ref: 01e267bc3c3db9698cd9b8f8d3faee1f1b0f2411 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 }