KOS_OP_ITEM_VAR_INPLACE

• Style: EXTRA (OPCOUNT, VAR, NOARG, NOARG).

• Stack: [..., obj, v0 .. v_{n-1}] → [...]. Reduce obj[key] in place with the count values left to right and store it back with the object on the stack and the key resolved by name.

• Cache: none; a VAR row survives lowering only for a name with no fast slot.

• Compiler form: Shaped by compile/inplace-item when OBJ is a symbol or KEY is a feeder and a value is not, so the fold could not reach the named operands. May lower to ITEM_FAST_INPLACE.

• Implementation: koskari/lib/opcode/ITEM_VAR_INPLACE.c