fn determine_shape(func: &ItemFn) -> Option<Shape>Expand description
The shape of a function annotated with #[sqlfunc], or None for a function
without SQL arguments.
Only the SQL arguments count, so a &self receiver and a trailing &RowArena are
skipped. A Variadic<T> or OptionalArg<T> argument makes the function variadic
regardless of how many arguments it has.