### 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 (p_context.type != GDScriptParser::COMPLETION_SUPER_METHOD) {
						r_type.type = p_context.current_class->get_datatype();
					} else {
						r_type.type = p_context.current_class->base_type;
					}
					found = true;
				}
			} break;
			case GDScriptParser::Node::IDENTIFIER: {
				const GDScriptParser::IdentifierNode *id = static_cast<const GDScriptParser::IdentifierNode *>(p_expression);
				found = _guess_identifier_type(p_context, id, r_type);
			} break;
			case GDScriptParser::Node::DICTIONARY: {
				
				const GDScriptParser::DictionaryNode *dn = static_cast<const GDScriptParser::DictionaryNode *>(p_expression);
				Dictionary d;
				bool full = true;
				for (int i = 0; i < dn->elements.size(); i++) {
					GDScriptCompletionIdentifier key;
					if (_guess_expression_type(p_context, dn->elements[i].key, key)) {
						if (!key.type.is_constant) {
							full = false;
							break;
						}
						GDScriptCompletionIdentifier value;
						if (_guess_expression_type(p_context, dn->elements[i].value, value)) {
							if (!value.type.is_constant) {
								full = false;
								break;
							}