Macro std_x::fns2

macro_rules! fns2 {
    (
      @Callback { $Callback : path }
      @Rest
      {
        $( $Item : item )*
      }
    ) => { ... };
    (
      @Callback { $Callback : path }
      @Rest {}
    ) => { ... };
    (
      @Callback { $Callback : path }
      @Rest { $( $Rest : tt )* }
    ) => { ... };
    (
      @Callback { $Callback : path }
      @Fns { $( $Fns : tt )* }
    ) => { ... };
}

Split functions.