VariantAttorney: replace ResultOfGetData with a trailing return type

src/ArduinoJson/Variant/VariantAttorney.hpp

@@ -14,20 +14,6 @@ ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
 // Grants access to the internal variant API
 class VariantAttorney {
-  // Tells whether getData() returns a const pointer
-  template <typename TClient>
-  struct ResultOfGetData {
-   protected:  // <- to avoid GCC's "all member functions in class are private"
-    static int probe(const VariantData*);
-    static char probe(VariantData*);
-
-    static TClient& client;
-
-   public:
-    typedef typename conditional<sizeof(probe(client.getData())) == sizeof(int),
-                                 const VariantData*, VariantData*>::type type;
-  };
-
  public:
   template <typename TClient>
   FORCE_INLINE static ResourceManager* getResourceManager(TClient& client) {
@@ -35,8 +21,8 @@ class VariantAttorney {
   }
 
   template <typename TClient>
-  FORCE_INLINE static typename ResultOfGetData<TClient>::type getData(
-      TClient& client) {
+  FORCE_INLINE static auto getData(TClient& client)
+      -> decltype(client.getData()) {
     return client.getData();
   }