I am encountering the following error in my project:
error: use of deleted function ‘C::C(int)’ note: ‘C::C(int)’ is implicitly deleted because the default definition would be ill-formed: error: use of deleted function ‘M::M()’
This is the code I am using:
struct M {
M(int){}
M() = delete; // Allowing this would work.
};
struct B {
B(int) {}
B() = delete;
};
struct C : public B {
using B::B;
M n = {5};
// C(int i) : B(i) {} // Adding this would work
};
C c{1};
Does anyone know why is this happening?
Clearly the language is willing to append more initialization on the end of the inherited constructor (as it's willing to call a default constructor). And clearly it's willing to implicitly add a call to the non-default constructor (the in class initialization) to the end of an explicitly defined constructor. But for some reason that I don't understand, it's not willing to do both at the same time.
According to this question, perfect forwarding isn't really perfect enough and shouldn't be used here.
Note: in the real case the constructor(s) for B are much more complex and subject to change, so manually forwarding stuff isn't really a viable option.
