qml: deprecate top-level components

Print a deprecation warning during the IR compilation in the
qqmltypecompiler.cpp when a top-level capital-c-Component is found.
Also fix all the tests in tst_qqmllanguage that use a top level
component (either by wrapping those Components into Items or by removing
the explicit redundant Component-wrapping). This implies also fixing
the line numbers for Components in tests that got wrapped into an Item.

[ChangeLog][QtQml][QQmlComponent] QQmlComponents in qml document roots
or in inline component roots are deprecated. Types defined in qml
documents or in inline components are automatically wrapped into
QQmlComponents when needed: those types really should not be inside a
Component{}.

Fixes: QTBUG-106547
Change-Id: I00630b879f52f681c98a1d4b804e3505f175b9d6
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmllanguage/data/EvilComponentType.qml b/tests/auto/qml/qqmllanguage/data/EvilComponentType.qml
new file mode 100644
index 0000000000..04a8503c85
--- /dev/null
+++ b/tests/auto/qml/qqmllanguage/data/EvilComponentType.qml
@@ -0,0 +1,6 @@
+import QtQuick 2.15
+
+Component {
+    id: trulyEvil
+    Item {}
+}