From 1e8493196efa4e05baa22461ba61b636ab2e662b Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Sun, 1 Mar 2020 07:57:34 -0800
Subject: [PATCH] Make compile-time checks in format_to handle references

---
 include/fmt/core.h   | 2 +-
 include/fmt/format.h | 7 +++----
 test/format-test.cc  | 2 ++
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index f5eb7e3ae895..0e6422d9f1a9 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -1460,7 +1460,7 @@ make_args_checked(const S& format_str,
       all_true<(!std::is_base_of<view, remove_reference_t<Args>>::value ||
                 !std::is_reference<Args>::value)...>::value,
       "passing views as lvalues is disallowed");
-  check_format_string<remove_const_t<remove_reference_t<Args>>...>(format_str);
+  check_format_string<Args...>(format_str);
   return {args...};
 }
 
diff --git a/include/fmt/format.h b/include/fmt/format.h
index acd7d9dc0bad..5d36a68276b5 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2641,10 +2641,9 @@ FMT_CONSTEXPR bool do_check_format_string(basic_string_view<Char> s,
 template <typename... Args, typename S,
           enable_if_t<(is_compile_string<S>::value), int>>
 void check_format_string(S format_str) {
-  FMT_CONSTEXPR_DECL bool invalid_format =
-      internal::do_check_format_string<typename S::char_type,
-                                       internal::error_handler, Args...>(
-          to_string_view(format_str));
+  FMT_CONSTEXPR_DECL bool invalid_format = internal::do_check_format_string<
+      typename S::char_type, internal::error_handler,
+      remove_const_t<remove_reference_t<Args>>...>(to_string_view(format_str));
   (void)invalid_format;
 }
 
diff --git a/test/format-test.cc b/test/format-test.cc
index 8bce69be20d9..b17306300bab 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1859,6 +1859,8 @@ TEST(FormatTest, CustomFormatCompileTimeString) {
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), Answer()));
   Answer answer;
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), answer));
+  char buf[10] = {};
+  fmt::format_to(buf, FMT_STRING("{}"), answer);
   const Answer const_answer = Answer();
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), const_answer));
 }