ref: d3ed26c37dedef85e3b193724facde2ee24acb64
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)) }