Use the same internal data type for conversion function

src/base/rss/rss_autodownloadrule.cpp

@@ -64,7 +64,7 @@ namespace
 
     QJsonValue triStateBoolToJsonValue(const TriStateBool &triStateBool)
     {
-        switch (static_cast<int>(triStateBool)) {
+        switch (static_cast<signed char>(triStateBool)) {
         case 0:  return false;
         case 1:  return true;
         default: return {};
@@ -82,7 +82,7 @@ namespace
 
     int triStateBoolToAddPausedLegacy(const TriStateBool &triStateBool)
     {
-        switch (static_cast<int>(triStateBool)) {
+        switch (static_cast<signed char>(triStateBool)) {
         case 0:  return 2; // never
         case 1:  return 1; // always
         default: return 0; // default

src/base/tristatebool.h

@@ -43,13 +43,13 @@ public:
         *this = boolean ? True : False;
     }
 
-    explicit constexpr operator int() const
+    TriStateBool &operator=(const TriStateBool &other) = default;  // TODO: add constexpr when using C++17
+
+    explicit constexpr operator signed char() const
     {
         return m_value;
     }
 
-    TriStateBool &operator=(const TriStateBool &other) = default;  // add constexpr when using C++17
-
     constexpr friend bool operator==(const TriStateBool &left, const TriStateBool &right)
     {
         return (left.m_value == right.m_value);