From: "tenderlovemaking (Aaron Patterson) via ruby-core" <ruby-core@...>
Date: 2022-12-29T18:36:52+00:00
Subject: [ruby-core:111509] [Ruby master Bug#19278] Constructing subclasses of Data with positional arguments

Issue #19278 has been updated by tenderlovemaking (Aaron Patterson).


I guess the fact that `new` doesn't behave the same way as `new` on every other class kind of ruins "usability" for me.  As an end user, it's not clear why this works:

```ruby
class Foo
  def initialize x:, y:
  end
end

class Bar < Foo
  def initialize(x, y)
    super(x:, y:)
  end
end

Bar.new(1, 2)
```

But this doesn't:

```ruby
Foo = Data.define(:x, :y)

class Bar < Foo
  def initialize(x, y)
    super(x:, y:)
  end
end

Bar.new(1, 2)
```

And even more confusingly:

```ruby
Foo = Data.define(:x, :y)

class Bar < Foo
  def initialize(x, y)
    super(x:, y:)
  end
end

Foo.new(1, 2) # this works
Bar.new(1, 2) # this doesn't
```

I should be able to call a constructor on the subclass in the same way that I could call the constructor on the super class.

----------------------------------------
Bug #19278: Constructing subclasses of Data with positional arguments
https://bugs.ruby-lang.org/issues/19278#change-100877

* 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.



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