stubtest crashes on `@override` + `@overload`

[jorenham]

When I annotate a method as

    @overload
    @override
    def __new__(cls, /, *, coerce: bool = True) -> Self: ...
    @overload
    def __new__(cls, /, *, na_object: _NaObjectT_co, coerce: bool = True) -> Self: ...

and run stubtest with mypy 1.15.0, I see the following traceback

Traceback (most recent call last):
  File ".venv/lib/python3.13/site-packages/mypy/stubtest.py", line 2123, in main
    return test_stubs(parse_options(sys.argv[1:]))
  File ".venv/lib/python3.13/site-packages/mypy/stubtest.py", line 1992, in test_stubs
    for error in test_module(module):
                 ~~~~~~~~~~~^^^^^^^^
  File ".venv/lib/python3.13/site-packages/mypy/stubtest.py", line 248, in test_module
    yield from verify(stub, runtime, [module_name])
  File ".venv/lib/python3.13/site-packages/mypy/stubtest.py", line 426, in verify_mypyfile
    yield from verify(stub_entry, runtime_entry, object_path + [entry])
  File ".venv/lib/python3.13/site-packages/mypy/stubtest.py", line 588, in verify_typeinfo
    yield from verify(stub_to_verify, runtime_attr, object_path + [entry])
  File ".venv/lib/python3.13/site-packages/mypy/stubtest.py", line 1187, in verify_overloadedfuncdef
    stub_sig = Signature.from_overloadedfuncdef(stub)
  File ".venv/lib/python3.13/site-packages/mypy/stubtest.py", line 845, in from_overloadedfuncdef
    assert func is not None
           ^^^^^^^^^^^^^^^^
AssertionError

The decoration order is irrelevant.

Some context

$ uv run python -c "import sys; print(sys.version)"
3.13.2 (main, Feb  7 2025, 04:13:54) [GCC 11.4.0]
$ uv run mypy --version
mypy 1.15.0 (compiled: yes)
$ uv run stubtest --version
stubtest 1.15.0

Reproducing

• clone https://github.com/numpy/numtype
• add @override to StringDType.__new__ in src/numpy-stubs/dtypes.pyi
• run stubtest with uv run tool/stubtest.py

[hauntsaninja]

It's too late at night for me to figure out how to get uv to look at my editable install, but I'd bet that #18815 would fix

[jorenham]

It's too late at night for me to figure out how to get uv to look at my editable install

You mean uv run --no-editable stubtest ...? That doesn't work for numtype, unless you remove all of the *.py from the numpy site-packages directory (see tool/unstub.py).
But it's easiest to use uv run tool/stubtest.py, which does both automatically in an isolated environment.

I'd bet that #18815 would fix

If you give me a minute, I can verify if it works.

[jorenham]

repro branch: https://github.com/numpy/numtype/tree/mypy-18814