Fix return type of StaticJsonDocument::operator=

CHANGELOG.md

@@ -15,6 +15,7 @@ HEAD
 * Fix `call of overloaded 'swap(BasicJsonDocument&, BasicJsonDocument&)' is ambiguous` (issue #1678)
 * Fix inconsistent pool size in `BasicJsonDocument`'s copy constructor
 * Support NUL in string values (issue #1646)
+* Fix return type of `StaticJsonDocument::operator=`
 
 v6.18.5 (2021-09-28)
 -------

src/ArduinoJson/Document/StaticJsonDocument.hpp

@@ -33,13 +33,13 @@ class StaticJsonDocument : public JsonDocument {
     set(src);
   }
 
-  StaticJsonDocument operator=(const StaticJsonDocument& src) {
+  StaticJsonDocument& operator=(const StaticJsonDocument& src) {
     set(src);
     return *this;
   }
 
   template <typename T>
-  StaticJsonDocument operator=(const T& src) {
+  StaticJsonDocument& operator=(const T& src) {
     set(src);
     return *this;
   }