Macro call_func_proc_macro 

macro_rules! call_func_proc_macro {
    (
        $implementations_mod_ident:ident,
        $exec_args_ident:ident,
        $exec_fn_mod_ident:ident,
        $args_tok_stream:ident
    ) => { ... };
}

Call a function proc-macro implementation function named exec.