error_chain::error_chain!

macro_rules! error_chain {
    (
        links {
            $( $link_error_path:path, $link_kind_path:path, $link_variant:ident;  ) *
        }

        foreign_links {
            $( $foreign_link_error_path:path, $foreign_link_variant:ident,
               $foreign_link_desc:expr;  ) *
        }

        errors {
            $( $error_chunks:tt ) *
        }

    ) => { ... };
    (
        types {
        }

        links {
            $( $link_error_path:path, $link_kind_path:path, $link_variant:ident;  ) *
        }

        foreign_links {
            $( $foreign_link_error_path:path, $foreign_link_variant:ident,
               $foreign_link_desc:expr;  ) *
        }

        errors {
            $( $error_chunks:tt ) *
        }

    ) => { ... };
    (
        types {
            $error_name:ident, $error_kind_name:ident,
            $chain_error_name:ident, $result_name:ident;
        }

        links {
            $( $link_error_path:path, $link_kind_path:path, $link_variant:ident;  ) *
        }

        foreign_links {
            $( $foreign_link_error_path:path, $foreign_link_variant:ident,
               $foreign_link_desc:expr;  ) *
        }

        errors {
            $( $error_chunks:tt ) *
        }

    ) => { ... };
}