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// P2280R4 - Using unknown pointers and references in constant expressions
// PR c++/106650
// { dg-do compile { target c++20 } }
#include <typeinfo>
using size_t = decltype(sizeof(42));
template <typename T, size_t N>
constexpr size_t array_size(T (&)[N]) {
return N;
}
void use_array(int const (&gold_medal_mel)[2]) {
constexpr auto gold = array_size(gold_medal_mel); // OK
}
constexpr auto olympic_mile() {
const int ledecky = 1500;
return []{ return ledecky; };
}
static_assert(olympic_mile()() == 1500); // OK
struct Swim {
constexpr int phelps() { return 28; }
virtual constexpr int lochte() { return 12; }
int coughlin = 12;
};
constexpr int how_many(Swim& swam) {
Swim* p = &swam;
return (p + 1 - 1)->phelps();
}
void splash(Swim& swam) {
static_assert(swam.phelps() == 28); // OK
static_assert((&swam)->phelps() == 28); // OK
Swim* pswam = &swam;
static_assert(pswam->phelps() == 28); // { dg-error "non-constant|not usable" }
static_assert(how_many(swam) == 28); // OK
static_assert(Swim().lochte() == 12); // OK
static_assert(swam.lochte() == 12); // { dg-error "non-constant|not a constant" }
static_assert(swam.coughlin == 12); // { dg-error "non-constant|not a constant" }
}
extern Swim dc;
extern Swim& trident;
constexpr auto& sandeno = typeid(dc); // OK, can only be typeid(Swim)
constexpr auto& gallagher = typeid(trident); // { dg-error "not a constant" }
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