qmllint: Warn about assigning numeric types to strings

While it is generally possible to assign a numeric to a value of string
type, this is not the case for literal bindings: There, the engine's
QQmlTypeValidator notices the mismatch, and rejects the program.
Bring qmllint in line with that behavior.
Additionally, teach parseLiteralBinding to treat constant
UnaryMinusExpressions as NumberLiteral bindings.

Change-Id: Iad221e90eb1de81cabdddf5d601cc30f53ef20d3
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>

src/qmlcompiler/qqmljsimportvisitor.cpp

@@ -1335,7 +1335,8 @@ void QQmlJSImportVisitor::parseLiteralBinding(const QString name,
     QString literalType;
     QQmlJSMetaPropertyBinding::BindingType bindingType = QQmlJSMetaPropertyBinding::Invalid;
 
-    switch (exprStatement->expression->kind) {
+    auto expr = exprStatement->expression;
+    switch (expr->kind) {
     case Node::Kind_TrueLiteral:
         value = true;
         literalType = u"bool"_qs;
@@ -1356,21 +1357,21 @@ void QQmlJSImportVisitor::parseLiteralBinding(const QString name,
         break;
     case Node::Kind_NumericLiteral:
         literalType = u"double"_qs;
-        value = cast<NumericLiteral *>(exprStatement->expression)->value;
+        value = cast<NumericLiteral *>(expr)->value;
         bindingType = QQmlJSMetaPropertyBinding::NumberLiteral;
         break;
     case Node::Kind_StringLiteral:
         literalType = u"string"_qs;
-        value = cast<StringLiteral *>(exprStatement->expression)->value.toString();
+        value = cast<StringLiteral *>(expr)->value.toString();
         bindingType = QQmlJSMetaPropertyBinding::StringLiteral;
         break;
     case Node::Kind_RegExpLiteral:
         literalType = u"regexp"_qs;
-        value = cast<RegExpLiteral *>(exprStatement->expression)->pattern.toString();
+        value = cast<RegExpLiteral *>(expr)->pattern.toString();
         bindingType = QQmlJSMetaPropertyBinding::RegExpLiteral;
         break;
     case Node::Kind_TemplateLiteral: {
-        auto templateLit = QQmlJS::AST::cast<QQmlJS::AST::TemplateLiteral *>(exprStatement->expression);
+        auto templateLit = QQmlJS::AST::cast<QQmlJS::AST::TemplateLiteral *>(expr);
         Q_ASSERT(templateLit);
         value = templateLit->value.toString();
         if (templateLit->hasNoSubstitution) {
@@ -1382,7 +1383,14 @@ void QQmlJSImportVisitor::parseLiteralBinding(const QString name,
         break;
     }
     default:
-        return;
+        if (QQmlJS::AST::UnaryMinusExpression *unaryMinus = QQmlJS::AST::cast<QQmlJS::AST::UnaryMinusExpression *>(expr)) {
+            if (QQmlJS::AST::NumericLiteral *lit = QQmlJS::AST::cast<QQmlJS::AST::NumericLiteral *>(unaryMinus->expression)) {
+                literalType = u"double"_qs;
+                bindingType = QQmlJSMetaPropertyBinding::NumberLiteral;
+                value = -lit->value;
+            }
+        }
+        break;
     }
 
     if (!QQmlJSMetaPropertyBinding::isLiteralBinding(bindingType))

src/qmlcompiler/qqmljstyperesolver.cpp

@@ -146,6 +146,9 @@ void QQmlJSTypeResolver::init(QQmlJSImportVisitor *visitor, QQmlJS::AST::Node *p
                                                  .arg(binding.literalTypeName())
                                                  .arg(property.typeName()),
                                          Log_Type, binding.sourceLocation());
+                } else if (property.type() == m_stringType && isNumeric(binding.literalType())) {
+                    m_logger->logWarning(u"Cannot assign a numeric constant to a string property"_qs,
+                                         Log_Type, binding.sourceLocation());
                 }
             }
         }

tests/auto/qml/qmllint/data/numberToStringProperty.qml

@@ -0,0 +1,5 @@
+import QtQml
+
+QtObject {
+    property string i: 1
+}

tests/auto/qml/qmllint/data/unaryMinusToStringProperty.qml

@@ -0,0 +1,5 @@
+import QtQml
+
+QtObject {
+    property string i: -1
+}

tests/auto/qml/qmllint/tst_qmllint.cpp

@@ -515,6 +515,16 @@ void TestQmllint::dirtyQmlCode_data()
         << QStringLiteral("Cannot assign binding of type QString to int")
         << QString()
         << false;
+    QTest::newRow("bad constant number to string")
+        << QStringLiteral("numberToStringProperty.qml")
+        << QStringLiteral("Cannot assign a numeric constant to a string property")
+        << QString()
+        << false;
+    QTest::newRow("bad unary minus to string")
+        << QStringLiteral("unaryMinusToStringProperty.qml")
+        << QStringLiteral("Cannot assign a numeric constant to a string property")
+        << QString()
+        << false;
     QTest::newRow("BadBinding")
             << QStringLiteral("badBinding.qml")
             << QStringLiteral("Binding assigned to \"doesNotExist\", but no property "