refactor: make Variant constructor explicit

ChangeLog

@@ -252,6 +252,7 @@ v2.x
     what before had to be obtained through `PollData::getAbsoluteTimeout()` call.
   - `PollData::getRelativeTimeout()` return type was changed to `std::chrono::microseconds`.
   - `IConnection::processPendingRequest()` was renamed to `IConnection::processPendingEvent()`.
+  - `Variant` constructor is now explicit.
 - Systemd of at least v238 is required to compile sdbus-c++
 - A proper fix for timeout handling
 - Fix for external event loops in which the event loop thread ID was not correctly initialized (now fixed and simplified by not needing the thread ID anymore)

include/sdbus-c++/Types.h

@@ -56,7 +56,7 @@ namespace sdbus {
         Variant();
 
         template <typename _ValueType>
-        /*explicit*/ Variant(const _ValueType& value) // TODO: Mark explicit in new major version so we don't break client code within v1
+        explicit Variant(const _ValueType& value)
             : Variant()
         {
             msg_.openVariant(signature_of<_ValueType>::str());

tests/integrationtests/DBusSignalsTests.cpp

@@ -103,7 +103,6 @@ TYPED_TEST(SdbusTestObject, EmitsSignalWithVariantSuccesfully)
 {
     double d = 3.14;
     this->m_adaptor->emitSignalWithVariant(sdbus::Variant{d});
-    this->m_adaptor->emitSignalWithVariant(d);
 
     ASSERT_TRUE(waitUntil(this->m_proxy->m_gotSignalWithVariant));
     ASSERT_THAT(this->m_proxy->m_variantFromSignal, DoubleEq(d));