Macro indirect_once::indirect_fn

macro_rules! indirect_fn {
    (resolver = $resolver: ident ; fn $name:ident($($arg: ident : $pty: ty),*) {}) => { ... };
    (resolver = $resolver: ident ; fn $name:ident($($arg: ident : $pty: ty),*) -> $ret: ty {}) => { ... };
}