| Issue |
61415
|
| Summary |
False positive error: pack expansion contains parameter pack '_UTypes' that has a different length (1 vs. 2) from outer parameter packs
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Romain-Geissler-1A
|
Hi,
This is an issue similar #58452, actually the snippet I posted in this issue is the same. Using libstc++'s 13 tuple implementation is still not possible when using `-std=c++2b`:
```
#include <tuple>
void g(std::tuple<std::tuple<int, int>>);
void f()
{
g(std::forward_as_tuple<std::tuple<int, int>>({0, 0}));
}
```
Godbolt output (https://godbolt.org/z/Meca376M6):
```
In file included from <source>:1:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:691:2: error: pack expansion contains parameter pack '_UTypes' that has a different length (1 vs. 2) from outer parameter packs
using __convertible = __and_<is_convertible<_UTypes, _Types>...>;
^~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:853:27: note: in instantiation of template type alias '__convertible' requested here
= _TCC<true>::template __convertible<_Args...>::value;
^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:948:12: note: in instantiation of static data member 'std::tuple<std::tuple<int, int> &&>::__convertible<int &, int &>' requested here
explicit(!__convertible<_UElements&...>)
^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:2000:36: note: while substituting deduced template arguments into function template 'tuple' [with _UElements = <int, int>]
{ return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
^
<source>:7:12: note: in instantiation of function template specialization 'std::forward_as_tuple<std::tuple<int, int>>' requested here
g(std::forward_as_tuple<std::tuple<int, int>>({0, 0}));
^
In file included from <source>:1:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:691:2: error: pack expansion contains parameter pack '_UTypes' that has a different length (1 vs. 2) from outer parameter packs
using __convertible = __and_<is_convertible<_UTypes, _Types>...>;
^~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:853:27: note: in instantiation of template type alias '__convertible' requested here
= _TCC<true>::template __convertible<_Args...>::value;
^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:959:12: note: in instantiation of static data member 'std::tuple<std::tuple<int, int> &&>::__convertible<const int, const int>' requested here
explicit(!__convertible<const _UElements...>)
^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.1/../../../../include/c++/13.0.1/tuple:2000:36: note: while substituting deduced template arguments into function template 'tuple' [with _UElements = <int, int>]
{ return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
^
<source>:7:12: note: in instantiation of function template specialization 'std::forward_as_tuple<std::tuple<int, int>>' requested here
g(std::forward_as_tuple<std::tuple<int, int>>({0, 0}));
^
2 errors generated.
Compiler returned: 1
```
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