Disallowed overlapping shapes between cells are not flagged if one shape completely overlaps the other.

[RTimothyEdwards]

The non-overlapping DRC error is most often associated with contact areas. The overlap prohibition keeps the contacts from being misaligned between parent and child cell.

However, if a contact area completely overlaps another area in another cell, it is not flagged, even though the same condition exists in which contact cuts may be misaligned between parent and child cells (or sibling cells).

This also appears to evade the "parent and child disagree on CIF" error during GDS write. I would have expected the DRC and GDS error catching to be independent and am not sure why neither one flags the issue.