Swift was designed around emojis it seems. First page in the manual shows how you can use emojis as variable names. I get why Apple wants to be clear how there are different ways to index into strings (even if this is motivated 99% by emojis), but still, the API didn't have to be this confusing or have so many breaking changes after GA.

The weird thing about arrays is they're different from all other objects, including NSArray which is by reference. No other language does it this way. C++ has pass-by-value vectors, but that's because everything else is too.