Function if

xs/sources/xsMapSet.c:1383–1389

		slot = slot->value.reference;
#if mxKeysGarbageCollection
	else if (slot->kind == XS_SYMBOL_KIND) {
		slot = fxGetKey(the, slot->value.symbol);
		if (slot->kind == XS_REFERENCE_KIND)
			slot = slot->value.reference;
		else
			slot = C_NULL;
	}
#endif
	else
		slot = C_NULL;