https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101477
Bug ID: 101477
Summary: Wrong location for unexpanded parameter pack in
function template
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
template<typename... Elements>
class tuple
{ };
template<typename... Elements>
tuple<Elements>
get(const tuple<Elements...>& t)
{
return t;
}
The error shows the wrong location:
t2.C:7:30: error: parameter packs not expanded with '...':
7 | get(const tuple<Elements...>&)
| ^
t2.C:7:30: note: 'Elements'
This case is especially confusing because the caret *almost* points to a
location where the pack *is* expanded, making it harder to spot the real
problem on the line above.
It should be:
t2.C:7:30: error: parameter packs not expanded with '...':
6 | tuple<Elements>
| ^~~~~~~~
t2.C:7:30: note: 'Elements'
Even better would be to give a fix-it hint suggesting to add the ... after
Element, although that might be counterproductive sometimes. For example, in
this case the compiler probably won't guess where to put the ...
template<typename... Elements>
std::conjunction<is_const<Elements>>
get(const tuple<Elements...>& t)
{
return t;
}
The user probably wants std::conjunction<is_const<Elements>...> not
std::conjunction<is_const<Elements...>>.
