Giambattista Valli has the answer in this question and he presented this style in his late collection in Paris Week Fall/Winter 2017/2018.The designer did a weird (at first place) combination while styled Nike leggings with sexy high-heeled boots and tops with lace or blazers.
So, if you want to combine leggings with formal tops, you have the confirmation from a top designer! Athleisure style continues to be the top choise of designers and we saw this style in the shows of many brands and designers.
Watch all the 3 looks from Giambattista’s Valli amazing show!