Inferred error set without an error union

If a function returns an error union, Zig can infer the error set automatically. Does this also somehow work for functions that don’t return error unions, but just errors? For example, is there a way to avoid having to explicitly specify the error{ A, B } error set here? fn mapError(x: i32) error{ A, B } { return if (x > 0) error.A else error.B; }