Something

using System;
using Parser;

...
	static void Main()
	{
	    Parsed<int> x = new Ok<int>(4);

	    // Is there any way to avoid having to write "Parsed<int>.Fn<int>"?

	    Console.WriteLine(x.Match(new Parsed<int>.Fn<int> {
		Ok = z => z.Value,
		Error = z => 9
	    }));

	}