ref: 76c34b542f0b5c0cd6cc60a9cef9d53b6fc899d1 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 }