🔨 fixed GCC warnings in #663

#663 (comment)

src/json.hpp

@@ -6872,6 +6872,11 @@ class json_ref
  is_rvalue(true)
  {}
 
+ // class should be movable only
+ json_ref(json_ref&&) = default;
+ json_ref(const json_ref&) = delete;
+ json_ref& operator=(const json_ref&) = delete;
+
  value_type moved_or_copied() const
  {
  if (is_rvalue)
@@ -6895,7 +6900,7 @@ class json_ref
  }
 
  private:
- mutable value_type owned_value;
+ mutable value_type owned_value = nullptr;
  value_type* value_ref = nullptr;
  const bool is_rvalue;
 };
@@ -9826,6 +9831,7 @@ class basic_json
  */
  template < typename ValueType, typename std::enable_if <
  not std::is_pointer<ValueType>::value and
+ not std::is_same<ValueType, detail::json_ref<basic_json>>::value and
  not std::is_same<ValueType, typename string_t::value_type>::value
 #ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
  and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value