<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/118218>118218</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Clang: modules and std::initializer_list do not like each other
</td>
</tr>
<tr>
<th>Labels</th>
<td>
clang
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
jijjijj
</td>
</tr>
</table>
<pre>
Clang version: 19.1.3
C++ version: 23
STL: from msvc
I was trying to compile nlohmann json using modules and I encountered an error (posting the original error for others who might google it):
```
C:\Users\username\.conan2\p\nlohm0567ffc90cfc1\p\include\nlohmann\detail\input\lexer.hpp:748:66: error: no matching constructor for initialization of 'std::initializer_list<char_int_type>' (aka 'initializer_list<int>')
748 | if (JSON_HEDLEY_UNLIKELY(!next_byte_in_range({0x80, 0xBF})))
```
I tried to reduce code to the minimum reproducible example and here's what I got (pay attention to the highlighted lines changing which kind of fixes the issue):
```
// main.cpp
import std;
import mod;
int main() {
lexer{}.func({1,1});
return 0;
}
```
```
// mod.cppm
module;
#include "inc.hpp"
export module mod;
export using ::lexer;
export using ::adapter;
```
<pre>
// inc.hpp
#pragma once
#include <initializer_list>
#include <string>
struct adapter {
using char_type = char;
};
template<typename InputAdapterType = adapter>
class lexer
{
using char_type = typename InputAdapterType::char_type; // <b><i>if I replace InputAdapterType here with adapter everything works fine</i></b>
using char_int_type = typename std::char_traits<char_type>::int_type;
public:
void func(std::initializer_list<char_int_type> ranges) {}
};
</pre>
<pre>
// std.cppm
module;
#define _BUILD_STD_MODULE // <b><i>if I delete this line everything works fine</i></b>
#include <intrin.h>
export module std;
#include <initializer_list>
#include <regex> // <b><i>if I delete this line everything works fine</i></b>
</pre>
<details>
<summary>The full error I get</summary>
```
C:/Users/username/CLionProjects/untitled23_1/std/modules/std.msvc.cppm:9:10: warning: '#include <filename>' attaches the declarations to the named module 'std', which is not usually intended; consider moving that directive before the module declaration [-Winclude-angled-in-module-purview]
9 | #include <initializer_list>
| ^
C:/Users/username/CLionProjects/untitled23_1/std/modules/std.msvc.cppm:7:15: warning: 'std' is a reserved name for a module [-Wreserved-module-identifier]
7 | export module std;
| ^
C:/Users/username/CLionProjects/untitled23_1/std/modules/std.msvc.cppm:10:10: warning: '#include <filename>' attaches the declarations to the named module 'std', which is not usually intended; consider moving that directive before the module declaration [-Winclude-angled-in-module-purview]
10 | #include <regex>
| ^
3 warnings generated.
[4/6] Building CXX object CMakeFiles/untitled23_1.dir/main.cpp.obj
FAILED: CMakeFiles/untitled23_1.dir/main.cpp.obj
C:\Tools\llvm\bin\clang++.exe -IC:/Users/username/CLionProjects/untitled23_1/include -IC:/Users/username/CLionProjects/untitled23_1/mod/../include -IC:/Users/username/CLionProjects/untitled23_1/std/include -O0 -std=c++23 -D_DEBUG -D_DLL -D_MT -Xclang --dependent-lib=msvcrtd -g -Xclang -gcodeview -MD -MT CMakeFiles/untitled23_1.dir/main.cpp.obj -MF CMakeFiles\untitled23_1.dir\main.cpp.obj.d @CMakeFiles\untitled23_1.dir\main.cpp.obj.modmap -o CMakeFiles/untitled23_1.dir/main.cpp.obj -c C:/Users/username/CLionProjects/untitled23_1/main.cpp
C:/Users/username/CLionProjects/untitled23_1/main.cpp:6:18: error: no matching constructor for initialization of 'std::initializer_list<char_int_type>' (aka 'initializer_list<int>')
6 | lexer{}.func({1,1});
| ^~~~~
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.42.34433\include\initializer_list:33:15: note: candidate constructor not viable: no known conversion from 'int' to 'const int *' for 1st argument
33 | constexpr initializer_list(const _Elem* _First_arg, const _Elem* _Last_arg) noexcept
| ^ ~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.42.34433\include\initializer_list:21:7: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 2 were provided
21 | class initializer_list {
| ^~~~~~~~~~~~~~~~
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.42.34433\include\initializer_list:21:7: note: candidate constructor (the implicit move constructor) not viable: requires 1 argument, but 2 were provided
21 | class initializer_list {
| ^~~~~~~~~~~~~~~~
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.42.34433\include\initializer_list:31:15: note: candidate constructor not viable: requires 0 arguments, but 2 were provided
31 | constexpr initializer_list() noexcept : _First(nullptr), _Last(nullptr) {}
| ^
C:\Users\username\CLionProjects\untitled23_1\mod\..\include\inc.hpp:17:52: note: passing argument to parameter 'ranges' here
17 | void func(std::initializer_list<char_int_type> ranges) {}
| ^
1 error generated.
```
</details>
</pre>
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