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API Reference — Cooperative Cleanup — Pattern 3

Pattern 3 — defer for received mailbox item

var slot: Slot = null;
defer if (slot) |poly| helpers.freeItem(poly, allocator);
try mailbox.receive(mbh, &slot, null);
// dispatch on slot.?.*.tag, process item
// item stays non-null until explicitly transferred or freed

Cleanup covers both the error path (receive failed) and the normal path (item processed and freed).

Next: Pattern 4 — transfer clears the slot.