code: func Sort(less, xs interface{}) {
  	chk := ty.Check(
  		new(func(func(ty.A, ty.A) bool, []ty.A)),
  		less, xs)
  
  	vless, vxs := chk.Args[0], chk.Args[1]
  	sort.Sort(&sortable{vless, vxs, swapperOf(vxs.Type().Elem())})
  }
docs: // Sort has a parametric type:
  //
  //	func Sort(less func(x1 A, x2 A) bool, []A)
  //
  // Sort uses the standard library `sort` package to sort `xs` in place.
  //
  // `less` should be a function that returns true if and only if `x1` is less
  // than `x2`.