Check class name to be a constant path node or a constant read node

Author: haldun

src/yarp.c

@@ -12304,6 +12304,11 @@ parse_expression_prefix(yp_parser_t *parser, yp_binding_power_t binding_power) {
             yp_constant_id_list_t locals = parser->current_scope->locals;
             yp_parser_scope_pop(parser);
             yp_do_loop_stack_pop(parser);
+
+            if (!YP_NODE_TYPE_P(constant_path, YP_CONSTANT_PATH_NODE) && !(YP_NODE_TYPE_P(constant_path, YP_CONSTANT_READ_NODE))) {
+                yp_diagnostic_list_append(&parser->error_list, constant_path->location.start, constant_path->location.end, YP_ERR_CLASS_NAME);
+            }
+
             return (yp_node_t *) yp_class_node_create(parser, &locals, &class_keyword, constant_path, &name, &inheritance_operator, superclass, statements, &parser->previous);
         }
         case YP_TOKEN_KEYWORD_DEF: {

test/yarp/errors_test.rb

@@ -1333,6 +1333,13 @@ def test_parameter_name_ending_with_bang_or_question_mark
       assert_errors expression(source), source, errors, compare_ripper: false
     end
 
+    def test_class_name
+      source = "class 0.X end"
+      assert_errors expression(source), source, [
+        ["Expected a constant name after `class`", 6..9],
+      ]
+    end
+
     private
 
     def assert_errors(expected, source, errors, compare_ripper: RUBY_ENGINE == "ruby")