From a4883790100b0da6f777ec154a525389f776a3c7 Mon Sep 17 00:00:00 2001
From: Slava Andrejev <vyac.andrejev@gmail.com>
Date: Sun, 19 Dec 2021 22:25:46 -0800
Subject: Add missing perfect forwarding in bound_mem_functor::operator()

This is a missed addition to the commit that allowed rvalue references
in slot parameters.
---
 sigc++/functors/mem_fun.h |  4 +++-
 tests/test_rvalue_ref.cc  | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/sigc++/functors/mem_fun.h b/sigc++/functors/mem_fun.h
index 65563a3..e3327fb 100644
--- a/sigc++/functors/mem_fun.h
+++ b/sigc++/functors/mem_fun.h
@@ -149,7 +149,9 @@ public:
    */
   decltype(auto) operator()(type_trait_take_t<T_arg>... a) const
   {
-    return std::invoke(this->func_ptr_, obj_.invoke(), a...);
+    return std::invoke(
+      this->func_ptr_, obj_.invoke(),
+      std::forward<type_trait_take_t<T_arg>>(a)...);
   }
 
   // protected:
diff --git a/tests/test_rvalue_ref.cc b/tests/test_rvalue_ref.cc
index 54b04f3..ec81d39 100644
--- a/tests/test_rvalue_ref.cc
+++ b/tests/test_rvalue_ref.cc
@@ -16,6 +16,12 @@ struct foo
   void operator()(MoveableStruct&& /* x */) { result_stream << "foo(MoveableStruct&&)"; }
 };
 
+struct A
+{
+  void foo(MoveableStruct &&) { result_stream << "A::foo(MoveableStruct&&)"; }
+};
+
+
 } // end anonymous namespace
 
 void
@@ -40,6 +46,17 @@ test_slot()
   util->check_result(result_stream, "foo(MoveableStruct&&)");
 }
 
+void
+test_mem_fun()
+{
+  sigc::slot<void(MoveableStruct &&)> slot;
+  A a;
+  slot = sigc::mem_fun(a, &A::foo);
+  MoveableStruct x;
+  slot(std::move(x));
+  util->check_result(result_stream, "A::foo(MoveableStruct&&)");
+}
+
 int
 main(int argc, char* argv[])
 {
@@ -49,6 +66,7 @@ main(int argc, char* argv[])
 
   test_signal();
   test_slot();
+  test_mem_fun();
 
   return util->get_result_and_delete_instance() ? EXIT_SUCCESS : EXIT_FAILURE;
 } // end main()
-- 
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