ref: 0c7eb9f0d093a78520e5cff889dc3fd9d7f6d4c7 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 }