struct A
ЮЖ>{
ЮЖ>  A();

ЮЖ>  A(A&);

ЮЖ>  template<class T>
ЮЖ>  A(const T&)
ЮЖ>  {}
ЮЖ>};

ЮЖ>struct B : A
ЮЖ>{
ЮЖ>  B();
ЮЖ>};

ЮЖ>int main()
ЮЖ>{
ЮЖ>  B b;
ЮЖ>  B b1 = b; // error
ЮЖ>}

S>When certain criteria are met, an implementation is allowed to omit the copy construction of a class object,
S>even if the copy constructor and/or destructor for the object have side effects.
S>...
S>— when a temporary class object that has not been bound to a reference (12.2) would be copied to a class
S>object with the same cv-unqualified type, the copy operation can be omitted by constructing the temporary
S>object directly into the target of the omitted copy

if the subobject is of class type, direct-initialization (8.5 [dcl.init]) is performed

For direct-initialization, the candidate functions are all the constructors of the class of the object being initialized.

13.3.1/2
ЮЖ>For the purposes of overload resolution, both static and non-static member functions have an implicit object parameter, but constructors do not.

The implicitly-declared copy constructor and implicitly-declared copy assignment operator cannot make a copy of a volatile lvalue

12.1/2
ЮЖ>A constructor is used to initialize objects of its class type.