Re: [boost] expected<T, E...> (Was: [outcome] High level summary of review feedback accepted so far)

4 Jun 2017


      Le 04/06/2017 à 18:05, Peter Dimov via Boost a écrit :
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Vicente J. Botet Escriba wrote:
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Vicente J. Botet Escriba wrote:
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enum unscoped_error
   {
       unscoped_other_error = 7
   };
expected test()
   {
       return unscoped_other_error; // returns 7.0
   }
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unexpected_type<E> is explicitly constructible from E. expected >> is implicitly constructible from unexpected_type<E>. This avoid
Le 04/06/2017 à 17:42, Peter Dimov via Boost a écrit :
this >> kind of ambiguities.
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Could you please try this code with your implementation?
It will work as yours. My concern is that this is not what we want, 
isn't it?
It's not, but what you say above - "this avoid this kind of 
ambiguities" - created the impression that you think that it isn't a 
problem.
It could be a problem for some. I'm one of the ones this is a problem. 
Thanks for pointing this case.
As I see it, this can be avoided by either making the constructor from 
T explicit as well, or by making the constructor from E implicit as well. 
I'm all for explicit constructors, from T and from E via unexpected_type<E>.
Vicente