[Bug c++/87970] New: Template Instantiation from empty parameter pack is not diagnosed in class specialization

[bruno.manga95 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87970

            Bug ID: 87970
           Summary: Template Instantiation from empty parameter pack is
                    not diagnosed in class specialization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bruno.manga95 at gmail dot com
  Target Milestone: ---

The following code compiles with g++ 8.1+, but fails with all the other
compilers which claim that we are trying to pass too many template arguments to
bar.

template <class T>
struct bar {};

template <class T>
struct foo {};

template <class T, int ...args>
struct foo<bar<T, args...>> {};

godbolt link: https://gcc.godbolt.org/z/pnyPvn