Remove userdata from Thread.start()

core/core_bind.cpp

@@ -1820,60 +1820,25 @@ void Thread::_start_func(void *ud) {
 		ERR_FAIL_MSG(vformat("Could not call function '%s' on previously freed instance to start thread %s.", t->target_callable.get_method(), t->get_id()));
 	}
 
-	Callable::CallError ce;
-	const Variant *arg[1] = { &t->userdata };
-	int argc = 0;
-	if (arg[0]->get_type() != Variant::NIL) {
-		// Just pass to the target function whatever came as user data
-		argc = 1;
-	} else {
-		// There are two cases of null user data:
-		// a) The target function has zero parameters and the caller is just honoring that.
-		// b) The target function has at least one parameter with no default and the caller is
-		//    leveraging the fact that user data defaults to null in Thread.start().
-		//    We care about the case of more than one parameter because, even if a thread
-		//    function can have one at most, out mindset here is to do our best with the
-		//    only/first one and let the call handle any other error conditions, like too
-		//    much arguments.
-		// We must check if we are in case b).
-		int target_param_count = 0;
-		int target_default_arg_count = 0;
-		Ref<Script> script = target_instance->get_script();
-		if (script.is_valid()) {
-			MethodInfo mi = script->get_method_info(t->target_callable.get_method());
-			target_param_count = mi.arguments.size();
-			target_default_arg_count = mi.default_arguments.size();
-		} else {
-			MethodBind *method = ClassDB::get_method(target_instance->get_class_name(), t->target_callable.get_method());
-			if (method) {
-				target_param_count = method->get_argument_count();
-				target_default_arg_count = method->get_default_argument_count();
-			}
-		}
-		if (target_param_count >= 1 && target_default_arg_count < target_param_count) {
-			argc = 1;
-		}
-	}
-
 	::Thread::set_name(t->target_callable.get_method());
 
-	t->target_callable.call(arg, argc, t->ret, ce);
+	Callable::CallError ce;
+	t->target_callable.call(nullptr, 0, t->ret, ce);
 	if (ce.error != Callable::CallError::CALL_OK) {
 		t->running.clear();
-		ERR_FAIL_MSG("Could not call function '" + t->target_callable.get_method().operator String() + "' to start thread " + t->get_id() + ": " + Variant::get_callable_error_text(t->target_callable, arg, argc, ce) + ".");
+		ERR_FAIL_MSG("Could not call function '" + t->target_callable.get_method().operator String() + "' to start thread " + t->get_id() + ": " + Variant::get_callable_error_text(t->target_callable, nullptr, 0, ce) + ".");
 	}
 
 	t->running.clear();
 }
 
-Error Thread::start(const Callable &p_callable, const Variant &p_userdata, Priority p_priority) {
+Error Thread::start(const Callable &p_callable, Priority p_priority) {
 	ERR_FAIL_COND_V_MSG(is_started(), ERR_ALREADY_IN_USE, "Thread already started.");
 	ERR_FAIL_COND_V(!p_callable.is_valid(), ERR_INVALID_PARAMETER);
 	ERR_FAIL_INDEX_V(p_priority, PRIORITY_MAX, ERR_INVALID_PARAMETER);
 
 	ret = Variant();
 	target_callable = p_callable;
-	userdata = p_userdata;
 	running.set();
 
 	Ref<Thread> *ud = memnew(Ref<Thread>(this));
@@ -1902,13 +1867,12 @@ Variant Thread::wait_to_finish() {
 	thread.wait_to_finish();
 	Variant r = ret;
 	target_callable = Callable();
-	userdata = Variant();
 
 	return r;
 }
 
 void Thread::_bind_methods() {
-	ClassDB::bind_method(D_METHOD("start", "callable", "userdata", "priority"), &Thread::start, DEFVAL(Variant()), DEFVAL(PRIORITY_NORMAL));
+	ClassDB::bind_method(D_METHOD("start", "callable", "priority"), &Thread::start, DEFVAL(PRIORITY_NORMAL));
 	ClassDB::bind_method(D_METHOD("get_id"), &Thread::get_id);
 	ClassDB::bind_method(D_METHOD("is_started"), &Thread::is_started);
 	ClassDB::bind_method(D_METHOD("is_alive"), &Thread::is_alive);

core/core_bind.h

@@ -551,7 +551,6 @@ class Thread : public RefCounted {
 
 protected:
 	Variant ret;
-	Variant userdata;
 	SafeFlag running;
 	Callable target_callable;
 	::Thread thread;
@@ -566,7 +565,7 @@ public:
 		PRIORITY_MAX
 	};
 
-	Error start(const Callable &p_callable, const Variant &p_userdata = Variant(), Priority p_priority = PRIORITY_NORMAL);
+	Error start(const Callable &p_callable, Priority p_priority = PRIORITY_NORMAL);
 	String get_id() const;
 	bool is_started() const;
 	bool is_alive() const;

doc/classes/Thread.xml

@@ -35,10 +35,11 @@
 		<method name="start">
 			<return type="int" enum="Error" />
 			<argument index="0" name="callable" type="Callable" />
-			<argument index="1" name="userdata" type="Variant" default="null" />
-			<argument index="2" name="priority" type="int" enum="Thread.Priority" default="1" />
+			<argument index="1" name="priority" type="int" enum="Thread.Priority" default="1" />
 			<description>
-				Starts a new [Thread] that calls [code]callable[/code] with [code]userdata[/code] passed as an argument. Even if no userdata is passed, [code]callable[/code] must accept one argument and it will be null. The [code]priority[/code] of the [Thread] can be changed by passing a value from the [enum Priority] enum.
+				Starts a new [Thread] that calls [code]callable[/code].
+				If the method takes some arguments, you can pass them using [method Callable.bind].
+				The [code]priority[/code] of the [Thread] can be changed by passing a value from the [enum Priority] enum.
 				Returns [constant OK] on success, or [constant ERR_CANT_CREATE] on failure.
 			</description>
 		</method>