ref: 4a1f9034d1e1c0f21a9c677c0b04b61aea3d3121 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 }