[Bug c++/80841] Fails to match template specialization with polymorphic non-type template argument

[daniel.kruegler at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80841

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |daniel.kruegler@googlemail.
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--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Jason Bell from comment #0)

An interesting case. Reduced example:

//#########################################
template <class T, T X>
struct A {};

template <class T, class U>
struct B {};

template <class T, T X>
struct B<T, A<T, X>> 
{
  using result = T;
};

static double input;

int main() {
  using result1 = typename B<int, A<int, 15>>::result; // OK
  using result2 = typename B<double*, A<double*, &input>>::result; // OK
  using result3 = typename B<double&, A<double&, input>>::result; // Error
}
//#########################################

results in:

prog.cc: In function 'int main()':
prog.cc:18:59: error: 'result' in 'struct B<double&, A<double&, input> >' does
not name a type
   using result3 = typename B<double&, A<double&, input>>::result;
                                                           ^~~~~~
Clang behaves exactly the same and from the compiler behaviour it looks like a
non-deducible situation, but I fail to match this with current non-deduced
context rules at the moment.