simplify range-for-only iterators using relaxed c++17 rules

ostd/coroutine.hh

@@ -1121,7 +1121,9 @@ public:
     /** Implements a minimal iterator just for range-based for loop.
       * Do not use directly.
       */
-    detail::generator_iterator<T> end() noexcept;
+    std::nullptr_t end() noexcept {
+        return nullptr;
+    }
 
     /** Swaps two generators' states. */
     void swap(generator &other) noexcept {
@@ -1239,7 +1241,9 @@ struct generator_range: input_range<generator_range<T>> {
     /** Implements a minimal iterator just for range-based for loop.
       * Do not use directly.
       */
-    detail::generator_iterator<T> end() noexcept;
+    std::nullptr_t end() noexcept {
+        return nullptr;
+    }
 
 private:
     generator<T> *p_gen;
@@ -1257,7 +1261,7 @@ namespace detail {
         generator_iterator() = delete;
         generator_iterator(generator<T> &g): p_gen(&g) {}
 
-        bool operator!=(generator_iterator const &) noexcept {
+        bool operator!=(std::nullptr_t) noexcept {
             return !p_gen->empty();
         }
 
@@ -1280,21 +1284,11 @@ detail::generator_iterator<T> generator<T>::begin() noexcept {
     return detail::generator_iterator<T>{*this};
 }
 
-template<typename T>
-detail::generator_iterator<T> generator<T>::end() noexcept {
-    return detail::generator_iterator<T>{*this};
-}
-
 template<typename T>
 detail::generator_iterator<T> generator_range<T>::begin() noexcept {
     return detail::generator_iterator<T>{*p_gen};
 }
 
-template<typename T>
-detail::generator_iterator<T> generator_range<T>::end() noexcept {
-    return detail::generator_iterator<T>{*p_gen};
-}
-
 /** @} */
 
 } /* namespace ostd */

ostd/range.hh

@@ -230,55 +230,23 @@ constexpr bool is_output_range = detail::is_output_range_base<T>;
 
 namespace detail {
     // range iterator
-
     template<typename T>
     struct range_iterator {
-        range_iterator(): p_range(), p_init(false) {}
-        explicit range_iterator(T const &range): p_range(), p_init(true) {
-            ::new(&get_ref()) T(range);
-        }
-        explicit range_iterator(T &&range): p_range(), p_init(true) {
-            ::new(&get_ref()) T(std::move(range));
-        }
-        range_iterator(const range_iterator &v): p_range(), p_init(true) {
-            ::new(&get_ref()) T(v.get_ref());
-        }
-        range_iterator(range_iterator &&v): p_range(), p_init(true) {
-            ::new(&get_ref()) T(std::move(v.get_ref()));
-        }
-        range_iterator &operator=(const range_iterator &v) {
-            destroy();
-            ::new(&get_ref()) T(v.get_ref());
-            p_init = true;
-            return *this;
-        }
-        range_iterator &operator=(range_iterator &&v) {
-            destroy();
-            swap(v);
-            return *this;
-        }
-        ~range_iterator() {
-            destroy();
-        }
+        range_iterator() = delete;
+        explicit range_iterator(T const &range): p_range(range) {}
+        explicit range_iterator(T &&range): p_range(std::move(range)) {}
         range_iterator &operator++() {
-            get_ref().pop_front();
+            p_range.pop_front();
             return *this;
         }
         range_reference_t<T> operator*() const {
-            return get_ref().front();
+            return p_range.front();
+        }
+        bool operator!=(std::nullptr_t) const {
+            return !p_range.empty();
         }
-        bool operator!=(range_iterator) const { return !get_ref().empty(); }
     private:
-        T &get_ref() { return *reinterpret_cast<T *>(&p_range); }
-        T const &get_ref() const { return *reinterpret_cast<T const *>(&p_range); }
-        void destroy() {
-            if (p_init) {
-                get_ref().~T();
-                p_init = false;
-            }
-        }
-        std::aligned_storage_t<sizeof(T), alignof(T)> p_range;
-        bool p_init;
+        std::decay_t<T> p_range;
     };
 }
 
@@ -553,8 +521,8 @@ struct input_range {
     detail::range_iterator<B> begin() const {
         return detail::range_iterator<B>(*static_cast<B const *>(this));
     }
-    detail::range_iterator<B> end() const {
-        return detail::range_iterator<B>();
+    std::nullptr_t end() const {
+        return nullptr;
     }
 
     template<typename Size>