Make the test suite more friendly to Clang 19 (#4912)

Co-authored-by: Stephan T. Lavavej <[email protected]>

Author: CaseyCarter

tests/libcxx/expected_results.txt

@@ -368,6 +368,7 @@ std/depr/depr.c.headers/tgmath_h.pass.cpp:2 FAIL
 
 # LLVM-95311 [clang] __has_unique_object_representations gives inconsistent answer based on instantiation order
 # A libc++ product code workaround (using `remove_all_extents_t`) and test coverage were added by LLVM-95314.
+# Fixed by LLVM-95432 in Clang 19.
 std/utilities/meta/meta.unary/meta.unary.prop/has_unique_object_representations.compile.pass.cpp:2 FAIL
 
 

tests/std/tests/P2286R8_text_formatting_range_formatter/test.cpp

@@ -44,9 +44,12 @@ struct std::formatter<test::range<Category, Element, IsSized, Diff, IsCommon, Eq
 
 template <class Category, class Element, class CharT>
 struct std::formatter<test::proxy_reference<Category, Element>, CharT> {
+private:
+    formatter<remove_cv_t<Element>, CharT> underlying;
+
 public:
     constexpr void set_debug_format()
-        requires requires { this->underlying.set_debug_format(); }
+        requires requires { underlying.set_debug_format(); }
     {
         underlying.set_debug_format();
     }
@@ -60,9 +63,6 @@ struct std::formatter<test::proxy_reference<Category, Element>, CharT> {
     auto format(const test::proxy_reference<Category, Element>& proxy, FormatContext& ctx) const {
         return underlying.format(static_cast<Element&>(proxy), ctx);
     }
-
-private:
-    formatter<remove_cv_t<Element>, CharT> underlying;
 };
 
 struct FormatAsX {};

tests/std/tests/P2374R4_views_cartesian_product_recommended_practices/test.compile.pass.cpp

@@ -175,7 +175,11 @@ constexpr void check_single_view() {
 
 enum class CheckConstAdaptor : bool { no, yes };
 
+#ifdef __clang__ // TRANSITION, LLVM-104189
+template <template <class...> class SimpleRangeAdaptor, CheckConstAdaptor CCA, class... Args>
+#else // ^^^ workaround / no workaround vvv
 template <template <class, class...> class SimpleRangeAdaptor, CheckConstAdaptor CCA, class... Args>
+#endif // ^^^ no workaround ^^^
 constexpr void check_simple_range_adaptor() {
     using ValTy = tuple<int>; // for ranges::elements_view
     using V1    = SimpleRangeAdaptor<all_t<array<ValTy, 100>>, Args...>; // owning_view