[Bug libstdc++/105790] New: cannot constructor std::tuple of non-movable types with conversions

[hui.xie1990 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105790

            Bug ID: 105790
           Summary: cannot constructor std::tuple of non-movable types
                    with conversions
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hui.xie1990 at gmail dot com
  Target Milestone: ---

```
#include <tuple>

struct Immovable{
    Immovable() = default;
    Immovable(Immovable&&) = delete;
};

struct ConvToImmovable{
    operator Immovable() const { return Immovable{};}
};

void test(){
   std::tuple<Immovable> t{ConvToImmovable{}};
}
```

The above code does not compile.

/opt/compiler-explorer/gcc-trunk-20220531/include/c++/13.0.0/tuple:91:11:
error: use of deleted function 'Immovable::Immovable(Immovable&&)'
   91 |         : _M_head_impl(std::forward<_UHead>(__h)) { }
      |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:5:5: note: declared here
    5 |     Immovable(Immovable&&) = delete;

According to the spec, as Immovable IS constructible from ConvToImmovable, so
the tuple's constructor that takes (UTypes&&...) should work.