Always use let for case statements

> In that it makes different things look the same.

Each case is a pattern match and a destructuring. They're the same thing, regardless of whether there are bound identifiers.

> How so?

I meant in terms of `let` vs. `var` for this purpose.

> My take is: use `let` only when you’re actually wanting to bind variables. Otherwise it makes it look like you are, which is confusing.

In other languages with pattern matching, there's no difference between a match that binds identifiers and one that simply matches.

I don't think there's any semantic difference in Swift either, so ultimately the choice is purely aesthetic to me. I find it easier to scan multiple `case` statements if they all start the same way. Missing `let`s just distract me, they don't communicate any useful information.

I'd be interested to hear @joshaber and @andymatuschak's (if I may) opinions on this too.