Issue #19278 has been updated by Eregon (Benoit Daloze). It seems hard to solve to me, without losing the significant advantages that @zverok mentions. Also inheriting from a Data class seems kind of an anti/rare pattern. One can of course: ```ruby Foo = Data.define(:x, :y) def custom end ... end ``` ---------------------------------------- Bug #19278: Constructing subclasses of Data with positional arguments https://bugs.ruby-lang.org/issues/19278#change-100881 * Author: tenderlovemaking (Aaron Patterson) * Status: Feedback * Priority: Normal * ruby -v: ruby 3.2.0 (2022-12-25 revision a528908271) [arm64-darwin22] * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- I'd expect both of the following subclasses to work, but the subclass that uses positional parameters raises an exception: ```ruby Foo = Data.define class Bar < Foo def initialize foo: p foo end end class Baz < Foo def initialize foo p foo end end Bar.new foo: 1 # Prints 1 Baz.new 1 # Raises ArgumentError ``` I'd expect the subclass that uses positional arguments to work. -- https://bugs.ruby-lang.org/