From ac9677323057b1ca31d157294b15ad0a74ae2b79 Mon Sep 17 00:00:00 2001
From: Matthias Moulin <matthias.moulin@gmail.com>
Date: Tue, 18 Jun 2024 20:27:40 +0200
Subject: [PATCH] Added missing std::declval for non-default-constructible
 types (#4024)

---
 include/fmt/ranges.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index 66329aae..12dc8fa8 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -619,11 +619,12 @@ struct formatter<
                     range_format::debug_string>> {
  private:
   using range_type = detail::maybe_const_range<R>;
-  using string_type = conditional_t<
-      std::is_constructible<detail::std_string_view<Char>,
-                            decltype(detail::range_begin(R())),
-                            decltype(detail::range_end(R()))>::value,
-      detail::std_string_view<Char>, std::basic_string<Char>>;
+  using string_type =
+      conditional_t<std::is_constructible<
+                        detail::std_string_view<Char>,
+                        decltype(detail::range_begin(std::declval<R>())),
+                        decltype(detail::range_end(std::declval<R>()))>::value,
+                    detail::std_string_view<Char>, std::basic_string<Char>>;
 
   formatter<string_type, Char> underlying_;