format std::reference_wrapper

fmtlib · Sep 16, 2024 · 8fac8c2 · 8fac8c2
1 parent 2a2f73f
commit 8fac8c2
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diff --git a/include/fmt/std.h b/include/fmt/std.h
@@ -17,6 +17,7 @@
 #  include <complex>
 #  include <cstdlib>
 #  include <exception>
+#  include <functional>
 #  include <memory>
 #  include <thread>
 #  include <type_traits>
@@ -700,3 +701,12 @@ template <typename T, typename Char> struct formatter<std::complex<T>, Char> {
 
 FMT_END_NAMESPACE
 #endif  // FMT_STD_H_
+
+namespace std {
+
+template <typename T>
+constexpr auto format_as(std::reference_wrapper<T> ref) -> T& {
+  return ref.get();
+}
+
+} // namespace std
diff --git a/test/std-test.cc b/test/std-test.cc
@@ -393,3 +393,8 @@ TEST(std_test, format_shared_ptr) {
   EXPECT_EQ(fmt::format("{}", fmt::ptr(sp.get())),
             fmt::format("{}", fmt::ptr(sp)));
 }
+
+TEST(std_test, format_reference_wrapper) {
+  int num = 35;
+  EXPECT_EQ("35", fmt::to_string(std::cref(num)));
+}