https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83476
Bug ID: 83476
Summary: Template argument deduction fails with reference auto
template parameter
Product: gcc
Version: 7.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gufideg at gmail dot com
Target Milestone: ---
As the title says, I have an auto reference template parameter which should be
deduced, but fails in this case:
constexpr auto lambda = []{};
template<auto& l>
struct Lambda {};
template<auto& l>
void test(Lambda<l>) {}
int main() {
test(Lambda<lambda>{});
}
The error is:
main.cpp: In function 'int main()':
main.cpp:10:26: error: no matching function for call to
'test(Lambda<lambda>)'
test(Lambda<lambda>{});
^
main.cpp:7:6: note: candidate: template<auto& l> void test(Lambda<l>)
void test(Lambda<l>) {}
^~~~
main.cpp:7:6: note: template argument deduction/substitution failed:
main.cpp:10:26: note: couldn't deduce template parameter 'l'
test(Lambda<lambda>{});
^
The non-type template parameter should be deduced as any other non type
template parameter.
Here's this example at godbolt: https://godbolt.org/g/HV4Wpf
