ios - Swift compatibility -

this might stupid question, trying grasp concept of new swift versions not clear me. along ios 8.3, apple introduced swift 1.2. if developing app compatible ios 8.0.0 , in swift, how new swift version affect older ios versions? can safely use newest swift syntax without concern users still on ios 8.0.0? feedback. best regards

it's not stupid question. don't worry, because right swift interpreter built each individual app, not system runs on. changes in swift don't change anything: each app continues run, because contains swift version compiled with.