From a2f3b703acd8ac776a12e7409b505aee46378462 Mon Sep 17 00:00:00 2001
From: Fredrik Sandhei <fredrik.sandhei@gmail.com>
Date: Thu, 29 Feb 2024 22:38:04 +0100
Subject: [PATCH] Lock json_compatible_type behind ifdef for now

---
 include/nlohmann/detail/meta/type_traits.hpp | 5 +++++
 single_include/nlohmann/json.hpp             | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/include/nlohmann/detail/meta/type_traits.hpp b/include/nlohmann/detail/meta/type_traits.hpp
index 8747a85e35..d539c5a4fa 100644
--- a/include/nlohmann/detail/meta/type_traits.hpp
+++ b/include/nlohmann/detail/meta/type_traits.hpp
@@ -684,11 +684,16 @@ inline constexpr bool value_in_range_of(T val)
 template<bool Value>
 using bool_constant = std::integral_constant<bool, Value>;
 
+// Locking the definition of json_compatible_type behind
+// JSON_HAS_THREE_WAY_COMPARISON because it seems difficult to
+// make use of this type trait well with friend functions. Fails on SFINAE.
+#if JSON_HAS_THREE_WAY_COMPARISON
 template <typename T, typename BasicJsonType, typename U = uncvref_t<T>>
 struct json_compatible_type
 {
     static constexpr auto value = !is_basic_json<U>::value && is_compatible_type<BasicJsonType, U>::value;
 };
+#endif
 
 ///////////////////////////////////////////////////////////////////////////////
 // is_c_string
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 44c7f5f3ff..80a34a7562 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -4091,11 +4091,16 @@ inline constexpr bool value_in_range_of(T val)
 template<bool Value>
 using bool_constant = std::integral_constant<bool, Value>;
 
+// Locking the definition of json_compatible_type behind
+// JSON_HAS_THREE_WAY_COMPARISON because it seems difficult to
+// make use of this type trait well with friend functions. Fails on SFINAE.
+#if JSON_HAS_THREE_WAY_COMPARISON
 template <typename T, typename BasicJsonType, typename U = uncvref_t<T>>
 struct json_compatible_type
 {
     static constexpr auto value = !is_basic_json<U>::value && is_compatible_type<BasicJsonType, U>::value;
 };
+#endif
 
 ///////////////////////////////////////////////////////////////////////////////
 // is_c_string