ref: 3303b2c61b4381500b39b1d3ce6f95b9a21ed4f4 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 }