fix: dpp::cluster::register_command with coroutine handler on windows (#1504)

Author: usyless

include/dpp/cluster.h

@@ -587,7 +587,12 @@ class DPP_EXPORT cluster {
 	 * @return bool Returns `true` if the command was registered successfully, or `false` if
 	 * the command with the same name already exists
 	 */
-	bool register_command(const std::string& name, const slashcommand_handler_t handler);
+	template <typename F>
+	std::enable_if_t<utility::callable_returns_v<F, void, const slashcommand_t&>, bool> register_command(const std::string& name, F&& handler) {
+		std::unique_lock lk(named_commands_mutex);
+		auto [_, inserted] = named_commands.try_emplace(name, std::forward<F>(handler));
+		return inserted;
+	}
 
 	/**
 	 * @brief Get the number of currently active HTTP(S) requests active in the cluster.
@@ -608,12 +613,12 @@ class DPP_EXPORT cluster {
 	 * the command with the same name already exists.
 	 */
 	template <typename F>
-	std::enable_if_t<std::is_same_v<std::invoke_result_t<F, const slashcommand_handler_t&>, dpp::task<void>>, bool>
-	register_command(const std::string& name, F&& handler){
+	requires (utility::callable_returns<F, dpp::task<void>, const slashcommand_t&>)
+	bool register_command(const std::string& name, F&& handler) {
 		std::unique_lock lk(named_commands_mutex);
-		auto [_, inserted] = named_commands.try_emplace(name, std::forward<F>(handler));
+		auto [_, inserted] = named_commands.try_emplace(name, std::in_place_type<co_slashcommand_handler_t>, std::forward<F>(handler));
 		return inserted;
-	};
+	}
 #endif
 
 	/**

src/dpp/cluster.cpp

@@ -638,12 +638,6 @@ cluster& cluster::set_request_timeout(uint16_t timeout) {
 	return *this;
 }
 
-bool cluster::register_command(const std::string &name, const slashcommand_handler_t handler) {
-	std::unique_lock lk(named_commands_mutex);
-	auto [_, inserted] = named_commands.try_emplace(name, handler);
-	return inserted;
-}
-
 bool cluster::unregister_command(const std::string &name) {
 	std::unique_lock lk(named_commands_mutex);
 	return named_commands.erase(name) == 1;