From 5f956f992048eaa770dc28c65ec0e441df5bc222 Mon Sep 17 00:00:00 2001
From: user202729 <25191436+user202729@users.noreply.github.com>
Date: Sun, 15 Mar 2026 12:09:51 +0700
Subject: [PATCH] Provide reasonable default definition for is_contiguous

---
 include/fmt/base.h | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/fmt/base.h b/include/fmt/base.h
index 49868b6d751a..e9515606d587 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -587,8 +587,21 @@ using string_view = basic_string_view<char>;
 template <typename T> class basic_appender;
 using appender = basic_appender<char>;
 
+namespace detail {
+
 // Checks whether T is a container with contiguous storage.
-template <typename T> struct is_contiguous : std::false_type {};
+template <typename T>
+auto is_contiguous_helper(int)
+    -> decltype(std::declval<T&>().data(), std::declval<T&>().size(),
+                std::declval<T&>().resize(size_t{}),
+                std::declval<T&>()[size_t{}], std::true_type{});
+
+template <typename T> auto is_contiguous_helper(...) -> std::false_type;
+
+}  // namespace detail
+
+template <typename T>
+struct is_contiguous : decltype(detail::is_contiguous_helper<T>(0)) {};
 
 class context;
 template <typename OutputIt, typename Char> class generic_context;