<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/56276>56276</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            can not find c++20 concepts head file
        </td>
    </tr>

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

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

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

<pre>
    `deepin(linux) system`+`vscode` + `clang` + `clangd` + `cmake`
```Cmd
FuXii@FuXii-PC:~$ code -v
1.68.1
30d9c6cd9483b2cc586687151bcbcd635f373630
x64

FuXii@FuXii-PC:~$ clang -v
Debian clang version 15.0.0-++20220622102607+46be5faaf034-1~exp1~20220622222616.569
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Candidate multilib: .;@m64
Selected multilib: .;@m64

FuXii@FuXii-PC:~$ clangd --version
Debian clangd version 15.0.0-++20220622102607+46be5faaf034-1~exp1~20220622222616.569
Features: linux
Platform: x86_64-pc-linux-gnu

FuXii@FuXii-PC:~$ cmake --version
cmake version 3.18.4

CMake suite maintained and supported by Kitware (kitware.com/cmake).

```

the `CMakelists.txt` write in:
```CXX
set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED true)
```
and the code in source file:
(the code is copy from cppreference)
```CXX
#include <concepts>
#include <iostream>
 
template<typename T, typename ... U>
concept IsAnyOf = (std::same_as<T, U> || ...);
 
template<typename T>
concept IsPrintable = std::integral<T> || std::floating_point<T> ||
    IsAnyOf<std::remove_cvref_t<std::remove_pointer_t<std::decay_t<T>>>, char, wchar_t>;
 
void println(IsPrintable auto const ... arguments)
{
    (std::wcout << ... << arguments) << '\n';
}
 
int main() { println("Example: ", 3.14, " : ", 42, " : [", 'a', L'-', L"Z]"); }
```
then build:
```Cmd
/data/home/FuXii/Projects/Turbo/samples/CPPStandardTest.cpp:1:10: fatal error: 'concepts' file not found
#include <concepts>
         ^~~~~~~~~~
1 error generated.
make[2]: *** [samples/CMakeFiles/CPPStandardTest.dir/build.make:82: samples/CMakeFiles/CPPStandardTest.dir/CPPStandardTest.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:3322: samples/CMakeFiles/CPPStandardTest.dir/all] Error 2
make: *** [Makefile:171: all] Error 2
The terminal process "/usr/bin/bash '-c', 'make'" terminated with exit code: 2.
```

</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJy1Vluv2jgQ_jXhxSJKHHLhgQcIsKq63T17eipV-4Ic2wFvc5PtcODf70wScoCyvUhdFGJnbM_3zXhm7KwW54UTeULKRlUOTQpVtSeHzok5GytLGHLoCt5Hw2shoUPgm0DLC1bt77_FtaBkX3CB460db4md7klL0Uu27WelnJnXtdOn1AmWTrxx6IwgEpke-2m-GyWu3_cDT8x5xMV8lgQZ5TxMoiiJ_dDPeMZFFIR5EAdRMECeotmA_T08pD4CrmWmWDUIj1IbVVfED13P9aboC7qiHqVeRKnv0ciLQTCLMhnmjOVeMJv6oFWeGmwuE-EX-ZEbRvMe4oXpvbRAgJySaBfNpg2fdo6f7qt2mHLQkglSgisKnNjURp36oXeVsawopFgrjUMO3bZGwzuDHexNrdtKEM4qoQSzkvyWpkT1q5gFc75aRbeuC69CZfDecw5vFSXRFSm6TX6d7sHqB9o_ykJyK8UvVpuOdMu2sAoXgT7XCVYQEOUlTkbwb036oWASZDodQufroBL_U1RtJbOtlgZZ92nciZ_AgXmty2-G23etwmS-N6oXXowJXD9xb5yUfsBx0yr0O1OVhT94F_YChE1Ta_R1dibvlX1lWsL-Jl_6rsvrEnavLyF07l5rHSvJtdAeJNacDrFQxhrXniwWo1eN6Arj574Qff7cSwykIk3SD8v3mx0Idx9fln-sl89rQqH2zb89Z_e8-evTu-fNmljdynH6HUe0GBl2hU1VxNSt5pLkqpBvvGjyNsVA25xJruuS8KbRMpdaVvwBwGiFQwNV8aKF5U6Q8hpmNxZiYfNoWNXGQn0px2EyuFGWDYQLsErtuZEVKyV5cWhKxi_XdcmncdkAQ96ZZXX-MwfVa9xFYwXaFSwNLNkxYJF2WnAhceIUHlSE1kByfZ_A13BPGsMpK2QHOeKBUO41KzrAN6xxPC9qqCbVftfUMPV21sADfoM1MDwu1LKsj3LHj7AVO_tgpFMo9e2YkJyddxec4QE_8APT2L5iB8c393441kqQBo0s8FS-Npi1tobwgNrYbQYcJW0pK9jqMTbi1Zst17vxyuvW4vbD060dutcqLjKHxk6YVthcqDnx-oYjEOrSGiC6hfHqirFD6ebEYDNlX7kp2gslYoYtfJIr8YzeCMPVIAdwhgSg-zu007c-_dsJ190sjCAyMrvLO0ioimStKsSD9L_cQ6DOwMkAQNtDXUKGbfsqSLdPuv4HzgPwyval1VkNreksQkn69PTRQl4zLV6ksS5kKWD4-PfQihxUFkRqXQ9ndDymJI27zCdVbUmOp-kPJTC5_Jxwg0X5v57-0tQjk72spIZ0EkMF7eppuKLovY7Vsn_Q6Ve2YRXdqseGCtWdwOhUt1MXLBOKyn5q_QP3uTWwIpuOt39D139E9wYE--hTJBIE9Of5wDXjDZ1eod_DXpBwo2PcbvJo6QtUcqgGpaogCBpdc2lMH-03N5iMmQOGxpQPoQ1Nf-TFmA2DBjwlX5U9EHlStjsgEJa6D0N-IhaBmAdzNrHKFnIBF7U-0BTe2i43DXIJL3LAWyYaNGl1sThY2-D9AbjhrQpA22w4i4vieGmmTZ8ZeEs0pu3cGkY0jiaHBc9pOIcbi8c9jwdJNsukYDLL_TDwkxkLJgXLZGEWmOXheqIWw21m7tHQD0I3jEUS-lEe-lTMRO7BbURCkSlcBHZrvZ_oRccha_cGBvvDfhxkxqh9JeVFPxTLQ60XXUqrScd20VH9F14HvZE">