Issue #19099 has been updated by okuramasafumi (Masafumi OKURA). I wonder if the code below is acceptable: ```ruby class C private_constant { X = ... } end ``` Here, `private_constant` takes a block and every constant defined there are private. This is especially useful when defining multiple private constants at once. ---------------------------------------- Feature #19099: Support `private_constant` for an undefined constant https://bugs.ruby-lang.org/issues/19099#change-100315 * Author: ujihisa (Tatsuhiro Ujihisa) * Status: Open * Priority: Normal ---------------------------------------- All the following discussion applies to `public_constant` too. Maybe `deprecate_constant` as well. ## Problem ```ruby class C X = ... private_constant :X end ``` The above idiom usually works fine, but when `...` part is long, like a 30-line Ruby Hash, it's very easy to miss the following `private_constant :X` part. ## Impossible solution ```ruby class C private_constant X = ... end ``` Like `private`, if the above notation could work, it would be awesome, but it breaks so many backward compatibility. The constant assignment returns its value but not the name of the constant, and we should keep the current behaviour. ## Proposed solution Allow the following new notation for `private_constant` by making constant private by name without actually resolving itself and raises an error. ``` ruby class C private_constant :X X = ... end ``` The current behaviour is to raise NameError. ``` /tmp/v8svpb4/95:2:in `private_constant': constant C::X1 not defined (NameError) private_constant :X1 ^^^^^^^^^^^^^^^^ from /tmp/v8svpb4/95:2:in `<class:C>' from /tmp/v8svpb4/95:1:in `<main>' ``` This proposal breaks this backward compatibility. Also I'm concerned about potential typos. It may be hard to find typos. ```ruby class C private_constant :BEHAVIOUR BEHAVIOR = 123 # Remains public unintentionally end ``` Maybe we need some sort of foolproof somewhere in this way. -- https://bugs.ruby-lang.org/