Macro forest_vm::actor_error

macro_rules! actor_error {
    ( fatal($msg:expr) ) => { ... };
    ( fatal($msg:literal $(, $ex:expr)+) ) => { ... };
    ( $code:ident; $msg:expr ) => { ... };
    ( $code:ident; $msg:literal $(, $ex:expr)+ ) => { ... };
}

Convenience macro for generating Actor Errors