Bindgen generates missing `type` generic on `Option` for internal class function pointer `typedef`

Input C/C++ Header

template< class T, class P >
class CCallResult : private CCallbackBase
{
public:
	typedef void (T::*func_t)( P*, bool );

	CCallResult();
	~CCallResult();
	
	void Set( SteamAPICall_t hAPICall, T *p, func_t func );
	bool IsActive() const;
	void Cancel();

	void SetGameserverFlag() { m_nCallbackFlags |= k_ECallbackFlagsGameServer; }
private:
	virtual void Run( void *pvParam );
	virtual void Run( void *pvParam, bool bIOFailure, SteamAPICall_t hSteamAPICall );
	virtual int GetCallbackSizeBytes() { return sizeof( P ); }

	SteamAPICall_t m_hAPICall;
	T *m_pObj;
	func_t m_Func;
};

Bindgen Invocation

let bindings = bindgen::Builder::default()
	.header(sdk_loc.join("public/steam/steam_api_flat.h").to_string_lossy())
	.header(sdk_loc.join("public/steam/steam_gameserver.h").to_string_lossy())
	.clang_arg("-xc++")
	.clang_arg("-std=c++11")
	.clang_arg(format!("-I{}", sdk_loc.join("public").display()))
	.rustfmt_bindings(true)
	.default_enum_style(bindgen::EnumVariation::Rust {
		non_exhaustive: true
	})
	.generate()
	.expect("Unable to generate bindings");

Actual Results

#[repr(C)]
pub struct CCallResult<T, P> {
	pub _base: CCallbackBase,
	pub m_hAPICall: SteamAPICall_t,
	pub m_pObj: *mut T,
	pub m_Func: CCallResult_func_t<P>,
	pub _phantom_0: ::std::marker::PhantomData<::std::cell::UnsafeCell<T>>,
	pub _phantom_1: ::std::marker::PhantomData<::std::cell::UnsafeCell<P>>,
}
pub type CCallResult_func_t<P> = ::std::option::Option;
pub type CCallback_func_t<P> = ::std::option::Option;

error[E0107]: missing generics for enum `Option`
    --> steamworks-rs\steamworks-sys\src\bindings_win32.rs:1455:47
     |
1455 | pub type CCallback_func_t<P> = ::std::option::Option;
     |                                               ^^^^^^ expected 1 generic argument

Expected Results

#[repr(C)]
pub struct CCallResult<T, P> {
	pub _base: CCallbackBase,
	pub m_hAPICall: SteamAPICall_t,
	pub m_pObj: *mut T,
	pub m_Func: CCallResult_func_t<P>,
	pub _phantom_0: ::std::marker::PhantomData<::std::cell::UnsafeCell<T>>,
	pub _phantom_1: ::std::marker::PhantomData<::std::cell::UnsafeCell<P>>,
}
pub type CCallResult_func_t<P> = ::std::option::Option<P>;
pub type CCallback_func_t<P> = ::std::option::Option<P>;

Reproduce the issue with the C++ header and bindgen::Builder invocation shown in the report, then inspect how bindgen represents the internal class function-pointer typedef. Compare the generated aliases with the expected Option

output and confirm the fix by regenerating bindings and compiling them without the missing-generic error.