Issue #19278 has been updated by zverok (Victor Shepelev).
Your example didn't demonstrate this difference.
I really don't understand point 3.
To be honest, I don't really care anymore.
It is a pity, after the thread this long. If you would've cared, you'd maybe spent a few minutes drafting an `initialize` that would work the way you want **and maintained the contract**, and my points would probably become more obvious. (FTR, the starting example of the ticket wasn't really illustrative because the point of creating `Data` with no members and then adding instance variables in `initialize` is unclear. `Data` is a value object that is good for value object goals, not a generic "just base class for anything".) But it is what it is, I think. ---------------------------------------- Bug #19278: Constructing subclasses of Data with positional arguments https://bugs.ruby-lang.org/issues/19278#change-100910 * Author: tenderlovemaking (Aaron Patterson) * Status: Rejected * 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/