ada27dfc01
KindOfInvalid is -1, so IS_REFCOUNTED_TYPE() == false, which will allow skipping a few tombstone checks in future array work. But also, it avoids declaring a magic constant outside the DataType enum, and sometimes gcc can generate better code for comparisons with 0 (ie type<0) than it can for 0x62, the value of KindOfTombstone.