https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90189

            Bug ID: 90189
           Summary: Spurious "error: parameter packs not expanded" when a
                    dependent name coincides
           Product: gcc
           Version: 9.0
               URL: https://godbolt.org/z/UuwYK4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lkoppel at uwaterloo dot ca
  Target Milestone: ---

Source:

struct A {
    using CommonName = char;
};

template <typename T, typename... CommonName>
struct B {
    using V = typename T::CommonName;
};

template struct B<A>;


Output:

<source>:7:37: error: parameter packs not expanded with '...':
    7 |     using V = typename T::CommonName;
      |                                     ^
<source>:7:37: note:         'CommonName'
Compiler returned: 1

Rejected by all GCC versions. Accepted by clang, msvc.

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