#![recursion_limit="128"]
macro_rules! blow {
    () => {};
    (_ $($rest:tt)*) => {
        pub mod a { blow!($($rest)*); }
        pub mod b { pub use super::a::*; }
    }
}

blow!(_ _ _ _ _ _ _ _
      _ _ _ _ _ _ _ _
      _ _ _ _ _ _ _ _
      _ _ _ _ _ _ _ _
      _ _ _ _ _ _ _ _
      _ _ _ _ _ _ _ _
      _ _ _ _ _ _ _ _
      _ _ _ _ _ _ _ _);