diff --git a/stl/inc/any b/stl/inc/any
index faaa26d96..66896cd95 100644
--- a/stl/inc/any
+++ b/stl/inc/any
@@ -9,7 +9,9 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <any> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <initializer_list>
 #include <type_traits>
 #include <typeinfo>
@@ -441,8 +443,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
-#pragma message("class any is only available with C++17 or later.")
 #endif // _HAS_CXX17
 
 #endif // _STL_COMPILER_PREPROCESSOR
diff --git a/stl/inc/charconv b/stl/inc/charconv
index 2c6aa3311..d038e666a 100644
--- a/stl/inc/charconv
+++ b/stl/inc/charconv
@@ -9,7 +9,9 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <charconv> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <float.h>
 #include <intrin0.h>
 #include <string.h>
@@ -3097,8 +3099,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
-#pragma message("The contents of <charconv> are only available with C++17 or later.")
 #endif // _HAS_CXX17
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _CHARCONV_
diff --git a/stl/inc/compare b/stl/inc/compare
index f78c80635..25afa907b 100644
--- a/stl/inc/compare
+++ b/stl/inc/compare
@@ -9,7 +9,9 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX20
+#if !_HAS_CXX20
+#pragma message("The contents of <compare> are available only with C++20 or later.")
+#else // ^^^ !_HAS_CXX20 / _HAS_CXX20 vvv
 #include <xtr1common>
 
 #pragma pack(push, _CRT_PACKING)
@@ -475,8 +477,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ C++20 / not C++20 vvv
-#pragma message("The contents of <compare> are only available with C++20 or later.")
 #endif // _HAS_CXX20
 
 #endif // _STL_COMPILER_PREPROCESSOR
diff --git a/stl/inc/concepts b/stl/inc/concepts
index 185243a63..7d507516c 100644
--- a/stl/inc/concepts
+++ b/stl/inc/concepts
@@ -9,7 +9,9 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#ifdef __cpp_lib_concepts
+#ifndef __cpp_lib_concepts
+#pragma message("The contents of <concepts> are available only with C++20 concepts support.")
+#else // ^^^ !defined(__cpp_lib_concepts) / defined(__cpp_lib_concepts) vvv
 #if defined(__clang__) && !defined(_SILENCE_CLANG_CONCEPTS_MESSAGE)
 #error Despite the presence of some Clang-related bits, this header currently does not support Clang. \
 You can define _SILENCE_CLANG_CONCEPTS_MESSAGE to silence this message and acknowledge that this is unsupported.
@@ -364,8 +366,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ <concepts> supported / <concepts> not supported vvv
-#pragma message("The contents of <concepts> are only available with C++20 concepts support.")
 #endif // __cpp_lib_concepts
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _CONCEPTS_
diff --git a/stl/inc/execution b/stl/inc/execution
index 5762f83ef..81ae2d6aa 100644
--- a/stl/inc/execution
+++ b/stl/inc/execution
@@ -9,7 +9,9 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <execution> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <algorithm>
 #include <atomic>
 #include <memory>
@@ -2839,10 +2841,10 @@ inline size_t _Get_stable_sort_tree_height(const size_t _Count, const size_t _Hw
     // go to the next smaller power of 2
     const auto _Count_max_tree_height = _Log_count_max_chunks & ~static_cast<size_t>(1);
 
-    const auto _Ideal_chunks       = _Hw_threads * _Oversubscription_multiplier;
-    const size_t _Log_ideal_chunks = _Floor_of_log_2(_Ideal_chunks);
+    const auto _Ideal_chunks           = _Hw_threads * _Oversubscription_multiplier;
+    const size_t _Log_ideal_chunks     = _Floor_of_log_2(_Ideal_chunks);
 #ifdef _WIN64
-    const size_t _Max_tree_height = 62; // to avoid ptrdiff_t overflow
+    const size_t _Max_tree_height      = 62; // to avoid ptrdiff_t overflow
 #else // ^^^ _WIN64 ^^^ // vvv !_WIN64 vvv
     const size_t _Max_tree_height = 30;
 #endif // _WIN64
@@ -5137,8 +5139,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
-#pragma message("Parallel algorithms are only available with C++17 or later.")
 #endif // _HAS_CXX17
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _EXECUTION_
diff --git a/stl/inc/filesystem b/stl/inc/filesystem
index ea4d09b01..e2f7ecc43 100644
--- a/stl/inc/filesystem
+++ b/stl/inc/filesystem
@@ -9,7 +9,9 @@
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <filesystem> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <algorithm>
 #include <chrono>
 #include <cwchar>
@@ -4330,8 +4332,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
-#pragma message("The contents of <filesystem> are only available with C++17 or later.")
 #endif // _HAS_CXX17
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _FILESYSTEM_
diff --git a/stl/inc/memory_resource b/stl/inc/memory_resource
index ddbb84a7a..8efe9f682 100644
--- a/stl/inc/memory_resource
+++ b/stl/inc/memory_resource
@@ -9,7 +9,9 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <memory_resource> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <vector>
 #include <xbit_ops.h>
 #include <xpolymorphic_allocator.h>
@@ -755,8 +757,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
-#pragma message("The contents of <memory_resource> are only available with C++17 or later.")
 #endif // _HAS_CXX17
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _MEMORY_RESOURCE_
diff --git a/stl/inc/optional b/stl/inc/optional
index 3d5708bc6..7b1aa33cc 100644
--- a/stl/inc/optional
+++ b/stl/inc/optional
@@ -8,7 +8,9 @@
 #define _OPTIONAL_
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <optional> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <exception>
 #include <initializer_list>
 #include <type_traits>
@@ -637,8 +639,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
-#pragma message("class template optional is only available with C++17 or later.")
 #endif // _HAS_CXX17
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _OPTIONAL_
diff --git a/stl/inc/ranges b/stl/inc/ranges
index d40da8562..9f63a30e0 100644
--- a/stl/inc/ranges
+++ b/stl/inc/ranges
@@ -8,7 +8,9 @@
 #define _RANGES_
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
-#ifdef __cpp_lib_concepts
+#ifndef __cpp_lib_concepts
+#pragma message("The contents of <ranges> are available only with C++20 concepts support.")
+#else // ^^^ !defined(__cpp_lib_concepts) / defined(__cpp_lib_concepts) vvv
 #include <iterator>
 
 #pragma pack(push, _CRT_PACKING)
@@ -34,8 +36,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-#else // ^^^ Concepts support / no Concepts vvv
-#pragma message("The contents of <ranges> are only available with C++20 concepts support.")
 #endif // __cpp_lib_concepts
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _RANGES_
diff --git a/stl/inc/string_view b/stl/inc/string_view
index 6acf42305..ff23b4096 100644
--- a/stl/inc/string_view
+++ b/stl/inc/string_view
@@ -9,10 +9,10 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <string_view> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <xstring>
-#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
-#pragma message("string_view is only available with C++17 or later.")
 #endif // _HAS_CXX17
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _STRING_VIEW_
diff --git a/stl/inc/variant b/stl/inc/variant
index a34234077..d23ff08f4 100644
--- a/stl/inc/variant
+++ b/stl/inc/variant
@@ -9,7 +9,9 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
-#if _HAS_CXX17
+#if !_HAS_CXX17
+#pragma message("The contents of <variant> are available only with C++17 or later.")
+#else // ^^^ !_HAS_CXX17 / _HAS_CXX17 vvv
 #include <exception>
 #include <initializer_list>
 #include <type_traits>
@@ -1156,7 +1158,7 @@ public:
                             (void) _That_ref; // TRANSITION, VSO-486357
                             constexpr size_t _That_idx = decltype(_That_ref)::_Idx;
 #ifdef __EDG__ // TRANSITION, VSO-657455
-                            constexpr size_t _My_idx = decltype(_My_ref)::_Idx + 0 * _That_idx;
+                            constexpr size_t _My_idx   = decltype(_My_ref)::_Idx + 0 * _That_idx;
 #else // ^^^ workaround ^^^ / vvv no workaround vvv
                             constexpr size_t _My_idx = decltype(_My_ref)::_Idx;
 #endif // TRANSITION, VSO-657455
@@ -1749,9 +1751,6 @@ _STD_END
 _STL_RESTORE_CLANG_WARNINGS
 #pragma warning(pop)
 #pragma pack(pop)
-
-#else // ^^^ _HAS_CXX17 ^^^ / vvv !_HAS_CXX17 vvv
-#pragma message("class template variant is only available with C++17 or later.")
 #endif // _HAS_CXX17
 #endif // _STL_COMPILER_PREPROCESSOR
 #endif // _VARIANT_