better error message when overrider cannot be matched to method

Author: jll63

test/compile_fail_override_method_not_found.cpp

@@ -0,0 +1,22 @@
+// Copyright (c) 2018-2025 Jean-Louis Leroy
+// Distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/openmethod.hpp>
+
+using boost::openmethod::virtual_;
+
+struct Animal {};
+struct Dog : Animal {};
+
+// Deliberately omit BOOST_OPENMETHOD(speak, ...) to trigger the static_assert.
+
+BOOST_OPENMETHOD_CLASSES(Animal, Dog);
+
+BOOST_OPENMETHOD_OVERRIDE(speak, (virtual_<Dog&>), void) {
+}
+
+int main() {
+    return 0;
+}