[swift-users] Type inference of array element type

[Toni Suter]

Thanks anyway! :-)

> Am 24.03.2017 um 12:03 schrieb Rien <Rien at balancingrock.nl>:
> 
> I always yield to proof ;-)
> 
> hope someone more knowledgable chips in...
> 
> Regards,
> Rien
> 
> Site: http://balancingrock.nl
> Blog: http://swiftrien.blogspot.com
> Github: http://github.com/Balancingrock
> Project: http://swiftfire.nl
> 
> 
> 
> 
> 
>> On 24 Mar 2017, at 11:53, Toni Suter <tonisuter at me.com> wrote:
>> 
>> Hmm, I don't know. It also works with other nominal types. For example:
>> 
>> struct S {
>>  var x: Int
>>  var y: Int
>> }
>> let s1 = S(x: 0, y: 1)
>> let s2 = S(x: 2, y: 3)
>> let arr = [s1, nil, s2]
>> print(type(of: arr)) 		// Array<Optional<S>>
>> 
>>> Am 24.03.2017 um 11:30 schrieb Rien <Rien at Balancingrock.nl>:
>>> 
>>> Btw, I just looked it up and it seems to me that inference only works for literals. Which probably means that tuples are out.
>>> 
>>> Regards,
>>> Rien
>>> 
>>> Site: http://balancingrock.nl
>>> Blog: http://swiftrien.blogspot.com
>>> Github: http://github.com/Balancingrock
>>> Project: http://swiftfire.nl
>>> 
>>> 
>>> 
>>> 
>>> 
>>>> On 24 Mar 2017, at 11:22, Rien via swift-users <swift-users at swift.org> wrote:
>>>> 
>>>> IMO this is a boundary problem.
>>>> How far do you want to go in letting the compiler deduce the actual type?
>>>> It is possible to make very elaborate constructs that would basically default to a complex tuple/array/dictionary construct with only Any?’s in them. (well, the dict would require a Hashable too)
>>>> 
>>>> Besides, the recent discussion on compile times illustrates another angle to this problem: if type inference is used extensively, compile times go to infinite…
>>>> 
>>>> So while I do not know if this is a bug or not, I would recommend not to use it anyhow.
>>>> 
>>>> Regards,
>>>> Rien
>>>> 
>>>> Site: http://balancingrock.nl
>>>> Blog: http://swiftrien.blogspot.com
>>>> Github: http://github.com/Balancingrock
>>>> Project: http://swiftfire.nl
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>>> On 24 Mar 2017, at 11:08, Toni Suter via swift-users <swift-users at swift.org> wrote:
>>>>> 
>>>>> Hi,
>>>>> 
>>>>> If I declare a variable and initialize it with an array literal whose elements are integer literals and nil literals,
>>>>> the compiler will infer the type Array<Optional<Int>> for that variable:
>>>>> 
>>>>> let arr = [1, nil, 3]
>>>>> print(type(of: arr)) 	// Array<Optional<Int>>
>>>>> 
>>>>> However, that only works with nominal types such as Int and String. If I do the same thing with an array of tuples,
>>>>> I get a compile error:
>>>>> 
>>>>> let arr = [(1, false), nil, (3, true)]		// error: type of expression is ambiguous without more context
>>>>> print(type(of: arr))
>>>>> 
>>>>> Why can't the compiler infer the type Array<Optional<(Int, Bool)>> in this example? Is there a reason for this or is it a bug?
>>>>> 
>>>>> Thanks and best regards,
>>>>> Toni
>>>>> 
>>>>> _______________________________________________
>>>>> swift-users mailing list
>>>>> swift-users at swift.org
>>>>> https://lists.swift.org/mailman/listinfo/swift-users
>>>> 
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>> 
>