Use `enable_if_t` instead of `enable_if`

src/ArduinoJson/Variant/VariantData.hpp

@@ -416,14 +416,14 @@ class VariantData {
   }
 
   template <typename T>
-  typename enable_if<sizeof(T) == 4>::type setFloat(T value, ResourceManager*) {
+  enable_if_t<sizeof(T) == 4> setFloat(T value, ResourceManager*) {
     ARDUINOJSON_ASSERT(type_ == VALUE_IS_NULL);  // must call clear() first
     type_ = VALUE_IS_FLOAT;
     content_.asFloat = value;
   }
 
   template <typename T>
-  typename enable_if<sizeof(T) == 8>::type setFloat(T value, ResourceManager*);
+  enable_if_t<sizeof(T) == 8> setFloat(T value, ResourceManager*);
 
   template <typename T>
   enable_if_t<is_signed<T>::value> setInteger(T value,

src/ArduinoJson/Variant/VariantImpl.hpp

@@ -65,8 +65,8 @@ inline const VariantExtension* VariantData::getExtension(
 #endif
 
 template <typename T>
-typename enable_if<sizeof(T) == 8>::type VariantData::setFloat(
-    T value, ResourceManager* resources) {
+enable_if_t<sizeof(T) == 8> VariantData::setFloat(T value,
+                                                  ResourceManager* resources) {
   ARDUINOJSON_ASSERT(type_ == VALUE_IS_NULL);  // must call clear() first
   (void)resources;                             // silence warning