[libc++][format] Adds flat_(|multi)map formatter.

[mordante]

These types should be formattable out-of-the-box. This patch validates that is true.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Mark de Wever (mordante)

Changes

This type should be formattable out-of-the-box. This patch validates that is true.

---

Full diff: https://github.com/llvm/llvm-project/pull/124418.diff

2 Files Affected:

• (modified) libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp (+8)
• (modified) libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h (+4)

diff --git a/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp b/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp
index 88a485a256c801..1f384fa48d2a47 100644
--- a/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp
@@ -24,6 +24,7 @@
 #include <concepts>
 #include <deque>
 #include <filesystem>
+#include <flat_map>
 #include <format>
 #include <forward_list>
 #include <list>
@@ -242,6 +243,13 @@ void test_P2286() {
   assert_is_formattable<std::multiset<int>, CharT>();
   assert_is_formattable<std::multimap<int, int>, CharT>();
 
+#if TEST_STD_VER >= 23
+  // assert_is_formattable<std::flat_set<int>, CharT>();
+  assert_is_formattable<std::flat_map<int, int>, CharT>();
+  // assert_is_formattable<std::flat_multiset<int>, CharT>();
+  // assert_is_formattable<std::flat_multimap<int, int>, CharT>();
+#endif // TEST_STD_VER >= 2
+
   assert_is_formattable<std::unordered_set<int>, CharT>();
   assert_is_formattable<std::unordered_map<int, int>, CharT>();
   assert_is_formattable<std::unordered_multiset<int>, CharT>();
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h
index fc638da9c840dc..c00288a1ecbd82 100644
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h
@@ -10,6 +10,7 @@
 #define TEST_STD_UTILITIES_FORMAT_FORMAT_RANGE_FORMAT_RANGE_FMTMAP_FORMAT_FUNCTIONS_TESTS_H
 
 #include <algorithm>
+#include <flat_map>
 #include <format>
 #include <map>
 #include <unordered_map>
@@ -442,6 +443,9 @@ void test_int(TestFunction check, ExceptionTest check_exception, auto&& input) {
 template <class CharT, class TestFunction, class ExceptionTest>
 void test_int(TestFunction check, ExceptionTest check_exception) {
   test_int<CharT>(check, check_exception, std::map<int, int>{{1, -1}, {42, -42}, {-42, 42}});
+#if TEST_STD_VER >= 23
+  test_int<CharT>(check, check_exception, std::flat_map<int, int>{{1, -1}, {42, -42}, {-42, 42}});
+#endif
 }
 
 //