[swift-evolution] [swift-evolution-announce] [Review] SE-0099: Restructuring Condition Clauses

[Brent Royal-Gordon]

> guard
>  x == 0 && a == b && c == d &&
>  let y = optional, w = optional2, v = optional 3 &&
>   z == 2
> else { ... }
> 
> Figuring out where to break the first line into expression and into condition (after the `d`) could be very challenging to the compiler.

I'm not sure it is. `let` and `case` are not valid in an expression, so an `&&` followed by `let` or `case` must be joining clauses. On the other side of things, Swift's `&&` doesn't ever produce an optional, so if we're parsing an expression at the top level of an if-let, an `&&` must indicate the end of the clause. An if-case *could* theoretically include an `&&`, but pattern matching against a boolean value seems like a fairly useless thing to do in a context that's specifically intended to test booleans.

-- 
Brent Royal-Gordon
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