From 67fc40922dff33fd434762e77f5279919e70fbf0 Mon Sep 17 00:00:00 2001
From: Antony Polukhin <antoshkka@gmail.com>
Date: Tue, 6 Oct 2026 13:16:56 +0300
Subject: [PATCH] Fixes for hash_value()

---
 include/boost/pfr/detail/detectors.hpp | 2 +-
 test/core/run/functions_for.cpp        | 1 +
 test/core/run/ops.cpp                  | 9 +++++++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/boost/pfr/detail/detectors.hpp b/include/boost/pfr/detail/detectors.hpp
index 6b8972ec..5774c2d0 100644
--- a/include/boost/pfr/detail/detectors.hpp
+++ b/include/boost/pfr/detail/detectors.hpp
@@ -54,7 +54,7 @@ namespace boost { namespace pfr { namespace detail {
 
     template <class S> auto hash_detector_msvc_helper(long) -> decltype(std::hash<S>{}(std::declval<S>()));
     template <class S> can_not_apply hash_detector_msvc_helper(int);
-    template <class T1, class T2> using hash_detector = decltype(hash_detector_msvc_helper<T1,T2>(1L));
+    template <class T1, class> using hash_detector = decltype(hash_detector_msvc_helper<T1>(1L));
 
 
     template <class S, class T> auto ostreamable_detector_msvc_helper(long) -> decltype(std::declval<S>() << std::declval<T>());
diff --git a/test/core/run/functions_for.cpp b/test/core/run/functions_for.cpp
index 49555237..8a53d591 100644
--- a/test/core/run/functions_for.cpp
+++ b/test/core/run/functions_for.cpp
@@ -56,6 +56,7 @@ void test_some_comparable_struct() {
     ss >> s4;
     std::cout << s4 << std::endl;
     BOOST_TEST_EQ(s1, s4);
+    BOOST_TEST_EQ(hash_value(s1), hash_value(s4));
     int i = 1, j = 2;
     BOOST_TEST_NE(i, j);
 }
diff --git a/test/core/run/ops.cpp b/test/core/run/ops.cpp
index 662cb840..ef6c4b71 100644
--- a/test/core/run/ops.cpp
+++ b/test/core/run/ops.cpp
@@ -66,6 +66,7 @@ void test_comparable_struct() {
 
 void test_empty_struct() {
     struct empty {};
+    BOOST_TEST_EQ(boost::pfr::hash_value(empty{}), boost::pfr::hash_value(empty{}));
     std::cout << boost::pfr::io(empty{});
     BOOST_TEST(boost::pfr::eq(empty{}, empty{}));
 }
@@ -85,11 +86,19 @@ struct comparable_struct {
 
 int main() {
     test_comparable_struct<foo::comparable_struct>();
+    BOOST_TEST_EQ(
+        boost::pfr::hash_value(foo::comparable_struct{}),
+        boost::pfr::hash_value(foo::comparable_struct{})
+    );
 
     struct local_comparable_struct {
         int i; short s; bool bl; int a,b,c,d,e,f;
     };
     test_comparable_struct<local_comparable_struct>();
+    BOOST_TEST_EQ(
+        boost::pfr::hash_value(local_comparable_struct{}),
+        boost::pfr::hash_value(local_comparable_struct{})
+    );
 
     struct local_comparable_struct_with_union {
         int i; short s; bool bl; int a,b,c,d,e; test_union u;