### Godot version

4.1.1

### System information

windows 11

### Issue description

When registering a type with class_name and using that class name to declare a variable in code only, autocomplete works as expected anywhere in other nodes/scenes. However, if making a custom scene node that extends a script with the class_name, if that custom scene is instantiated in a different scene, even if the type is specified, it only shows the parent node's functions and not any of the extended functionality. I have made a basic project showing the issue

### Steps to reproduce

I have made a very simple project showing the issue. https://github.com/mmmmmmmmmmmmmmmmmmmdonuts/godot_4_autocomplete_issue essentially, the extended Node scene will only show the custom function when both the type is specified as well as the type afterwards following "as" 
e.g. `@onready var my_class_4: MyClass = $MyClass4 as MyClass`

### Minimal reproduction project

https://github.com/mmmmmmmmmmmmmmmmmmmdonuts/godot_4_autocomplete_issue
const GDScriptParser::IfNode *_if = static_cast<const GDScriptParser::IfNode *>(p_context.current_suite->statements[i]);
				c.current_suite = _if->true_block;
				_find_last_return_in_block(c, r_last_return_line, r_last_returned_value);
				if (_if->false_block) {
					c.current_suite = _if->false_block;
					_find_last_return_in_block(c, r_last_return_line, r_last_returned_value);
				}
			} break;
			case GDScriptParser::Node::MATCH: {
				const GDScriptParser::MatchNode *match = static_cast<const GDScriptParser::MatchNode *>(p_context.current_suite->statements[i]);
				for (int j = 0; j < match->branches.size(); j++) {
					c.current_suite = match->branches[j]->block;
					_find_last_return_in_block(c, r_last_return_line, r_last_returned_value);
				}
			} break;
			case GDScriptParser::Node::RETURN: {
				const GDScriptParser::ReturnNode *ret = static_cast<const GDScriptParser::ReturnNode *>(p_context.current_suite->statements[i]);
				if (ret->return_value) {
					if (ret->start_line > r_last_return_line) {
						r_last_return_line = ret->start_line;
						*r_last_returned_value = ret->return_value;
					}
				}
			} break;
			default:
				break;
		}
	}
}
static bool _guess_method_return_type_from_base(GDScriptParser::CompletionContext &p_context, const GDScriptCompletionIdentifier &p_base, const StringName &p_method, GDScriptCompletionIdentifier &r_type) {