I don't know about Swift but equating a REPL to interactivity is a horrible disservice to Lisp (and Smalltalk).

For example, Python has a REPL but it is not very well suited for interactive programming. For example Python does not handle you redefining a module after you import it without some voodoo. Nor it has forward references. For example in Lisp I can define a method that especialices on a class I haven't yet defined. Or define a function that calls function B which I will define later in the code. Nor have I seen something akin the slime Inspector and presentations, which are not quite there as the Symbolics Genera environment for interactive programming