ref: 01d9c59aa0f27db7bd3b9b8c1978c9a65c5e60a0 dir: /lib/std/swap.myr/
pkg std = generic swap : (a : @a#, b : @a# -> void) ;; generic swap = {a : @a#, b : @a# var t t = a# a# = b# b# = t }