| Issue |
92676
|
| Summary |
[libc++] std::expected does not work properly with std::any
|
| Labels |
libc++
|
| Assignees |
|
| Reporter |
Hackerl
|
Compilation errors will occur when using types like `std::expected<std::any, int>`, but both gcc and msvc can compile normally.
for example: https://godbolt.org/z/nYaEafoah
```c++
#include <expected>
#include <any>
#include <memory>
int main() {
auto core = std::make_shared<std::expected<std::any, int>>();
return 0;
}
```
output:
```
In file included from <source>:1:
In file included from /opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/expected:44:
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__expected/expected.h:540:14: error: satisfaction of constraint '__can_convert<_Up, _OtherErr, const _Up &, const _OtherErr &>::value' depends on itself
540 | requires __can_convert<_Up, _OtherErr, const _Up&, const _OtherErr&>::value
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__expected/expected.h:540:14: note: while substituting template arguments into constraint _expression_ here
540 | requires __can_convert<_Up, _OtherErr, const _Up&, const _OtherErr&>::value
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__type_traits/is_copy_constructible.h:25:38: note: while checking constraint satisfaction for template 'expected<std::any, int>' required here
25 | : public integral_constant<bool, __is_constructible(_Tp, __add_lvalue_reference_t<typename add_const<_Tp>::type>)> {
| ^~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__type_traits/is_copy_constructible.h:25:38: note: while substituting deduced template arguments into function template 'expected' [with _Up = std::any, _OtherErr = int]
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/any:211:35: note: in instantiation of template class 'std::is_copy_constructible<std::expected<std::any, int>>' requested here
211 | is_copy_constructible<_Tp>::value> >
| ^
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/any:460:6: note: in instantiation of default argument for 'any<std::expected<std::any, int> &, decay_t<expected<any, int> &>>' required here
460 | any::any(_ValueType&& __v) : __h_(nullptr) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
461 | __any_imp::_Handler<_Tp>::__create(*this, std::forward<_ValueType>(__v));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
462 | }
| ~
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__type_traits/is_constructible.h:22:103: note: (skipping 11 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
22 | struct _LIBCPP_TEMPLATE_VIS is_constructible : public integral_constant<bool, __is_constructible(_Tp, _Args...)> {};
| ^
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__memory/shared_ptr.h:306:10: note: in instantiation of template class 'std::__compressed_pair<std::allocator<std::expected<std::any, int>>, std::expected<std::any, int>>' requested here
306 | struct _ALIGNAS_TYPE(_CompressedPair) _Storage {
| ^
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__config:617:30: note: expanded from macro '_ALIGNAS_TYPE'
617 | # define _ALIGNAS_TYPE(x) alignas(x)
| ^
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__memory/shared_ptr.h:325:17: note: in instantiation of member class 'std::__shared_ptr_emplace<std::expected<std::any, int>, std::allocator<std::expected<std::any, int>>>::_Storage' requested here
325 | static_assert(_LIBCPP_ALIGNOF(_Storage) == _LIBCPP_ALIGNOF(_CompressedPair), "");
| ^
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__config:616:34: note: expanded from macro '_LIBCPP_ALIGNOF'
616 | # define _LIBCPP_ALIGNOF(_Tp) alignof(_Tp)
| ^
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__memory/shared_ptr.h:823:51: note: in instantiation of template class 'std::__shared_ptr_emplace<std::expected<std::any, int>, std::allocator<std::expected<std::any, int>>>' requested here
823 | ::new ((void*)std::addressof(*__guard.__get())) _ControlBlock(__a, std::forward<_Args>(__args)...);
| ^
/opt/compiler-explorer/clang-18.1.0/bin/../include/c++/v1/__memory/shared_ptr.h:831:15: note: in instantiation of function template specialization 'std::allocate_shared<std::expected<std::any, int>, std::allocator<std::expected<std::any, int>>, void>' requested here
831 | return std::allocate_shared<_Tp>(allocator<_Tp>(), std::forward<_Args>(__args)...);
| ^
<source>:6:22: note: in instantiation of function template specialization 'std::make_shared<std::expected<std::any, int>, void>' requested here
6 | auto core = std::make_shared<std::expected<std::any, int>>();
| ^
1 error generated.
Compiler returned: 1
```
Another example: https://godbolt.org/z/sfqPT7T1W
```c++
#include <expected>
#include <any>
#include <utility>
static std::expected<std::any, int> a;
std::expected<std::any, int> test() {
return std::move(a);
}
int main() {
test();
return 0;
}
```
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