From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2026-05-18T21:13:04+00:00
Subject: [ruby-core:125540] [Ruby Bug#21844] Inconsistent ArgumentError message for Data::define.new

Issue #21844 has been updated by Eregon (Benoit Daloze).


@nobu Was it intentional to keep accepting `String` and `to_str` kwargs in addition to Symbols?
>From what matz said above I would expect only Symbols are accepted, which would be valuable to optimize `Data#initialize` better.

----------------------------------------
Bug #21844: Inconsistent ArgumentError message for Data::define.new
https://bugs.ruby-lang.org/issues/21844#change-117366

* Author: jnchito (Junichi Ito)
* Status: Closed
* ruby -v: ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [arm64-darwin25]
* Backport: 3.2: WONTFIX, 3.3: REQUIRED, 3.4: REQUIRED, 4.0: DONE
----------------------------------------
The code below shows `Data::define.new` treats symbol and string keys equivalently:

``` ruby
C = Data.define(:a, :b)

C.new(a: 1, b: 1)
#=> #<data C a=1, b=1>

C.new('a' => 1, 'b' => 1)
#=> #<data C a=1, b=1>
```

But it acts differently when detecting missing keywords:

```ruby
C.new(a: 1)
#=> 'Data#initialize': missing keyword: :b (ArgumentError)
C.new('a' => 1)
#=> 'Data#initialize': missing keywords: :a, :b (ArgumentError)
```

I feel it should work like this:

```ruby
C.new('a' => 1)
#=> 'Data#initialize': missing keyword: :b (ArgumentError)
```

I created a PR to fix it:

https://github.com/ruby/ruby/pull/15910



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