ref: 954b2fd7a8a0a65a077b61a5932ed54d3e3ef6a5 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 }