KOS_OP_CALL_ATTR

• Style: EXTRA. Schema: CONST (attr name), COUNT (npos), NOARG, NOARG.

• Stack: [..., obj, arg_0, ..., arg_{N-1}] → [..., result]. Attr name from constant pool (EXTRA row). obj.name is resolved as an attribute read would resolve it, then invoked. An unbound plain function found on the class is called as fn(obj, *args); a bound method, an instance-dict callable or a descriptor’s result is called as callable(*args).

• Invariants: Stack has at least 1 + N elements (obj, N args). Resolved attribute must be callable or TypeError.

• Receiver: the resolution decides whether obj is passed: an unbound plain function from the class gets it as the first argument; anything else is called with the arguments alone. A Koskari callable runs in the evaluator; any other callable is called and its result pushed, awaited when awaitable.

Example: "hello".upper() (0 args). Pool: 0 = “upper”, 1 = “hello”. EXTRA row 0: a0 = cpool index of “upper”, a1 = 0 (npos).

index	opcode	arg	arg view	comment
0	CONST	1	1 (“hello”)	stack: […, obj]
1	CALL_ATTR	0	0 (extra idx)	resolve obj.upper; call; push result. stack: […, “HELLO”]
2	RETURN	1	1

Example: c.add_one(41) (1 arg, unbound method). Pool: 0 = “add_one”, 1 = c, 2 = 41. EXTRA row 0: a0 = cpool index of “add_one”, a1 = 1 (npos).

index	opcode	arg	arg view	comment
0	CONST	1	1 (c)	stack: […, obj]
1	CONST	2	2 (41)	stack: […, obj, 41]
2	CALL_ATTR	0	0 (extra idx)	resolve; call add_one(c, 41); push 42. stack: […, 42]
3	RETURN	1	1