[GDScript] Fix `get_argument_count` for lambda `Callable`s

modules/gdscript/gdscript_lambda_callable.cpp

@@ -84,7 +84,7 @@ int GDScriptLambdaCallable::get_argument_count(bool &r_is_valid) const {
 		return 0;
 	}
 	r_is_valid = true;
-	return function->get_argument_count();
+	return function->get_argument_count() - captures.size();
 }
 
 void GDScriptLambdaCallable::call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const {
@@ -204,7 +204,7 @@ int GDScriptLambdaSelfCallable::get_argument_count(bool &r_is_valid) const {
 		return 0;
 	}
 	r_is_valid = true;
-	return function->get_argument_count();
+	return function->get_argument_count() - captures.size();
 }
 
 void GDScriptLambdaSelfCallable::call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const {

modules/gdscript/tests/scripts/runtime/features/lambda_bind_argument_count.gd

@@ -0,0 +1,18 @@
+# https://github.com/godotengine/godot/issues/93952
+
+func foo():
+	pass
+
+func test():
+	var a: int
+
+	var lambda_self := func (x: int) -> void:
+		foo()
+		print(a, x)
+
+	print(lambda_self.get_argument_count())  # Should print 1.
+
+	var lambda_non_self := func (x: int) -> void:
+		print(a, x)
+
+	print(lambda_non_self.get_argument_count())  # Should print 1.

modules/gdscript/tests/scripts/runtime/features/lambda_bind_argument_count.out

@@ -0,0 +1,3 @@
+GDTEST_OK
+1
+1