Джентельмены! Вот такой вот код:

using System.Drawing;
namespace Scan
{
    class Scanner
    {
        enum PixelColor {
            | Black
            | White
            | EOFLine
            | EOFFile
        }
        static GetNextPixel ( x:int, y:int, bmp:Bitmap) : int * int * Bitmap * PixelColor
        {
            when (x==bmp.Size.Width)
                def _height=bmp.Height;
                match (y){
                    |_height =>  (x, y, bmp, PixelColor.EOFFile)
                    | _ =>  (0, y+1, bmp, PixelColor.EOFLine)
                }
            when (bmp.GetPixel(x,y) == System.Drawing.Color.Black)
                {(x+1, y, bmp, PixelColor.Black)}
            (x+1, y, bmp, PixelColor.White)
        }
        
        static Parse(filePath:string):void
        {
            def bmp=Bitmap(filePath, false);
            _=GetNextPixel(0, 0, bmp);
        }

        static Main() : void
        {
            _=Parse("barcode.bmp")
        }
    }
}

дает следующие ворнинги:

>C:\Program Files\Nemerle\ncc.exe -no-color -r System.Windows.Forms -r System.Data -t exe scan.n -o scan.exe
scan.n:19:1:19:6: warning: N10005: ignored computed value of type (int * int * System.Drawing.Bitmap * Scan.Scanner.PixelColor)
scan.n:19:1:19:6: hint: use `_ = ...'; or -nowarn:10005 to avoid the warning
scan.n:24:2:24:33: warning: N10005: ignored computed value of type (int * int * System.Drawing.Bitmap * Scan.Scanner.PixelColor)
scan.n:21:3:21:4: warning: this match clause is unused
>Exit code: 0

Не понял о чем ворнинги?