It is not fair to judge Lattner's ability or commitment to safety based upon Xcode and Swift. One of these predates him, the other is the result of his decisions (no doubt) but also countless decisions of others, including those above his pay grade at Apple.
Xcode is basically the evolution of something designed for NEXT. Swift is a solution to various problems in application development. I'm not aware if he (et.al.) had real time processing or safety critical devices in mind with 3.0.2.