code: func Set(xs interface{}) interface{} {
  	chk := ty.Check(
  		new(func([]ty.A) map[ty.A]bool),
  		xs)
  	vxs, tset := chk.Args[0], chk.Returns[0]
  
  	vtrue := reflect.ValueOf(true)
  	vset := reflect.MakeMap(tset)
  	xsLen := vxs.Len()
  	for i := 0; i < xsLen; i++ {
  		vset.SetMapIndex(vxs.Index(i), vtrue)
  	}
  	return vset.Interface()
  }
docs: // Set has a parametric type:
  //
  //	func Set(xs []A) map[A]bool
  //
  // Set creates a set from a list.