[ruby-core:113968] [Ruby master Feature#19742] Introduce `Module#anonymous?`

Issue #19742 has been updated by ioquatix (Samuel Williams). There is another formulation of the opposite of "anonymous" which could be the following: ```ruby class Module def permanent? Object.const_get(self.name).equal?(self) end end ``` This would be true if the object is reachable by the name it says it is. It's a little slower, but perhaps a better approach. We might be able to optimise it internally if the object/module know's it's parent namespace and name within that namespace (i.e. don't need to use `const_get`). So it might be true that `anonymous?` and `permanent?` are related but different. ---------------------------------------- Feature #19742: Introduce `Module#anonymous?` https://bugs.ruby-lang.org/issues/19742#change-103625 * 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/