qml/parser: Implement nullish coalescing

Implements the '??' operator as specified in https://github.com/tc39/proposal-nullish-coalescing.

Also adds a few tests.

Task-number: QTBUG-77926
Change-Id: I3993450c192d11bf1ade0662d945c1553b4c6976
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 8 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmllanguage/data/nullishCoalescing_LHS_Or.qml b/tests/auto/qml/qqmllanguage/data/nullishCoalescing_LHS_Or.qml
new file mode 100644
index 0000000000..8864524d0d
--- /dev/null
+++ b/tests/auto/qml/qqmllanguage/data/nullishCoalescing_LHS_Or.qml
@@ -0,0 +1,8 @@
+import QtQuick 2.0
+
+Component {
+    Component.onCompleted: {
+        // Should cause an error since having either || or && on any side of the coalescing operator is banned by the specification
+        var bad_lhs_or = 3 || 4 ?? 0;
+    }
+}