[ruby-core:120174] [Ruby master Bug#20943] Constant defined in `Data` block

["nobu (Nobuyoshi Nakada) via ruby-core" <ruby-core@ml.ruby-lang.org>]

Issue #20943 has been reported by nobu (Nobuyoshi Nakada).

----------------------------------------
Bug #20943: Constant defined in `Data` block
https://bugs.ruby-lang.org/issues/20943

* Author: nobu (Nobuyoshi Nakada)
* Status: Open
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
>From https://github.com/ruby/ruby/pull/12274:
> A couple times in code review I've seen constants inadvertently leak to top level from within a `Struct` or `Data` do block. I think it would be nice to show reopening the `Data` class when a constant is defined, so the constant is defined within the namespace. In this case, `Measure::NONE` instead of top level `Object::NONE`. It would also show readers that it's okay to reopen a `Data` class, which seems nice since some folk might not realize. Thanks for considering!

However, I think that `NONE` probably might be intended to be defined under `Measure`.

Current:
```ruby
Measure = Data.define(:amount, :unit) do
  NONE = Data.define
end
p NONE #=> NONE
```

Another:
```ruby
Measure = Data.define(:amount, :unit) do
  NONE = Data.define
  p NONE #=> Measure::NONE
end
p NONE # uninitialized constant NONE (NameError)
```

@zverok How do think?



-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
 ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/