### 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
continue;
							}
							if (key.value == index.value) {
								r_type.assigned_expression = dn->elements[i].value;
								found = _guess_expression_type(p_context, dn->elements[i].value, r_type);
								break;
							}
						}
					}
					
					if (!found && index.value.is_num()) {
						int idx = index.value;
						const GDScriptParser::ArrayNode *an = nullptr;
						if (subscript->base->type == GDScriptParser::Node::ARRAY) {
							an = static_cast<const GDScriptParser::ArrayNode *>(subscript->base);
						} else if (base.assigned_expression && base.assigned_expression->type == GDScriptParser::Node::ARRAY) {
							an = static_cast<const GDScriptParser::ArrayNode *>(base.assigned_expression);
						}
						if (an && idx >= 0 && an->elements.size() > idx) {
							r_type.assigned_expression = an->elements[idx];
							found = _guess_expression_type(c, an->elements[idx], r_type);
							break;
						}
					}
					
					if (!found && (index.value.get_type() == Variant::STRING || index.value.get_type() == Variant::NODE_PATH)) {
						StringName id = index.value;
						found = _guess_identifier_type_from_base(c, base, id, r_type);
					} else if (!found && index.type.kind == GDScriptParser::DataType::BUILTIN) {
						Callable::CallError err;