declare discriminated union in function parameter

[Xyncgas]

This function takes two choices, you are standing up or down

let Meditate (direction : |Up |Down) =
    match direction with
    | Up -> 0
    | Down -> 1

Because direction is only used by this function, and we don't want any more directions to appear in the future, it's appropriate to the audience for us to restrict the type of direction to be used only by this function. Meanwhile it's a waste in space to put the declaration in its own line because it serves only for this function, therefore we instead say there're things that belong to a function such as its parameter types.

[Xyncgas]

Maybe this's related :#538