# Pastebin nXDhimPG
that's what this error is telling you:

/Users/sean/Dropbox/Private/Code/pony/andrea/a.pony:23:28: argument not a subtype of parameter
    h.assert_eq[Player](p, Blank) // This work if all primitives are Equatable[Cell] but not explicitly Equatable[Player]
                           ^
    Info:
    /Users/sean/Dropbox/Private/Code/pony/andrea/a.pony:9:1: Blank val is not a subtype of White val
    primitive Blank is Equatable[Cell]
    ^
    /Users/sean/Dropbox/Private/Code/pony/andrea/a.pony:9:1: Blank val is not a subtype of Black val
    primitive Blank is Equatable[Cell]
    ^
    /Users/sean/Dropbox/Private/Code/pony/andrea/a.pony:9:1: Blank val is not a subtype of any element of (White val | Black val)
    primitive Blank is Equatable[Cell]