<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/99430>99430</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] clang-cl main branch refuses to compile MSVC's tuple template when targeting C++23
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

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

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

<pre>
    Something regressed recently with regards to compiling the Visual Studio 2022 (17.10.4) implementation of `std::tuple` and `std::tie` when using `/std:c++latest`.

I rebuild my LLVM toolchain every couple of weeks or so. This is the revision I tested today, where I first noticed this problem:
```
llvmorg-19-init-17993-gedfe25064e13
```

This is the revision I have been using for the past few weeks, which did **not** fail to compile this test case:
```
llvmorg-19-init-16022-g2051736f7bc3
```

Command line:
```
> clang-cl /std:c++latest /c test.cpp
```

Mostly minimized testcase:
```c++
#include <tuple>

struct Version {
 unsigned int major = 0;
        unsigned int minor = 0;
 unsigned int release = 0;
        unsigned int patch = 0;

 constexpr auto operator<=>(const Version &_other) const
        {
 return std::tuple(major, minor, release, patch) <=> std::tuple(_other.major, _other.minor, _other.release, _other.patch);
 }
};
```

Result:

```
In file included from test.cpp:1:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(208,101): error: pack expansion contains
      parameter packs '_TTypes' and '_Indices' that have different lengths (1 vs. 4)
  208 |     (requires { typename _Synth_three_way_result<_TTypes, tuple_element_t<_Indices, _UTuple>>; } && ...)
      | ~~~~~~~                  ~~~~~~~~                  ^
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: while checking constraint
      satisfaction for class template partial specialization '_Three_way_comparison_result_with_tuple_like<unsigned int, std::tuple<unsigned int,
      unsigned int, unsigned int, unsigned int>, 0ULL, 1ULL, 2ULL, 3ULL>' required here
  214 | using _Three_way_comparison_result_with_tuple_like_t =
      | ^~~~~
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: during template argument deduction
      for class template partial specialization '_Three_way_comparison_result_with_tuple_like<tuple<_TTypes...>, _UTuple,
 index_sequence<_Indices...>>' [with _TTypes = <unsigned int>, _UTuple = std::tuple<unsigned int, unsigned int, unsigned int, unsigned int>,
 _Indices = <0, 1, 2, 3>]
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: in instantiation of template class
 'std::_Three_way_comparison_result_with_tuple_like<std::tuple<unsigned int>, std::tuple<unsigned int, unsigned int, unsigned int, unsigned
      int>>' requested here
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(804,12): note: in instantiation of template type
      alias '_Three_way_comparison_result_with_tuple_like_t' requested here
  804 | -> _Three_way_comparison_result_with_tuple_like_t<tuple, _Other> {
 |            ^
test.cpp(11,51): note: while substituting deduced template arguments into function template 'operator<=>' [with _Other = std::tuple<unsigned int,
      unsigned int, unsigned int, unsigned int>]
   11 |                 return std::tuple(major, minor, release, patch) <=> std::tuple(_other.major, _other.minor, _other.release, _other.patch);
      | ^
In file included from test.cpp:1:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(208,101): error: pack expansion contains
      parameter packs '_TTypes' and '_Indices' that have different lengths (2 vs. 4)
  208 |     (requires { typename _Synth_three_way_result<_TTypes, tuple_element_t<_Indices, _UTuple>>; } && ...)
      | ~~~~~~~                  ~~~~~~~~                  ^
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: while checking constraint
      satisfaction for class template partial specialization '_Three_way_comparison_result_with_tuple_like<unsigned int, unsigned int,
      std::tuple<unsigned int, unsigned int, unsigned int, unsigned int>, 0ULL, 1ULL, 2ULL, 3ULL>' required here
  214 | using _Three_way_comparison_result_with_tuple_like_t =
      | ^~~~~
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: during template argument deduction
      for class template partial specialization '_Three_way_comparison_result_with_tuple_like<tuple<_TTypes...>, _UTuple,
 index_sequence<_Indices...>>' [with _TTypes = <unsigned int, unsigned int>, _UTuple = std::tuple<unsigned int, unsigned int, unsigned int,
 unsigned int>, _Indices = <0, 1, 2, 3>]
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: in instantiation of template class
 'std::_Three_way_comparison_result_with_tuple_like<std::tuple<unsigned int, unsigned int>, std::tuple<unsigned int, unsigned int, unsigned
      int, unsigned int>>' requested here
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(804,12): note: in instantiation of template type
      alias '_Three_way_comparison_result_with_tuple_like_t' requested here
  804 | -> _Three_way_comparison_result_with_tuple_like_t<tuple, _Other> {
 |            ^
test.cpp(11,51): note: while substituting deduced template arguments into function template 'operator<=>' [with _Other = std::tuple<unsigned int,
      unsigned int, unsigned int, unsigned int>]
   11 |                 return std::tuple(major, minor, release, patch) <=> std::tuple(_other.major, _other.minor, _other.release, _other.patch);
      | ^
In file included from test.cpp:1:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(208,101): error: pack expansion contains
      parameter packs '_TTypes' and '_Indices' that have different lengths (3 vs. 4)
  208 |     (requires { typename _Synth_three_way_result<_TTypes, tuple_element_t<_Indices, _UTuple>>; } && ...)
      | ~~~~~~~                  ~~~~~~~~                  ^
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: while checking constraint
      satisfaction for class template partial specialization '_Three_way_comparison_result_with_tuple_like<unsigned int, unsigned int, unsigned
      int, std::tuple<unsigned int, unsigned int, unsigned int, unsigned int>, 0ULL, 1ULL, 2ULL, 3ULL>' required here
 214 | using _Three_way_comparison_result_with_tuple_like_t =
      | ^~~~~
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: during template argument deduction
      for class template partial specialization '_Three_way_comparison_result_with_tuple_like<tuple<_TTypes...>, _UTuple,
 index_sequence<_Indices...>>' [with _TTypes = <unsigned int, unsigned int, unsigned int>, _UTuple = std::tuple<unsigned int, unsigned int,
 unsigned int, unsigned int>, _Indices = <0, 1, 2, 3>]
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(214,1): note: in instantiation of template class
 'std::_Three_way_comparison_result_with_tuple_like<std::tuple<unsigned int, unsigned int, unsigned int>, std::tuple<unsigned int, unsigned
      int, unsigned int, unsigned int>>' requested here
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\tuple(804,12): note: in instantiation of template type
      alias '_Three_way_comparison_result_with_tuple_like_t' requested here
  804 | -> _Three_way_comparison_result_with_tuple_like_t<tuple, _Other> {
 |            ^
test.cpp(11,51): note: while substituting deduced template arguments into function template 'operator<=>' [with _Other = std::tuple<unsigned int,
      unsigned int, unsigned int, unsigned int>]
   11 |                 return std::tuple(major, minor, release, patch) <=> std::tuple(_other.major, _other.minor, _other.release, _other.patch);
      | ^
3 errors generated.
```

</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzsWt9v2zgS_mvol0EMiZIs-8EPiZwAAVrc4Zrtq0FTI4tbitSSVFLvw_7tB1Lyj7hO27S52x5ORmBZ0pCc4ffNzIeAzFqxVYhLkt2QbDVhnau1Wbodr_Vko8vd8oNu0NVCbcHg1qC1WIJBjsrJHTwJV_vnzJQWnAaum1ZIb-xqhI_CdkzCB9eVQgONKAVC53E-jaNpSugCRNNKbFA55oRWoCsgs8i6kiTXJLl2XSuRzCJgqnz-QoTHTzUq6KxfjcwiQu96A07oDaE3kjm0jsyiKYlWJLruv-_B4KYTsoRmB-_efXwPTmvJayYU4COaHXDtl_W-PCF-sqANWD2Fh1pYEDbEZfBRWO_wPfg1sASnS7YjtPA-GYR7qISxDpR2gvvXfnBr9EZi40PoHZpFw1-4lfKx0WZ7FS-uhBLuKs4Xi-Rqi2WFNItmKcbJxXH99wvu1ewRYYOHfaq0CSYtsw4qfOpj7B0XvIZSlEDoNaHXSrv-B1RMyCO22Afj4wbOLH53OLOI0qstjbI4T2ZVvuFfC6fQTeNRl0K9uAJJboFLprZXXMJl9P1jHnyd8rb9ynrvtfV0boQSjfjTI4bWXQ5vWGB4ShOhuOxKBJIUPWGT29OZrTMdd_ARTYCE5MNI6FTIvBKEctCw37UBkqwgIsneYvg8NxTqS8NnFgYlMovfM1nLHK_PDAdzrpV1-Lk1wDqnQbdomNOGJAVJVj5EOg8mx8DobK1djcbndXj1fOFj4AZdZxScpTmdhz3wVAwx-h9DKP5ncNVPffDgywn69aeHefb3--mG-5NZhyf7yY-7RfLVsB356rg1l5jzL7SddEeaXLK8V1D5zBmoUkJldHOkZXIdH8YX_ldW_NPorWEN3AmJlmTFe8GNtrpyz2sqyQpfVUlW3CqHpjXCIsmKjwXJigetZRj6IdzG6TSNpkkyj3KSFYMnJCv2m0ejOaFFHMVhH64BjfFwX0PL-CfAzy1TAWeulWNC2VN0W2ZYgw5NMLZAaL5-eNi1aAnN--pN8_W9KgXvH7maub42laKq0KByIFFtXW1Dh4BHOwXfIfar0GgOJC96JtG5wT86YdB6VoHbtahYg7D-sFOuXrvaIK6f2G5tBmyKgzcFhHjX2LeddXh5cKyA9W8P-xz2fzeeCJ7ahM5gOp2eeNRzuoC_-g988fnrxTcku_27wY5TD_YAtdLO1znfAiQCr5F_8r0iJLFhQj3LZMucsBXjoWH7dsIls74fNK2vuZ4LTjAJtkUumBR_9q09UOIAjG8lzAir1YDR2guJdY-NFJ-QJMVppfLQnKX7FwanTp6P_eq9L2YFRL-9e-ev8XClwzXxV2-Sw8C6EnyPPzAzTgMP-v76mhjXzpfecz6R7Naz5pckSNmZIO32WDOz7XwaQYllFxhxGs1_khx7DgyJ7VOzh3GfwAc-CFXi57XFPzpUHE_SfRjTQ0uymyBlh_lCTzyn2LMFgsW3KPkDPBy83ju5dyQK1Ay8DKT0xtnqlySJUCCUdUw5cVD1BwIEPux7LM0PG_hK-L--8T1QbwbOKaeH6Y_1oJf_x4Lwt4ExjwIY9DVo-M55Gh2TgtnXZuPavbQXAPOoL45XXq-9ctJ9kvuc-0cQlsntiYrcq4HznnpQVXQe-4TJLnc5222sE65zvqCF8hVE_1lhsx5wDVWn-n53MCA0vyCJT-pI8Pi7isTP9K3s2D7i-HxLwud_QWyf9r5RMP-IYKajYB4F8zeKxzOf3l64jAJ6FNDfENCXefOWgvrC_8P2q4yC-scF9WXgfhisc0F9YfpRYI8CexTYo8D-VQR2MgrsUWD_RH_7hQT3qLf_X_X22-vvS3r7hVVG_f12-vsn9fi39Peox0c9Purx_6oeT3p1a2GLyu8yltOLJ0km5TIpF8mCTXAZ5zSm-XxG00m9zKNqXqZVSbMceUrTLEoynjK64Auc0Vk2EUsa0TTK43mUZnmUTjcRn2Oa0nxBkzndcJJG2DAhp1I-NlNtthNhbYfLxSJNoolkG5Q2nBKkNJy6Ij6NVxOz9PZXm25rSRpJYZ09zuCEk-FoYT8iWx0PbDVMKNgYpngNBqvOoj09ZBaKAM1tr46PPAxn_hwzWwxELvrDWDSZdEYua-da61Gjd4TebYWru82U64bQO-_ScLlqjf4duSP0LkRoCb3rg3xc0n8HAAD__9NL3ZU">