P2166R1 Prohibiting basic_string And basic_string_view Construction From nullptr

stl/inc/xstring

@@ -1278,6 +1278,10 @@ public:
 #endif // _CONTAINER_DEBUG_LEVEL > 0
     }
 
+#if _HAS_CXX23
+    constexpr basic_string_view(nullptr_t) = delete;
+#endif // _HAS_CXX23
+
 #ifdef __cpp_lib_concepts
     // clang-format off
     template <contiguous_iterator _It, sized_sentinel_for<_It> _Se>
@@ -2534,6 +2538,10 @@ public:
         _Proxy._Release();
     }
 
+#if _HAS_CXX23
+    _CONSTEXPR20_CONTAINER basic_string(nullptr_t) = delete;
+#endif // _HAS_CXX23
+
     _CONSTEXPR20_CONTAINER basic_string(_CRT_GUARDOVERFLOW const size_type _Count, const _Elem _Ch)
         : _Mypair(_Zero_then_variadic_args_t{}) {
         // construct from _Count * _Ch
@@ -3100,6 +3108,10 @@ public:
         return *this;
     }
 
+#if _HAS_CXX23
+    _CONSTEXPR20_CONTAINER basic_string& operator=(nullptr_t) = delete;
+#endif // _HAS_CXX23
+
     _CONSTEXPR20_CONTAINER basic_string& operator+=(const basic_string& _Right) {
         return append(_Right);
     }

tests/std/tests/P0220R1_string_view/test.cpp

@@ -1088,6 +1088,13 @@ static_assert(u8"abc"sv[1] == u8'b');
 static_assert(noexcept(u8"abc"sv));
 #endif // __cpp_char8_t
 
+// P2166R1 Prohibit std::basic_string and std::basic_string_view construction from nullptr
+#if _HAS_CXX23
+static_assert(!is_constructible_v<string_view, nullptr_t>, "constructing string_view from nullptr_t is prohibited");
+static_assert(!is_constructible_v<string, nullptr_t>, "constructing string from nullptr_t is prohibited");
+static_assert(!is_assignable_v<string, nullptr_t>, "assigning string to nullptr_t is prohibited");
+#endif
+
 int main() {
     test_case_default_constructor();
     test_case_ntcts_constructor();