Issue #20943 has been updated by byroot (Jean Boussier). Yeah, that's a common mistake with `Struct.new` / `Data.define` / `Class.new` That's why with `Struct` you'd often see: ```ruby class Something < Struct.new(:a, :b) ... end ``` Which is a bit wasteful as you define two classes instead of one, but not a big deal. I kinda wish this would be valid syntax: ```ruby class Something = Struct.new(:a, :b) ... end ``` ---------------------------------------- Bug #20943: Constant defined in `Data.define` block https://bugs.ruby-lang.org/issues/20943#change-110934 * 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/