Fix noexcept specification

Author: miscco

stl/inc/ranges

@@ -3771,13 +3771,16 @@ namespace ranges {
             }
 
             _NODISCARD constexpr decltype(auto) operator*() const
-                noexcept(noexcept(_STD get<_Index>(*_Current))) /* strengthened */ {
-                if constexpr (is_reference_v<range_reference_t<_Base>>) {
-                    return _STD get<_Index>(*_Current);
-                } else {
-                    using _ElemTy = remove_cv_t<tuple_element_t<_Index, range_reference_t<_Base>>>;
-                    return static_cast<_ElemTy>(_STD get<_Index>(*_Current));
-                }
+                noexcept(noexcept(_STD get<_Index>(*_Current))) /* strengthened */
+                requires is_reference_v<range_reference_t<_Base>> {
+                return _STD get<_Index>(*_Current);
+            }
+
+            _NODISCARD constexpr decltype(auto) operator*() const noexcept(
+                is_nothrow_move_constructible_v<remove_cv_t<tuple_element_t<_Index, range_reference_t<_Base>>>> //
+                    && noexcept(_STD get<_Index>(*_Current))) /* strengthened */ {
+                using _ElemTy = remove_cv_t<tuple_element_t<_Index, range_reference_t<_Base>>>;
+                return static_cast<_ElemTy>(_STD get<_Index>(*_Current));
             }
 
             constexpr _Iterator& operator++() noexcept(noexcept(++_Current)) /* strengthened */ {
@@ -3840,16 +3843,22 @@ namespace ranges {
 
             _NODISCARD constexpr decltype(auto) operator[](const difference_type _Idx) const
                 noexcept(noexcept(_STD get<_Index>(*(_Current + _Idx)))) /* strengthened */
+                requires random_access_range<_Base>&& is_reference_v<range_reference_t<_Base>> {
+#if _ITERATOR_DEBUG_LEVEL != 0
+                _Verify_offset(_Idx);
+#endif // _ITERATOR_DEBUG_LEVEL != 0
+                return _STD get<_Index>(*(_Current + _Idx));
+            }
+
+            _NODISCARD constexpr decltype(auto) operator[](const difference_type _Idx) const noexcept(
+                is_nothrow_move_constructible_v<remove_cv_t<tuple_element_t<_Index, range_reference_t<_Base>>>> //
+                    && noexcept(_STD get<_Index>(*(_Current + _Idx)))) /* strengthened */
                 requires random_access_range<_Base> {
 #if _ITERATOR_DEBUG_LEVEL != 0
                 _Verify_offset(_Idx);
 #endif // _ITERATOR_DEBUG_LEVEL != 0
-                if constexpr (is_reference_v<range_reference_t<_Base>>) {
-                    return _STD get<_Index>(*(_Current + _Idx));
-                } else {
-                    using _ElemTy = remove_cv_t<tuple_element_t<_Index, range_reference_t<_Base>>>;
-                    return static_cast<_ElemTy>(_STD get<_Index>(*(_Current + _Idx)));
-                }
+                using _ElemTy = remove_cv_t<tuple_element_t<_Index, range_reference_t<_Base>>>;
+                return static_cast<_ElemTy>(_STD get<_Index>(*(_Current + _Idx)));
             }
 
             _NODISCARD friend constexpr bool operator==(const _Iterator& _Left, const _Iterator& _Right) noexcept(

tests/std/tests/P0896R4_views_drop/test.cpp

@@ -510,6 +510,21 @@ int main() {
         test_one(lst, only_four_ints);
     }
 
+    // Validate a non-view borrowed range
+    {
+        constexpr span s{some_ints};
+        STATIC_ASSERT(test_one(s, expected_output));
+        test_one(s, expected_output);
+    }
+
+    { // Validate a view borrowed range
+
+        constexpr auto v =
+            views::iota(0ull, ranges::size(some_ints)) | std::views::transform([](auto i) { return some_ints[i]; });
+        STATIC_ASSERT(test_one(v));
+        test_one(v);
+    }
+
     // Validate an output range
     STATIC_ASSERT((output_range_test(), true));
     output_range_test();