pdb fails when setting a breakpoint to function names with return-type annotations

[baco]

Bug report

Bug description:

When having return-type annotations on a function:

def foo() -> int:
    return 0

and trying to establish a breakpoint on the name of the function:

(Pdb) break foo

PDB raises the following exception (snipped):

Traceback (most recent call last):
  File "/usr/lib/python3.13/pdb.py", line 1137, in do_break
    lineno = int(arg)
ValueError: invalid literal for int() with base 10: 'foo'

During handling of the above exception, another exception occurred:

...
SyntaxError: 'return' outside function
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /usr/lib/python3.13/dis.py(76)_try_compile()
-> return compile(source, name, 'exec')

This also happens with temporary breakpoins tbreak. This was tested using Python versions from Debian official repositories. The failure appears in 3.13.0 and was not present in 3.12.6.

Analyzing with @asottile they point out that the following lines: Lib/pdb.py:121, Lib/pdb.py:141 may be causing this behavior. They also provided further probing of the issue:

(Pdb) p compile(funcdef, filename, 'exec').co_consts
('return', <code object main at 0x102b73020, file "/private/tmp/y/t3.py", line 1>, None)
(Pdb) p funcdef
'def main() -> int:\n    pass\n'

I think it's expecting to find the code object there.
it's due to the disassembly

(Pdb) dis.dis(compile('def f() -> int: pass', filename, 'exec'))
  0           RESUME                   0

  1           LOAD_CONST               0 ('return')
              LOAD_NAME                0 (int)
              BUILD_TUPLE              2
              LOAD_CONST               1 (<code object f at 0x102b73020, file "/private/tmp/y/t3.py", line 1>)
              MAKE_FUNCTION
              SET_FUNCTION_ATTRIBUTE   4 (annotations)
              STORE_NAME               1 (f)
              RETURN_CONST             2 (None)

Disassembly of <code object f at 0x102b73020, file "/private/tmp/y/t3.py", line 1>:
  1           RESUME                   0
              RETURN_CONST             0 (None)

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-125884: Support breakpoint on functions with annotations #125892