owner_ptr (replaces unique_ptr)

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#ifndef KUT_OWNERPTR_H
#define KUT_OWNERPTR_H
#pragma once

#include <cassert>
#include <utility>
#include <type_traits>

namespace kut
{
    //Based on Corrade's Pointer but with some differences
    //https://github.com/mosra/corrade/blob/master/src/Corrade/Containers/Pointer.h

    template<typename T>
    class owner_ptr
    {
        //Don't use/allow this class for arrays
        static_assert(!std::is_array<T>::value, "owner_ptr cannot refer to arrays");
        //Used in the move constructors for convertible types
        template<typename U> friend class owner_ptr;

    public:
        //Some typedefs to match unique_ptr, I don't bother to use them internally
        using pointer = T*;
        using element_type = T;

        //implicit construction of null pointer
        owner_ptr(std::nullptr_t = nullptr) noexcept : _p() {}
        //explicit construction with a pointer value
        explicit owner_ptr(T* p) noexcept : _p(p) {}

        //copy constructor is deleted
        owner_ptr(const owner_ptr<T>&) = delete;
        //move constructor
        template<typename U>
        owner_ptr(owner_ptr<U>&& other) noexcept : _p(static_cast<T*>(other._p))
        {
            other._p = nullptr;
        }

        //assignment copy is deleted
        owner_ptr<T>& operator=(const owner_ptr<T>&) = delete;
        //move assignment
        template<typename U>
        owner_ptr<T>& operator=(owner_ptr<U>&& other) noexcept
        {
            //swap our pointers
            auto temp = other._p;
            other._p = static_cast<U*>(_p);
            _p = static_cast<T*>(temp);
        }

        //comparisons to null pointer
        bool operator==(std::nullptr_t) const noexcept { return _p == nullptr; }
        bool operator!=(std::nullptr_t) const noexcept { return _p != nullptr; }

        //destructor
        ~owner_ptr() { delete _p; }

        //bool conversion to check validity
        explicit operator bool() const noexcept { return _p; }

        //retrieve underlying pointer
        T* get() noexcept { return _p; }
        const T* get() const noexcept { return _p; }

        //call through to pointer object
        T* operator->() noexcept
        {
            assert(_p);
            return _p;
        }

        const T* operator->() const noexcept
        {
            assert(p);
            return _p;
        }

        //dereference to underlying object
        T& operator*() noexcept
        {
            assert(p);
            return _p;
        }

        const T& operator*() const noexcept
        {
            assert(p);
            return _p;
        }

        //clear out the pointer
        void reset(T* pointer = nullptr) noexcept
        {
            delete _p;
            _p = pointer;
        }

        T* release() noexcept
        {
            auto ptr = _p;
            _p = nullptr;
            return ptr;
        }

    private:
        T* _p;
    };

    //reverse equality comparisons
    template<typename T> bool operator==(std::nullptr_t, const owner_ptr<T>& p) { return p == nullptr; }
    template<typename T> bool operator!=(std::nullptr_t, const owner_ptr<T>& p) { return p != nullptr; }

    //make_unique equivalent, construct pointer and underlying object
    template<typename T, typename... Args>
    inline owner_ptr<T> make_owner(Args&&... args)
    {
        return owner_ptr<T>(new T(std::forward<Args>(args)...));
    }
}

#endif