ref: 9a2f63d47a96bf522e6c5d39e215b2e6a9e600c7 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 }