ref: d48c3220b5bbf3604b0b16d344d3cc0c17c5f8a7 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 }