ref: b2d29ed0eebd0e3e2c162b5e83d6d0e8b6ddee57 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 }