https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100592
Bug ID: 100592
Summary: Bogus "qualifiers cannot be applied" error with
reference type produced by dependent alias template
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rs2740 at gmail dot com
Target Milestone: ---
template<bool>
struct meta {
template<class T, class U>
using if_c = T;
};
template<>
struct meta<false> {
template<class T, class U>
using if_c = U;
};
template <bool B, class T, class U>
using if_c = typename meta<B>::template if_c<T, U>;
template<class>
inline constexpr bool b = false;
template <class T>
using foo = if_c<b<T>, int, T>;
template<class T>
struct type {};
template <typename T>
using test = type<foo<T> const&>;
template<class T>
test<T> f();
void g() {
f<int&>();
}
GCC rejects:
<source>: In function 'void g()':
<source>:32:12: error: no matching function for call to 'f<int&>()'
32 | f<int&>();
| ~~~~~~~^~
<source>:29:9: note: candidate: 'template<class T> test<T> f()'
29 | test<T> f();
| ^
<source>:29:9: note: template argument deduction/substitution failed:
<source>: In substitution of 'template<class T> using test = type<const
typename meta<b<T> >::if_c<int, T>&> [with T = int&]':
<source>:29:9: required by substitution of 'template<class T> test<T> f()
[with T = int&]'
<source>:32:12: required from here
<source>:26:7: error: 'const' qualifiers cannot be applied to
'meta<false>::if_c<int, int&>' {aka 'int&'}
26 | using test = type<foo<T> const&>;
| ^~~~
