetType<T>(T obj)

        {

            return typeof(T);

        }

        public static void Main(string[] args)

        {

            // 為啥兩個不同型態的return type可以推導?

            var t = Invoke(() => Nullable(), () => Struct()) ?? throw new Exception("???");

            //Console.WriteLine(t.GetType().Name);

            // 為啥沒加上throw那寫法 return type會有變化?

            var t2 = Invoke(() => Nullable(), () => Struct());

            //Console.WriteLine(GetType(t2).Name);// t.GetType().Name prints DateTime without nullable

        }

    }

}

​