`obj.:method` obj.:method is introduced at r66667 by #12125 and #13581. It encourages the functional programming style in Ruby. But this shorthand syntax is just for methods of `self` without arguments. It causes another feature requests like #16273 (and lambda compositions like #15428). Such features will introduce a new view of Ruby but no one illustrates the whole picture yet. I worried about such patch work may cause a conflict with future expansion of functional programing style or a just a garbage feature. `.:` .: syntax is introduced introduce in 2.7.0 preview1, not released in production yet. How about reverting at this time and re-introduce with a big picture.