Macro flex_error::define_suberror

macro_rules! define_suberror {
    ( $tracer:ty;
    $name:ident;
    $suberror:ident;
    ( $( $arg_name:ident: $arg_type:ty ),* )
    $( [ $source:ty ] )?
  ) => { ... };
}

Internal macro used to define suberror structs