Sorry for the resend! Some of my previous e-mail was left out for some reason.
Here it is again, as it should have been:
> On Aug 18, 2016, at 12:43 AM, Sikhapol Saijit via swift-evolution
> <[email protected] <mailto:[email protected]>> wrote:
>
> 1. Is it intentional that try? can be used with a "non-method-call" and
> return an optional of the type that follows?
a. I’m not sure what you mean by “non-method-call”, since the thing you called
in your example *was* a function that was marked with “throws”. Using try? on a
non-throwing function or method does indeed produce a warning.
b. I’m not an Apple employee or a member of the development team, but I think
it probably is intentional. There are two levels of optionality going on here;
one, the possibility that the throwing method could have failed, and the other,
that the optional result may or may not contain a value. Either of those two
things being nil could mean quite different things, so the double-optional
makes sense.
> 2. Should we design try? to have higher precedence than as? or any operators
> at all?
> My intuition tells me that
> let a = try? couldFailButWillNot() as? Int
> should be equivalent to
> let a = (try? couldFailButWillNot()) as? Int
This is more debatable whether it *should* be the case, but it’s worth pointing
out that try/try?/try! work on the entire rest of the line, which means you can
include more throwing calls and not have to put an ! each time:
func foo() throws -> Int { return 3 }
func bar() throws -> Int { return 5 }
if let i = try? foo() + bar() { // not try foo() + try bar()
print("i is \(i)")
}
Or this:
func foo() throws -> Int { return 3 }
func bar(_ i: Int) throws -> Int { return i + 2 }
if let i = try? bar(foo()) { // not bar(try foo())
print("i is \(i)")
}
So multiple throwing statements can be used on a single line without having to
throw “try” all over the place. Now, whether that’s worth the admittedly
confusing behavior you noted above is probably a decent topic for debate.
Charles_______________________________________________
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