From 5e9dfa354c5cc6bc8c165cdc1ede174330a4fe68 Mon Sep 17 00:00:00 2001
From: Shawn Zhong <github@shawnzhong.com>
Date: Tue, 7 Feb 2023 03:24:39 -0600
Subject: [PATCH] Make const-correct

---
 include/fmt/ranges.h | 4 ++--
 test/ranges-test.cc  | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index 8e24aba2..fae425f9 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -678,9 +678,9 @@ struct formatter<T, Char,
                  enable_if_t<detail::is_container_adaptor_like<T>::value>>
     : formatter<typename T::container_type, Char> {
   template <typename FormatContext>
-  auto format(T& t, FormatContext& ctx) const -> decltype(ctx.out()) {
+  auto format(const T& t, FormatContext& ctx) const -> decltype(ctx.out()) {
     struct getter : T {
-      static auto get(T& t) -> typename T::container_type& {
+      static auto get(const T& t) -> const typename T::container_type& {
         return t.*(&getter::c);  // Access c through the derived class.
       }
     };
diff --git a/test/ranges-test.cc b/test/ranges-test.cc
index 0ce88ba4..e1d384d7 100644
--- a/test/ranges-test.cc
+++ b/test/ranges-test.cc
@@ -424,6 +424,7 @@ TEST(ranges_test, container_adaptor) {
     s.push(1);
     s.push(2);
     EXPECT_EQ(fmt::format("{}", s), "[1, 2]");
+    EXPECT_EQ(fmt::format("{}", const_cast<const decltype(s)&>(s)), "[1, 2]");
   }
 
   {