[new compiler] Cleanup empty string handling

Ensure that the empty string always has index 0, that simplifies the code in a
few places and makes it easier to check for the empty string in other places
where there's no access to the string pool itself.

Change-Id: Icd204aec478e8350ef3fee75d89bda1f88cffe26
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

4 files changed, 23 insertions, 26 deletions

diff --git a/src/qml/compiler/qqmlcodegenerator.cpp b/src/qml/compiler/qqmlcodegenerator.cpp
index 04c4e5f598..ccf7e47e26 100644
--- a/src/qml/compiler/qqmlcodegenerator.cpp
+++ b/src/qml/compiler/qqmlcodegenerator.cpp
@@ -54,6 +54,8 @@
 
 QT_USE_NAMESPACE
 
+static const quint32 emptyStringIndex = 0;
+
 DEFINE_BOOL_CONFIG_OPTION(lookupHints, QML_LOOKUP_HINTS);
 
 using namespace QtQml;
@@ -156,9 +158,10 @@ void QmlObject::appendFunction(Function *f)
     target->functions->append(f);
 }
 
-QString QmlObject::appendBinding(Binding *b, bool isListBinding, bool bindToDefaultProperty)
+QString QmlObject::appendBinding(Binding *b, bool isListBinding)
 {
-    if (!isListBinding && !bindToDefaultProperty
+    const bool bindingToDefaultProperty = (b->propertyNameIndex == 0);
+    if (!isListBinding && !bindingToDefaultProperty
         && b->type != QV4::CompiledData::Binding::Type_GroupProperty
         && b->type != QV4::CompiledData::Binding::Type_AttachedProperty
         && !(b->flags & QV4::CompiledData::Binding::IsOnAssignment)) {
@@ -231,7 +234,7 @@ bool QQmlCodeGenerator::generateFromQml(const QString &code, const QUrl &url, co
     this->pool = output->jsParserEngine.pool();
     this->jsGenerator = &output->jsGenerator;
 
-    emptyStringIndex = registerString(QString());
+    Q_ASSERT(registerString(QString()) == emptyStringIndex);
 
     sourceCode = code;
 
@@ -950,15 +953,13 @@ void QQmlCodeGenerator::appendBinding(const AST::SourceLocation &nameLocation, q
         return;
     }
 
-    const bool bindingToDefaultProperty = (propertyNameIndex == emptyStringIndex);
-
     Binding *binding = New<Binding>();
     binding->propertyNameIndex = propertyNameIndex;
     binding->location.line = nameLocation.startLine;
     binding->location.column = nameLocation.startColumn;
     binding->flags = 0;
     setBindingValue(binding, value);
-    QString error = bindingsTarget()->appendBinding(binding, /*isListBinding*/false, bindingToDefaultProperty);
+    QString error = bindingsTarget()->appendBinding(binding, /*isListBinding*/false);
     if (!error.isEmpty()) {
         recordError(nameLocation, error);
     }
@@ -971,8 +972,6 @@ void QQmlCodeGenerator::appendBinding(const AST::SourceLocation &nameLocation, q
         return;
     }
 
-    const bool bindingToDefaultProperty = (propertyNameIndex == emptyStringIndex);
-
     Binding *binding = New<Binding>();
     binding->propertyNameIndex = propertyNameIndex;
     binding->location.line = nameLocation.startLine;
@@ -987,7 +986,7 @@ void QQmlCodeGenerator::appendBinding(const AST::SourceLocation &nameLocation, q
         binding->flags |= QV4::CompiledData::Binding::InitializerForReadOnlyDeclaration;
 
     // No type name on the initializer means it must be a group property
-    if (stringAt(_objects.at(objectIndex)->inheritedTypeNameIndex).isEmpty())
+    if (_objects.at(objectIndex)->inheritedTypeNameIndex == emptyStringIndex)
         binding->type = QV4::CompiledData::Binding::Type_GroupProperty;
     else
         binding->type = QV4::CompiledData::Binding::Type_Object;
@@ -998,7 +997,7 @@ void QQmlCodeGenerator::appendBinding(const AST::SourceLocation &nameLocation, q
         binding->flags |= QV4::CompiledData::Binding::IsListItem;
 
     binding->value.objectIndex = objectIndex;
-    QString error = bindingsTarget()->appendBinding(binding, isListItem, bindingToDefaultProperty);
+    QString error = bindingsTarget()->appendBinding(binding, isListItem);
     if (!error.isEmpty()) {
         recordError(nameLocation, error);
     }
@@ -1100,7 +1099,7 @@ bool QQmlCodeGenerator::resolveQualifiedId(AST::UiQualifiedId **nameToResolve, Q
         int objIndex = defineQMLObject(0, AST::SourceLocation(), 0, 0);
         binding->value.objectIndex = objIndex;
 
-        QString error = (*object)->appendBinding(binding, /*isListBinding*/false, /*bindingToDefaultProperty*/false);
+        QString error = (*object)->appendBinding(binding, /*isListBinding*/false);
         if (!error.isEmpty()) {
             recordError(qualifiedIdElement->identifierToken, error);
             return false;
@@ -1128,7 +1127,7 @@ void QQmlCodeGenerator::recordError(const AST::SourceLocation &location, const Q
 void QQmlCodeGenerator::collectTypeReferences()
 {
     foreach (QmlObject *obj, _objects) {
-        if (!stringAt(obj->inheritedTypeNameIndex).isEmpty()) {
+        if (obj->inheritedTypeNameIndex != emptyStringIndex) {
             QV4::CompiledData::TypeReference &r = _typeReferences.add(obj->inheritedTypeNameIndex, obj->location);
             r.needsCreation = true;
         }
diff --git a/src/qml/compiler/qqmlcodegenerator_p.h b/src/qml/compiler/qqmlcodegenerator_p.h
index 5475d7f57a..ed94a99726 100644
--- a/src/qml/compiler/qqmlcodegenerator_p.h
+++ b/src/qml/compiler/qqmlcodegenerator_p.h
@@ -161,7 +161,7 @@ struct QmlObject
 {
     Q_DECLARE_TR_FUNCTIONS(QmlObject)
 public:
-    int inheritedTypeNameIndex;
+    quint32 inheritedTypeNameIndex;
     quint32 idIndex;
     int indexOfDefaultProperty;
 
@@ -191,7 +191,7 @@ public:
     QString appendProperty(QmlProperty *prop, const QString &propertyName, bool isDefaultProperty, const AST::SourceLocation &defaultToken, AST::SourceLocation *errorLocation);
     void appendFunction(Function *f);
 
-    QString appendBinding(Binding *b, bool isListBinding, bool bindToDefaultProperty);
+    QString appendBinding(Binding *b, bool isListBinding);
 
 private:
     PoolList<QmlProperty> *properties;
@@ -305,7 +305,7 @@ public:
 
     static QQmlScript::LocationSpan location(AST::SourceLocation start, AST::SourceLocation end);
 
-    int registerString(const QString &str) const { return jsGenerator->registerString(str); }
+    quint32 registerString(const QString &str) const { return jsGenerator->registerString(str); }
     template <typename _Tp> _Tp *New() { return pool->New<_Tp>(); }
 
     QString stringAt(int index) const { return jsGenerator->strings.at(index); }
@@ -330,7 +330,6 @@ public:
     QString sourceCode;
     QUrl url;
     QV4::Compiler::JSUnitGenerator *jsGenerator;
-    quint32 emptyStringIndex;
 };
 
 struct Q_QML_EXPORT QmlUnitGenerator
diff --git a/src/qml/compiler/qqmltypecompiler.cpp b/src/qml/compiler/qqmltypecompiler.cpp
index 41dcd669a3..6197ddf5d0 100644
--- a/src/qml/compiler/qqmltypecompiler.cpp
+++ b/src/qml/compiler/qqmltypecompiler.cpp
@@ -397,7 +397,7 @@ bool QQmlPropertyCacheCreator::buildMetaObjectRecursively(int objectIndex, int r
         Q_ASSERT(referencingObjectIndex >= 0);
         QQmlPropertyCache *parentCache = propertyCaches.at(referencingObjectIndex);
         Q_ASSERT(parentCache);
-        Q_ASSERT(!stringAt(instantiatingBinding->propertyNameIndex).isEmpty());
+        Q_ASSERT(instantiatingBinding->propertyNameIndex != 0);
 
         bool notInRevision = false;
         instantiatingProperty = PropertyResolver(parentCache).property(stringAt(instantiatingBinding->propertyNameIndex), &notInRevision);
@@ -434,8 +434,7 @@ bool QQmlPropertyCacheCreator::buildMetaObjectRecursively(int objectIndex, int r
         }
     }
 
-    QString typeName = stringAt(obj->inheritedTypeNameIndex);
-    if (!typeName.isEmpty()) {
+    if (obj->inheritedTypeNameIndex != 0) {
         QQmlCompiledData::TypeReference *typeRef = resolvedTypes->value(obj->inheritedTypeNameIndex);
         Q_ASSERT(typeRef);
         baseTypeCache = typeRef->createPropertyCache(QQmlEnginePrivate::get(enginePrivate));
@@ -1004,10 +1003,9 @@ void QQmlComponentAndAliasResolver::findAndRegisterImplicitComponents(const QtQm
             continue;
 
         QQmlPropertyData *pd = 0;
-        QString propertyName = stringAt(binding->propertyNameIndex);
-        if (!propertyName.isEmpty()) {
+        if (binding->propertyNameIndex != 0) {
             bool notInRevision = false;
-            pd = propertyResolver.property(propertyName, &notInRevision);
+            pd = propertyResolver.property(stringAt(binding->propertyNameIndex), &notInRevision);
         } else {
             pd = defaultProperty;
         }
@@ -1045,7 +1043,7 @@ void QQmlComponentAndAliasResolver::findAndRegisterImplicitComponents(const QtQm
         QtQml::Binding *syntheticBinding = pool->New<QtQml::Binding>();
         *syntheticBinding = *binding;
         syntheticBinding->type = QV4::CompiledData::Binding::Type_Object;
-        QString error = syntheticComponent->appendBinding(syntheticBinding, /*isListBinding*/false, /*bindingToDefaultProperty*/false);
+        QString error = syntheticComponent->appendBinding(syntheticBinding, /*isListBinding*/false);
         Q_ASSERT(error.isEmpty());
         Q_UNUSED(error);
 
@@ -1065,7 +1063,7 @@ bool QQmlComponentAndAliasResolver::resolve()
     const int objCountWithoutSynthesizedComponents = qmlObjects->count();
     for (int i = 0; i < objCountWithoutSynthesizedComponents; ++i) {
         const QtQml::QmlObject *obj = qmlObjects->at(i);
-        if (stringAt(obj->inheritedTypeNameIndex).isEmpty())
+        if (obj->inheritedTypeNameIndex == 0)
             continue;
 
         QQmlCompiledData::TypeReference *tref = resolvedTypes->value(obj->inheritedTypeNameIndex);
@@ -1131,8 +1129,7 @@ bool QQmlComponentAndAliasResolver::collectIdsAndAliases(int objectIndex)
 {
     const QtQml::QmlObject *obj = qmlObjects->at(objectIndex);
 
-    QString id = stringAt(obj->idIndex);
-    if (!id.isEmpty()) {
+    if (obj->idIndex != 0) {
         if (_idToObjectIndex.contains(obj->idIndex)) {
             recordError(obj->locationOfIdProperty, tr("id is not unique"));
             return false;
diff --git a/src/qml/compiler/qv4compiler.cpp b/src/qml/compiler/qv4compiler.cpp
index 7fb10d5f42..bc47b815f2 100644
--- a/src/qml/compiler/qv4compiler.cpp
+++ b/src/qml/compiler/qv4compiler.cpp
@@ -53,6 +53,8 @@ QV4::Compiler::JSUnitGenerator::JSUnitGenerator(QQmlJS::V4IR::Module *module, in
     if (headerSize == -1)
         headerSize = sizeof(QV4::CompiledData::Unit);
     this->headerSize = headerSize;
+    // Make sure the empty string always gets index 0
+    registerString(QString());
 }
 
 int QV4::Compiler::JSUnitGenerator::registerString(const QString &str)