Add invoke_obj_test

test/Jamfile

@@ -30,3 +30,4 @@ run shared_lock_test.cpp ;
 run shared_lock_test.cpp : : : <exception-handling>off : shared_lock_test_nx ;
 
 run invoke_fn_test.cpp ;
+run invoke_obj_test.cpp ;

test/invoke_obj_test.cpp

@@ -0,0 +1,57 @@
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/compat/invoke.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+struct F
+{
+    int operator()()
+    {
+        return -1;
+    }
+
+    int operator()( int x1 ) noexcept
+    {
+        return x1;
+    }
+
+    int operator()( int x1, int x2 ) const
+    {
+        return 10*x1+x2;
+    }
+
+    int operator()( int x1, int x2, int x3 ) const noexcept
+    {
+        return 100*x1 + 10*x2 + x3;
+    }
+};
+
+int main()
+{
+    {
+        BOOST_TEST_EQ( boost::compat::invoke( F() ), -1 );
+        BOOST_TEST_EQ( boost::compat::invoke( F(), 1 ), 1 );
+        BOOST_TEST_EQ( boost::compat::invoke( F(), 1, 2 ), 12 );
+        BOOST_TEST_EQ( boost::compat::invoke( F(), 1, 2, 3 ), 123 );
+    }
+
+    {
+        F f;
+
+        BOOST_TEST_EQ( boost::compat::invoke( f ), -1 );
+        BOOST_TEST_EQ( boost::compat::invoke( f, 1 ), 1 );
+        BOOST_TEST_EQ( boost::compat::invoke( f, 1, 2 ), 12 );
+        BOOST_TEST_EQ( boost::compat::invoke( f, 1, 2, 3 ), 123 );
+    }
+
+    {
+        F const f = {};
+
+        BOOST_TEST_EQ( boost::compat::invoke( f, 1, 2 ), 12 );
+        BOOST_TEST_EQ( boost::compat::invoke( f, 1, 2, 3 ), 123 );
+    }
+
+    return boost::report_errors();
+}