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 the LOAD_CONST bytecode:

import dis f = lambda: ... for pos in f.__code__.co_positions(): print(*pos) dis.dis(f)

This outputs, in Python 3.11:

2 2 0 0 2 2 12 15 2 2 0 0 2 0 RESUME 0 2 LOAD_CONST 1 (Ellipsis) 4 RETURN_VALUE 

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

2 2 0 0 2 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 for RETURN_CONST in Python 3.12+:

import dis def f(): return ... for pos in f.__code__.co_positions(): print(*pos) dis.dis(f)

which outputs:

2 2 0 0 3 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