<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJylUsGO2yAQ_Rp8GdVyMI7XBx82zqanSJVaVXvFMHZoiUkBZ7X79R07aZPsrraHSmDDm-HNg3mt08_1t50JoJxGlq1Zds-W2XnM24j7g5URgeWNsjIElj9AiH5UETbOsXx1PvYm-4QAXGNv2CBN04nxL_UJ3W4Zf5dgDl-fge25fv5wWlxra4iHPlOM8lm5YuX6A8X_UMcbuEZvyq2kn_jh4wI3pDfnH99Xd7oFkdP38XyN7pJz2ypqo1QKDxE1tM_wuWlADhq2X783k_Z2jNBYOfTg8QeqGMBEeDJxB3FH6pYZeu-o0D0YUmwURc0QohyikdG4AVwH46CxMwMVuFyLl--oJJQYU1jj3k2UsIvxQA2-Z3xDo1cq7Z1unY2p8z0hLzSP7eKo_MtDef0EDTkTOu_2ryhImfrpjug7655S5faE_aIplryoxELQssx5UVRVoutcV3klEznGnfP1BrVPRm_rV6LoLcb2TGXt8c_v08G76cFoa0IYkZywKfJlVia7WnB1J2SFxTLnJdVTSsqFuMOskChxoRMrW7ShZsWKcT7gE8wUtGbFOvl_BabmGaeRFQuRZ0KkRSWFEF0uyk4rvlgykeFeGptOPNNbJ76eKduxDxS0JsRwCZI_TT8gzoJJYTTRYv1FejKBvTQ9HFARYF5OzphddJTeSG3UJUv6ftzjQD4ir_WD86iTWX89i_8NsoRdWA>53607</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Partial template specialization with variadic template argument is ignored
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Fedr
      </td>
    </tr>
</table>

<pre>
    This code
```
template <class> struct Foo;

template <
  template <template <class ...> class> class MM,
  template <class...> class M
>
struct Foo<MM<M>> {};

template <template <class ...> class, class ...>
struct Bar { };

template <class ...> 
struct X {};

Foo<Bar<X>> f;
```
is accepted by GCC and MSVC, but Clang rejects it with the `error: implicit instantiation of undefined template 'Foo<Bar<X>>'`. Demo:  https://gcc.godbolt.org/z/vb1vcrzE7

Code from https://stackoverflow.com/q/46259414/7325599
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyFUk2PmzAQ_TXmMioi2MBy4LAhSU-RKrWq9uoviFsHp7ZJtPvrO5C0SXZXu5IN9pvxm_fGFk49Nz92JoB0SpNsRbJHUmaXMW-j3h8sjxoIbaXlIRC6hhD9KCNsnCN0eTn2JvuMANxib9ggTdOJ8T_1Gd1uSf4uwRy-PQPbS326Pi9utbXIg58phvmkWpJq9YHiT9TlLdyid-WW3E_88HGBO9K780_vqzu7QHL8Pl1sdNec-6vCa-RS6kPUCsQzfG1b4IOC7fef7aRdjBFay4cevP6lZQxgIpxM3EHcoboy0947LPQIBhUbiVEzhMiHaHg0bgDXwTgo3ZkBC1xt5dU7KhFFxhRWeu8mStjFeMALfiT5BkcvZdo7JZyNqfM9Ii84j2JxlP5lXd22oMWXCZ13-1cUqEz-dkftO-tOqXR7xP7gZGVe1GzBcFnRvCjqOlENVTWteRJNtLr5xj1aslcL4aAlAubl7HPuyZF7w5WR1yzu-3GvB-wKdq4fnNcqGb1tXjnDw6O46LH2-O_35eDd1HXcmhBGjc9pU9Ayq5Jd01FVKFEsxEOmKaOLungQoix1ySupxQNLLBfahoYUS5Lngz7BTIFrUqwS0-RZjiMrFoxmjKVFzRljHWVVp2S-KAnL9J4bm046pnYnvpklibEPGLQmxHAN4hNFe1rP5ZCfj3HnfLPRyidz3WbW_RdK3Ef0">