Issue #19416 has been updated by mame (Yusuke Endoh). Just for record. What made matz change his mind was the following code I wrote. ```ruby Cons = Struct.new(:car, :cdr) Nil = Struct.new() ``` All we need to change Ruby is a simple code that shows a use case. ---------------------------------------- Bug #19416: Inconsistent behaviour for Struct.new without any member_names https://bugs.ruby-lang.org/issues/19416#change-102261 * Author: herwin (Herwin W) * Status: Open * Priority: Normal * ruby -v: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x86_64-linux-gnu] * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- When I simply declare a Struct without any arguments, I get an error: ``` irb(main):001:0> Struct.new (irb):1:in `new': wrong number of arguments (given 0, expected 1+) (ArgumentError) from (irb):1:in `<main>' ``` But Struct has an option to pass a class name as the first argument, which will create the struct as a constant in the Struct namespace. If this argument is given, there is no ArgumentError ``` irb(main):002:0> Struct.new('Foo') => Struct::Foo ``` This results in a rather pointless class ``` irb(main):003:0> Struct::Foo.new(1) (irb):3:in `initialize': struct size differs (ArgumentError) from (irb):3:in `new' irb(main):004:0> Struct::Foo.new => #<struct Struct::Foo> ``` This behaviour is not documented in the Struct class, but I would guess this is not how it is intended to be. -- https://bugs.ruby-lang.org/