QmlCompiler: Add support for LoadElement on strings

In JavaScript the [] operator on strings returns a string. QString's
operator[] returns a QChar, but we can easily create a string from that.

Fixes: QTBUG-103371
Change-Id: Id5c960f00ecc7a5dfe30ccbcaac3ffb2a30308b9
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

6 files changed, 45 insertions, 5 deletions

diff --git a/src/qmlcompiler/qqmljscodegenerator.cpp b/src/qmlcompiler/qqmljscodegenerator.cpp
index 8568154e3c..8c89745a37 100644
--- a/src/qmlcompiler/qqmljscodegenerator.cpp
+++ b/src/qmlcompiler/qqmljscodegenerator.cpp
@@ -622,7 +622,9 @@ void QQmlJSCodeGenerator::generate_LoadElement(int base)
 
     const QQmlJSRegisterContent baseType = registerType(base);
 
-    if (!m_typeResolver->isNumeric(m_state.accumulatorIn()) || !baseType.isList()) {
+    if (!m_typeResolver->isNumeric(m_state.accumulatorIn())
+            || (!baseType.isList()
+                && !m_typeResolver->registerIsStoredIn(baseType, m_typeResolver->stringType()))) {
         reject(u"LoadElement with non-list base type or non-numeric arguments"_s);
         return;
     }
@@ -662,11 +664,16 @@ void QQmlJSCodeGenerator::generate_LoadElement(int base)
 
     const auto elementType = m_typeResolver->valueType(baseType);
 
+    QString access = baseName + u".at("_s + indexName + u')';
+
+    // TODO: Once we get a char type in QML, use it here.
+    if (m_typeResolver->registerIsStoredIn(baseType, m_typeResolver->stringType()))
+        access = u"QString("_s + access + u")"_s;
+
     m_body += u"if ("_s + indexName + u" >= 0 && "_s + indexName
-            + u" < "_s + baseName + u".count())\n"_s;
+            + u" < "_s + baseName + u".size())\n"_s;
     m_body += u"    "_s + m_state.accumulatorVariableOut + u" = "_s +
-            conversion(elementType, m_state.accumulatorOut(),
-                       baseName + u".at("_s + indexName + u')') + u";\n"_s;
+            conversion(elementType, m_state.accumulatorOut(), access) + u";\n"_s;
     m_body += u"else\n"_s
             + voidAssignment;
 }
diff --git a/src/qmlcompiler/qqmljstypepropagator.cpp b/src/qmlcompiler/qqmljstypepropagator.cpp
index 7f859061fa..27e120a832 100644
--- a/src/qmlcompiler/qqmljstypepropagator.cpp
+++ b/src/qmlcompiler/qqmljstypepropagator.cpp
@@ -652,7 +652,8 @@ void QQmlJSTypePropagator::generate_LoadElement(int base)
 {
     const QQmlJSRegisterContent baseRegister = m_state.registers[base];
 
-    if (baseRegister.storedType()->accessSemantics() != QQmlJSScope::AccessSemantics::Sequence
+    if ((baseRegister.storedType()->accessSemantics() != QQmlJSScope::AccessSemantics::Sequence
+         && !m_typeResolver->registerIsStoredIn(baseRegister, m_typeResolver->stringType()))
             || !m_typeResolver->isNumeric(m_state.accumulatorIn())) {
         const auto jsValue = m_typeResolver->globalType(m_typeResolver->jsValueType());
         addReadAccumulator(jsValue);
diff --git a/src/qmlcompiler/qqmljstyperesolver.cpp b/src/qmlcompiler/qqmljstyperesolver.cpp
index c01cf5dfb3..623772027f 100644
--- a/src/qmlcompiler/qqmljstyperesolver.cpp
+++ b/src/qmlcompiler/qqmljstyperesolver.cpp
@@ -1178,6 +1178,8 @@ QQmlJSRegisterContent QQmlJSTypeResolver::valueType(const QQmlJSRegisterContent
             return scope->valueType();
         else if (equals(scope, m_jsValueType) || equals(scope, m_varType))
             return m_jsValueType;
+        else if (equals(scope, m_stringType))
+            return m_stringType;
         return QQmlJSScope::ConstPtr();
     };
 
diff --git a/tests/auto/qml/qmlcppcodegen/data/typedArray.qml b/tests/auto/qml/qmlcppcodegen/data/typedArray.qml
index f9a40f5584..8d94d0832f 100644
--- a/tests/auto/qml/qmlcppcodegen/data/typedArray.qml
+++ b/tests/auto/qml/qmlcppcodegen/data/typedArray.qml
@@ -10,8 +10,17 @@ QtObject {
     property list<date> values4: [aDate, aDate, aDate]
     property list<real> values5: [1, 2, 3.4, "30", undefined, null]
     property list<QtObject> values6: [self, self, self]
+    property string values7: "abcdef"
 
     property int inIntList: values3[1]
     property date inDateList: values4[2]
     property real inRealList: values5[3]
+    property string inCharList: values7[5]
+
+    function stringAt10(s: string): int {
+        if (!s[10])
+            return 10;
+        else
+            return 20;
+    }
 }
diff --git a/tests/auto/qml/qmlcppcodegen/data/valueTypeLists.qml b/tests/auto/qml/qmlcppcodegen/data/valueTypeLists.qml
index 83325641ab..cf58ae68c5 100644
--- a/tests/auto/qml/qmlcppcodegen/data/valueTypeLists.qml
+++ b/tests/auto/qml/qmlcppcodegen/data/valueTypeLists.qml
@@ -4,6 +4,7 @@ QtObject {
     property list<rect> rectList: [ Qt.rect(1,2,3,4), Qt.rect(5,6,7,8), Qt.rect(9,10,11,12) ]
     property list<string> stringList: ["aaa", "bbb", "ccc"]
     property list<int> intList: [5, 6, 7, 8]
+    property string charList: "abcde"
 
     property var rectInBounds: rectList[0]
     property var rectOutOfBounds: rectList[32]
@@ -11,4 +12,6 @@ QtObject {
     property var stringOutOfBounds: stringList[33]
     property var intInBounds: intList[2]
     property var intOutOfBounds: intList[34]
+    property var charInBounds: charList[3]
+    property var charOutOfBounds: charList[35]
 }
diff --git a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
index b4993d1752..84c5ad2deb 100644
--- a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
+++ b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
@@ -1955,6 +1955,20 @@ void tst_QmlCppCodegen::typedArray()
     QCOMPARE(o->property("inIntList").toInt(), 2);
     QCOMPARE(qvariant_cast<QDateTime>(o->property("inDateList")), date);
     QCOMPARE(o->property("inRealList").toDouble(), 30.0);
+    QCOMPARE(o->property("inCharList").toString(), QStringLiteral("f"));
+
+    const QMetaObject *metaObject = o->metaObject();
+    QMetaMethod method = metaObject->method(metaObject->indexOfMethod("stringAt10(QString)"));
+    QVERIFY(method.isValid());
+
+    // If LoadElement threw an exception the function would certainly return neither 10 nor 20.
+    int result = 0;
+    method.invoke(
+                o.data(), Q_RETURN_ARG(int, result), Q_ARG(QString, QStringLiteral("a")));
+    QCOMPARE(result, 10);
+    method.invoke(
+                o.data(), Q_RETURN_ARG(int, result), Q_ARG(QString, QStringLiteral("aaaaaaaaaaa")));
+    QCOMPARE(result, 20);
 }
 
 void tst_QmlCppCodegen::prefixedType()
@@ -2126,6 +2140,10 @@ void tst_QmlCppCodegen::valueTypeLists()
     QCOMPARE(qvariant_cast<int>(o->property("intInBounds")), 7);
     QVERIFY(o->metaObject()->indexOfProperty("intOutOfBounds") > 0);
     QVERIFY(!o->property("intOutOfBounds").isValid());
+
+    QCOMPARE(qvariant_cast<QString>(o->property("charInBounds")), QStringLiteral("d"));
+    QVERIFY(o->metaObject()->indexOfProperty("charOutOfBounds") > 0);
+    QVERIFY(!o->property("charOutOfBounds").isValid());
 }
 
 void tst_QmlCppCodegen::boundComponents()