Remove usages of deprecated APIs of corelib

- Replaced the usages of deprecated APIs of corelib by corresponding
  alternatives in the library code and documentation.

- Modified the tests to make them build when deprecated APIs disabled:
    * Made the the parts of the tests testing the deprecated APIs to
      be compiled conditionally, only when the corresponding methods are
      enabled.
    * If the test-case tests only the deprecated API, but not the
      corresponding replacement, added tests for the replacement.

Task-number: QTBUG-76491
Task-number: QTBUG-76539
Task-number: QTBUG-76541
Change-Id: I62ed4a5b530a965ec3f6502c6480808f938921aa
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/auto/corelib/tools/collections/tst_collections.cpp b/tests/auto/corelib/tools/collections/tst_collections.cpp
index e2ce5cb9f9..e79a4dba29 100644
--- a/tests/auto/corelib/tools/collections/tst_collections.cpp
+++ b/tests/auto/corelib/tools/collections/tst_collections.cpp
@@ -1994,13 +1994,17 @@ void tst_Collections::qstring()
     QString nonNull = "";
     QVERIFY(null.left(10).isNull());
     QVERIFY(null.mid(0).isNull());
+    QVERIFY(null.isNull());
+    QVERIFY(!nonNull.isNull());
 
+#if QT_DEPRECATED_SINCE(5, 9)
     QVERIFY(null == QString::null);
     QVERIFY(QString::null  == null);
     QVERIFY(nonNull != QString::null);
     QVERIFY(QString::null != nonNull);
     QVERIFY(null == nonNull);
     QVERIFY(QString::null == QString::null);
+#endif
 
     QString fill = "123";
     fill.fill('a');