| Message ID | 2f002596-5592-62be-27b1-bd6b3d71266b@oracle.com |
|---|---|
| State | New |
| Headers | show |
| Series | [C++] Improve grokdeclarator error | expand |
On 9/26/19 3:39 PM, Paolo Carlini wrote:
> +template void foo<int>( // { dg-error "15:template-id .foo<int>. used as a declarator" }
That's a strange diagnostic message; there's nothing wrong with using a
template-id as a declarator. Why are we even calling grokdeclarator
when we hit EOF in the middle of the declarator?
Jason
Hi, On 28/09/19 04:05, Jason Merrill wrote: > On 9/26/19 3:39 PM, Paolo Carlini wrote: >> +template void foo<int>( // { dg-error "15:template-id .foo<int>. >> used as a declarator" } > > That's a strange diagnostic message; there's nothing wrong with using > a template-id as a declarator. Why are we even calling grokdeclarator > when we hit EOF in the middle of the declarator? It's indeed a weird situation. Note, by the way, that for template void foo<int>; we end up giving the same diagnostic, only, the location was already fine. Anyway, to explain why I say weird, clang believes it's dealing with an explicit instantiation: explicit instantiation of 'foo' does not refer to a function template, variable template, member function, member class, or static data member whereas EDG gives: declaration is incompatible with function template "void foo<<unnamed>>()" I *think* what we are issuing is closer in spirit to the latter, we don't get fooled into thinking it's an instantiation and we say that as a declaration doesn't work either. See what I mean? Removing completely the diagnostic code doesn't seem fine either because we end up with very confusing wordings like variable or field declared void or worse we mention variable templates, depending on the type (I already mentioned this). Thus, all in all, would it make sense to simply issue something closer to EDG? Thanks, Paolo.
On Mon, Sep 30, 2019 at 6:54 AM Paolo Carlini <paolo.carlini@oracle.com> wrote: > > On 28/09/19 04:05, Jason Merrill wrote: > > On 9/26/19 3:39 PM, Paolo Carlini wrote: > >> +template void foo<int>( // { dg-error "15:template-id .foo<int>. > >> used as a declarator" } > > > > That's a strange diagnostic message; there's nothing wrong with using > > a template-id as a declarator. Why are we even calling grokdeclarator > > when we hit EOF in the middle of the declarator? > > It's indeed a weird situation. Note, by the way, that for > > template void foo<int>; > > we end up giving the same diagnostic, only, the location was already fine. > > Anyway, to explain why I say weird, clang believes it's dealing with an > explicit instantiation: > > explicit instantiation of 'foo' does not refer to a function template, > variable template, member function, member class, or static data member > > whereas EDG gives: > > declaration is incompatible with function template "void foo<<unnamed>>()" > > I *think* what we are issuing is closer in spirit to the latter, we > don't get fooled into thinking it's an instantiation and we say that as > a declaration doesn't work either. See what I mean? Well, it is an explicit instantiation, the problem (as EDG says) is that the instantiation declaration doesn't match the template. > Removing completely > the diagnostic code doesn't seem fine either because we end up with very > confusing wordings like > > variable or field declared void > > or worse we mention variable templates, depending on the type (I already > mentioned this). Any thought about my question about why we're calling grokdeclarator in the first place? > Thus, all in all, would it make sense to simply issue something closer > to EDG? Probably. Jason
Hi, On 30/09/19 20:46, Jason Merrill wrote: > On Mon, Sep 30, 2019 at 6:54 AM Paolo Carlini <paolo.carlini@oracle.com> wrote: >> On 28/09/19 04:05, Jason Merrill wrote: >>> On 9/26/19 3:39 PM, Paolo Carlini wrote: >>>> +template void foo<int>( // { dg-error "15:template-id .foo<int>. >>>> used as a declarator" } >>> That's a strange diagnostic message; there's nothing wrong with using >>> a template-id as a declarator. Why are we even calling grokdeclarator >>> when we hit EOF in the middle of the declarator? >> It's indeed a weird situation. Note, by the way, that for >> >> template void foo<int>; >> >> we end up giving the same diagnostic, only, the location was already fine. >> >> Anyway, to explain why I say weird, clang believes it's dealing with an >> explicit instantiation: >> >> explicit instantiation of 'foo' does not refer to a function template, >> variable template, member function, member class, or static data member >> >> whereas EDG gives: >> >> declaration is incompatible with function template "void foo<<unnamed>>()" >> >> I *think* what we are issuing is closer in spirit to the latter, we >> don't get fooled into thinking it's an instantiation and we say that as >> a declaration doesn't work either. See what I mean? > Well, it is an explicit instantiation, the problem (as EDG says) is > that the instantiation declaration doesn't match the template. Definitely it doesn't. > >> Removing completely >> the diagnostic code doesn't seem fine either because we end up with very >> confusing wordings like >> >> variable or field declared void >> >> or worse we mention variable templates, depending on the type (I already >> mentioned this). > Any thought about my question about why we're calling grokdeclarator > in the first place? Yes. If you look at cp_parser_explicit_instantiation, clearly cp_parser_declarator doesn't return a cp_error_declarator and in such cases we always call grokdeclarator. Do you think we should error out here instead, much earlier? Currently grokdeclarator does quite a bit of work before the diagnostic. Paolo..
On Mon, Sep 30, 2019 at 3:25 PM Paolo Carlini <paolo.carlini@oracle.com> wrote: > > On 30/09/19 20:46, Jason Merrill wrote: > > On Mon, Sep 30, 2019 at 6:54 AM Paolo Carlini <paolo.carlini@oracle.com> wrote: > >> On 28/09/19 04:05, Jason Merrill wrote: > >>> On 9/26/19 3:39 PM, Paolo Carlini wrote: > >>>> +template void foo<int>( // { dg-error "15:template-id .foo<int>. > >>>> used as a declarator" } > >>> That's a strange diagnostic message; there's nothing wrong with using > >>> a template-id as a declarator. Why are we even calling grokdeclarator > >>> when we hit EOF in the middle of the declarator? > >> It's indeed a weird situation. Note, by the way, that for > >> > >> template void foo<int>; > >> > >> we end up giving the same diagnostic, only, the location was already fine. > >> > >> Anyway, to explain why I say weird, clang believes it's dealing with an > >> explicit instantiation: > >> > >> explicit instantiation of 'foo' does not refer to a function template, > >> variable template, member function, member class, or static data member > >> > >> whereas EDG gives: > >> > >> declaration is incompatible with function template "void foo<<unnamed>>()" > >> > >> I *think* what we are issuing is closer in spirit to the latter, we > >> don't get fooled into thinking it's an instantiation and we say that as > >> a declaration doesn't work either. See what I mean? > > Well, it is an explicit instantiation, the problem (as EDG says) is > > that the instantiation declaration doesn't match the template. > > Definitely it doesn't. > > > > >> Removing completely > >> the diagnostic code doesn't seem fine either because we end up with very > >> confusing wordings like > >> > >> variable or field declared void > >> > >> or worse we mention variable templates, depending on the type (I already > >> mentioned this). > > Any thought about my question about why we're calling grokdeclarator > > in the first place? > > Yes. If you look at cp_parser_explicit_instantiation, clearly > cp_parser_declarator doesn't return a cp_error_declarator and in such > cases we always call grokdeclarator. Do you think we should error out > here instead, much earlier? Currently grokdeclarator does quite a bit of > work before the diagnostic. I would expect a cp_error_declarator for this case. Jason
Index: testsuite/g++.dg/diagnostic/template-id-as-declarator-1.C =================================================================== --- testsuite/g++.dg/diagnostic/template-id-as-declarator-1.C (nonexistent) +++ testsuite/g++.dg/diagnostic/template-id-as-declarator-1.C (working copy) @@ -0,0 +1,5 @@ +template<typename> +void foo() {} + +template void foo<int>( // { dg-error "15:template-id .foo<int>. used as a declarator" } +// { dg-error "expected" "" { target *-*-* } .-1 } Index: cp/decl.c =================================================================== --- cp/decl.c (revision 276151) +++ cp/decl.c (working copy) @@ -12078,9 +12078,9 @@ grokdeclarator (const cp_declarator *declarator, && !FUNC_OR_METHOD_TYPE_P (type) && !variable_template_p (TREE_OPERAND (unqualified_id, 0))) { - error ("template-id %qD used as a declarator", - unqualified_id); - unqualified_id = dname; + error_at (id_loc, "template-id %qD used as a declarator", + unqualified_id); + return error_mark_node; } /* If TYPE is a FUNCTION_TYPE, but the function name was explicitly