ref: c5a41d7c6bb10c1f384cce78953355b1c0c1e6f2 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 }