from_python and from_cpp must be marked as noexcept?

[zhqrbitee]

Hi,
Based on the docs here: https://nanobind.readthedocs.io/en/latest/porting.html#type-casters, from_python and from_cpp must be marked as noexcept.

1. So my question is why? It just feel strange to me to mark some complicate conversion logic as noexcept.
2. What would happen if I didn't mark them as noexcept?

[wjakob]

If you raise exceptions from a type caster missing the noexcept annotation, it will break dispatch of functions with multiple overloads.

See b3c3723 for the rationale.