fix: try adding & everywhere

Author: henryiii

include/pybind11/pybind11.h

@@ -1967,26 +1967,26 @@ struct iterator_state {
 
 // Note: these helpers take the iterator by non-const reference because some
 // iterators in the wild can't be dereferenced when const. C++ needs the extra parens in decltype.
-template <typename Iterator, typename ResultType = decltype((*std::declval<Iterator>()))>
+template <typename Iterator, typename ResultType = decltype((*std::declval<Iterator &>()))>
 struct iterator_access {
-    using result_type = decltype((*std::declval<Iterator>()));
+    using result_type = decltype((*std::declval<Iterator &>()));
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     result_type operator()(Iterator &it) const {
         return *it;
     }
 };
 
-template <typename Iterator, typename ResultType = decltype(((*std::declval<Iterator>()).first)) >
+template <typename Iterator, typename ResultType = decltype(((*std::declval<Iterator &>()).first)) >
 struct iterator_key_access {
-    using result_type = decltype(((*std::declval<Iterator>()).first));
+    using result_type = decltype(((*std::declval<Iterator &>()).first));
     result_type operator()(Iterator &it) const {
         return (*it).first;
     }
 };
 
-template <typename Iterator, typename ResultType = decltype(((*std::declval<Iterator>()).second))>
+template <typename Iterator, typename ResultType = decltype(((*std::declval<Iterator &>()).second))>
 struct iterator_value_access {
-    using result_type = decltype(((*std::declval<Iterator>()).second));
+    using result_type = decltype(((*std::declval<Iterator &>()).second));
     result_type operator()(Iterator &it) const {
         return (*it).second;
     }