Re: [swift-users] Type inference of array element type

[Toni Suter via swift-users]

Ok, I submitted a bug report (https://bugs.swift.org/browse/SR-4347 
) and I'll try to fix it in the
next few days.

Thanks and best regards
Toni

> Am 24.03.2017 um 18:51 schrieb Mark Lacey :
> 
>> 
>> On Mar 24, 2017, at 3:08 AM, Toni Suter via swift-users 
>> > 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 for that variable:
>> 
>> let arr = [1, nil, 3]
>> print(type(of: arr)) // Array
>> 
>> 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> in this 
>> example? Is there a reason for this or is it a bug?
> 
> Offhand it seems like we should be able to properly handle this. Can you open 
> a bug report at bugs.swift.org ?
> 
> Mark
> 
>> 
>> Thanks and best regards,
>> Toni
>> 
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Re: [swift-users] Type inference of array element type

[Mark Lacey via swift-users]

> On Mar 24, 2017, at 3:08 AM, Toni Suter via swift-users 
>  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 for that variable:
> 
> let arr = [1, nil, 3]
> print(type(of: arr))  // Array
> 
> 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> in this 
> example? Is there a reason for this or is it a bug?

Offhand it seems like we should be able to properly handle this. Can you open a 
bug report at bugs.swift.org ?

Mark

> 
> Thanks and best regards,
> Toni
> 
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Re: [swift-users] Type inference of array element type

[Rien via swift-users]

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  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
> 
>> Am 24.03.2017 um 11:30 schrieb Rien :
>> 
>> 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  
>>> 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 
  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 for that variable:
 
 let arr = [1, nil, 3]
 print(type(of: arr))   // Array
 
 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> in this 
 example? Is there a reason for this or is it a bug?
 
 Thanks and best regards,
 Toni
 
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 swift-users@swift.org
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> 

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