[Bug c++/122389] New: Fold expression of a pack as a default template argument for a lambda rejected

[gulackeg at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122389

            Bug ID: 122389
           Summary: Fold expression of a pack as a default template
                    argument for a lambda rejected
           Product: gcc
           Version: 15.2.1
            Status: UNCONFIRMED
          Keywords: c++-lambda, rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gulackeg at gmail dot com
  Target Milestone: ---

Test code:

    // https://godbolt.org/z/z663r51oG

    template <int... Is> void f() {
      // - Clang/MSVC: OK
      // - GCC: error: operand of fold expression has no unexpanded
      //   parameter packs [-Wtemplate-body]
      // - EDG: error: fold expression does not refer to a parameter pack
      (..., []<int I = Is> {});
    }