Cleanup tst_qdatastream

Make NColorRoles constexpr and use static_assert() to verify that it
has a proper size.

Pick-to: 6.9 6.8
Change-Id: I40351e4815e248fe8cc07e906099172d5be531d0
Reviewed-by: Thiago Macieira <[email protected]>

Author: isolovev

tests/auto/corelib/serialization/qdatastream/tst_qdatastream.cpp

@@ -276,7 +276,7 @@ private slots:
     QString m_previousCurrent;
 };
 
-static int NColorRoles[] = {
+static constexpr int NColorRoles[] = {
     QPalette::NoRole,              // No Version
     QPalette::NoRole,              // Qt_1_0
     QPalette::HighlightedText + 1, // Qt_2_0
@@ -300,9 +300,11 @@ static int NColorRoles[] = {
     QPalette::PlaceholderText + 1, // Qt_6_0
     QPalette::Accent + 1,     // Qt_6_6
     QPalette::Accent + 1,     // Qt_6_7
-    0                              // add the correct value for Qt_5_14 here later
 };
 
+// +1, because we start from "No Version"
+static_assert(std::size(NColorRoles) == QDataStream::Qt_DefaultCompiledVersion + 1);
+
 // Testing get/set functions
 void tst_QDataStream::getSetCheck()
 {