### 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
Variant base_val;
						Variant::construct(base.type.builtin_type, base_val, nullptr, 0, err);
						bool valid = false;
						Variant res = base_val.get(index.value, &valid);
						if (valid) {
							r_type = _type_from_variant(res);
							r_type.value = Variant();
							r_type.type.is_constant = false;
							found = true;
						}
					}
				}
			} break;
			case GDScriptParser::Node::BINARY_OPERATOR: {
				const GDScriptParser::BinaryOpNode *op = static_cast<const GDScriptParser::BinaryOpNode *>(p_expression);
				if (op->variant_op == Variant::OP_MAX) {
					break;
				}
				GDScriptParser::CompletionContext context = p_context;
				context.current_line = op->start_line;
				GDScriptCompletionIdentifier p1;
				GDScriptCompletionIdentifier p2;
				if (!_guess_expression_type(context, op->left_operand, p1)) {
					found = false;
					break;
				}
				if (!_guess_expression_type(context, op->right_operand, p2)) {
					found = false;
					break;
				}