9 files changed, 169 insertions, 105 deletions
diff --git a/src/qmlcompiler/qdeferredpointer_p.h b/src/qmlcompiler/qdeferredpointer_p.h
index e19676d7ea..8a72c7a913 100644
--- a/src/qmlcompiler/qdeferredpointer_p.h
+++ b/src/qmlcompiler/qdeferredpointer_p.h
@@ -47,15 +47,24 @@
 QT_BEGIN_NAMESPACE
 
 template<typename T>
+class QDeferredSharedPointer;
+
+template<typename T>
+class QDeferredWeakPointer;
+
+template<typename T>
 class QDeferredFactory
 {
 public:
-    T create() const;
     bool isValid() const;
-};
 
-template<typename T>
-class QDeferredWeakPointer;
+private:
+    friend class QDeferredSharedPointer<const T>;
+    friend class QDeferredWeakPointer<const T>;
+    friend class QDeferredSharedPointer<T>;
+    friend class QDeferredWeakPointer<T>;
+    void populate(const QSharedPointer<T> &) const;
+};
 
 template<typename T>
 class QDeferredSharedPointer
@@ -179,7 +188,7 @@ private:
         if (Factory *f = factory()) {
             Factory localFactory;
             std::swap(localFactory, *f); // Swap before executing, to avoid recursion
-            const_cast<std::remove_const_t<T> &>(*m_data) = localFactory.create();
+            localFactory.populate(m_data.template constCast<std::remove_const_t<T>>());
         }
     }
 
@@ -245,8 +254,8 @@ private:
             if (factory->isValid()) {
                 Factory localFactory;
                 std::swap(localFactory, *factory); // Swap before executing, to avoid recursion
-                const_cast<std::remove_const_t<T> &>(*(m_data.toStrongRef()))
-                        = localFactory.create();
+                localFactory.populate(
+                        m_data.toStrongRef().template constCast<std::remove_const_t<T>>());
             }
         }
     }
diff --git a/src/qmlcompiler/qqmljscompiler.cpp b/src/qmlcompiler/qqmljscompiler.cpp
index c765a1c94e..14811c2aa2 100644
--- a/src/qmlcompiler/qqmljscompiler.cpp
+++ b/src/qmlcompiler/qqmljscompiler.cpp
@@ -645,7 +645,8 @@ void QQmlJSAotCompiler::setDocument(
     m_logger->setCode(irDocument->code);
     m_unitGenerator = &irDocument->jsGenerator;
     m_entireSourceCodeLines = irDocument->code.split(u'\n');
-    QQmlJSImportVisitor visitor(m_importer, m_logger,
+    QQmlJSScope::Ptr target = QQmlJSScope::create();
+    QQmlJSImportVisitor visitor(target, m_importer, m_logger,
                                 resourcePathInfo.canonicalPath() + u'/',
                                 m_qmldirFiles);
     m_typeResolver.init(&visitor, irDocument->program);
diff --git a/src/qmlcompiler/qqmljsimportvisitor.cpp b/src/qmlcompiler/qqmljsimportvisitor.cpp
index 4f8a916940..5e1318fca2 100644
--- a/src/qmlcompiler/qqmljsimportvisitor.cpp
+++ b/src/qmlcompiler/qqmljsimportvisitor.cpp
@@ -74,15 +74,17 @@ inline QString getScopeName(const QQmlJSScope::ConstPtr &scope, QQmlJSScope::Sco
     return scope->baseTypeName();
 }
 
-QQmlJSImportVisitor::QQmlJSImportVisitor(QQmlJSImporter *importer, QQmlJSLogger *logger,
-                                         const QString &implicitImportDirectory,
-                                         const QStringList &qmldirFiles)
+QQmlJSImportVisitor::QQmlJSImportVisitor(
+        const QQmlJSScope::Ptr &target, QQmlJSImporter *importer, QQmlJSLogger *logger,
+        const QString &implicitImportDirectory, const QStringList &qmldirFiles)
     : m_implicitImportDirectory(implicitImportDirectory),
       m_qmldirFiles(qmldirFiles),
-      m_currentScope(QQmlJSScope::create(QQmlJSScope::JSFunctionScope)),
+      m_currentScope(QQmlJSScope::create()),
+      m_exportedRootScope(target),
       m_importer(importer),
       m_logger(logger)
 {
+    m_currentScope->setScopeType(QQmlJSScope::JSFunctionScope);
     Q_ASSERT(logger); // must be valid
 
     m_globalScope = m_currentScope;
@@ -116,10 +118,10 @@ QQmlJSImportVisitor::QQmlJSImportVisitor(QQmlJSImporter *importer, QQmlJSLogger
 
 QQmlJSImportVisitor::~QQmlJSImportVisitor() = default;
 
-void QQmlJSImportVisitor::enterEnvironment(QQmlJSScope::ScopeType type, const QString &name,
-                                           const QQmlJS::SourceLocation &location)
+void QQmlJSImportVisitor::populateCurrentScope(
+        QQmlJSScope::ScopeType type, const QString &name, const QQmlJS::SourceLocation &location)
 {
-    m_currentScope = QQmlJSScope::create(type, m_currentScope);
+    m_currentScope->setScopeType(type);
     setScopeName(m_currentScope, type, name);
     m_currentScope->setIsComposite(true);
     m_currentScope->setFilePath(QFileInfo(m_logger->fileName()).absoluteFilePath());
@@ -127,6 +129,22 @@ void QQmlJSImportVisitor::enterEnvironment(QQmlJSScope::ScopeType type, const QS
     m_scopesByIrLocation.insert({ location.startLine, location.startColumn }, m_currentScope);
 }
 
+void QQmlJSImportVisitor::enterRootScope(QQmlJSScope::ScopeType type, const QString &name, const QQmlJS::SourceLocation &location)
+{
+    QQmlJSScope::reparent(m_currentScope, m_exportedRootScope);
+    m_currentScope = m_exportedRootScope;
+    populateCurrentScope(type, name, location);
+}
+
+void QQmlJSImportVisitor::enterEnvironment(QQmlJSScope::ScopeType type, const QString &name,
+                                           const QQmlJS::SourceLocation &location)
+{
+    QQmlJSScope::Ptr newScope = QQmlJSScope::create();
+    QQmlJSScope::reparent(m_currentScope, newScope);
+    m_currentScope = std::move(newScope);
+    populateCurrentScope(type, name, location);
+}
+
 bool QQmlJSImportVisitor::enterEnvironmentNonUnique(QQmlJSScope::ScopeType type,
                                                     const QString &name,
                                                     const QQmlJS::SourceLocation &location)
@@ -295,11 +313,6 @@ void QQmlJSImportVisitor::resolveAliasesAndIds()
     }
 }
 
-QQmlJSScope::Ptr QQmlJSImportVisitor::result() const
-{
-    return m_exportedRootScope;
-}
-
 QString QQmlJSImportVisitor::implicitImportDirectory(
         const QString &localFile, QQmlJSResourceFileMapper *mapper)
 {
@@ -1048,28 +1061,34 @@ void QQmlJSImportVisitor::breakInheritanceCycles(const QQmlJSScope::Ptr &origina
         if (scopes.contains(scope)) {
             QString inheritenceCycle;
             for (const auto &seen : qAsConst(scopes)) {
-                if (!inheritenceCycle.isEmpty())
-                    inheritenceCycle.append(QLatin1String(" -> "));
                 inheritenceCycle.append(seen->baseTypeName());
+                inheritenceCycle.append(QLatin1String(" -> "));
             }
+            inheritenceCycle.append(scopes.first()->baseTypeName());
 
-            m_logger->log(QStringLiteral("%1 is part of an inheritance cycle: %2")
-                                  .arg(scope->internalName())
-                                  .arg(inheritenceCycle),
-                          Log_InheritanceCycle, scope->sourceLocation());
+            const QString message = QStringLiteral("%1 is part of an inheritance cycle: %2")
+                                            .arg(scope->internalName(), inheritenceCycle);
+            m_logger->log(message, Log_InheritanceCycle, scope->sourceLocation());
             originalScope->clearBaseType();
+            originalScope->setBaseTypeError(message);
             break;
         }
 
         scopes.append(scope);
 
         const auto newScope = scope->baseType();
-        if (newScope.isNull() && !scope->baseTypeName().isEmpty()) {
-            m_logger->log(scope->baseTypeName()
-                                  + QStringLiteral(" was not found. Did you add all import paths?"),
-                          Log_Import, scope->sourceLocation(), true, true,
-                          QQmlJSUtils::didYouMean(scope->baseTypeName(), m_rootScopeImports.keys(),
-                                                  scope->sourceLocation()));
+        if (newScope.isNull()) {
+            const QString error = scope->baseTypeError();
+            const QString name = scope->baseTypeName();
+            if (!error.isEmpty()) {
+                m_logger->log(error, Log_Import, scope->sourceLocation(), true, true);
+            } else if (!name.isEmpty()) {
+                m_logger->log(
+                        name + QStringLiteral(" was not found. Did you add all import paths?"),
+                        Log_Import, scope->sourceLocation(), true, true,
+                        QQmlJSUtils::didYouMean(scope->baseTypeName(), m_rootScopeImports.keys(),
+                                                scope->sourceLocation()));
+            }
         }
 
         scope = newScope;
@@ -1206,10 +1225,11 @@ bool QQmlJSImportVisitor::visit(UiObjectDefinition *definition)
 
     Q_ASSERT(!superType.isEmpty());
     if (superType.front().isUpper()) {
-        enterEnvironment(QQmlJSScope::QMLScope, superType, definition->firstSourceLocation());
-        if (!m_exportedRootScope) {
-            m_exportedRootScope = m_currentScope;
-            m_exportedRootScope->setIsSingleton(m_rootIsSingleton);
+        if (rootScopeIsValid()) {
+            enterEnvironment(QQmlJSScope::QMLScope, superType, definition->firstSourceLocation());
+        } else {
+            enterRootScope(QQmlJSScope::QMLScope, superType, definition->firstSourceLocation());
+            m_currentScope->setIsSingleton(m_rootIsSingleton);
         }
 
         const QTypeRevision revision = QQmlJSScope::resolveTypes(
@@ -1223,7 +1243,7 @@ bool QQmlJSImportVisitor::visit(UiObjectDefinition *definition)
     } else {
         enterEnvironmentNonUnique(QQmlJSScope::GroupedPropertyScope, superType,
                                   definition->firstSourceLocation());
-        Q_ASSERT(m_exportedRootScope);
+        Q_ASSERT(rootScopeIsValid());
         QQmlJSScope::resolveTypes(m_currentScope, m_rootScopeImports, &m_usedTypes);
     }
 
@@ -2118,7 +2138,7 @@ void QQmlJSImportVisitor::endVisit(QQmlJS::AST::UiObjectBinding *uiob)
 
 bool QQmlJSImportVisitor::visit(ExportDeclaration *)
 {
-    Q_ASSERT(!m_exportedRootScope.isNull());
+    Q_ASSERT(rootScopeIsValid());
     Q_ASSERT(m_exportedRootScope != m_globalScope);
     Q_ASSERT(m_currentScope == m_globalScope);
     m_currentScope = m_exportedRootScope;
@@ -2127,18 +2147,17 @@ bool QQmlJSImportVisitor::visit(ExportDeclaration *)
 
 void QQmlJSImportVisitor::endVisit(ExportDeclaration *)
 {
-    Q_ASSERT(!m_exportedRootScope.isNull());
+    Q_ASSERT(rootScopeIsValid());
     m_currentScope = m_exportedRootScope->parentScope();
     Q_ASSERT(m_currentScope == m_globalScope);
 }
 
 bool QQmlJSImportVisitor::visit(ESModule *module)
 {
-    enterEnvironment(QQmlJSScope::JSLexicalScope, QStringLiteral("module"),
-                     module->firstSourceLocation());
-    Q_ASSERT(m_exportedRootScope.isNull());
-    m_exportedRootScope = m_currentScope;
-    m_exportedRootScope->setIsScript(true);
+    Q_ASSERT(!rootScopeIsValid());
+    enterRootScope(
+            QQmlJSScope::JSLexicalScope, QStringLiteral("module"), module->firstSourceLocation());
+    m_currentScope->setIsScript(true);
     importBaseModules();
     leaveEnvironment();
     return true;
@@ -2152,9 +2171,10 @@ void QQmlJSImportVisitor::endVisit(ESModule *)
 bool QQmlJSImportVisitor::visit(Program *)
 {
     Q_ASSERT(m_globalScope == m_currentScope);
-    Q_ASSERT(m_exportedRootScope.isNull());
-    m_exportedRootScope = m_currentScope;
+    Q_ASSERT(!rootScopeIsValid());
+    *m_exportedRootScope = std::move(*QQmlJSScope::clone(m_currentScope));
     m_exportedRootScope->setIsScript(true);
+    m_currentScope = m_exportedRootScope;
     importBaseModules();
     return true;
 }
diff --git a/src/qmlcompiler/qqmljsimportvisitor_p.h b/src/qmlcompiler/qqmljsimportvisitor_p.h
index 69714ced36..e9347a49f0 100644
--- a/src/qmlcompiler/qqmljsimportvisitor_p.h
+++ b/src/qmlcompiler/qqmljsimportvisitor_p.h
@@ -61,12 +61,13 @@ struct QQmlJSResourceFileMapper;
 class Q_QMLCOMPILER_PRIVATE_EXPORT QQmlJSImportVisitor : public QQmlJS::AST::Visitor
 {
 public:
-    QQmlJSImportVisitor(QQmlJSImporter *importer, QQmlJSLogger *logger,
+    QQmlJSImportVisitor(const QQmlJSScope::Ptr &target,
+                        QQmlJSImporter *importer, QQmlJSLogger *logger,
                         const QString &implicitImportDirectory,
                         const QStringList &qmldirFiles = QStringList());
     ~QQmlJSImportVisitor();
 
-    QQmlJSScope::Ptr result() const;
+    QQmlJSScope::Ptr result() const { return m_exportedRootScope; }
 
     QQmlJSLogger *logger() { return m_logger; }
 
@@ -161,7 +162,7 @@ protected:
     QStringList m_qmldirFiles;
     QQmlJSScope::Ptr m_currentScope;
     QQmlJSScope::Ptr m_savedBindingOuterScope;
-    QQmlJSScope::Ptr m_exportedRootScope;
+    const QQmlJSScope::Ptr m_exportedRootScope;
     QQmlJSScope::ConstPtr m_globalScope;
     QQmlJSScopesById m_scopesById;
     QQmlJSImporter::ImportedTypes m_rootScopeImports;
@@ -226,6 +227,7 @@ protected:
     void breakInheritanceCycles(const QQmlJSScope::Ptr &scope);
     void checkDeprecation(const QQmlJSScope::ConstPtr &scope);
     void checkGroupedAndAttachedScopes(QQmlJSScope::ConstPtr scope);
+    bool rootScopeIsValid() const { return m_exportedRootScope->sourceLocation().isValid(); }
 
     QQmlJSLogger *m_logger;
     enum class LiteralOrScriptParseResult { Invalid, Script, Literal };
@@ -300,6 +302,10 @@ private:
             const QString &what,
             const QQmlJS::SourceLocation &srcLocation = QQmlJS::SourceLocation());
     void addImportWithLocation(const QString &name, const QQmlJS::SourceLocation &loc);
+    void populateCurrentScope(QQmlJSScope::ScopeType type, const QString &name,
+                              const QQmlJS::SourceLocation &location);
+    void enterRootScope(QQmlJSScope::ScopeType type, const QString &name,
+                           const QQmlJS::SourceLocation &location);
 };
 
 QT_END_NAMESPACE
diff --git a/src/qmlcompiler/qqmljslinter.cpp b/src/qmlcompiler/qqmljslinter.cpp
index 83145e8b3e..e8ca914b04 100644
--- a/src/qmlcompiler/qqmljslinter.cpp
+++ b/src/qmlcompiler/qqmljslinter.cpp
@@ -311,7 +311,8 @@ QQmlJSLinter::LintResult QQmlJSLinter::lintFile(const QString &filename,
             m_logger->setFileName(m_useAbsolutePath ? info.absoluteFilePath() : filename);
             m_logger->setCode(code);
             m_logger->setSilent(silent || json);
-            QQmlJSImportVisitor v { &m_importer, m_logger.get(),
+            QQmlJSScope::Ptr target = QQmlJSScope::create();
+            QQmlJSImportVisitor v { target, &m_importer, m_logger.get(),
                                     QQmlJSImportVisitor::implicitImportDirectory(
                                             m_logger->fileName(), m_importer.resourceFileMapper()),
                                     qmldirFiles };
diff --git a/src/qmlcompiler/qqmljsscope.cpp b/src/qmlcompiler/qqmljsscope.cpp
index a13fa32790..5b23b247b3 100644
--- a/src/qmlcompiler/qqmljsscope.cpp
+++ b/src/qmlcompiler/qqmljsscope.cpp
@@ -92,23 +92,23 @@ static bool searchBaseAndExtensionTypes(QQmlJSScopePtr type, const Action &check
     return false;
 }
 
-QQmlJSScope::QQmlJSScope(ScopeType type, const QQmlJSScope::Ptr &parentScope)
-    : m_parentScope(parentScope), m_scopeType(type) {}
-
-QQmlJSScope::Ptr QQmlJSScope::create(ScopeType type, const QQmlJSScope::Ptr &parentScope)
+void QQmlJSScope::reparent(const QQmlJSScope::Ptr &parentScope, const QQmlJSScope::Ptr &childScope)
 {
-    QSharedPointer<QQmlJSScope> childScope(new QQmlJSScope{type, parentScope});
+    if (const QQmlJSScope::Ptr parent = childScope->m_parentScope.toStrongRef())
+        parent->m_childScopes.removeOne(childScope);
     if (parentScope)
-        parentScope->m_childScopes.push_back(childScope);
-    return childScope;
+        parentScope->m_childScopes.append(childScope);
+    childScope->m_parentScope = parentScope;
 }
 
 QQmlJSScope::Ptr QQmlJSScope::clone(const ConstPtr &origin)
 {
     if (origin.isNull())
         return QQmlJSScope::Ptr();
-    QQmlJSScope::Ptr cloned = create(origin->m_scopeType, origin->m_parentScope);
+    QQmlJSScope::Ptr cloned = create();
     *cloned = *origin;
+    if (QQmlJSScope::Ptr parent = cloned->parentScope())
+        parent->m_childScopes.append(cloned);
     return cloned;
 }
 
@@ -382,8 +382,9 @@ QTypeRevision QQmlJSScope::resolveType(
         const QQmlJSScope::Ptr &self, const QQmlJSScope::ContextualTypes &context,
         QSet<QString> *usedTypes)
 {
-    const auto baseType = findType(self->m_baseTypeName, context, usedTypes);
-    if (!self->m_baseType.scope && !self->m_baseTypeName.isEmpty())
+    const QString baseTypeName = self->baseTypeName();
+    const auto baseType = findType(baseTypeName, context, usedTypes);
+    if (!self->m_baseType.scope && !baseTypeName.isEmpty())
         self->m_baseType = { baseType.scope, baseType.revision };
 
     if (!self->m_attachedType && !self->m_attachedTypeName.isEmpty())
@@ -447,7 +448,7 @@ void QQmlJSScope::updateChildScope(
             const auto propertyIt = type->m_properties.find(childScope->internalName());
             if (propertyIt != type->m_properties.end()) {
                 childScope->m_baseType.scope = QQmlJSScope::ConstPtr(propertyIt->type());
-                childScope->m_baseTypeName = propertyIt->typeName();
+                childScope->setBaseTypeName(propertyIt->typeName());
                 return true;
             }
             return false;
@@ -457,7 +458,7 @@ void QQmlJSScope::updateChildScope(
         if (const auto attachedBase = findType(
                     childScope->internalName(), contextualTypes, usedTypes).scope) {
             childScope->m_baseType.scope = attachedBase->attachedType();
-            childScope->m_baseTypeName = attachedBase->attachedTypeName();
+            childScope->setBaseTypeName(attachedBase->attachedTypeName());
         }
         break;
     default:
@@ -508,8 +509,10 @@ void QQmlJSScope::resolveEnums(const QQmlJSScope::Ptr &self, const QQmlJSScope::
         if (it->type())
             continue;
         Q_ASSERT(intType); // We need an "int" type to resolve enums
-        auto enumScope = QQmlJSScope::create(EnumScope, self);
-        enumScope->m_baseTypeName = QStringLiteral("int");
+        QQmlJSScope::Ptr enumScope = QQmlJSScope::create();
+        reparent(self, enumScope);
+        enumScope->m_scopeType = EnumScope;
+        enumScope->setBaseTypeName(QStringLiteral("int"));
         enumScope->m_baseType.scope = intType;
         enumScope->m_semantics = AccessSemantics::Value;
         enumScope->m_internalName = self->internalName() + QStringLiteral("::") + it->name();
@@ -761,6 +764,28 @@ bool QQmlJSScope::isNameDeferred(const QString &name) const
     return isDeferred;
 }
 
+void QQmlJSScope::setBaseTypeName(const QString &baseTypeName)
+{
+    m_flags.setFlag(HasBaseTypeError, false);
+    m_baseTypeNameOrError = baseTypeName;
+}
+
+QString QQmlJSScope::baseTypeName() const
+{
+    return m_flags.testFlag(HasBaseTypeError) ? QString() : m_baseTypeNameOrError;
+}
+
+void QQmlJSScope::setBaseTypeError(const QString &baseTypeError)
+{
+    m_flags.setFlag(HasBaseTypeError);
+    m_baseTypeNameOrError = baseTypeError;
+}
+
+QString QQmlJSScope::baseTypeError() const
+{
+    return m_flags.testFlag(HasBaseTypeError) ? m_baseTypeNameOrError : QString();
+}
+
 QString QQmlJSScope::attachedTypeName() const
 {
     QString name;
@@ -792,7 +817,7 @@ bool QQmlJSScope::isResolved() const
     const bool nameIsEmpty = (m_scopeType == ScopeType::AttachedPropertyScope
                               || m_scopeType == ScopeType::GroupedPropertyScope)
             ? m_internalName.isEmpty()
-            : m_baseTypeName.isEmpty();
+            : m_baseTypeNameOrError.isEmpty();
     if (nameIsEmpty)
         return true;
     if (m_baseType.scope.isNull())
@@ -865,31 +890,29 @@ bool QQmlJSScope::Export::isValid() const
     return m_version.isValid() || !m_package.isEmpty() || !m_type.isEmpty();
 }
 
-QQmlJSScope QDeferredFactory<QQmlJSScope>::create() const
+void QDeferredFactory<QQmlJSScope>::populate(const QSharedPointer<QQmlJSScope> &scope) const
 {
     QQmlJSTypeReader typeReader(m_importer, m_filePath);
-    QQmlJSScope::Ptr result = typeReader();
+    typeReader(scope);
     m_importer->m_globalWarnings.append(typeReader.errors());
-    result->setInternalName(internalName());
-    QQmlJSScope::resolveEnums(result, m_importer->builtinInternalNames().value(u"int"_qs).scope);
+    scope->setInternalName(internalName());
+    QQmlJSScope::resolveEnums(scope, m_importer->builtinInternalNames().value(u"int"_qs).scope);
 
-    if (m_isSingleton && !result->isSingleton()) {
+    if (m_isSingleton && !scope->isSingleton()) {
         m_importer->m_globalWarnings.append(
                 { QStringLiteral(
                           "Type %1 declared as singleton in qmldir but missing pragma Singleton")
-                          .arg(result->internalName()),
+                          .arg(scope->internalName()),
                   QtCriticalMsg, QQmlJS::SourceLocation() });
-        result->setIsSingleton(true);
-    } else if (!m_isSingleton && result->isSingleton()) {
+        scope->setIsSingleton(true);
+    } else if (!m_isSingleton && scope->isSingleton()) {
         m_importer->m_globalWarnings.append(
                 { QStringLiteral("Type %1 not declared as singleton in qmldir "
                                  "but using pragma Singleton")
-                          .arg(result->internalName()),
+                          .arg(scope->internalName()),
                   QtCriticalMsg, QQmlJS::SourceLocation() });
-        result->setIsSingleton(false);
+        scope->setIsSingleton(false);
     }
-
-    return std::move(*result);
 }
 
 bool QQmlJSScope::canAssign(const QQmlJSScope::ConstPtr &derived) const
diff --git a/src/qmlcompiler/qqmljsscope_p.h b/src/qmlcompiler/qqmljsscope_p.h
index da670f0c71..f68c5d0596 100644
--- a/src/qmlcompiler/qqmljsscope_p.h
+++ b/src/qmlcompiler/qqmljsscope_p.h
@@ -95,7 +95,8 @@ public:
         CustomParser = 0x10,
         Array = 0x20,
         InlineComponent = 0x40,
-        WrappedInImplicitComponent = 0x80
+        WrappedInImplicitComponent = 0x80,
+        HasBaseTypeError = 0x100
     };
     Q_DECLARE_FLAGS(Flags, Flag)
     Q_FLAGS(Flags);
@@ -241,8 +242,7 @@ public:
         UnnamedPropertyTarget // default property bindings, where property name is unspecified
     };
 
-    static QQmlJSScope::Ptr create(ScopeType type = QQmlJSScope::QMLScope,
-                                   const QQmlJSScope::Ptr &parentScope = QQmlJSScope::Ptr());
+    static QQmlJSScope::Ptr create() { return QSharedPointer<QQmlJSScope>(new QQmlJSScope); }
     static QQmlJSScope::Ptr clone(const QQmlJSScope::ConstPtr &origin);
     static QQmlJSScope::ConstPtr findCurrentQMLScope(const QQmlJSScope::ConstPtr &scope);
 
@@ -256,6 +256,8 @@ public:
         return QQmlJSScope::WeakConstPtr(m_parentScope).toStrongRef();
     }
 
+    static void reparent(const QQmlJSScope::Ptr &parentScope, const QQmlJSScope::Ptr &childScope);
+
     void insertJSIdentifier(const QString &name, const JavaScriptIdentifier &identifier);
 
     // inserts property as qml identifier as well as the corresponding
@@ -264,6 +266,7 @@ public:
     bool isIdInCurrentScope(const QString &id) const;
 
     ScopeType scopeType() const { return m_scopeType; }
+    void setScopeType(ScopeType type) { m_scopeType = type; }
 
     void addOwnMethod(const QQmlJSMetaMethod &method) { m_methods.insert(method.methodName(), method); }
     QMultiHash<QString, QQmlJSMetaMethod> ownMethods() const { return m_methods; }
@@ -322,11 +325,15 @@ public:
 
     // If isComposite(), this is the QML/JS name of the prototype. Otherwise it's the
     // relevant base class (in the hierarchy starting from QObject) of a C++ type.
-    void setBaseTypeName(const QString &baseTypeName) { m_baseTypeName = baseTypeName; }
-    QString baseTypeName() const { return m_baseTypeName; }
+    void setBaseTypeName(const QString &baseTypeName);
+    QString baseTypeName() const;
+
     QQmlJSScope::ConstPtr baseType() const { return m_baseType.scope; }
     QTypeRevision baseTypeRevision() const { return m_baseType.revision; }
+
     void clearBaseType() { m_baseType = {}; }
+    void setBaseTypeError(const QString &baseTypeError);
+    QString baseTypeError() const;
 
     void addOwnProperty(const QQmlJSMetaProperty &prop) { m_properties.insert(prop.propertyName(), prop); }
     QHash<QString, QQmlJSMetaProperty> ownProperties() const { return m_properties; }
@@ -552,7 +559,7 @@ public:
     };
 
 private:
-    QQmlJSScope(ScopeType type, const QQmlJSScope::Ptr &parentScope = QQmlJSScope::Ptr());
+    QQmlJSScope() = default;
     QQmlJSScope(const QQmlJSScope &) = default;
     QQmlJSScope &operator=(const QQmlJSScope &) = default;
 
@@ -587,7 +594,7 @@ private:
 
     QString m_filePath;
     QString m_internalName;
-    QString m_baseTypeName;
+    QString m_baseTypeNameOrError;
 
     // We only need the revision for the base type as inheritance is
     // the only relation between two types where the revisions matter.
@@ -627,8 +634,6 @@ public:
         m_filePath(filePath), m_importer(importer)
     {}
 
-    QQmlJSScope create() const;
-
     bool isValid() const
     {
         return !m_filePath.isEmpty() && m_importer != nullptr;
@@ -645,6 +650,14 @@ public:
     }
 
 private:
+    friend class QDeferredSharedPointer<QQmlJSScope>;
+    friend class QDeferredSharedPointer<const QQmlJSScope>;
+    friend class QDeferredWeakPointer<QQmlJSScope>;
+    friend class QDeferredWeakPointer<const QQmlJSScope>;
+
+    // Should only be called when lazy-loading the type in a deferred pointer.
+    void populate(const QSharedPointer<QQmlJSScope> &scope) const;
+
     QString m_filePath;
     QQmlJSImporter *m_importer = nullptr;
     bool m_isSingleton = false;
diff --git a/src/qmlcompiler/qqmljstypereader.cpp b/src/qmlcompiler/qqmljstypereader.cpp
index ae3c0becfe..753fbe12f8 100644
--- a/src/qmlcompiler/qqmljstypereader.cpp
+++ b/src/qmlcompiler/qqmljstypereader.cpp
@@ -40,13 +40,13 @@
 
 QT_BEGIN_NAMESPACE
 
-QQmlJSScope::Ptr QQmlJSTypeReader::operator()()
+bool QQmlJSTypeReader::operator ()(const QSharedPointer<QQmlJSScope> &scope)
 {
     using namespace QQmlJS::AST;
     const QFileInfo info { m_file };
-    QString baseName = info.baseName();
-    const QString scopeName = baseName.endsWith(QStringLiteral(".ui")) ? baseName.chopped(3)
-                                                                       : baseName;
+    const QString baseName = info.baseName();
+    scope->setInternalName(baseName.endsWith(QStringLiteral(".ui")) ? baseName.chopped(3)
+                                                                    : baseName);
 
     QQmlJS::Engine engine;
     QQmlJS::Lexer lexer(&engine);
@@ -55,16 +55,10 @@ QQmlJSScope::Ptr QQmlJSTypeReader::operator()()
     const bool isESModule = lowerSuffix == QLatin1String("mjs");
     const bool isJavaScript = isESModule || lowerSuffix == QLatin1String("js");
 
-    auto errorResult = [&](){
-        QQmlJSScope::Ptr result = QQmlJSScope::create(
-                    isJavaScript ? QQmlJSScope::JSLexicalScope : QQmlJSScope::QMLScope);
-        result->setInternalName(scopeName);
-        return result;
-    };
 
     QFile file(m_file);
     if (!file.open(QFile::ReadOnly))
-        return errorResult();
+        return false;
 
     QString code = QString::fromUtf8(file.readAll());
     file.close();
@@ -76,11 +70,11 @@ QQmlJSScope::Ptr QQmlJSTypeReader::operator()()
                                                     : parser.parseProgram())
                                       : parser.parse();
     if (!success)
-        return errorResult();
+        return false;
 
     QQmlJS::AST::Node *rootNode = parser.rootNode();
     if (!rootNode)
-        return errorResult();
+        return false;
 
     QQmlJSLogger logger;
     logger.setFileName(m_file);
@@ -88,13 +82,10 @@ QQmlJSScope::Ptr QQmlJSTypeReader::operator()()
     logger.setSilent(true);
 
     QQmlJSImportVisitor membersVisitor(
-            m_importer, &logger,
+            scope, m_importer, &logger,
             QQmlJSImportVisitor::implicitImportDirectory(m_file, m_importer->resourceFileMapper()));
     rootNode->accept(&membersVisitor);
-    auto result = membersVisitor.result();
-    Q_ASSERT(result);
-    result->setInternalName(scopeName);
-    return result;
+    return true;
 }
 
 QT_END_NAMESPACE
diff --git a/src/qmlcompiler/qqmljstypereader_p.h b/src/qmlcompiler/qqmljstypereader_p.h
index 4dcdc3dc7f..f4dd8ceb15 100644
--- a/src/qmlcompiler/qqmljstypereader_p.h
+++ b/src/qmlcompiler/qqmljstypereader_p.h
@@ -59,7 +59,7 @@ public:
         , m_file(file)
     {}
 
-    QQmlJSScope::Ptr operator()();
+    bool operator()(const QSharedPointer<QQmlJSScope> &scope);
     QList<QQmlJS::DiagnosticMessage> errors() const { return m_errors; }
 
 private: