[Bug c++/57248] string parameter to constexpr functions

["daniel.kruegler at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57248

--- Comment #7 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Paolo Carlini from comment #6)
> However, it's true that all the up to
> date compilers I have at hand reject it with the same kind of error about
> get at:
> 
>    return std::get<index(array)>(t1);
> 
> like for my reduced testcase in Comment #5.

Ouch, you are right - I overlooked the very important fact that *within*
function extract the expression

index(array)

cannot be a constant expression, because we have an argument value involved! In
the context of a constexpr function any argument value itself cannot be a
constant expression, because the decision for something being a constant
expression is always context-independent.

I'm very sorry for having mislead Paolo with my original remark, indeed the
original test case is *invalid* because it is based on the assumption that a
constexpr function argument itself could be a constant expression.
>From gcc-bugs-return-463140-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Oct 02 20:52:46 2014
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Subject: [Bug c++/57460] [C++11] Sfinae doesn't respect dependent context
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57460

--- Comment #2 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Jason Merrill from comment #1)
> But there is no T that would cause check<(EXPR,T())> to be valid, so no
> valid specialization can be generated for the template, so the program is
> ill-formed (no diagnostic required).

After rethinking about it, I agree.
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Subject: [Bug c++/57460] [C++11] Sfinae doesn't respect dependent context
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57460

--- Comment #3 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
I tried to close the issue as INVALID, but it seems that I cannot do that by
myself.
>From gcc-bugs-return-463142-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Oct 02 21:22:48 2014
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Subject: [Bug c++/57460] [C++11] Sfinae doesn't respect dependent context
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57460

Marc Glisse <glisse at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Daniel Krügler from comment #3)
> I tried to close the issue as INVALID, but it seems that I cannot do that by
> myself.

Strange, as the reporter you should be able to.
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Subject: [Bug c++/57460] [C++11] Sfinae doesn't respect dependent context
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--- Comment #5 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Marc Glisse from comment #4)
> (In reply to Daniel Krügler from comment #3)
> > I tried to close the issue as INVALID, but it seems that I cannot do that by
> > myself.
> 
> Strange, as the reporter you should be able to.

Thanks Marc, for your help. I might have been looking at the wrong place,
because when trying to do it now, it would seem to work.
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Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2008-08-16 22:55:22         |2014-10-2

--- Comment #15 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Hi Mikael,

do you think you can do this using the scalarizer?

If not, I might try to do it using front-end
optimization, because I don't know what the scalarizer
is really about :-)