optional: use #if instead of #ifndef, fixes #3859

Author: Théo Delrieu

include/nlohmann/detail/conversions/from_json.hpp

@@ -48,7 +48,7 @@ inline void from_json(const BasicJsonType& j, typename std::nullptr_t& n)
 }
 
 #ifdef JSON_HAS_CPP_17
-#ifndef JSON_USE_IMPLICIT_CONVERSIONS
+#if !JSON_USE_IMPLICIT_CONVERSIONS
 template<typename BasicJsonType, typename T>
 void from_json(const BasicJsonType& j, std::optional<T>& opt)
 {
@@ -297,13 +297,13 @@ void())
 
 template < typename BasicJsonType, typename T, std::size_t... Idx >
 std::array<T, sizeof...(Idx)> from_json_inplace_array_impl(BasicJsonType&& j,
-        identity_tag<std::array<T, sizeof...(Idx)>> /*unused*/, index_sequence<Idx...> /*unused*/)
+                     identity_tag<std::array<T, sizeof...(Idx) >> /*unused*/, index_sequence<Idx...> /*unused*/)
 {
     return { { std::forward<BasicJsonType>(j).at(Idx).template get<T>()... } };
 }
 
 template < typename BasicJsonType, typename T, std::size_t N >
-auto from_json(BasicJsonType&& j, identity_tag<std::array<T, N>> tag)
+auto from_json(BasicJsonType&& j, identity_tag<std::array<T, N >> tag)
 -> decltype(from_json_inplace_array_impl(std::forward<BasicJsonType>(j), tag, make_index_sequence<N> {}))
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
@@ -402,7 +402,7 @@ std::tuple<Args...> from_json_tuple_impl_base(BasicJsonType&& j, index_sequence<
 }
 
 template < typename BasicJsonType, class A1, class A2 >
-std::pair<A1, A2> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::pair<A1, A2>> /*unused*/, priority_tag<0> /*unused*/)
+std::pair<A1, A2> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::pair<A1, A2 >> /*unused*/, priority_tag<0> /*unused*/)
 {
     return {std::forward<BasicJsonType>(j).at(0).template get<A1>(),
             std::forward<BasicJsonType>(j).at(1).template get<A2>()};
@@ -411,11 +411,11 @@ std::pair<A1, A2> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::pair
 template<typename BasicJsonType, typename A1, typename A2>
 inline void from_json_tuple_impl(BasicJsonType&& j, std::pair<A1, A2>& p, priority_tag<1> /*unused*/)
 {
-    p = from_json_tuple_impl(std::forward<BasicJsonType>(j), identity_tag<std::pair<A1, A2>> {}, priority_tag<0> {});
+    p = from_json_tuple_impl(std::forward<BasicJsonType>(j), identity_tag<std::pair<A1, A2 >> {}, priority_tag<0> {});
 }
 
 template<typename BasicJsonType, typename... Args>
-std::tuple<Args...> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::tuple<Args...>> /*unused*/, priority_tag<2> /*unused*/)
+std::tuple<Args...> from_json_tuple_impl(BasicJsonType&& j, identity_tag<std::tuple<Args... >> /*unused*/, priority_tag<2> /*unused*/)
 {
     return from_json_tuple_impl_base<BasicJsonType, Args...>(std::forward<BasicJsonType>(j), index_sequence_for<Args...> {});
 }
@@ -493,7 +493,7 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)
 struct from_json_fn
 {
     template<typename BasicJsonType, typename T>
-    auto operator()(const BasicJsonType& j, T&& val) const
+    auto operator()(const BasicJsonType & j, T&& val) const
     noexcept(noexcept(from_json(j, std::forward<T>(val))))
     -> decltype(from_json(j, std::forward<T>(val)))
     {