[Bug c++/85576] New: A template union containing a friend function causes non-template type used as a template error

[malcolm.parsons at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85576

            Bug ID: 85576
           Summary: A template union containing a friend function causes
                    non-template type used as a template error
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: malcolm.parsons at gmail dot com
  Target Milestone: ---

For this code:

template <typename T>
union Union {
    friend bool operator==(const Union& a, const Union& b) {
        return true;
    }
    T t;
};

Union<int> i;

GCC reports an error:

<source>:9:10: error: non-template type 'Union' used as a template

 Union<int> i;

          ^


Clang and MSVC both accept this code: https://godbolt.org/g/S9p7hw