Re: Option flatten does not use an implicit conversion

But all traversables implement flatten with an implicit 
conversion: https://github.com/scala/scala/blob/2.12.x/src/library/scala/collection/generic/GenericTraversableTemplate.scala#L169
There's this comment though: /*<:<!!!*/ which I couldn't track in github. 
So I'd guess that for backward compatibility reasons this was kept but 
flatten on Option came at a later point when they realized that an implicit 
conversion brings troubles?

Do you have an example of a surprising behavior if Option.flatten were to 
use an implicit conversion?

Thanks

On Friday, March 4, 2016 at 4:18:59 PM UTC+1, nafg wrote:
>
> I think he means it should use the equivalent of view bounds, rather than 
> requiring evidence that it's an actual subtype. def flatten[B](implicit 
> view: A => Option[B]): ...
>
> The answer is the same issue with all implicit conversions: They make 
> behavior more surprising and less type-constrained.
>
>
> On Fri, Mar 4, 2016 at 10:01 AM Oliver Ruebenacker <[email protected] 
> <javascript:>> wrote:
>
>>
>>      Hello,
>>
>>   How would it work with an implicit conversion?
>>
>>      Best, Oliver
>>
>> On Fri, Mar 4, 2016 at 5:33 AM, Bruno Bieth <[email protected] 
>> <javascript:>> wrote:
>>
>>> I was surprised that Some(Success(1)).flatten does not compile?
>>> What is the rationale behind this:
>>>
>>> def flatten[B](implicit ev: A <:< Option[B]): Option[B] = if (isEmpty) 
>>> None else ev(this.get)
>>>
>>> Why not having an implicit conversion: (implicit conv: A => Option[B])?
>>>
>>> Bruno
>>>
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>>
>>
>> -- 
>> Oliver Ruebenacker
>> Senior Software Engineer, Diabetes Portal 
>> <http://www.type2diabetesgenetics.org/>, Broad Institute 
>> <http://www.broadinstitute.org/>
>>
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