[Bug c++/100592] New: Bogus "qualifiers cannot be applied" error with reference type produced by dependent alias template

["rs2740 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

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&>;
      |       ^~~~