Mutable C++ lvalue arguments for immutable or rvalue Python types

[aldanor]

I was wondering whether pybind11 happily accepting this kind of functions could be misleading:

.def("f", [](int& x) { x = 42; })

One may assume that pushing back to a std::vector<>& would update the list (although a related example is in the docs). Basically, for non-opaque types that require type conversion, is it possible to disable passing them as non-const refs, or do we not have this info at compile time?

[aldanor]

Btw not directly related but hilarious nevertheless:

enum class Foo { A = 1, B = 2 };

py::enum_<Foo>(m, "Foo")
 .value("A", Foo::A)
 .value("B", Foo::B);

m.def("f", [](Foo& x) { x = Foo::B; });

>>> f(Foo.A)
>>> print(Foo.A)
Foo.B