ref: cc61b84219f29c4bf874e579986ef77bcc6a0ad3
dir: /test/trait.myr/
use std trait frobable @a = frob : (val : @a -> @a) ;; impl frobable int = frob = {val -> val * 2 } ;; generic foo = {x : @a::frobable -> frob(x) } const main = { std.exit(foo(12)) }