Properly implement extensions

Input C/C++ Header

class Gyro {
 public:
  virtual void Calibrate() = 0;
};

class SomeGyro : public Gyro {
 public:
  void Calibrate() final;
};

Bindgen Invocation

$ bindgen test.hpp

Actual Results

/* automatically generated by rust-bindgen 0.59.2 */

#[repr(C)]
pub struct Gyro__bindgen_vtable(::std::os::raw::c_void);
#[repr(C)]
#[derive(Debug, Copy, Clone)]
pub struct Gyro {
    pub vtable_: *const Gyro__bindgen_vtable,
}
#[test]
fn bindgen_test_layout_Gyro() {
    assert_eq!(
        ::std::mem::size_of::<Gyro>(),
        8usize,
        concat!("Size of: ", stringify!(Gyro))
    );
    assert_eq!(
        ::std::mem::align_of::<Gyro>(),
        8usize,
        concat!("Alignment of ", stringify!(Gyro))
    );
}
#[repr(C)]
#[derive(Debug, Copy, Clone)]
pub struct SomeGyro {
    pub _base: Gyro,
}
#[test]
fn bindgen_test_layout_SomeGyro() {
    assert_eq!(
        ::std::mem::size_of::<SomeGyro>(),
        8usize,
        concat!("Size of: ", stringify!(SomeGyro))
    );
    assert_eq!(
        ::std::mem::align_of::<SomeGyro>(),
        8usize,
        concat!("Alignment of ", stringify!(SomeGyro))
    );
}
extern "C" {
    #[link_name = "\u{1}_ZN8SomeGyro9CalibrateEv"]
    pub fn SomeGyro_Calibrate(this: *mut ::std::os::raw::c_void);
}

Expected Results

An implementation of SomeGyro::Calibrate, instead of SomeGyro_Calibrate. Frankly, I'm not sure how I would get my hands on a *mut os::raw::c_void that points to a SomeGyro on the Rust side.

Reproduce the issue with the supplied C++ header in test.hpp and the bindgen test.hpp command, then trace how the generated Rust bindings represent SomeGyro::Calibrate. Compare the generated free function with the requested implementation behavior; done means the bindings expose the expected implementation rather than requiring an opaque *mut c_void.