[RFC][libc++][test] Improves C++ Standard filtering.

This is a proof-of-concept how we could improve the C++ language filtering
in lit. There will be a Discourse post for adding feedback on the
approach.

Author: mordante

libcxx/test/std/input.output/iostream.format/print.fun/includes.compile.pass.cpp

@@ -5,7 +5,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// REQUIRES: standard-ge-c++23
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 

libcxx/test/std/input.output/iostream.format/print.fun/no_file_description.pass.cpp

@@ -5,7 +5,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: standard-le-c++20
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 

libcxx/test/std/localization/locale.stdcvt/depr.verify.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++03, c++11, c++14, c++26
+// UNSUPPORTED: standard-le-c++14, standard-ge-c++26
 // UNSUPPORTED: no-wide-characters
 
 // <codecvt>

libcxx/test/std/localization/locales/locale.convenience/conversions/conversions.buffer/depr.verify.cpp

@@ -6,7 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++03, c++11, c++14, c++26
+// REQUIRES: standard-ge-c++17
+// UNSUPPORTED: standard-ge-c++26
 
 // XFAIL: no-wide-characters
 

libcxx/test/std/localization/locales/locale.convenience/conversions/conversions.string/depr.verify.cpp

@@ -8,7 +8,7 @@
 
 // ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX26_REMOVED_WSTRING_CONVERT
 
-// UNSUPPORTED: c++03, c++11, c++14, c++26
+// UNSUPPORTED: standard-le-c++14, standard-ge-c++26
 // UNSUPPORTED: no-wide-characters
 
 // <codecvt>

libcxx/test/std/strings/basic.string/string.capacity/reserve.deprecated_in_cxx20.verify.cpp

@@ -10,7 +10,7 @@
 
 // void reserve(); // Deprecated in C++20
 
-// UNSUPPORTED: c++03, c++11, c++14, c++17, c++26
+// UNSUPPORTED: standard-le-c++17, standard-ge-c++26
 
 #include <string>
 

libcxx/utils/libcxx/test/params.py

@@ -169,7 +169,9 @@ def getSuitableClangTidy(cfg):
             AddFeature(std),
             AddSubstitution("%{cxx_std}", re.sub(r"\+", "x", std)),
             AddCompileFlag(lambda cfg: getStdFlag(cfg, std)),
-        ],
+        ]
+        + [AddFeature(f"standard-ge-{s}") for s in _allStandards if s <= std]
+        + [AddFeature(f"standard-le-{s}") for s in _allStandards if s >= std],
     ),
     Parameter(
         name="optimization",