From 9d5ad7e0cd599cb4bf6386a831f0f4918c7f2c8f Mon Sep 17 00:00:00 2001
From: Alexey Ochapov <a.ochapov@octaviangaming.com>
Date: Tue, 18 Aug 2020 19:57:31 +0300
Subject: [PATCH] add support for fallback_formatter in detail::write

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

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 7dbe90c2..a862309a 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1841,7 +1841,9 @@ OutputIt write(OutputIt out, const void* value) {
   return write_ptr<Char>(out, to_uintptr(value), nullptr);
 }
 
-template <typename Char, typename OutputIt, typename T>
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(
+              has_formatter<T, basic_format_context<OutputIt, Char>>::value)>
 auto write(OutputIt out, const T& value) -> typename std::enable_if<
     mapped_type_constant<T, basic_format_context<OutputIt, Char>>::value ==
         type::custom_type,
@@ -1850,6 +1852,17 @@ auto write(OutputIt out, const T& value) -> typename std::enable_if<
   return formatter<T>().format(value, ctx);
 }
 
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(has_fallback_formatter<
+                        T, basic_format_context<OutputIt, Char>>::value)>
+auto write(OutputIt out, const T& value) -> typename std::enable_if<
+    mapped_type_constant<T, basic_format_context<OutputIt, Char>>::value ==
+        type::custom_type,
+    OutputIt>::type {
+  basic_format_context<OutputIt, Char> ctx(out, {}, {});
+  return fallback_formatter<T>().format(value, ctx);
+}
+
 // An argument visitor that formats the argument and writes it via the output
 // iterator. It's a class and not a generic lambda for compatibility with C++11.
 template <typename OutputIt, typename Char> struct default_arg_formatter {