Prevent unused_argument warning when passing arg to parent constructor

This requires creating the FunctionNode object a bit sooner, and setting
it as the current_function while parsing the parent constructor call
arguments.

Note that the return type has not yet been parsed at this point, but
that doesn't seem to be a problem.

Fixes #22139

modules/gdscript/gdscript_parser.cpp

@@ -3752,6 +3752,19 @@ void GDScriptParser::_parse_class(ClassNode *p_class) {
 				BlockNode *block = alloc_node<BlockNode>();
 				block->parent_class = p_class;
 
+				FunctionNode *function = alloc_node<FunctionNode>();
+				function->name = name;
+				function->arguments = arguments;
+				function->argument_types = argument_types;
+				function->default_values = default_values;
+				function->_static = _static;
+				function->line = fnline;
+#ifdef DEBUG_ENABLED
+				function->arguments_usage = arguments_usage;
+#endif // DEBUG_ENABLED
+				function->rpc_mode = rpc_mode;
+				rpc_mode = MultiplayerAPI::RPC_MODE_DISABLED;
+
 				if (name == "_init") {
 
 					if (_static) {
@@ -3782,7 +3795,9 @@ void GDScriptParser::_parse_class(ClassNode *p_class) {
 								parenthesis++;
 								while (true) {
 
+									current_function = function;
 									Node *arg = _parse_and_reduce_expression(p_class, _static);
+									current_function = NULL;
 									cparent->arguments.push_back(arg);
 
 									if (tokenizer->get_token() == GDScriptTokenizer::TK_COMMA) {
@@ -3826,19 +3841,7 @@ void GDScriptParser::_parse_class(ClassNode *p_class) {
 					return;
 				}
 
-				FunctionNode *function = alloc_node<FunctionNode>();
-				function->name = name;
 				function->return_type = return_type;
-				function->arguments = arguments;
-				function->argument_types = argument_types;
-				function->default_values = default_values;
-				function->_static = _static;
-				function->line = fnline;
-#ifdef DEBUG_ENABLED
-				function->arguments_usage = arguments_usage;
-#endif // DEBUG_ENABLED
-				function->rpc_mode = rpc_mode;
-				rpc_mode = MultiplayerAPI::RPC_MODE_DISABLED;
 
 				if (_static)
 					p_class->static_functions.push_back(function);