### 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
if (indent_stack.size()) {
			ilevel = indent_stack.back()->get();
		}
		if (tc > ilevel) {
			indent_stack.push_back(tc);
		} else if (tc < ilevel) {
			while (indent_stack.size() && indent_stack.back()->get() > tc) {
				indent_stack.pop_back();
			}
			if (indent_stack.size() && indent_stack.back()->get() != tc) {
				indent_stack.push_back(tc); 
			}
		}
		if (i >= p_from_line) {
			l = indent.repeat(indent_stack.size()) + st;
		} else if (i > p_to_line) {
			break;
		}
		lines.write[i] = l;
	}
	p_code = "";
	for (int i = 0; i < lines.size(); i++) {
		if (i > 0) {
			p_code += "\n";
		}
		p_code += lines[i];
	}
}
#ifdef TOOLS_ENABLED
static Error _lookup_symbol_from_base(const GDScriptParser::DataType &p_base, const String &p_symbol, bool p_is_function, GDScriptLanguage::LookupResult &r_result) {