changyu added a comment.
I moved some template param checks from
`Parser::ParseTemplateDeclarationOrSpecialization` to
`Parser::ParseConceptDefinition` and `Sema::ActOnConceptDefinition`.
================
Comment at: lib/Parse/ParseTemplate.cpp:181
+ TemplateParameterList *TPL = ParamLists[0];
+ if (TPL->getLAngleLoc().getLocWithOffset(1) == TPL->getRAngleLoc()) {
+ Diag(TPL->getTemplateLoc(),
----------------
faisalv wrote:
> changyu wrote:
> > There's one problem here.
> >
> > I added this `if` in attempt to catch the following case (but it's wrong)
> > ```
> > template<> concept D1 = true; // expected-error {{expected template
> > parameter}}
> > ```
> > The problem is I'm not sure how to differentiate between the above
> > situation and the following
> > ```
> > template<concept T> concept D1 = true; // expected-error {{expected
> > template parameter}}
> > ```
> > Both have an empty template parameter list. The latter case has diagnostic
> > printed by `ParseNonTypeTemplateParameter` while the former has not (so we
> > try to catch it here).
> >
> > What should we do?
> >
>
> I was thinking that we would just emit a (redundant in the case of a bad
> template parameter) message in Sema if the template-parameters are empty that
> explicit specializations are not allowed here. while it would be a little
> misleading in the invalid template parameter case - to fix this robustly
> would require some fine-tuning and correcting some of the
> handshaking/error-propagation between the parsing of the template parameters
> and the code that calls it, I think. I would vote for not holding up this
> patch for that, unless you feel strongly you'd like to fix that behavior -
> then we can try and work on that first?
>
> Thoughts?
>
>
Sure, let's fix that in another patch. I added a note for this in
cxx2a-concept-declaration.cpp.
https://reviews.llvm.org/D40381
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