gistfile1.txt

meth f a b : int // dispatch based on runtime type of a and b

interface baseOfTAndV
    f _ baseOfUAndW
end

interface baseOfUAndW
    f baseOfTAndV _
end

struct T; end
struct U; end
struct V; end
struct W; end

impl f (a: T) (b: U) : int; …; end

impl f (a: V) (b: W) : int; …; end

var a: baseOfTAndV = random [makeT!, makeV!]
var b: baseOfUAndW = random [makeU!, makeW!]
f a b // error; f T W and f U V not implemented