factory pattern with nim concepts

nim_concept_factory.nim

type Frame* = concept x, type T 
  T.newFrame is T

type Arch = enum
    x86
    mips

proc translateExp[T : Frame]() = 
    discard T.newFrame()

type 
    X86Frame = object
        i: int 
    MipsFrame = object
        i:int

proc newFrame(x:typedesc[X86Frame]) : X86Frame = 
    return X86Frame(i:42)

proc newFrame(x:typedesc[MipsFrame]) : MipsFrame = 
    return MipsFrame(i:42)

let arch = mips
case arch 
of x86:
    translateExp[X86Frame]()
of mips:
    translateExp[MipsFrame]()