Re: Elementary question about complete_type vs tsubst_flags_t

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi,

On 07/10/2015 03:42 PM, Jason Merrill wrote:
> On 07/10/2015 07:26 AM, Paolo Carlini wrote:
> > I have an old question about an issue which I noticed a while ago, and
> > for example clearly shows up in c++/62085: in a few places in pt.c we
> > call complete_type from functions getting a tsubst_flags_t. Clearly,
> > complete_type often calls instantiate_class_template_1, which, in turn,
> > often calls tsubst with an hard-coded tf_error. Thus possible errors
> > coming from an initial tf_none.
>
> Yep.  Those errors are outside the "immediate context" of the 
> substitution, so SFINAE doesn't apply to them.  In C++ we don't back 
> out of a class instantiation.
Good. Thus in practice the "immediate context" theory boils down to 
those irrevocable instantiations, that wasn't completely clear to me, 
thanks.

Does that imply that c++/62085 should be closed? The compilers I have 
here aren't all in agreement: EDG rejects the testcase like GCC but 
recent clangs don't, likewise SolarisStudio.

Thanks again,
Paolo.