The 3 options offered there by the core team represent a false choice and shouldn’t be setting a precedent without considering the wider picture!
We have to recognize that the source of tension in the name pitched in proposal stems from the original sin of contains. This added half of the natural API and was named in isolation to be “Swifty” without regards to prior art in other languages. The natural desire for symmetry forces the new proposed dual method to rather strange place: suffix extension containsOnly. This shrinks available design space to the pigeonhole of gramaticality of argument labels in futile effort to restore fluidity and clarity at the point of use. I think the remaining names are quite schwifty!
At this point, we are dealing solely with symptoms of self-inflicted wounds.
Additional pressure for the whole naming process comes from the looming ABI stability. I don’t fully understand all its implication, but numerous anecdotes dropped around forum talk of “having to live with current APIs forever” and a need to “get things right the first time” aren’t exactly calming... Did I miss some explainer of what exactly happenes to standard library from evolution perspective? Are we really about to launch for Proxima Centaury and what we have on board now is all there is?!
If so, I should be panicking much more…