Consider the following code:
#include <initializer_list>
class C {
public:
C() = delete;
C(int) {}
};
class D {
public:
D(std::initializer_list<C> il) {}
};
int main()
{
std::initializer_list<C> il{}; // fine: empty list, no need to construct C
D d2(il); // fine: calls initializer_list ctor with empty list
D d3{il}; // ditto
D d4({}); // still fine
D d5{{}}; // error: use of deleted function 'C::C()'
// WHY is the constructor of 'C' required here?
}
I thought D d5{{}}; would call the initializer_list constructor of D with an empty list. And, as the list is empty, the constructor of C would not be called. However, it does not compile:
error: use of deleted function
'C::C()'--D d5{{}};
What is the rationale behind this error?
Update
An issue on page 55 in Scott Meyer's "Effective Modern C++" made me think that having empty braces in a braced initialization would call the initializer_list constructor with an empty list. That is wrong. For details, see this blog post from the author.
