API Reference — Cooperative Cleanup

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These patterns follow from the slot rule.
Place cleanup before acquisition.
The defer becomes a no-op when the slot is null — either because acquisition failed, or because the item was transferred.

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Pattern 1 — defer-put-early (pool item)

var slot: Slot = null;
defer pl.put(&slot);              // no-op if slot == null
try pl.get(TAG, .new_only, &slot);
// ... work ...
// on transfer: slot = null → defer runs as no-op
// on no transfer: defer recycles item

Put before get — safe because Pool.put is a no-op on null.

If the pool may be closed while the item is held, Pool.put leaves slot non-null (caller retains
held). Add a fallback destroy to avoid a leak:

var slot: Slot = null;
defer EventPolyHelper.destroy(alloc, &slot); // fallback: frees if Pool.put left slot non-null
defer pl.put(&slot);                   // primary: recycles to pool (clears slot on success)
// defers run LIFO: Pool.put first, then destroy (no-op if Pool.put cleared slot)

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