Re: [Boost-users] [Variant] Bug assigning similar, but different concrete types during assignment / ctor relay

Subject: Re: [Boost-users] [Variant] Bug assigning similar, but different concrete types during assignment / ctor relay
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2018-11-18 23:14:24

On Sun, Nov 18, 2018 at 6:09 PM Michael Powell <mwpowellhtx_at_[hidden]> wrote:
>
> of AST going on, and two different Variants going on...
> On Sun, Nov 18, 2018 at 6:00 PM Michael Powell <mwpowellhtx_at_[hidden]> wrote:
> >
> > Hello,
> >
> > I've got a Boost.Variant confusion going on during ctor relay.

No, I take that back, I really do have some confusion going on in
Variant. It wants to see my Integer type as a Floating Point, and the
Which is indicating as much. When it comes time for me to use that
later during a type trait driven string print, I get a bad_get
exception because Which mis-reported the type.

> > I have two types participating in the Variant, an Integer type and a
> > Floating Point type. Both are Numeric as a base class. i.e. something
> > like:
> >
> > template<typename T>
> > struct numeric {};
> >
> > struct integer : numeric<long> {};
> >
> > struct floating_point : numeric<double> {};
> >
> > Then:
> >
> > using constant_value = boost::variant<..., floating_point, integer, ...>;
> >
> > Somewhere during the handling, I have a test case in which I have a
> > constant_value{} starting out in life as an integer{}.
> >
> > However, somewhere during handling, variant is misinterpreting integer
> > (which=3) as a floating_point (which=2).
> >
> > This is incorrect, of course.
> >
> > I could force the issue, I suppose and re-set the value to the
> > integer, but I'd like to understand the issue. I think it's a bug in
> > variant, or perhaps a "feature" confusing integer with floating_point
> > along base class numeric lines?
> >
> > Any ideas