Replace add() with add<T>() (add(T) is still supported)

src/ArduinoJson/Array/JsonArray.hpp

@@ -41,10 +41,21 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
     return JsonArrayConst(data_, resources_);
   }
 
+  // Appends a new (empty) element to the array.
+  // Returns a reference to the new element.
+  // https://arduinojson.org/v6/api/jsonarray/add/
+  template <typename T>
+  typename detail::enable_if<!detail::is_same<T, JsonVariant>::value, T>::type
+  add() const {
+    return add<JsonVariant>().to<T>();
+  }
+
   // Appends a new (null) element to the array.
   // Returns a reference to the new element.
   // https://arduinojson.org/v6/api/jsonarray/add/
-  JsonVariant add() const {
+  template <typename T>
+  typename detail::enable_if<detail::is_same<T, JsonVariant>::value, T>::type
+  add() const {
     return JsonVariant(detail::ArrayData::addElement(data_, resources_),
                        resources_);
   }
@@ -53,14 +64,14 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   // https://arduinojson.org/v6/api/jsonarray/add/
   template <typename T>
   FORCE_INLINE bool add(const T& value) const {
-    return add().set(value);
+    return add<JsonVariant>().set(value);
   }
 
   // Appends a value to the array.
   // https://arduinojson.org/v6/api/jsonarray/add/
   template <typename T>
   FORCE_INLINE bool add(T* value) const {
-    return add().set(value);
+    return add<JsonVariant>().set(value);
   }
 
   // Returns an iterator to the first element of the array.
@@ -126,7 +137,7 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   // Creates an array and appends it to the array.
   // https://arduinojson.org/v6/api/jsonarray/createnestedarray/
   FORCE_INLINE JsonArray createNestedArray() const {
-    return add().to<JsonArray>();
+    return add<JsonArray>();
   }
 
   operator JsonVariantConst() const {

src/ArduinoJson/Array/JsonArrayImpl.hpp

@@ -10,7 +10,7 @@
 ARDUINOJSON_BEGIN_PUBLIC_NAMESPACE
 
 inline JsonObject JsonArray::createNestedObject() const {
-  return add().to<JsonObject>();
+  return add<JsonObject>();
 }
 
 ARDUINOJSON_END_PUBLIC_NAMESPACE
@@ -19,12 +19,12 @@ ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
 template <typename TDerived>
 inline JsonArray VariantRefBase<TDerived>::createNestedArray() const {
-  return add().template to<JsonArray>();
+  return add<JsonArray>();
 }
 
 template <typename TDerived>
 inline JsonObject VariantRefBase<TDerived>::createNestedObject() const {
-  return add().template to<JsonObject>();
+  return add<JsonObject>();
 }
 
 template <typename TDerived>

src/ArduinoJson/Array/Utilities.hpp

@@ -34,7 +34,7 @@ inline typename detail::enable_if<
 copyArray(const T* src, size_t len, const TDestination& dst) {
   bool ok = true;
   for (size_t i = 0; i < len; i++) {
-    ok &= copyArray(src[i], dst.add());
+    ok &= copyArray(src[i], dst.template add<JsonVariant>());
   }
   return ok;
 }

src/ArduinoJson/Document/JsonDocument.hpp

@@ -161,7 +161,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   // Creates an array and appends it to the root array.
   // https://arduinojson.org/v6/api/jsondocument/createnestedarray/
   JsonArray createNestedArray() {
-    return add().to<JsonArray>();
+    return add<JsonArray>();
   }
 
   // Creates an array and adds it to the root object.
@@ -181,7 +181,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   // Creates an object and appends it to the root array.
   // https://arduinojson.org/v6/api/jsondocument/createnestedobject/
   JsonObject createNestedObject() {
-    return add().to<JsonObject>();
+    return add<JsonObject>();
   }
 
   // Creates an object and adds it to the root object.
@@ -264,10 +264,21 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
     return JsonVariantConst(data_.getElement(index, &resources_), &resources_);
   }
 
+  // Appends a new (empty) element to the root array.
+  // Returns a reference to the new element.
+  // https://arduinojson.org/v6/api/jsondocument/add/
+  template <typename T>
+  typename detail::enable_if<!detail::is_same<T, JsonVariant>::value, T>::type
+  add() {
+    return add<JsonVariant>().to<T>();
+  }
+
   // Appends a new (null) element to the root array.
   // Returns a reference to the new element.
   // https://arduinojson.org/v6/api/jsondocument/add/
-  FORCE_INLINE JsonVariant add() {
+  template <typename T>
+  typename detail::enable_if<detail::is_same<T, JsonVariant>::value, T>::type
+  add() {
     return JsonVariant(data_.addElement(&resources_), &resources_);
   }
 
@@ -275,14 +286,14 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   // https://arduinojson.org/v6/api/jsondocument/add/
   template <typename TValue>
   FORCE_INLINE bool add(const TValue& value) {
-    return add().set(value);
+    return add<JsonVariant>().set(value);
   }
 
   // Appends a value to the root array.
   // https://arduinojson.org/v6/api/jsondocument/add/
   template <typename TChar>
   FORCE_INLINE bool add(TChar* value) {
-    return add().set(value);
+    return add<JsonVariant>().set(value);
   }
 
   // Removes an element of the root array.

src/ArduinoJson/Variant/JsonVariant.hpp

@@ -87,7 +87,9 @@ ARDUINOJSON_END_PUBLIC_NAMESPACE
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
 template <typename TDerived>
-inline JsonVariant VariantRefBase<TDerived>::add() const {
+template <typename T>
+inline typename enable_if<is_same<T, JsonVariant>::value, T>::type
+VariantRefBase<TDerived>::add() const {
   return JsonVariant(
       detail::VariantData::addElement(getOrCreateData(), getResourceManager()),
       getResourceManager());

src/ArduinoJson/Variant/VariantRefBase.hpp

@@ -136,23 +136,32 @@ class VariantRefBase : public VariantTag {
     return VariantData::nesting(getData(), getResourceManager());
   }
 
+  // Appends a new (empty) element to the array.
+  // Returns a reference to the new element.
+  // https://arduinojson.org/v6/api/jsonvariant/add/
+  template <typename T>
+  typename enable_if<!is_same<T, JsonVariant>::value, T>::type add() const {
+    return add<JsonVariant>().template to<T>();
+  }
+
   // Appends a new (null) element to the array.
   // Returns a reference to the new element.
   // https://arduinojson.org/v6/api/jsonvariant/add/
-  FORCE_INLINE JsonVariant add() const;
+  template <typename T>
+  typename enable_if<is_same<T, JsonVariant>::value, T>::type add() const;
 
   // Appends a value to the array.
   // https://arduinojson.org/v6/api/jsonvariant/add/
   template <typename T>
   FORCE_INLINE bool add(const T& value) const {
-    return add().set(value);
+    return add<JsonVariant>().set(value);
   }
 
   // Appends a value to the array.
   // https://arduinojson.org/v6/api/jsonvariant/add/
   template <typename T>
   FORCE_INLINE bool add(T* value) const {
-    return add().set(value);
+    return add<JsonVariant>().set(value);
   }
 
   // Removes an element of the array.
@@ -261,7 +270,6 @@ class VariantRefBase : public VariantTag {
     return VariantAttorney::getOrCreateData(derived());
   }
 
- private:
   FORCE_INLINE ArduinoJson::JsonVariant getVariant() const;
 
   FORCE_INLINE ArduinoJson::JsonVariantConst getVariantConst() const {