Policy: Slots

Concern: How do slot operators constrain co-installation and rebuilds?

PMS / Portage: Slots allow multiple versions of a CN; operators include :slot, :*, := (slot equality / rebuild on sub-slot change), and sub-slots (:1/A). Same slot, different versions conflict.

Literals:

• Slot component inside package_dependency / candidate selection
• Slot occupancy constraints attached during :install resolve
• Assumptions: slot_conflict, related model issues

Owns: Rules/Resolving/candidate.pl, Rules/Resolving/cnselect.pl, slot-aware ranking keys, version/slot facts from the knowledge cache.

Invariants:

• Explicit :N admits only that slot; :* admits any slot (prefer newest eligible).
• := binds the parent to the child’s chosen slot/sub-slot for rebuild semantics.
• Two selected versions of the same CN in the same slot is a conflict (negative unless resolved by replace/upgrade path).
• Distinct slots of the same CN may co-install when policy allows (multi-slot).

Examples: test41, test42, test43, test48, test68.
See also: Dependency, Choice.