To answer my own question: "swift" or "swiftc" w/o -frontend invokes the driver, which launches both the -frontend and other tools like ld. The Swift REPL (Re

To answer my own question: "swift" or "swiftc" w/o -frontend invokes the driver, which launches both the -frontend and other tools like ld. The Swift REPL (Read-Eval-Print-Loop) acts like an interpreter. Valid statements, expressions, and declarations are immediately compiled and executed.