[ruby-core:116255] [Ruby master Feature#19742] Introduce `Module#anonymous?`

Issue #19742 has been updated by ioquatix (Samuel Williams). I think we can assume this is a fair definition, but I'd like to confirm it with @matz: ```ruby class Module def permanent? if name = self.name Object.const_get(self.name).equal?(self) end rescue NameError false end def anonymous? !permanent? end end ``` However, alternatively, we could defer to whether a class has (or had) a permanent name. The problem is, they are subtly different. The former (example) is quite a robust definition, while the latter (depending on whether a permanent name has or was assigned) is more prone to edge cases (like `const_remove` as discussed). ---------------------------------------- Feature #19742: Introduce `Module#anonymous?` https://bugs.ruby-lang.org/issues/19742#change-106276 * Author: ioquatix (Samuel Williams) * Status: Open * Priority: Normal ---------------------------------------- As a follow-on <from https://bugs.ruby-lang.org/issues/19521>gt;, I'd like propose we introduce `Module#anonymous?`. In some situations, like logging/formatting, serialisation/deserialization, debugging or meta-programming, we might like to know if a class is a proper constant or not. However, this brings about some other issues which might need to be discussed. After assigning a constant, then removing it, the internal state of Ruby still believes that the class name is permanent, even thought it's no longer true. e.g. ``` m = Module.new m.anonymous? # true M = m m.anonyomous # false Object.send(:remove_const, :M) M # uninitialized constant M (NameError) m.anonymous? # false ``` Because RCLASS data structure is not updated after the constant is removed, internally the state still has a "permanent class name". I want to use this proposal to discuss this issue and whether there is anything we should do about such behaviour (or even if it's desirable). Proposed PR: https://github.com/ruby/ruby/pull/7966 cc @fxn -- https://bugs.ruby-lang.org/