[Alphasite_]

For Swift, a lot of the designs were due to the ability to automatically transform Objective-C apis into swift APIs. The big issue from what i can tell is in extracting the first parameters name from the method name automatically.

[mikeash]

That doesn't really explain the defaults, though. Translation could override the defaults if that fit better. This already happens when translating C functions, as none of the parameters get external names.