Should PyO3 fail to compile if a function name equals a reserved Python keyword?

[pemistahl]

I'm pretty new to PyO3 and have just incidentally found out that PyO3 allows to compile a function or method with its name being equal to a reserved Python keyword such as from or import. Trying to call such a function from Python expectedly results in a SyntaxError: invalid syntax.

Shouldn't PyO3 prohibit compiling such functions or at least suggest to rename them? This isn't documented anywhere either.

Minimal Rust example to reproduce:

#[pyclass]
struct Builder {}

#[pymethods]
impl Builder {
    #[classmethod]
    fn from(cls: &PyType) {}
}

#[pymodule]
fn foo(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
    m.add_class::<Builder>()?;
    Ok(())
}

This fails in Python because from is a reserved keyword:

>>> from foo import Builder
>>> Builder.from()
  File "<stdin>", line 1
    Builder.from()
                ^^^^
SyntaxError: invalid syntax

What is your opinion?

[davidhewitt]

I suppose getattr(Builder, 'from')() would work but is extremely ugly.

Warnings are hard to do well in proc macros (we have a bit of a nasty hack for deprecations). I would be open to a PR which made this an error with a #[pyo3] option to allow. But I'm also fine with this just as-is until we get the ability to warn nicely.

[mejrs]

A warning would be nice, but there isn't a proper way to emit warnings. Perhaps once something like rust-lang/rust#54140 lands we should do it.