[swift-evolution] [Idea] Use optionals for non-optional parameters

[Justin Jia]

> On Aug 15, 2016, at 4:09 PM, Charlie Monroe <charlie at charliemonroe.net> wrote:
> 
> The example above was to better demonstrate the problem with *when* to evaluate the latter argument. Why should both arguments be evaluated *before* the if statement? If both calls return Optionals, 
> 
> if let x = bar(42), y = baz(42) { ... }
> 
> is how would I write it without the suggested syntax - baz(42) will *not* be evaluated if bar(42) returns nil. Which bears a question why would 
> 
> foo(bar(42)?, baz(42)?) 
> 
> evaluate both arguments even if the first one is nil, making it incosistent with the rest of the language?

I see your point. I understand that maybe 1/2 of the people think we should evaluate both arguments and 1/2 of the people think we should only evaluate the first argument.

I changed my idea a little bit. Now I think you are right. We should only evaluate the first argument in your example. It’s not only because of inconsistent, but also because the language should at least provide a way to “short-circuit” to rest of the arguments.

If they want to opt-out this behavior, they can always write:

```
let x = bar(42)
let y = baz(42)
foo(x?, y?)
```

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