a.txt

moritz:~$ cat program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TestProject
{
    class Program
    {
        static void Main(string[] args)
        {
            return;

            Console.WriteLine("asdf");
        }
    }
}

moritz@:~$ mcs program.cs
program.cs(15,13): warning CS0162: Unreachable code detected
Compilation succeeded - 1 warning(s)
moritz@phoon:~$