Question

Quote from n3337 12.3.1/3

A non-explicit copy/move constructor (12.8) is a converting
constructor. An implicitly-declared copy/move constructor is not an
explicit constructor; it may be called for implicit type conversions.

Quote from ANSI ISO IEC 14882 2003

A non-explicit copy-constructor (12.8) is a converting constructor. An
implicitly-declared copy constructor is not an explicit constructor;
it may be called for implicit type conversions.

I have no ideas, how copy-constructor can be used for implicit type conversions. And if it’s misprint/error in standard, why it’s not corrected since C++03 standard? Any links and examples (if we can use it for type conversions) are really appreciated.

Answer 1

A copy constructor can convert from an object of a derived type by slicing it:

struct A {};
struct B : A {};

B b;
A a = b; // uses A::A(A const&) to convert B to A