QmlCompiler: Add missing parentheses to in-place arithmetic operations

Fixes: QTBUG-104512
Change-Id: I3d592eeda5cefd9e9805b1811b37bebec5d6fc9c
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 7230508c3bf7d42fc2d262d29f9302ac46c3a4f0)

4 files changed, 42 insertions, 1 deletions

diff --git a/src/qmlcompiler/qqmljscodegenerator.cpp b/src/qmlcompiler/qqmljscodegenerator.cpp
index 24fbdfe140..d4402a0599 100644
--- a/src/qmlcompiler/qqmljscodegenerator.cpp
+++ b/src/qmlcompiler/qqmljscodegenerator.cpp
@@ -2324,7 +2324,7 @@ void QQmlJSCodeGenerator::generateInPlaceOperation(const QString &cppOperator)
     m_body += u"auto converted = "_s + var + u";\n"_s;
     m_body += m_state.accumulatorVariableOut + u" = "_s + conversion(
                 m_typeResolver->original(m_state.accumulatorOut()),
-                m_state.accumulatorOut(), cppOperator + u"converted"_s) + u";\n"_s;
+                m_state.accumulatorOut(), u'(' + cppOperator + u"converted)"_s) + u";\n"_s;
     m_body += u"}\n"_s;
     generateOutputVariantConversion(m_typeResolver->containedType(original));
 }
diff --git a/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt b/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
index ae2a172654..2228f4ad22 100644
--- a/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
+++ b/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
@@ -55,6 +55,7 @@ set(qml_files
     compositesingleton.qml
     construct.qml
     contextParam.qml
+    conversionDecrement.qml
     conversions.qml
     conversions2.qml
     curlygrouped.qml
diff --git a/tests/auto/qml/qmlcppcodegen/data/conversionDecrement.qml b/tests/auto/qml/qmlcppcodegen/data/conversionDecrement.qml
new file mode 100644
index 0000000000..fdce0fe65c
--- /dev/null
+++ b/tests/auto/qml/qmlcppcodegen/data/conversionDecrement.qml
@@ -0,0 +1,18 @@
+pragma Strict
+import QtQml
+
+QtObject {
+    id: panelGrid
+    property var pages: 4
+    property int currentPageIndex: 0
+
+    onPagesChanged: {
+        if (panelGrid.currentPageIndex === 0) {
+            panelGrid.currentPageIndex = panelGrid.pages - 2
+        } else if (panelGrid.currentPageIndex === panelGrid.pages - 1) {
+            panelGrid.currentPageIndex = 0
+        } else {
+            panelGrid.currentPageIndex -= 1
+        }
+    }
+}
diff --git a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
index 40b0fb78c2..81179be36d 100644
--- a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
+++ b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
@@ -123,6 +123,7 @@ private slots:
     void objectToString();
     void throwObjectName();
     void javaScriptArgument();
+    void conversionDecrement();
 };
 
 void tst_QmlCppCodegen::simpleBinding()
@@ -2242,6 +2243,27 @@ void tst_QmlCppCodegen::javaScriptArgument()
     QCOMPARE(o->property("d").toString(), u"9"_qs);
 }
 
+void tst_QmlCppCodegen::conversionDecrement()
+{
+    QQmlEngine engine;
+    QQmlComponent c(&engine, QUrl(u"qrc:/TestTypes/conversionDecrement.qml"_s));
+
+    QVERIFY2(c.isReady(), qPrintable(c.errorString()));
+
+    QScopedPointer<QObject> o(c.create());
+    QVERIFY(!o.isNull());
+
+    QCOMPARE(o->property("currentPageIndex").toInt(), 0);
+    o->setProperty("pages", 5);
+    QCOMPARE(o->property("currentPageIndex").toInt(), 3);
+    o->setProperty("pages", 4);
+    QCOMPARE(o->property("currentPageIndex").toInt(), 0);
+    o->setProperty("pages", 6);
+    QCOMPARE(o->property("currentPageIndex").toInt(), 4);
+    o->setProperty("pages", 60);
+    QCOMPARE(o->property("currentPageIndex").toInt(), 3);
+}
+
 void tst_QmlCppCodegen::runInterpreted()
 {
 #ifdef Q_OS_ANDROID