[Bug c++/120875] New: internal compiler error: in unify, at cp/pt.cc:25494 since 11.1

[mario.rodriguezb1 at um dot es via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120875

            Bug ID: 120875
           Summary: internal compiler error: in unify, at cp/pt.cc:25494
                    since 11.1
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mario.rodriguezb1 at um dot es
  Target Milestone: ---

Program:

```
template <typename T, T...>
struct bar;
template <int... Xs, typename T>
struct bar<T, Xs...> {};
```

Stack dump:

```
<source>:4:8: internal compiler error: in unify, at cp/pt.cc:25494
    4 | struct bar<T, Xs...> {};
      |        ^~~~~~~~~~~~~
0x2844425 diagnostic_context::diagnostic_impl(rich_location*,
diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag
(*) [1], diagnostic_t)
        ???:0
0x2866fc6 internal_error(char const*, ...)
        ???:0
0xaede72 fancy_abort(char const*, int, char const*)
        ???:0
0xd73097 maybe_process_partial_specialization(tree_node*)
        ???:0
0xd166e3 c_parse_file()
        ???:0
0xe7e469 c_common_parse_file()
        ???:0
```

To quickly reproduce:

https://godbolt.org/z/Ks818d19M