https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59254
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2015-03-23 00:00:00 |2020-7-29
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
If I add a declaration of an explicit specialization A<long> we get another
unhelpful error:
namespace outer {
inline namespace inner {
template<typename T> struct A;
}
template<typename T> struct A;
template struct A<int>;
template<> struct A<long>;
}
n.cc:8:19: error: 'A' is not a class template
8 | template struct A<int>;
| ^
n.cc:8:19: error: template argument required for 'struct A'
n.cc:10:21: error: 'A' is not a class template
10 | template<> struct A<long>;
| ^
n.cc:10:21: error: template specifiers not specified in declaration of
'template<class T> struct outer::A'
I have no idea what "template specifiers not specified in declaration" means.
Clang is more clear about the problem (the class template is declared twice and
so causes ambiguities):
n.cc:8:19: error: reference to 'A' is ambiguous
template struct A<int>;
^
n.cc:6:31: note: candidate found by name lookup is 'outer::A'
template<typename T> struct A;
^
n.cc:3:33: note: candidate found by name lookup is 'outer::inner::A'
template<typename T> struct A;
^
n.cc:8:19: error: explicit instantiation of undefined template 'outer::A<int>'
template struct A<int>;
^
n.cc:6:31: note: template is declared here
template<typename T> struct A;
^
n.cc:10:21: error: reference to 'A' is ambiguous
template<> struct A<long>;
^
n.cc:6:31: note: candidate found by name lookup is 'outer::A'
template<typename T> struct A;
^
n.cc:3:33: note: candidate found by name lookup is 'outer::inner::A'
template<typename T> struct A;
^
EDG does well too:
"n.cc", line 8: error: "outer::A" is ambiguous
template struct A<int>;
^
"n.cc", line 8: error: invalid explicit instantiation declaration
template struct A<int>;
^
"n.cc", line 10: error: "outer::A" is ambiguous
template<> struct A<long>;
^
3 errors detected in the compilation of "n.cc".
