[libc++][test] Selects proper C++23 field.

[Mordante]

Summary

D149553 changes the name of the LangOptions member. This change allows
libc++ to work with either name.

[philnik]

LGTM % nit.

libcxx/test/tools/clang_tidy_checks/uglify_attributes.cpp

32–44

This should also work.

[Mordante]

Rebased and addresses review comment.

[Mordante]

Thanks for the review!

libcxx/test/tools/clang_tidy_checks/uglify_attributes.cpp

32–44

I expected a simpler solution was indeed possible. Thanks for the suggestion.

libcxx/test/tools/clang_tidy_checks/uglify_attributes.cpp

 bool isUgly(std::string_view str) {
   if (str.size() < 2)
     return false;
   if (str[0] == '_' && str[1] >= 'A' && str[1] <= 'Z')
     return true;
   return str.find("__") != std::string_view::npos;
 }
 
+// Starting with Clang 17 ToT C++23 support is provided by CPlusPlus23 instead
+// of C++23 support is provided by CPlusPlus2b. To allow a smooth transition for
+// libc++ use "reflection" to select the proper member. Since the change
+// happens in the development cycle it's not possible to use #ifdefs.
+template <class T>
+bool CPlusPlus23(const T& lang_opts)
+  requires requires { T::CPlusPlus2b; }
+{
+  return lang_opts.CPlusPlus2b;
+}
+
+template <class T>
+bool CPlusPlus23(const T& lang_opts)
+  requires requires { T::CPlusPlus23; }
+{
+  return lang_opts.CPlusPlus23;
+}
+
 std::vector<const char*> get_standard_attributes(const clang::LangOptions& lang_opts) {
   std::vector<const char*> attributes = {"noreturn", "carries_dependency"};
 
   if (lang_opts.CPlusPlus14)
     attributes.emplace_back("deprecated");
 
   if (lang_opts.CPlusPlus17) {
     attributes.emplace_back("fallthrough");
     attributes.emplace_back("nodiscard");
     attributes.emplace_back("maybe_unused");
   }
 
   if (lang_opts.CPlusPlus20) {
     attributes.emplace_back("likely");
     attributes.emplace_back("unlikely");
     attributes.emplace_back("no_unique_address");
   }
 
-  if (lang_opts.CPlusPlus2b) {
+  if (CPlusPlus23(lang_opts)) {
     attributes.emplace_back("assume");
   }
 
   return attributes;
 }
 
 AST_MATCHER(clang::Attr, isPretty) {
   if (Node.isKeywordAttribute())