## Cannot construct constexpr array from braced-init-list

Question

I've implemented a constexpr array like this:

```
template <typename T>
class const_array {
const T* p;
unsigned n;
public:
template <unsigned N>
constexpr const_array(const T(&a)[N]): p(a), n(N) { }
constexpr unsigned size() const { return n; }
};
int main(int argc, char* argv[]) {
// works
static_assert(const_array<double>{{1.,2.,3.}}.size() == 3);
// works
constexpr const_array<double> a1((const double[]){1.,2.,3.});
static_assert(a1.size() == 3);
// doesn't compile
constexpr const_array<double> a2{{1.,2.,3.}};
static_assert(a2.size() == 3);
}
```

Can someone explain to me why the third assert doesn't compile when the first two do? I'm using `gcc 6.2.0`

. I'm getting

```
: In function 'int main(int, char**)':
: error: 'const_array<double>{((const double*)(&<anonymous>)), 3u}' is not a constant expression
constexpr const_array<double> a2{{1.,2.,3.}};
^
test/const_array.cc:31:3: error: non-constant condition for static assertion
static_assert(a2.size() == 3);
^~~~~~~~~~~~~
```

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## Answers to Cannot construct constexpr array from braced-init-list ( 0 )