polymorphism.h

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#ifndef VCL_CONCEPTS_POLYMORPHISM_H
#define VCL_CONCEPTS_POLYMORPHISM_H
 
#include "const_correctness.h"
 
#include <concepts>
#include <memory>
 
namespace vcl {
 
template<typename T>
concept Cloneable = requires (T&& obj) {
    // TODO: Right now, this concept can be used only with a base class that has
    // a clone method, because the concept requires that the return type of the
    // clone method is a shared pointer to the same class as the object. This is
    // not always the case, especially when the clone method is overridden in
    // derived classes. We need to find a way to make this concept work with
    // overridden clone methods.
    //
    // However, we should also consider the consequences of this change for the
    // class vcl::PolymorphicObjectVector, which relies on this concept to
    // determine if an object can be cloned, and stores objects of the Base
    // class in a vector.
    //
    // Example:
    // class Base {
    // public:
    //     virtual std::shared_ptr<Base> clone() const = 0;
    // };
    //
    // class Derived : public Base {
    // public:
    //     std::shared_ptr<Derived> clone() const { ... }
    // };
    //
    // static_assert(vcl::Cloneable<Base>, ""); // OK
    // static_assert(vcl::Cloneable<Derived>, ""); // Error, but should work
    { obj.clone() } -> std::same_as<std::shared_ptr<std::remove_cvref_t<T>>>;
};
 
} // namespace vcl
 
#endif // VCL_CONCEPTS_POLYMORPHISM_H