Proposed resolution:

This wording is relative to N4950.

1. Modify [any.nonmembers] as indicated:

   template<class T>
     const T* any_cast(const any* operand) noexcept;
   template<class T>
     T* any_cast(any* operand) noexcept;
   

   -8- Mandates: is_void_v<T> is false.

   -9- Returns: If operand != nullptr && operand->type() == typeid(T) is true, a pointer to the object contained by operand; otherwise, nullptr.

   […]

[ 2023-11-11 Approved at November 2023 meeting in Kona. Status changed: Voting → WP. ]

[ 2023-06-14 Varna; Move to Ready ]

Poll: 7-0-1

[ 2023-06-14 Varna; Jonathan provides improved wording ]

[ 2022-02 Currently ill-formed in MSVC ("error C2338: std::any cannot contain void") and returns null pointer in libstdc++ and libc++. ]

[ 2020-02 LWG discussion in Prague did not reach consensus. Status to Open. ]

There was discussion about whether or not any_cast<void>(a) should be ill-formed, or return nullptr.

Poll "should it return nullptr" was 0-4-5-5-1.

[ 2019-11 Priority to 2 during Monday issue prioritization in Belfast. There is implementation divergence here. ]

any foo;
void* p = any_cast<void>(&foo);

Per [any.nonmembers]/9, since the operand isn't nullptr and operand->type() == typeid(T) (because T = void in this case), we should return a pointer to the object contained by operand. But there is no such object.

We need to handle the T = void case, probably by just explicitly returning nullptr.