[Bug c++/110344] [C++26] P2738R1 - constexpr cast from void*

[jason at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110344

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |jason at gcc dot gnu.org

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
Reduced version of the paper's testcase that we already (wrongly) accept:

class Doer {
private:
  const void *ob;
  int (*fn)(const void *);
public:
  template <typename T>
  constexpr Doer(const T &t)
    : ob{&t},
      fn{[](const void *p) { return static_cast<const T *>(p)->doit(); }}
  {}
  constexpr int operator()() const { return fn(ob); }
};
struct Thing { constexpr int doit() const { return 42; }; };
static_assert (Doer(Thing())() == 42);