A modern programming language that makes developers happier.

kotlinlang

The only point which “indirectly improve performance” that I see is that functional style is much easier to use with asynchronous code and convertatation of synchronous functional code to asynchronous is much more simple thing than refactoring of syncronous imperative to asyncronous. Same with concurrency.
So it can improve general performance when you use more asynchronous and concurrent operations and do not block the  main thread.

that's a good point :thinking_face:  I usually include that under reliability of apps but I guess it could technically make your apps perform better too

Actually RxJava is most popular library to work with async code on Android already uses functional style