ref: 4ea0da6b6c5c6b8c7c3ba3f70b210b647f612ed2 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 }