Function union_soup_within 

pub fn union_soup_within(
    rings: &[Ring],
    options: OverlayOptions,
    execution: &ExecutionOptions,
) -> Result<ReportedUnion, OverlayRefusal>

union_soup_with under the caller’s execution options (#338), as overlay_within is overlay_with: the tolerance is ExecutionOptions::tolerance, and a memory budget refuses the subdivision with OverlayRefusal::BudgetExceeded before it would hold more. Without a budget it is union_soup_with exactly.