Give compile-time error if registering a class without its own `_bind_methods()` function

(cherry picked from commit ca46ef4d256c727a116366334b705ecda0a06c5d)

include/godot_cpp/classes/wrapped.hpp

@@ -171,6 +171,7 @@ protected:
                                                                                                                                                                                        \
 public:                                                                                                                                                                                \
 	typedef m_class self_type;                                                                                                                                                         \
+	typedef m_inherits parent_type;                                                                                                                                                    \
                                                                                                                                                                                        \
 	static void initialize_class() {                                                                                                                                                   \
 		static bool initialized = false;                                                                                                                                               \
@@ -334,6 +335,7 @@ private:
 private:                                                                                                                                                                               \
 	inline static ::godot::internal::EngineClassRegistration<m_class> _gde_engine_class_registration_helper;                                                                           \
 	void operator=(const m_class &p_rval) {}                                                                                                                                           \
+	friend class ::godot::ClassDB;                                                                                                                                                     \
                                                                                                                                                                                        \
 protected:                                                                                                                                                                             \
 	virtual const GDExtensionInstanceBindingCallbacks *_get_bindings_callbacks() const override {                                                                                      \
@@ -343,6 +345,8 @@ protected:
 	m_class(const char *p_godot_class) : m_inherits(p_godot_class) {}                                                                                                                  \
 	m_class(GodotObject *p_godot_object) : m_inherits(p_godot_object) {}                                                                                                               \
                                                                                                                                                                                        \
+	static void _bind_methods() {}                                                                                                                                                     \
+                                                                                                                                                                                       \
 	static void (*_get_bind_methods())() {                                                                                                                                             \
 		return nullptr;                                                                                                                                                                \
 	}                                                                                                                                                                                  \
@@ -385,6 +389,7 @@ protected:
                                                                                                                                                                                        \
 public:                                                                                                                                                                                \
 	typedef m_class self_type;                                                                                                                                                         \
+	typedef m_inherits parent_type;                                                                                                                                                    \
                                                                                                                                                                                        \
 	static void initialize_class() {}                                                                                                                                                  \
                                                                                                                                                                                        \

include/godot_cpp/core/class_db.hpp

@@ -174,6 +174,7 @@ public:
 template <typename T, bool is_abstract>
 void ClassDB::_register_class(bool p_virtual) {
 	static_assert(TypesAreSame<typename T::self_type, T>::value, "Class not declared properly, please use GDCLASS.");
+	static_assert(!FunctionsAreSame<T::self_type::_bind_methods, T::parent_type::_bind_methods>::value, "Class must declare 'static void _bind_methods'.");
 	static_assert(!std::is_abstract_v<T> || is_abstract, "Class is abstract, please use GDREGISTER_ABSTRACT_CLASS.");
 	instance_binding_callbacks[T::get_class_static()] = &T::_gde_binding_callbacks;
 

include/godot_cpp/core/type_info.hpp

@@ -58,6 +58,16 @@ struct TypesAreSame<A, A> {
 	static bool const value = true;
 };
 
+template <auto A, auto B>
+struct FunctionsAreSame {
+	static bool const value = false;
+};
+
+template <auto A>
+struct FunctionsAreSame<A, A> {
+	static bool const value = true;
+};
+
 template <typename B, typename D>
 struct TypeInherits {
 	static D *get_d();