SE-0231 — Optional iteration

[Joe_Groff]

@michelf

Unfortunately, inout isn't possible with the result of ?? [] . And unless a lot of things change, neither will it work with a function returning a wrapper collection.

This is a good observation. The problem of mutation through wrapper collections, however, is one we know we already have, and will have to address in the move-only future. @Ben_Cohen and I have discussed some possible approaches that could eventually allow for this.