How to detect when the result of Array#sort isn't captured?

[cstyles]

Is your feature request related to a problem? Please describe.

Apologies if this already exists but I couldn't find anything by searching. Is there a way to report when the result of something like Array#sort or Hash#merge isn't captured?

Describe the solution you'd like

I'd like to see a cop that will detect when these types of methods are called but their return value isn't stored in a variable, passed as an argument, or used in some other way. In that case, I would like it if rubocop would suggest Array#sort! or Hash#merge! to do the operation in-place.

edit: It occurred to me after the fact that it's not always apparent that we're calling sort or merge on an Array or Hash and we wouldn't necessarily want to suggest sort! for other (possibly user-defined) classes where sort might have side effects. So I don't think this is easy to implement, at least not for a dynamically typed language like Ruby.

[buehmann]

I haven't tried this, but it looks as if https://docs.rubocop.org/en/stable/cops_lint/#lintvoid could do the trick.

[cstyles]

Oh wow, that's exactly what I wanted!

It looks like the list of methods that it checks for doesn't include merge. I just opened a PR to add it. Thanks for your help!