Bug report

Bug description:

In Python 3.11, the code object of a lambda function that returns a constant value used to have location information provided for theLOAD_CONST bytecode:

importdisf=lambda: ...forposinf.__code__.co_positions():print(*pos)dis.dis(f)

This outputs, in Python 3.11:

2 2 0 02 2 12 152 2 0 0  2           0 RESUME                   0              2 LOAD_CONST               1 (Ellipsis)              4 RETURN_VALUE

However, since Python 3.12, whereRETURN_CONST was introduced, the same code now outputs:

2 2 0 02 2 0 0  2           RESUME                   0              RETURN_CONST             1 (Ellipsis)

with no precise location information found in any of the bytecode produced.

Note that a regular function that returns a constant value correctly provides precise location information forRETURN_CONST in Python 3.12+:

importdisdeff():return ...forposinf.__code__.co_positions():print(*pos)dis.dis(f)

which outputs:

2 2 0 03 3 11 14  2           RESUME                   0  3           RETURN_CONST             1 (Ellipsis)

CPython versions tested on:

3.11, 3.12, CPython main branch

Operating systems tested on:

Linux, Windows

Linked PRs

• gh-120722: Propogate instruction location in optimization of LOAD_CONST + RETURN_VALUE with RETURN_CONST #120723
• gh-120722: Set position on RETURN_VALUE in lambda #120724
• [3.13] gh-120722: Set position on RETURN_VALUE in lambda (GH-120724) #120738
• [3.12] gh-120722: Set position on RETURN_VALUE in lambda (GH-120724) #120739