[swift-users] Type inference of array element type

[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 <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
>> 
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