[swift-users] [swift-evolution] Best way to handle escaping function that might throw

[Pierre Monod-Broca]

@Howard
I was thinking the same about the constraint.

Does that mean that Never should be a subtype of Error (maybe it is already) ? Else you couldn't say throws(Never) or FSTore<Never>

@Howard
I'm not sure about <>, it should stay reserved for generics, IMHO.

Pierre

> Le 13 janv. 2017 à 01:11, Howard Lovatt via swift-users <swift-users at swift.org> a écrit :
> 
> @Anton, Yes that would work and we would get typed throws, which I like. As an aside, I think E would have to be constrained to be an Error, `<E: Error>`, and maybe `throws<E>` reads better because you are used to types in angle brackets.
> 
>   -- Howard.
> 
>> On 13 January 2017 at 08:32, Anton Zhilin <antonyzhilin at gmail.com> wrote:
>> The best way to deal with such situations should be typed throws. Then rethrows should be removed and replaced with generics in throws clause. E == Never ⇔ function does not throw.
>> 
>> struct FStore<E> {
>>     let f: () throws(E) -> Void
>>     init(_ f: @escaping () throws(E) -> Void) { self.f = f }
>>     func call() throws(E) { try f() }
>> }
>> 
>> let store = FStore<Never>({ print("Hello") })
>> store.call()
>> [Phase2]
>> 
> 
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