Two interesting things for you here, both concerning the same thing.
1. Taylor Swift wrote the topliney bits of 'This Is What You Came For', the song Calvin eventually released with Rihanna. Swift's 'rep' (PR) confirmed this to People, doing so under the pseudonym Nils Sjoberg.
2. Calvin has also announced that Taylor's vocals are (somewhere) in the song.
https://twitter.com/CalvinHarris/status/753256456711843840
https://twitter.com/CalvinHarris/status/753257779775668224
Well that's quite interesting isn't it?
YES IT IS. IT'S BLOODY INTERESTING.