Re: [boost] Implicit cast rules

Subject: Re: [boost] Implicit cast rules
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2011-05-24 10:35:16

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On Tuesday, May 24, 2011, Gregory Crosswhite wrote:
> Hey everyone,
> 
> Would someone please explain to me the implicit cast rule that prevents
> the following from compiling, and/or if there is a way around it?

It's standard behavior of static_cast 5.2.9 paragraph 2.  If you did the 
conversion implicitly instead of explicitly with static_cast, then the 
boost::optional constructor that is causing you trouble would not be 
considered (since it is explicit).

> I can tell what is happening; it would seem that the implicit cast rule
> selects the optional() constructor before it even looks at my more
> specific cast operator.  I'm just confused about why this should be,
> since I see no reason why constructor casts should be prioritized over
> operator casts.  Is this just the way it is, a GCC quirk, something I'm
> doing wrong, etc?

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