[Bug c++/119247] New: accepts-invalid non-constexpr variable as template argument in a lambda when used for another template

[raul at tambre dot ee via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119247

            Bug ID: 119247
           Summary: accepts-invalid non-constexpr variable as template
                    argument in a lambda when used for another template
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: raul at tambre dot ee
  Target Milestone: ---

Created attachment 60723
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=60723&action=edit
Bug sample

The following

  template<typename>
  struct array;

  template<auto variable>
  using get_type = decltype(variable);

  void foo()
  {
     auto lambda{[](auto variable)
     {
        using alias = array<get_type<variable>>;
     }};

     lambda(int{});
  }

Clang and MSVC reject this as "non-type template argument is not a constant
expression".
Removing the array<> from get_type<variable> causes GCC to fail with the same
error.
Due to this I accidentally wrote that worked with GCC but not the others.