[libcxx] [clang-tools-extra] [mlir] [clang] [libc] [llvm] [flang] [lld] [compiler-rt] [lldb] [libc++][format] P2637R3: Member `visit` (`std::basic_format_arg`) (PR #76449)

[Mark de Wever via cfe-commits]

================
@@ -19,19 +19,25 @@
 #include "test_macros.h"
 #include "make_string.h"
 
+#if _LIBCPP_STD_VER >= 26
+TEST_CLANG_DIAGNOSTIC_IGNORED("-Wdeprecated-declarations")
+#endif
+
 template <class Context, class To, class From>
 void test(From value) {
   auto store = std::make_format_args<Context>(value);
   const std::basic_format_args<Context> format_args{store};
 
-  std::visit_format_arg(
-      [v = To(value)](auto a) {
-        if constexpr (std::is_same_v<To, decltype(a)>)
-          assert(v == a);
-        else
-          assert(false);
-      },
-      format_args.get(0));
+  auto visitor = [v = To(value)](auto a) {
+    if constexpr (std::is_same_v<To, decltype(a)>)
+      assert(v == a);
+    else
+      assert(false);
+  };
+#if _LIBCPP_STD_VER >= 26
+  format_args.get(0).visit(visitor);
+#endif
+  std::visit_format_arg(visitor, format_args.get(0));
----------------
mordante wrote:

If we put this in an `#else` we don't need to disable deprecated warnings right?
This function tests `get` so we don't need to add coverage for the visitor.

This means the code looks like what you did in libcxx/test/support/test_basic_format_arg.h

https://github.com/llvm/llvm-project/pull/76449