staticmethod silently drops first argument when typed as Bound<'_, Self> / PyRef<'_, Self> / Py<Self>

[termoshtt]

Summary

When a #[staticmethod] declares its first parameter with a self-shaped type (PyRef<'_, Self>, PyRefMut<'_, Self>, Bound<'_, Self>, &Bound<'_, Self>, or Py<Self>), the parameter is silently dropped from the generated .pyi stub. The runtime function still expects the argument, so the stub disagrees with the actual signature.

Reproduction

#[gen_stub_pymethods]
#[pymethods]
impl A {
    #[staticmethod]
    fn from_bound(a: Bound<'_, Self>) -> usize {
        a.borrow().x
    }
}

Generated stub:

@staticmethod
def from_bound() -> int: ...   # `a` is missing

Root cause

parse_args in pyo3-stub-gen-derive/src/gen_stub/arg.rs skips first-position arguments matching the receiver shapes whenever the inner generic is the literal Self. It has no knowledge of MethodType, so the same skip fires for #[staticmethod] (and would for free #[pyfunction]s if Self were syntactically writable there).

Note

This is a pre-existing issue. It existed before #455 for PyRef<'_, Self> / PyRefMut<'_, Self> and was extended to Bound/Py by that PR. #455 strictly improves the common (instance method) case; this edge was surfaced during review and is being tracked separately.

Possible fixes

• Plumb MethodType (or just an is_static flag) into parse_args and skip the receiver only for instance methods.
• Move receiver detection out of parse_args and into method.rs, where the method kind is already known.

Severity

Low. Self-shaped first arguments on #[staticmethod] are very unusual in practice — but the failure mode (silent stub/runtime divergence) is bad, so a fix is worth doing once the structural change above is on the table.