stupid constexpr tricks

You shouldn't expect this to compile, for several reasons, but it does.

https://compiler-explorer.com/z/sb1648Wrr

```cpp
constexpr auto make_val() {
 return 10;
}

int main()
{
 const auto x = 42;
 const auto y = [](){ return 43; }();

 const auto result = [](){
 return x + y + make_val();
 }();

 static_assert(result == 95);
}
```