path: root/src/qmldom/qqmldomitem_p.h

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**
** Copyright (C) 2020 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtQml module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
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** information use the contact form at https://www.qt.io/contact-us.
**
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** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
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** $QT_END_LICENSE$
**/
#ifndef QMLDOMITEM_H
#define QMLDOMITEM_H

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//

#include "qqmldom_global.h"
#include "qqmldom_fwd_p.h"
#include "qqmldomconstants_p.h"
#include "qqmldomstringdumper_p.h"
#include "qqmldompath_p.h"
#include "qqmldomerrormessage_p.h"
#include "qqmldomfunctionref_p.h"
#include "qqmldomfilewriter_p.h"
#include "qqmldomlinewriter_p.h"

#include <QtCore/QMap>
#include <QtCore/QMultiMap>
#include <QtCore/QSet>
#include <QtCore/QString>
#include <QtCore/QStringView>
#include <QtCore/QDebug>
#include <QtCore/QDateTime>
#include <QtCore/QMutex>
#include <QtCore/QCborValue>
#include <QtQml/private/qqmljssourcelocation_p.h>

#include <memory>
#include <typeinfo>
#include <utility>
#include <type_traits>
#include <variant>
#include <optional>
#include <cstddef>

QT_BEGIN_NAMESPACE

namespace QQmlJS {
// we didn't have enough 'O's to properly name everything...
namespace Dom {

class Path;

Q_DECLARE_LOGGING_CATEGORY(writeOutLog);

constexpr bool domTypeIsObjWrap(DomType k);
constexpr bool domTypeIsValueWrap(DomType k);
constexpr bool domTypeIsDomElement(DomType);
constexpr bool domTypeIsOwningItem(DomType);
constexpr bool domTypeIsUnattachedOwningItem(DomType);
QMLDOM_EXPORT bool domTypeIsExternalItem(DomType k);
QMLDOM_EXPORT bool domTypeIsTopItem(DomType k);
QMLDOM_EXPORT bool domTypeIsContainer(DomType k);
constexpr bool domTypeCanBeInline(DomType k)
{
    switch (k) {
    case DomType::Empty:
    case DomType::Map:
    case DomType::List:
    case DomType::ListP:
    case DomType::ConstantData:
    case DomType::SimpleObjectWrap:
    case DomType::Reference:
        return true;
    default:
        return false;
    }
}
QMLDOM_EXPORT bool domTypeIsScope(DomType k);

QMLDOM_EXPORT QMap<DomType,QString> domTypeToStringMap();
QMLDOM_EXPORT QString domTypeToString(DomType k);
QMLDOM_EXPORT QMap<DomKind, QString> domKindToStringMap();
QMLDOM_EXPORT QString domKindToString(DomKind k);

QMLDOM_EXPORT QCborValue locationToData(SourceLocation loc, QStringView strValue=u"");

inline bool noFilter(DomItem &, const PathEls::PathComponent &, DomItem &)
{
    return true;
}

using DirectVisitor = function_ref<bool(const PathEls::PathComponent &, function_ref<DomItem()>)>;
// using DirectVisitor = function_ref<bool(Path, DomItem &)>;

namespace {
template<typename T>
struct IsMultiMap : std::false_type
{
};

template<typename Key, typename T>
struct IsMultiMap<QMultiMap<Key, T>> : std::true_type
{
};

template<typename T>
struct IsMap : std::false_type
{
};

template<typename Key, typename T>
struct IsMap<QMap<Key, T>> : std::true_type
{
};

template<typename... Ts>
using void_t = void;

template<typename T, typename = void>
struct IsDomObject : std::false_type
{
};

template<typename T>
struct IsDomObject<T, void_t<decltype(T::kindValue)>> : std::true_type
{
};

template<typename T, typename = void>
struct IsInlineDom : std::false_type
{
};

template<typename T>
struct IsInlineDom<T, void_t<decltype(T::kindValue)>>
    : std::integral_constant<bool, domTypeCanBeInline(T::kindValue)>
{
};

template<typename T>
struct IsInlineDom<T *, void_t<decltype(T::kindValue)>> : std::true_type
{
};

template<typename T>
struct IsInlineDom<std::shared_ptr<T>, void_t<decltype(T::kindValue)>> : std::true_type
{
};

template<typename T>
struct IsSharedPointerToDomObject : std::false_type
{
};

template<typename T>
struct IsSharedPointerToDomObject<std::shared_ptr<T>> : IsDomObject<T>
{
};

template<typename T, typename = void>
struct IsList : std::false_type
{
};

template<typename T>
struct IsList<T, void_t<typename T::value_type>> : std::true_type
{
};

}

template<typename T>
union SubclassStorage {
    int i;
    T lp;
    T *data() { return reinterpret_cast<T *>(this); }
    const T *data() const { return reinterpret_cast<const T *>(this); }
    SubclassStorage() { }
    SubclassStorage(T &&el) { el.moveTo(data()); }
    SubclassStorage(const T *el) { el->copyTo(data()); }
    SubclassStorage(const SubclassStorage &o) : SubclassStorage(o.data()) { }
    SubclassStorage(const SubclassStorage &&o) : SubclassStorage(o.data()) { }
    SubclassStorage &operator=(const SubclassStorage &o)
    {
        data()->~T();
        o.data()->copyTo(data());
        return *this;
    }
    ~SubclassStorage() { data()->~T(); }
};

class QMLDOM_EXPORT DomBase{
public:
    virtual ~DomBase() = default;

    // minimal overload set:
    virtual DomType kind() const = 0;
    virtual DomKind domKind() const;
    virtual Path pathFromOwner(DomItem &self) const = 0;
    virtual Path canonicalPath(DomItem &self) const = 0;
    virtual bool
    iterateDirectSubpaths(DomItem &self,
                          DirectVisitor visitor) = 0; // iterates the *direct* subpaths, returns
                                                      // false if a quick end was requested
    bool iterateDirectSubpathsConst(DomItem &self, DirectVisitor)
            const; // iterates the *direct* subpaths, returns false if a quick end was requested

    virtual DomItem containingObject(
            DomItem &self) const; // the DomItem corresponding to the canonicalSource source
    virtual void
    dump(DomItem &, Sink sink, int indent,
         function_ref<bool(DomItem &, const PathEls::PathComponent &, DomItem &)> filter) const;
    virtual quintptr id() const;
    QString typeName() const;

    virtual QList<QString> fields(DomItem &self) const;
    virtual DomItem field(DomItem &self, QStringView name) const;

    virtual index_type indexes(DomItem &self) const;
    virtual DomItem index(DomItem &self, index_type index) const;

    virtual QSet<QString> const keys(DomItem &self) const;
    virtual DomItem key(DomItem &self, QString name) const;

    virtual QString canonicalFilePath(DomItem &self) const;

    virtual void writeOut(DomItem &self, OutWriter &lw) const;

    virtual QCborValue value() const {
        return QCborValue();
    }
};

inline DomKind kind2domKind(DomType k)
{
    switch (k) {
    case DomType::Empty:
        return DomKind::Empty;
    case DomType::List:
    case DomType::ListP:
        return DomKind::List;
    case DomType::Map:
        return DomKind::Map;
    case DomType::ConstantData:
        return DomKind::Value;
    default:
        return DomKind::Object;
    }
}

class QMLDOM_EXPORT Empty final : public DomBase
{
public:
    constexpr static DomType kindValue = DomType::Empty;
    DomType kind() const override {  return kindValue; }

    Empty *operator->() { return this; }
    const Empty *operator->() const { return this; }
    Empty &operator*() { return *this; }
    const Empty &operator*() const { return *this; }

    Empty();
    quintptr id() const override { return ~quintptr(0); }
    Path pathFromOwner(DomItem &self) const override;
    Path canonicalPath(DomItem &self) const override;
    DomItem containingObject(DomItem &self) const override;
    bool iterateDirectSubpaths(DomItem &self, DirectVisitor) override;
    void dump(DomItem &, Sink s, int indent,
              function_ref<bool(DomItem &, const PathEls::PathComponent &, DomItem &)> filter)
            const override;
};

class QMLDOM_EXPORT DomElement: public DomBase {
protected:
    DomElement& operator=(const DomElement&) = default;
public:
    DomElement(Path pathFromOwner = Path());
    DomElement(const DomElement &o) = default;
    Path pathFromOwner(DomItem &self) const override;
    Path pathFromOwner() const { return m_pathFromOwner; }
    Path canonicalPath(DomItem &self) const override;
    DomItem containingObject(DomItem &self) const override;
    virtual void updatePathFromOwner(Path newPath);
private:
    Path m_pathFromOwner;
};

class QMLDOM_EXPORT Map final : public DomElement
{
public:
    constexpr static DomType kindValue = DomType::Map;
    DomType kind() const override {  return kindValue; }

    Map *operator->() { return this; }
    const Map *operator->() const { return this; }
    Map &operator*() { return *this; }
    const Map &operator*() const { return *this; }

    using LookupFunction = std::function<DomItem(DomItem &, QString)>;
    using Keys = std::function<QSet<QString>(DomItem &)>;
    Map(Path pathFromOwner, LookupFunction lookup, Keys keys, QString targetType);
    quintptr id() const override;
    bool iterateDirectSubpaths(DomItem &self, DirectVisitor) override;
    QSet<QString> const keys(DomItem &self) const override;
    DomItem key(DomItem &self, QString name) const override;

    template<typename T>
    static Map fromMultiMapRef(
            Path pathFromOwner, QMultiMap<QString, T> &mmap,
            std::function<DomItem(DomItem &, const PathEls::PathComponent &c, T &)> elWrapper);
    template<typename T>
    static Map
    fromMapRef(Path pathFromOwner, QMap<QString, T> &mmap,
               std::function<DomItem(DomItem &, const PathEls::PathComponent &, T &)> elWrapper);

private:
    LookupFunction m_lookup;
    Keys m_keys;
    QString m_targetType;
};

class QMLDOM_EXPORT List final : public DomElement
{
public:
    constexpr static DomType kindValue = DomType::List;
    DomType kind() const override {  return kindValue; }

    List *operator->() { return this; }
    const List *operator->() const { return this; }
    List &operator*() { return *this; }
    const List &operator*() const { return *this; }

    using LookupFunction = std::function<DomItem(DomItem &, index_type)>;
    using Length = std::function<index_type(DomItem &)>;
    using IteratorFunction =
            std::function<bool(DomItem &, function_ref<bool(index_type, function_ref<DomItem()>)>)>;

    List(Path pathFromOwner, LookupFunction lookup, Length length, IteratorFunction iterator, QString elType);
    quintptr id() const override;
    bool iterateDirectSubpaths(DomItem &self, DirectVisitor) override;
    void
    dump(DomItem &, Sink s, int indent,
         function_ref<bool(DomItem &, const PathEls::PathComponent &, DomItem &)>) const override;
    index_type indexes(DomItem &self) const override;
    DomItem index(DomItem &self, index_type index) const override;

    template<typename T>
    static List
    fromQList(Path pathFromOwner, QList<T> list,
              std::function<DomItem(DomItem &, const PathEls::PathComponent &, T &)> elWrapper,
              ListOptions options = ListOptions::Normal);
    template<typename T>
    static List
    fromQListRef(Path pathFromOwner, QList<T> &list,
                 std::function<DomItem(DomItem &, const PathEls::PathComponent &, T &)> elWrapper,
                 ListOptions options = ListOptions::Normal);
    void writeOut(DomItem &self, OutWriter &ow, bool compact) const;
    void writeOut(DomItem &self, OutWriter &ow) const override { writeOut(self, ow, true); }

private:
    LookupFunction m_lookup;
    Length m_length;
    IteratorFunction m_iterator;
    QString m_elType;
};

class QMLDOM_EXPORT ListPBase : public DomElement
{
public:
    constexpr static DomType kindValue = DomType::ListP;
    DomType kind() const override { return kindValue; }

    ListPBase(Path pathFromOwner, const QList<void *> &pList, QString elType)
        : DomElement(pathFromOwner), m_pList(pList), m_elType(elType)
    {
    }
    bool iterateDirectSubpaths(DomItem &self, DirectVisitor v) override;
    virtual void copyTo(ListPBase *) const { Q_ASSERT(false); };
    virtual void moveTo(ListPBase *) const { Q_ASSERT(false); };
    quintptr id() const override { return quintptr(0); }
    index_type indexes(DomItem &) const override { return index_type(m_pList.size()); }
    void writeOut(DomItem &self, OutWriter &ow, bool compact) const;
    void writeOut(DomItem &self, OutWriter &ow) const override { writeOut(self, ow, true); }

protected:
    QList<void *> m_pList;
    QString m_elType;
};

template<typename T>
class QMLDOM_EXPORT ListPT final : public ListPBase
{
public:
    constexpr static DomType kindValue = DomType::ListP;

    ListPT(Path pathFromOwner, QList<T *> pList, QString elType = QString(),
           ListOptions options = ListOptions::Normal)
        : ListPBase(pathFromOwner, {},
                    (elType.isEmpty() ? QLatin1String(typeid(T).name()) : elType))
    {
        static_assert(sizeof(ListPBase) == sizeof(ListPT),
                      "ListPT does not have the same size as ListPBase");
        static_assert(alignof(ListPBase) == alignof(ListPT),
                      "ListPT does not have the same size as ListPBase");
        m_pList.reserve(pList.size());
        if (options == ListOptions::Normal) {
            for (void *p : pList)
                m_pList.append(p);
        } else if (options == ListOptions::Reverse) {
            for (qsizetype i = pList.length(); i-- != 0;)
                // probably writing in reverse and reading sequentially would be better
                m_pList.append(pList.at(i));
        } else {
            Q_ASSERT(false);
        }
    }
    void copyTo(ListPBase *t) const override { new (t) ListPT(*this); }
    void moveTo(ListPBase *t) const override { new (t) ListPT(std::move(*this)); }
    bool iterateDirectSubpaths(DomItem &self, DirectVisitor v) override;

    DomItem index(DomItem &self, index_type index) const override;
};

class QMLDOM_EXPORT ListP
{
public:
    constexpr static DomType kindValue = DomType::ListP;
    template<typename T>
    ListP(Path pathFromOwner, QList<T *> pList, QString elType = QString(),
          ListOptions options = ListOptions::Normal)
        : list(ListPT<T>(pathFromOwner, pList, elType, options))
    {
    }
    ListP() = delete;

    ListPBase *operator->() { return list.data(); }
    const ListPBase *operator->() const { return list.data(); }
    ListPBase &operator*() { return *list.data(); }
    const ListPBase &operator*() const { return *list.data(); }

private:
    SubclassStorage<ListPBase> list;
};

class QMLDOM_EXPORT ConstantData final : public DomElement
{
public:
    constexpr static DomType kindValue = DomType::ConstantData;
    DomType kind() const override { return kindValue; }

    enum class Options {
        MapIsMap,
        FirstMapIsFields
    };

    ConstantData *operator->() { return this; }
    const ConstantData *operator->() const { return this; }
    ConstantData &operator*() { return *this; }
    const ConstantData &operator*() const { return *this; }

    ConstantData(Path pathFromOwner, QCborValue value, Options options = Options::MapIsMap);
    bool iterateDirectSubpaths(DomItem &self, DirectVisitor) override;
    quintptr id() const override;
    DomKind domKind() const override;
    QCborValue value() const override { return m_value; }
    Options options() const { return m_options; }
private:
    QCborValue m_value;
    Options m_options;
};

class QMLDOM_EXPORT SimpleObjectWrapBase : public DomElement
{
public:
    constexpr static DomType kindValue = DomType::SimpleObjectWrap;
    DomType kind() const final override { return m_kind; }

    quintptr id() const final override { return m_id; }
    DomKind domKind() const final override { return m_domKind; }

    template <typename T>
    T const *as() const
    {
        if (m_options & SimpleWrapOption::ValueType) {
            if (m_value.metaType().id() == QMetaType::fromType<T>().id())
                return reinterpret_cast<const T *>(m_value.constData());
            return nullptr;
        } else {
            return m_value.value<T *>();
        }
    }
    template <typename T>
    T *mutableAs()
    {
        if (m_options & SimpleWrapOption::ValueType) {
            if (m_value.metaType().id() == QMetaType::fromType<T>().id())
                return reinterpret_cast<T *>(m_value.data());
            return nullptr;
        } else {
            return m_value.value<T *>();
        }
    }
    SimpleObjectWrapBase() = delete;
    virtual void copyTo(SimpleObjectWrapBase *) const { Q_ASSERT(false); }
    virtual void moveTo(SimpleObjectWrapBase *) const { Q_ASSERT(false); }
    bool iterateDirectSubpaths(DomItem &, DirectVisitor) override
    {
        Q_ASSERT(false);
        return true;
    }

protected:
    friend class TestDomItem;
    SimpleObjectWrapBase(Path pathFromOwner, QVariant value, quintptr idValue,
                         DomType kind = kindValue,
                         SimpleWrapOptions options = SimpleWrapOption::None)
        : DomElement(pathFromOwner),
          m_kind(kind),
          m_domKind(kind2domKind(kind)),
          m_value(value),
          m_id(idValue),
          m_options(options)
    {
    }

    DomType m_kind;
    DomKind m_domKind;
    QVariant m_value;
    quintptr m_id;
    SimpleWrapOptions m_options;
};

template<typename T>
class QMLDOM_EXPORT SimpleObjectWrapT final : public SimpleObjectWrapBase
{
public:
    constexpr static DomType kindValue = DomType::SimpleObjectWrap;

    bool iterateDirectSubpaths(DomItem &self, DirectVisitor visitor) override
    {
        return mutableAsT()->iterateDirectSubpaths(self, visitor);
    }

    void writeOut(DomItem &self, OutWriter &lw) const override;

    T const *asT() const
    {
        if constexpr (domTypeIsValueWrap(T::kindValue)) {
            if (m_value.metaType().id() == QMetaType::fromType<T>().id())
                return reinterpret_cast<const T *>(m_value.constData());
            return nullptr;
        } else if constexpr (domTypeIsObjWrap(T::kindValue)) {
            return m_value.value<T *>();
        } else {
            Q_ASSERT_X(false, "SimpleObjectWrapT", "wrapping of unexpected type");
        }
    }

    T *mutableAsT()
    {
        if (domTypeIsValueWrap(T::kindValue)) {
            if (m_value.metaType().id() == QMetaType::fromType<T>().id())
                return reinterpret_cast<T *>(m_value.data());
            return nullptr;
        } else if constexpr (domTypeIsObjWrap(T::kindValue)) {
            return m_value.value<T *>();
        } else {
            Q_ASSERT_X(false, "SimpleObjectWrap", "wrapping of unexpected type");
            return nullptr;
        }
    }

    void copyTo(SimpleObjectWrapBase *target) const override
    {
        static_assert(sizeof(SimpleObjectWrapBase) == sizeof(SimpleObjectWrapT),
                      "Size mismatch in SimpleObjectWrapT");
        static_assert(alignof(SimpleObjectWrapBase) == alignof(SimpleObjectWrapT),
                      "Size mismatch in SimpleObjectWrapT");
        new (target) SimpleObjectWrapT(*this);
    }

    void moveTo(SimpleObjectWrapBase *target) const override
    {
        static_assert(sizeof(SimpleObjectWrapBase) == sizeof(SimpleObjectWrapT),
                      "Size mismatch in SimpleObjectWrapT");
        static_assert(alignof(SimpleObjectWrapBase) == alignof(SimpleObjectWrapT),
                      "Size mismatch in SimpleObjectWrapT");
        new (target) SimpleObjectWrapT(std::move(*this));
    }

    SimpleObjectWrapT(Path pathFromOwner, QVariant v, quintptr idValue, SimpleWrapOptions o)
        : SimpleObjectWrapBase(pathFromOwner, v, idValue, T::kindValue, o)
    {
        Q_ASSERT(domTypeIsValueWrap(T::kindValue) == bool(o & SimpleWrapOption::ValueType));
    }
};

class QMLDOM_EXPORT SimpleObjectWrap
{
public:
    constexpr static DomType kindValue = DomType::SimpleObjectWrap;

    SimpleObjectWrapBase *operator->() { return wrap.data(); }
    const SimpleObjectWrapBase *operator->() const { return wrap.data(); }
    SimpleObjectWrapBase &operator*() { return *wrap.data(); }
    const SimpleObjectWrapBase &operator*() const { return *wrap.data(); }

    template<typename T>
    static SimpleObjectWrap fromObjectRef(Path pathFromOwner, T &value)
    {
        return SimpleObjectWrap(pathFromOwner, value);
    }
    SimpleObjectWrap() = delete;

private:
    template<typename T>
    SimpleObjectWrap(Path pathFromOwner, T &value)
    {
        using BaseT = std::decay_t<T>;
        if constexpr (domTypeIsObjWrap(BaseT::kindValue)) {
            new (wrap.data()) SimpleObjectWrapT<BaseT>(pathFromOwner, QVariant::fromValue(&value),
                                                       quintptr(&value), SimpleWrapOption::None);
        } else if constexpr (domTypeIsValueWrap(BaseT::kindValue)) {
            new (wrap.data()) SimpleObjectWrapT<BaseT>(pathFromOwner, QVariant::fromValue(value),
                                                       quintptr(0), SimpleWrapOption::ValueType);
        } else {
            qCWarning(domLog) << "Unexpected object to wrap in SimpleObjectWrap: "
                              << domTypeToString(BaseT::kindValue);
            Q_ASSERT_X(false, "SimpleObjectWrap",
                       "simple wrap of unexpected object"); // allow? (mocks for testing,...)
            new (wrap.data())
                    SimpleObjectWrapT<BaseT>(pathFromOwner, nullptr, 0, SimpleWrapOption::None);
        }
    }
    SubclassStorage<SimpleObjectWrapBase> wrap;
};

class QMLDOM_EXPORT Reference final : public DomElement
{
    Q_GADGET
public:
    constexpr static DomType kindValue = DomType::Reference;
    DomType kind() const override {  return kindValue; }

    Reference *operator->() { return this; }
    const Reference *operator->() const { return this; }
    Reference &operator*() { return *this; }
    const Reference &operator*() const { return *this; }

    bool shouldCache() const;
    Reference(Path referredObject = Path(), Path pathFromOwner = Path(), const SourceLocation & loc = SourceLocation());
    quintptr id() const override;
    bool iterateDirectSubpaths(DomItem &self, DirectVisitor) override;
    DomItem field(DomItem &self, QStringView name) const override;
    QList<QString> fields(DomItem &self) const override;
    index_type indexes(DomItem &) const override { return 0; }
    DomItem index(DomItem &, index_type) const override;
    QSet<QString> const keys(DomItem &) const override { return {}; }
    DomItem key(DomItem &, QString) const override;

    DomItem get(DomItem &self, ErrorHandler h = nullptr, QList<Path> *visitedRefs = nullptr) const;
    QList<DomItem> getAll(DomItem &self, ErrorHandler h = nullptr,
                          QList<Path> *visitedRefs = nullptr) const;

    Path referredObjectPath;
};

using ElementT = std::variant<
        Empty, Map, List, ListP, ConstantData, SimpleObjectWrap, Reference, GlobalComponent *,
        JsResource *, QmlComponent *, QmltypesComponent *, EnumDecl *, MockObject *, ModuleScope *,
        AstComments *, AttachedInfo *, DomEnvironment *, DomUniverse *, ExternalItemInfoBase *,
        ExternalItemPairBase *, GlobalScope *, JsFile *, QmlDirectory *, QmlFile *, QmldirFile *,
        QmlObject *, QmltypesFile *, LoadInfo *, MockOwner *, ModuleIndex *, ScriptExpression *>;

using TopT = std::variant<std::shared_ptr<DomEnvironment>, std::shared_ptr<DomUniverse>>;

using OwnerT =
        std::variant<std::shared_ptr<ModuleIndex>, std::shared_ptr<MockOwner>,
                     std::shared_ptr<ExternalItemInfoBase>, std::shared_ptr<ExternalItemPairBase>,
                     std::shared_ptr<QmlDirectory>, std::shared_ptr<QmldirFile>,
                     std::shared_ptr<JsFile>, std::shared_ptr<QmlFile>,
                     std::shared_ptr<QmltypesFile>, std::shared_ptr<GlobalScope>,
                     std::shared_ptr<ScriptExpression>, std::shared_ptr<AstComments>,
                     std::shared_ptr<LoadInfo>, std::shared_ptr<AttachedInfo>,
                     std::shared_ptr<DomEnvironment>, std::shared_ptr<DomUniverse>>;

inline bool emptyChildrenVisitor(Path, DomItem &, bool)
{
    return true;
}

class MutableDomItem;

class QMLDOM_EXPORT DomItem {
    Q_DECLARE_TR_FUNCTIONS(DomItem);
public:
    using Callback = function<void(Path, DomItem &, DomItem &)>;

    using InternalKind = DomType;
    using Visitor = function_ref<bool(Path, DomItem &)>;
    using ChildrenVisitor = function_ref<bool(Path, DomItem &, bool)>;

    static ErrorGroup domErrorGroup;
    static ErrorGroups myErrors();
    static ErrorGroups myResolveErrors();
    static DomItem empty;

    enum class CopyOption { EnvConnected, EnvDisconnected };

    template<typename F>
    auto visitMutableEl(F f)
    {
        return std::visit(f, this->m_element);
    }
    template<typename F>
    auto visitEl(F f)
    {
        return std::visit(f, this->m_element);
    }

    explicit operator bool() const { return m_kind != DomType::Empty; }
    InternalKind internalKind() const {
        return m_kind;
    }
    QString internalKindStr() const { return domTypeToString(internalKind()); }
    DomKind domKind() const
    {
        if (m_kind == DomType::ConstantData)
            return std::get<ConstantData>(m_element).domKind();
        else
            return kind2domKind(m_kind);
    }

    Path canonicalPath();

    DomItem filterUp(function_ref<bool(DomType k, DomItem &)> filter, FilterUpOptions options);
    DomItem containingObject();
    DomItem container();
    DomItem owner();
    DomItem top();
    DomItem environment();
    DomItem universe();

    DomItem qmlObject(GoTo option = GoTo::Strict,
                      FilterUpOptions options = FilterUpOptions::ReturnOuter);
    DomItem fileObject(GoTo option = GoTo::Strict);
    DomItem rootQmlObject(GoTo option = GoTo::Strict);
    DomItem globalScope();
    DomItem component(GoTo option = GoTo::Strict);
    DomItem scope(FilterUpOptions options = FilterUpOptions::ReturnOuter);

    // convenience getters
    DomItem get(ErrorHandler h = nullptr, QList<Path> *visitedRefs = nullptr);
    QList<DomItem> getAll(ErrorHandler h = nullptr, QList<Path> *visitedRefs = nullptr);
    bool isOwningItem() { return domTypeIsOwningItem(internalKind()); }
    bool isExternalItem() { return domTypeIsExternalItem(internalKind()); }
    bool isTopItem() { return domTypeIsTopItem(internalKind()); }
    bool isContainer() { return domTypeIsContainer(internalKind()); }
    bool isScope() { return domTypeIsScope(internalKind()); }
    bool isCanonicalChild(DomItem &child);
    bool hasAnnotations();
    QString name() { return field(Fields::name).value().toString(); }
    DomItem pragmas() { return field(Fields::pragmas); }
    DomItem ids() { return field(Fields::ids); }
    QString idStr() { return field(Fields::idStr).value().toString(); }
    DomItem propertyInfos() { return field(Fields::propertyInfos); }
    PropertyInfo propertyInfoWithName(QString name);
    QSet<QString> propertyInfoNames();
    DomItem propertyDefs() { return field(Fields::propertyDefs); }
    DomItem bindings() { return field(Fields::bindings); }
    DomItem methods() { return field(Fields::methods); }
    DomItem enumerations() { return field(Fields::enumerations); }
    DomItem children() { return field(Fields::children); }
    DomItem child(index_type i) { return field(Fields::children).index(i); }
    DomItem annotations()
    {
        if (hasAnnotations())
            return field(Fields::annotations);
        else
            return DomItem();
    }

    bool resolve(Path path, Visitor visitor, ErrorHandler errorHandler,
                 ResolveOptions options = ResolveOption::None, Path fullPath = Path(),
                 QList<Path> *visitedRefs = nullptr);

    DomItem operator[](Path path);
    DomItem operator[](QStringView component);
    DomItem operator[](const QString &component);
    DomItem operator[](const char16_t *component)
    {
        return (*this)[QStringView(component)];
    } // to avoid clash with stupid builtin ptrdiff_t[DomItem&], coming from C
    DomItem operator[](index_type i) { return index(i); }
    DomItem operator[](int i) { return index(i); }
    index_type size() { return indexes() + keys().size(); }
    index_type length() { return size(); }

    DomItem path(Path p, ErrorHandler h = &defaultErrorHandler);
    DomItem path(QString p, ErrorHandler h = &defaultErrorHandler);
    DomItem path(QStringView p, ErrorHandler h = &defaultErrorHandler);

    QList<QString> fields();
    DomItem field(QStringView name);

    index_type indexes();
    DomItem index(index_type);
    bool visitIndexes(function_ref<bool(DomItem &)> visitor);

    QSet<QString> keys();
    QStringList sortedKeys();
    DomItem key(QString name);
    DomItem key(QStringView name) { return key(name.toString()); }
    bool visitKeys(function_ref<bool(QString, DomItem &)> visitor);

    QList<DomItem> values();
    void writeOutPre(OutWriter &lw);
    void writeOut(OutWriter &lw);
    void writeOutPost(OutWriter &lw);
    DomItem writeOutForFile(OutWriter &ow, WriteOutChecks extraChecks);
    DomItem writeOut(QString path, int nBackups = 2,
                     const LineWriterOptions &opt = LineWriterOptions(), FileWriter *fw = nullptr,
                     WriteOutChecks extraChecks = WriteOutCheck::Default);

    bool visitTree(Path basePath, ChildrenVisitor visitor,
                   VisitOptions options = VisitOption::Default,
                   ChildrenVisitor openingVisitor = emptyChildrenVisitor,
                   ChildrenVisitor closingVisitor = emptyChildrenVisitor);
    bool visitPrototypeChain(function_ref<bool(DomItem &)> visitor,
                             VisitPrototypesOptions options = VisitPrototypesOption::Normal,
                             ErrorHandler h = nullptr, QSet<quintptr> *visited = nullptr,
                             QList<Path> *visitedRefs = nullptr);
    bool visitDirectAccessibleScopes(function_ref<bool(DomItem &)> visitor,
                                     VisitPrototypesOptions options = VisitPrototypesOption::Normal,
                                     ErrorHandler h = nullptr, QSet<quintptr> *visited = nullptr,
                                     QList<Path> *visitedRefs = nullptr);
    bool
    visitStaticTypePrototypeChains(function_ref<bool(DomItem &)> visitor,
                                   VisitPrototypesOptions options = VisitPrototypesOption::Normal,
                                   ErrorHandler h = nullptr, QSet<quintptr> *visited = nullptr,
                                   QList<Path> *visitedRefs = nullptr);
    bool visitScopeChain(function_ref<bool(DomItem &)> visitor,
                         LookupOptions = LookupOption::Normal, ErrorHandler h = nullptr,
                         QSet<quintptr> *visited = nullptr, QList<Path> *visitedRefs = nullptr);
    bool visitLocalSymbolsNamed(QString name, function_ref<bool(DomItem &)> visitor);
    QSet<QString> localSymbolNames();
    bool visitLookup1(QString symbolName, function_ref<bool(DomItem &)> visitor,
                      LookupOptions = LookupOption::Normal, ErrorHandler h = nullptr,
                      QSet<quintptr> *visited = nullptr, QList<Path> *visitedRefs = nullptr);
    bool visitLookup(QString symbolName, function_ref<bool(DomItem &)> visitor,
                     LookupType type = LookupType::Symbol, LookupOptions = LookupOption::Normal,
                     ErrorHandler errorHandler = nullptr, QSet<quintptr> *visited = nullptr,
                     QList<Path> *visitedRefs = nullptr);
    bool visitSubSymbolsNamed(QString name, function_ref<bool(DomItem &)> visitor);
    DomItem proceedToScope(ErrorHandler h = nullptr, QList<Path> *visitedRefs = nullptr);
    QList<DomItem> lookup(QString symbolName, LookupType type = LookupType::Symbol,
                          LookupOptions = LookupOption::Normal,
                          ErrorHandler errorHandler = nullptr);
    DomItem lookupFirst(QString symbolName, LookupType type = LookupType::Symbol,
                        LookupOptions = LookupOption::Normal, ErrorHandler errorHandler = nullptr);

    quintptr id();
    Path pathFromOwner();
    QString canonicalFilePath();
    DomItem fileLocationsTree();
    DomItem fileLocations();
    MutableDomItem makeCopy(CopyOption option = CopyOption::EnvConnected);
    bool commitToBase();
    DomItem refreshed() { return top().path(canonicalPath()); }
    QCborValue value();

    void dumpPtr(Sink sink);
    void dump(Sink, int indent = 0,
              function_ref<bool(DomItem &, const PathEls::PathComponent &, DomItem &)> filter =
                      noFilter);
    FileWriter::Status
    dump(QString path,
         function_ref<bool(DomItem &, const PathEls::PathComponent &, DomItem &)> filter = noFilter,
         int nBackups = 2, int indent = 0, FileWriter *fw = nullptr);
    QString toString();
    QString toString() const
    {
        DomItem self = *this;
        return self.toString();
    }

    // OwnigItem elements
    int derivedFrom();
    int revision();
    QDateTime createdAt();
    QDateTime frozenAt();
    QDateTime lastDataUpdateAt();

    void addError(ErrorMessage msg);
    ErrorHandler errorHandler();
    void clearErrors(ErrorGroups groups = ErrorGroups({}), bool iterate = true);
    // return false if a quick exit was requested
    bool iterateErrors(function_ref<bool(DomItem source, ErrorMessage msg)> visitor, bool iterate,
                       Path inPath = Path());

    bool iterateSubOwners(function_ref<bool(DomItem &owner)> visitor);
    bool iterateDirectSubpaths(DirectVisitor v);

    template<typename T>
    DomItem subDataItem(const PathEls::PathComponent &c, T value,
                        ConstantData::Options options = ConstantData::Options::MapIsMap);
    template<typename T>
    DomItem subDataItemField(QStringView f, T value,
                             ConstantData::Options options = ConstantData::Options::MapIsMap)
    {
        return subDataItem(PathEls::Field(f), value, options);
    }
    template<typename T>
    DomItem subValueItem(const PathEls::PathComponent &c, T value,
                         ConstantData::Options options = ConstantData::Options::MapIsMap);
    template<typename T>
    bool dvValue(DirectVisitor visitor, const PathEls::PathComponent &c, T value,
                 ConstantData::Options options = ConstantData::Options::MapIsMap);
    template<typename T>
    bool dvValueField(DirectVisitor visitor, QStringView f, T value,
                      ConstantData::Options options = ConstantData::Options::MapIsMap)
    {
        return this->dvValue<T>(visitor, PathEls::Field(f), value, options);
    }
    template<typename F>
    bool dvValueLazy(DirectVisitor visitor, const PathEls::PathComponent &c, F valueF,
                     ConstantData::Options options = ConstantData::Options::MapIsMap);
    template<typename F>
    bool dvValueLazyField(DirectVisitor visitor, QStringView f, F valueF,
                          ConstantData::Options options = ConstantData::Options::MapIsMap)
    {
        return this->dvValueLazy(visitor, PathEls::Field(f), valueF, options);
    }
    DomItem subLocationItem(const PathEls::PathComponent &c, SourceLocation loc,
                            QStringView code = QStringView())
    {
        return this->subDataItem(c, locationToData(loc, code));
    }
    // bool dvSubReference(DirectVisitor visitor, const PathEls::PathComponent &c, Path
    // referencedObject);
    DomItem subReferencesItem(const PathEls::PathComponent &c, QList<Path> paths);
    DomItem subReferenceItem(const PathEls::PathComponent &c, Path referencedObject);
    bool dvReference(DirectVisitor visitor, const PathEls::PathComponent &c, Path referencedObject)
    {
        return dvItem(visitor, c, [c, this, referencedObject]() {
            return this->subReferenceItem(c, referencedObject);
        });
    }
    bool dvReferences(DirectVisitor visitor, const PathEls::PathComponent &c, QList<Path> paths)
    {
        return dvItem(visitor, c, [c, this, paths]() { return this->subReferencesItem(c, paths); });
    }
    bool dvReferenceField(DirectVisitor visitor, QStringView f, Path referencedObject)
    {
        return dvReference(visitor, PathEls::Field(f), referencedObject);
    }
    bool dvReferencesField(DirectVisitor visitor, QStringView f, QList<Path> paths)
    {
        return dvReferences(visitor, PathEls::Field(f), paths);
    }
    bool dvItem(DirectVisitor visitor, const PathEls::PathComponent &c, function_ref<DomItem()> it)
    {
        return visitor(c, it);
    }
    bool dvItemField(DirectVisitor visitor, QStringView f, function_ref<DomItem()> it)
    {
        return dvItem(visitor, PathEls::Field(f), it);
    }
    DomItem subListItem(const List &list);
    DomItem subMapItem(const Map &map);
    DomItem subObjectWrapItem(SimpleObjectWrap obj)
    {
        return DomItem(m_top, m_owner, m_ownerPath, obj);
    }
    template<typename Owner>
    DomItem subOwnerItem(const PathEls::PathComponent &c, Owner o)
    {
        if constexpr (domTypeIsUnattachedOwningItem(Owner::element_type::kindValue))
            return DomItem(m_top, o, canonicalPath().appendComponent(c), o.get());
        else
            return DomItem(m_top, o, Path(), o.get());
    }
    template<typename T>
    DomItem wrap(const PathEls::PathComponent &c, T &obj);
    template<typename T>
    DomItem wrapField(QStringView f, T &obj)
    {
        return wrap<T>(PathEls::Field(f), obj);
    }
    template<typename T>
    bool dvWrap(DirectVisitor visitor, const PathEls::PathComponent &c, T &obj);
    template<typename T>
    bool dvWrapField(DirectVisitor visitor, QStringView f, T &obj)
    {
        return dvWrap<T>(visitor, PathEls::Field(f), obj);
    }

    DomItem() = default;
    DomItem(std::shared_ptr<DomEnvironment>);
    DomItem(std::shared_ptr<DomUniverse>);

    void loadFile(QString filePath, QString logicalPath,
                  std::function<void(Path, DomItem &, DomItem &)> callback, LoadOptions loadOptions,
                  std::optional<DomType> fileType = std::optional<DomType>());
    void loadFile(QString canonicalFilePath, QString logicalPath, QString code, QDateTime codeDate,
                  std::function<void(Path, DomItem &, DomItem &)> callback, LoadOptions loadOptions,
                  std::optional<DomType> fileType = std::optional<DomType>());
    void loadModuleDependency(QString uri, Version v,
                              std::function<void(Path, DomItem &, DomItem &)> callback = nullptr,
                              ErrorHandler = nullptr);
    void loadBuiltins(std::function<void(Path, DomItem &, DomItem &)> callback = nullptr,
                      ErrorHandler = nullptr);
    void loadPendingDependencies();

    // --- start of potentially dangerous stuff, make private? ---

    std::shared_ptr<DomTop> topPtr();
    std::shared_ptr<OwningItem> owningItemPtr();

    // keep the DomItem around to ensure that it doesn't get deleted
    template<typename T, typename std::enable_if<std::is_base_of_v<DomBase, T>, bool>::type = true>
    T const *as()
    {
        if (m_kind == T::kindValue) {
            if constexpr (domTypeIsObjWrap(T::kindValue) || domTypeIsValueWrap(T::kindValue))
                return std::get<SimpleObjectWrap>(m_element)->as<T>();
            else
                return static_cast<T const *>(base());
        }
        return nullptr;
    }

    template<typename T, typename std::enable_if<!std::is_base_of_v<DomBase, T>, bool>::type = true>
    T const *as()
    {
        if (m_kind == T::kindValue) {
            Q_ASSERT(domTypeIsObjWrap(m_kind) || domTypeIsValueWrap(m_kind));
            return std::get<SimpleObjectWrap>(m_element)->as<T>();
        }
        return nullptr;
    }

    template<typename T>
    std::shared_ptr<T> ownerAs();

    template<typename Owner, typename T>
    DomItem copy(Owner owner, Path ownerPath, T base)
    {
        Q_ASSERT(m_top);
        static_assert(IsInlineDom<std::decay_t<T>>::value, "Expected an inline item or pointer");
        return DomItem(m_top, owner, ownerPath, base);
    }

    template<typename Owner>
    DomItem copy(Owner owner, Path ownerPath)
    {
        Q_ASSERT(m_top);
        return DomItem(m_top, owner, ownerPath, owner.get());
    }

    template<typename T>
    DomItem copy(T base)
    {
        Q_ASSERT(m_top);
        using BaseT = std::decay_t<T>;
        static_assert(!std::is_same_v<BaseT, ElementT>,
                      "variant not supported, pass in the stored types");
        static_assert(IsInlineDom<BaseT>::value, "expected either a pointer or an inline item");
        if constexpr (IsSharedPointerToDomObject<BaseT>::value) {
            return DomItem(m_top, base, Path(), base.get());
        } else {
            return DomItem(m_top, m_owner, m_ownerPath, base);
        }
    }

private:
    DomBase const *base();
    template <typename T, typename std::enable_if<std::is_base_of<DomBase, T>::value, bool>::type = true>
    T *mutableAs() {
        if (m_kind == T::kindValue) {
            if constexpr (domTypeIsObjWrap(T::kindValue) || domTypeIsValueWrap(T::kindValue))
                return static_cast<SimpleObjectWrapBase *>(mutableBase())->mutableAs<T>();
            else
                return static_cast<T *>(mutableBase());
        }
        return nullptr;
    }

    template <typename T, typename std::enable_if<!std::is_base_of<DomBase, T>::value, bool>::type = true>
    T *mutableAs() {
        if (m_kind == T::kindValue) {
            Q_ASSERT(domTypeIsObjWrap(m_kind) || domTypeIsValueWrap(m_kind));
            return static_cast<SimpleObjectWrapBase *>(mutableBase())->mutableAs<T>();
        }
        return nullptr;
    }
    DomBase *mutableBase();
    template<typename Env, typename Owner>
    DomItem(Env, Owner, Path, std::nullptr_t) : DomItem()
    {
    }
    template<typename Env, typename Owner, typename T,
             typename = std::enable_if_t<IsInlineDom<std::decay_t<T>>::value>>
    DomItem(Env env, Owner owner, Path ownerPath, T el)
        : m_top(env), m_owner(owner), m_ownerPath(ownerPath), m_element(el)
    {
        using BaseT = std::decay_t<T>;
        if constexpr (std::is_pointer_v<BaseT>) {
            if (!el || el->kind() == DomType::Empty) { // avoid null ptr, and allow only a
                // single kind of Empty
                m_kind = DomType::Empty;
                m_top.reset();
                m_owner.reset();
                m_ownerPath = Path();
                m_element = Empty();
            } else {
                using DomT = std::remove_pointer_t<BaseT>;
                m_element = el;
                m_kind = DomT::kindValue;
            }
        } else {
            static_assert(!std::is_same_v<BaseT, ElementT>,
                          "variant not supported, pass in the internal type");
            m_kind = el->kind();
        }
    }
    friend class DomBase;
    friend class DomElement;
    friend class Map;
    friend class List;
    friend class QmlObject;
    friend class DomUniverse;
    friend class DomEnvironment;
    friend class ExternalItemInfoBase;
    friend class ConstantData;
    friend class MutableDomItem;
    friend class ScriptExpression;
    friend class AstComments;
    friend class AttachedInfo;
    friend class TestDomItem;
    friend bool operator==(const DomItem &, const DomItem &);
    DomType m_kind = DomType::Empty;
    std::optional<TopT> m_top;
    std::optional<OwnerT> m_owner;
    Path m_ownerPath;
    ElementT m_element = Empty();
};

bool operator==(const DomItem &o1, const DomItem &o2);
inline bool operator!=(const DomItem &o1, const DomItem &o2)
{
    return !(o1 == o2);
}

template<typename T>
Map Map::fromMultiMapRef(
        Path pathFromOwner, QMultiMap<QString, T> &mmap,
        std::function<DomItem(DomItem &, const PathEls::PathComponent &, T &)> elWrapper)
{
    return Map(
            pathFromOwner,
            [&mmap, elWrapper](DomItem &self, QString key) {
                auto it = mmap.find(key);
                auto end = mmap.cend();
                if (it == end)
                    return DomItem();
                else {
                    // special case single element (++it == end || it.key() != key)?
                    QList<T *> values;
                    while (it != end && it.key() == key)
                        values.append(&(*it++));
                    ListP ll(self.pathFromOwner().appendComponent(PathEls::Key(key)), values,
                             QString(), ListOptions::Reverse);
                    return self.copy(ll);
                }
            },
            [&mmap](DomItem &) { return QSet<QString>(mmap.keyBegin(), mmap.keyEnd()); },
            QLatin1String(typeid(T).name()));
}

template<typename T>
Map Map::fromMapRef(
        Path pathFromOwner, QMap<QString, T> &map,
        std::function<DomItem(DomItem &, const PathEls::PathComponent &, T &)> elWrapper)
{
    return Map(
            pathFromOwner,
            [&map, elWrapper](DomItem &self, QString key) {
                if (!map.contains(key))
                    return DomItem();
                else {
                    return elWrapper(self, PathEls::Key(key), map[key]);
                }
            },
            [&map](DomItem &) { return QSet<QString>(map.keyBegin(), map.keyEnd()); },
            QLatin1String(typeid(T).name()));
}

template<typename T>
List List::fromQList(
        Path pathFromOwner, QList<T> list,
        std::function<DomItem(DomItem &, const PathEls::PathComponent &, T &)> elWrapper,
        ListOptions options)
{
    index_type len = list.length();
    if (options == ListOptions::Reverse) {
        return List(
                pathFromOwner,
                [list, elWrapper](DomItem &self, index_type i) mutable {
                    if (i < 0 || i >= list.length())
                        return DomItem();
                    return elWrapper(self, PathEls::Index(i), list[list.length() - i - 1]);
                },
                [len](DomItem &) { return len; }, nullptr, QLatin1String(typeid(T).name()));
    } else {
        return List(
                pathFromOwner,
                [list, elWrapper](DomItem &self, index_type i) mutable {
                    if (i < 0 || i >= list.length())
                        return DomItem();
                    return elWrapper(self, PathEls::Index(i), list[i]);
                },
                [len](DomItem &) { return len; }, nullptr, QLatin1String(typeid(T).name()));
    }
}

template<typename T>
List List::fromQListRef(
        Path pathFromOwner, QList<T> &list,
        std::function<DomItem(DomItem &, const PathEls::PathComponent &, T &)> elWrapper,
        ListOptions options)
{
    if (options == ListOptions::Reverse) {
        return List(
                pathFromOwner,
                [&list, elWrapper](DomItem &self, index_type i) {
                    if (i < 0 || i >= list.length())
                        return DomItem();
                    return elWrapper(self, PathEls::Index(i), list[list.length() - i - 1]);
                },
                [&list](DomItem &) { return list.length(); }, nullptr,
                QLatin1String(typeid(T).name()));
    } else {
        return List(
                pathFromOwner,
                [&list, elWrapper](DomItem &self, index_type i) {
                    if (i < 0 || i >= list.length())
                        return DomItem();
                    return elWrapper(self, PathEls::Index(i), list[i]);
                },
                [&list](DomItem &) { return list.length(); }, nullptr,
                QLatin1String(typeid(T).name()));
    }
}

class QMLDOM_EXPORT OwningItem: public DomBase {
protected:
    virtual std::shared_ptr<OwningItem> doCopy(DomItem &self) const = 0;

public:
    OwningItem(const OwningItem &o);
    OwningItem(int derivedFrom=0);
    OwningItem(int derivedFrom, QDateTime lastDataUpdateAt);
    OwningItem(const OwningItem &&) = delete;
    OwningItem &operator=(const OwningItem &&) = delete;
    static int nextRevision();

    Path canonicalPath(DomItem &self) const override = 0;

    bool iterateDirectSubpaths(DomItem &self, DirectVisitor) override;
    std::shared_ptr<OwningItem> makeCopy(DomItem &self) const { return doCopy(self); }
    Path pathFromOwner() const { return Path(); }
    Path pathFromOwner(DomItem &) const override final { return Path(); }
    DomItem containingObject(DomItem &self) const override;
    int derivedFrom() const;
    virtual int revision() const;

    QDateTime createdAt() const;
    virtual QDateTime lastDataUpdateAt() const;
    virtual void refreshedDataAt(QDateTime tNew);

    // explicit freeze handling needed?
    virtual bool frozen() const;
    virtual bool freeze();
    QDateTime frozenAt() const;

    virtual void addError(DomItem &self, ErrorMessage msg);
    void addErrorLocal(ErrorMessage msg);
    void clearErrors(ErrorGroups groups = ErrorGroups({}));
    // return false if a quick exit was requested
    bool iterateErrors(DomItem &self, function_ref<bool(DomItem source, ErrorMessage msg)> visitor,
                       Path inPath = Path());
    QMultiMap<Path, ErrorMessage> localErrors() const {
        QMutexLocker l(mutex());
        return m_errors;
    }

    virtual bool iterateSubOwners(DomItem &self, function_ref<bool(DomItem &owner)> visitor);

    QBasicMutex *mutex() const { return &m_mutex; }
private:
    mutable QBasicMutex m_mutex;
    int m_derivedFrom;
    int m_revision;
    QDateTime m_createdAt;
    QDateTime m_lastDataUpdateAt;
    QDateTime m_frozenAt;
    QMultiMap<Path, ErrorMessage> m_errors;
    QMap<ErrorMessage, quint32> m_errorsCounts;
};

template<typename T>
std::shared_ptr<T> DomItem::ownerAs()
{
    if constexpr (domTypeIsOwningItem(T::kindValue)) {
        if (m_owner) {
            if constexpr (T::kindValue == DomType::AttachedInfo) {
                if (std::holds_alternative<std::shared_ptr<AttachedInfo>>(*m_owner))
                    return std::static_pointer_cast<T>(
                            std::get<std::shared_ptr<AttachedInfo>>(*m_owner));
            } else if constexpr (T::kindValue == DomType::ExternalItemInfo) {
                if (std::holds_alternative<std::shared_ptr<ExternalItemInfoBase>>(*m_owner))
                    return std::static_pointer_cast<T>(
                            std::get<std::shared_ptr<ExternalItemInfoBase>>(*m_owner));
            } else if constexpr (T::kindValue == DomType::ExternalItemPair) {
                if (std::holds_alternative<std::shared_ptr<ExternalItemPairBase>>(*m_owner))
                    return std::static_pointer_cast<T>(
                            std::get<std::shared_ptr<ExternalItemPairBase>>(*m_owner));
            } else {
                if (std::holds_alternative<std::shared_ptr<T>>(*m_owner)) {
                    return std::get<std::shared_ptr<T>>(*m_owner);
                }
            }
        }
    } else {
        Q_ASSERT_X(false, "DomItem::ownerAs", "unexpected non owning value in ownerAs");
    }
    return std::shared_ptr<T> {};
}

template<int I>
struct rank : rank<I - 1>
{
    static_assert(I > 0, "");
};
template<>
struct rank<0>
{
};

template<typename T>
auto writeOutWrap(const T &t, DomItem &self, OutWriter &lw, rank<1>)
        -> decltype(t.writeOut(self, lw))
{
    t.writeOut(self, lw);
}

template<typename T>
auto writeOutWrap(const T &, DomItem &, OutWriter &, rank<0>) -> void
{
    qCWarning(writeOutLog) << "Ignoring writeout to wrapped object not supporting it ("
                           << typeid(T).name();
}
template<typename T>
auto writeOutWrap(const T &t, DomItem &self, OutWriter &lw) -> void
{
    writeOutWrap(t, self, lw, rank<1>());
}

template<typename T>
void SimpleObjectWrapT<T>::writeOut(DomItem &self, OutWriter &lw) const
{
    writeOutWrap<T>(*asT(), self, lw);
}

QDebug operator<<(QDebug debug, const DomItem &c);

class MutableDomItem {
public:
    using CopyOption = DomItem::CopyOption;

    explicit operator bool() const
    {
        return bool(m_owner);
    } // this is weaker than item(), but normally correct
    DomType internalKind() { return item().internalKind(); }
    QString internalKindStr() { return domTypeToString(internalKind()); }
    DomKind domKind() { return kind2domKind(internalKind()); }

    Path canonicalPath() { return m_owner.canonicalPath().path(m_pathFromOwner); }
    MutableDomItem containingObject()
    {
        if (m_pathFromOwner)
            return MutableDomItem(m_owner, m_pathFromOwner.split().pathToSource);
        else {
            DomItem cObj = m_owner.containingObject();
            return MutableDomItem(cObj.owner(), (domTypeIsOwningItem(cObj.internalKind()) ? Path() :cObj.pathFromOwner()));
        }
    }

    MutableDomItem container()
    {
        if (m_pathFromOwner)
            return MutableDomItem(m_owner, m_pathFromOwner.dropTail());
        else {
            return MutableDomItem(item().container());
        }
    }

    MutableDomItem qmlObject(GoTo option = GoTo::Strict,
                             FilterUpOptions fOptions = FilterUpOptions::ReturnOuter)
    {
        return MutableDomItem(item().qmlObject(option, fOptions));
    }
    MutableDomItem fileObject(GoTo option = GoTo::Strict)
    {
        return MutableDomItem(item().fileObject(option));
    }
    MutableDomItem rootQmlObject(GoTo option = GoTo::Strict)
    {
        return MutableDomItem(item().rootQmlObject(option));
    }
    MutableDomItem globalScope() { return MutableDomItem(item().globalScope()); }
    MutableDomItem scope() { return MutableDomItem(item().scope()); }

    MutableDomItem component(GoTo option = GoTo::Strict)
    {
        return MutableDomItem { item().component(option) };
    }
    MutableDomItem owner() { return MutableDomItem(m_owner); }
    MutableDomItem top() { return MutableDomItem(item().top()); }
    MutableDomItem environment() { return MutableDomItem(item().environment()); }
    MutableDomItem universe() { return MutableDomItem(item().universe()); }
    Path pathFromOwner() { return m_pathFromOwner; }
    MutableDomItem operator[](const Path &path) { return MutableDomItem(item()[path]); }
    MutableDomItem operator[](QStringView component) { return MutableDomItem(item()[component]); }
    MutableDomItem operator[](const QString &component)
    {
        return MutableDomItem(item()[component]);
    }
    MutableDomItem operator[](const char16_t *component)
    {
        // to avoid clash with stupid builtin ptrdiff_t[MutableDomItem&], coming from C
        return MutableDomItem(item()[QStringView(component)]);
    }
    MutableDomItem operator[](index_type i) { return MutableDomItem(item().index(i)); }

    MutableDomItem path(const Path &p) { return MutableDomItem(item().path(p)); }
    MutableDomItem path(const QString &p) { return path(Path::fromString(p)); }
    MutableDomItem path(QStringView p) { return path(Path::fromString(p)); }

    QList<QString> const fields() { return item().fields(); }
    MutableDomItem field(QStringView name) { return MutableDomItem(item().field(name)); }
    index_type indexes() { return item().indexes(); }
    MutableDomItem index(index_type i) { return MutableDomItem(item().index(i)); }

    QSet<QString> const keys() { return item().keys(); }
    MutableDomItem key(QString name) { return MutableDomItem(item().key(name)); }
    MutableDomItem key(QStringView name) { return key(name.toString()); }

    void
    dump(Sink s, int indent = 0,
         function_ref<bool(DomItem &, const PathEls::PathComponent &, DomItem &)> filter = noFilter)
    {
        item().dump(s, indent, filter);
    }
    FileWriter::Status
    dump(QString path,
         function_ref<bool(DomItem &, const PathEls::PathComponent &, DomItem &)> filter = noFilter,
         int nBackups = 2, int indent = 0, FileWriter *fw = nullptr)
    {
        return item().dump(path, filter, nBackups, indent, fw);
    }
    void writeOut(OutWriter &lw) { return item().writeOut(lw); }
    MutableDomItem writeOut(QString path, int nBackups = 2,
                            const LineWriterOptions &opt = LineWriterOptions(),
                            FileWriter *fw = nullptr)
    {
        return MutableDomItem(item().writeOut(path, nBackups, opt, fw));
    }

    MutableDomItem fileLocations() { return MutableDomItem(item().fileLocations()); }
    MutableDomItem makeCopy(CopyOption option = CopyOption::EnvConnected)
    {
        return item().makeCopy(option);
    }
    bool commitToBase() { return item().commitToBase(); }
    QString canonicalFilePath() { return item().canonicalFilePath(); }

    MutableDomItem refreshed() { return MutableDomItem(item().refreshed()); }

    QCborValue value() { return item().value(); }

    QString toString() { return item().toString(); }

    // convenience getters
    QString name() { return item().name(); }
    MutableDomItem pragmas() { return item().pragmas(); }
    MutableDomItem ids() { return MutableDomItem::item().ids(); }
    QString idStr() { return item().idStr(); }
    MutableDomItem propertyDefs() { return MutableDomItem(item().propertyDefs()); }
    MutableDomItem bindings() { return MutableDomItem(item().bindings()); }
    MutableDomItem methods() { return MutableDomItem(item().methods()); }
    MutableDomItem children() { return MutableDomItem(item().children()); }
    MutableDomItem child(index_type i) { return MutableDomItem(item().child(i)); }
    MutableDomItem annotations() { return MutableDomItem(item().annotations()); }

    //    // OwnigItem elements
    int derivedFrom() { return m_owner.derivedFrom(); }
    int revision() { return m_owner.revision(); }
    QDateTime createdAt() { return m_owner.createdAt(); }
    QDateTime frozenAt() { return m_owner.frozenAt(); }
    QDateTime lastDataUpdateAt() { return m_owner.lastDataUpdateAt(); }

    void addError(ErrorMessage msg) { item().addError(msg); }
    ErrorHandler errorHandler();

    // convenience setters
    MutableDomItem addPrototypePath(Path prototypePath);
    MutableDomItem setNextScopePath(Path nextScopePath);
    MutableDomItem setPropertyDefs(QMultiMap<QString, PropertyDefinition> propertyDefs);
    MutableDomItem setBindings(QMultiMap<QString, Binding> bindings);
    MutableDomItem setMethods(QMultiMap<QString, MethodInfo> functionDefs);
    MutableDomItem setChildren(QList<QmlObject> children);
    MutableDomItem setAnnotations(QList<QmlObject> annotations);
    MutableDomItem setScript(std::shared_ptr<ScriptExpression> exp);
    MutableDomItem setCode(QString code);
    MutableDomItem addPropertyDef(PropertyDefinition propertyDef,
                                  AddOption option = AddOption::Overwrite);
    MutableDomItem addBinding(Binding binding, AddOption option = AddOption::Overwrite);
    MutableDomItem addMethod(MethodInfo functionDef, AddOption option = AddOption::Overwrite);
    MutableDomItem addChild(QmlObject child);
    MutableDomItem addAnnotation(QmlObject child);
    MutableDomItem addPreComment(const Comment &comment, QString regionName = QString());
    MutableDomItem addPreComment(const Comment &comment, QStringView regionName)
    {
        return addPreComment(comment, regionName.toString());
    }
    MutableDomItem addPostComment(const Comment &comment, QString regionName = QString());
    MutableDomItem addPostComment(const Comment &comment, QStringView regionName)
    {
        return addPostComment(comment, regionName.toString());
    }

    MutableDomItem() = default;
    MutableDomItem(DomItem owner, Path pathFromOwner):
        m_owner(owner), m_pathFromOwner(pathFromOwner)
    {}
    MutableDomItem(DomItem item):
        m_owner(item.owner()), m_pathFromOwner(item.pathFromOwner())
    {}

    std::shared_ptr<DomTop> topPtr() { return m_owner.topPtr(); }
    std::shared_ptr<OwningItem> owningItemPtr() { return m_owner.owningItemPtr(); }

    template<typename T>
    T const *as()
    {
        return item().as<T>();
    }

    template <typename T>
    T *mutableAs() {
        Q_ASSERT(!m_owner || !m_owner.owningItemPtr()->frozen());
        return item().mutableAs<T>();
    }

    template<typename T>
    std::shared_ptr<T> ownerAs()
    {
        return m_owner.ownerAs<T>();
    }
    // it is dangerous to assume it stays valid when updates are preformed...
    DomItem item() { return m_owner.path(m_pathFromOwner); }

    friend bool operator==(const MutableDomItem o1, const MutableDomItem &o2)
    {
        return o1.m_owner == o2.m_owner && o1.m_pathFromOwner == o2.m_pathFromOwner;
    }
    friend bool operator!=(const MutableDomItem &o1, const MutableDomItem &o2)
    {
        return !(o1 == o2);
    }

private:
    DomItem m_owner;
    Path m_pathFromOwner;
};

QDebug operator<<(QDebug debug, const MutableDomItem &c);

template<typename K, typename T>
Path insertUpdatableElementInMultiMap(Path mapPathFromOwner, QMultiMap<K, T> &mmap, K key,
                                      const T &value, AddOption option = AddOption::KeepExisting,
                                      T **valuePtr = nullptr)
{
    if (option == AddOption::Overwrite) {
        auto it = mmap.find(key);
        if (it != mmap.end()) {
            T &v = *it;
            v = value;
            if (++it != mmap.end() && it.key() == key) {
                qWarning() << " requested overwrite of " << key
                           << " that contains aleready multiple entries in" << mapPathFromOwner;
            }
            Path newPath = mapPathFromOwner.key(key).index(0);
            v.updatePathFromOwner(newPath);
            if (valuePtr)
                *valuePtr = &v;
            return newPath;
        }
    }
    mmap.insert(key, value);
    auto it = mmap.find(key);
    auto it2 = it;
    int nVal = 0;
    while (it2 != mmap.end() && it2.key() == key) {
       ++nVal;
        ++it2;
    }
    Path newPath = mapPathFromOwner.key(key).index(nVal-1);
    T &v = *it;
    v.updatePathFromOwner(newPath);
    if (valuePtr)
        *valuePtr = &v;
    return newPath;
}

template<typename T>
Path appendUpdatableElementInQList(Path listPathFromOwner, QList<T> &list, const T &value,
                                   T **vPtr = nullptr)
{
    int idx = list.length();
    list.append(value);
    Path newPath = listPathFromOwner.index(idx);
    T &targetV = list[idx];
    targetV.updatePathFromOwner(newPath);
    if (vPtr)
        *vPtr = &targetV;
    return newPath;
}

template <typename T, typename K = QString>
void updatePathFromOwnerMultiMap(QMultiMap<K, T> &mmap, Path newPath)
{
    auto it = mmap.begin();
    auto end = mmap.end();
    index_type i = 0;
    K name;
    QList<T*> els;
    while (it != end) {
        if (i > 0 && name != it.key()) {
            Path pName = newPath.key(QString(name));
            for (T *el : els)
                el->updatePathFromOwner(pName.index(--i));
            els.clear();
            els.append(&(*it));
            name = it.key();
            i = 1;
        } else {
            els.append(&(*it));
            name = it.key();
            ++i;
        }
        ++it;
    }
    Path pName = newPath.key(name);
    for (T *el : els)
        el->updatePathFromOwner(pName.index(--i));
}

template <typename T>
void updatePathFromOwnerQList(QList<T> &list, Path newPath)
{
    auto it = list.begin();
    auto end = list.end();
    index_type i = 0;
    while (it != end)
        (it++)->updatePathFromOwner(newPath.index(i++));
}

constexpr bool domTypeIsObjWrap(DomType k)
{
    switch (k) {
    case DomType::Binding:
    case DomType::EnumItem:
    case DomType::ErrorMessage:
    case DomType::Export:
    case DomType::Id:
    case DomType::Import:
    case DomType::ImportScope:
    case DomType::MethodInfo:
    case DomType::MethodParameter:
    case DomType::ModuleAutoExport:
    case DomType::Pragma:
    case DomType::PropertyDefinition:
    case DomType::Version:
    case DomType::Comment:
    case DomType::CommentedElement:
    case DomType::RegionComments:
    case DomType::FileLocations:
    case DomType::UpdatedScriptExpression:
        return true;
    default:
        return false;
    }
}

constexpr bool domTypeIsValueWrap(DomType k)
{
    switch (k) {
    case DomType::PropertyInfo:
        return true;
    default:
        return false;
    }
}

constexpr bool domTypeIsDomElement(DomType k)
{
    switch (k) {
    case DomType::ModuleScope:
    case DomType::QmlObject:
    case DomType::ConstantData:
    case DomType::SimpleObjectWrap:
    case DomType::Reference:
    case DomType::Map:
    case DomType::List:
    case DomType::ListP:
    case DomType::EnumDecl:
    case DomType::JsResource:
    case DomType::QmltypesComponent:
    case DomType::QmlComponent:
    case DomType::GlobalComponent:
    case DomType::MockObject:
        return true;
    default:
        return false;
    }
}

constexpr bool domTypeIsOwningItem(DomType k)
{
    switch (k) {
    case DomType::ModuleIndex:

    case DomType::MockOwner:

    case DomType::ExternalItemInfo:
    case DomType::ExternalItemPair:

    case DomType::QmlDirectory:
    case DomType::QmldirFile:
    case DomType::JsFile:
    case DomType::QmlFile:
    case DomType::QmltypesFile:
    case DomType::GlobalScope:

    case DomType::ScriptExpression:
    case DomType::AstComments:

    case DomType::LoadInfo:
    case DomType::AttachedInfo:

    case DomType::DomEnvironment:
    case DomType::DomUniverse:
        return true;
    default:
        return false;
    }
}

constexpr bool domTypeIsUnattachedOwningItem(DomType k)
{
    switch (k) {
    case DomType::ScriptExpression:
    case DomType::AstComments:
    case DomType::AttachedInfo:
        return true;
    default:
        return false;
    }
}

template<typename T>
DomItem DomItem::subValueItem(const PathEls::PathComponent &c, T value,
                              ConstantData::Options options)
{
    using BaseT = std::remove_cv_t<std::remove_reference_t<T>>;
    if constexpr (
            std::is_base_of_v<
                    QCborValue,
                    BaseT> || std::is_base_of_v<QCborArray, BaseT> || std::is_base_of_v<QCborMap, BaseT>) {
        return DomItem(m_top, m_owner, m_ownerPath,
                       ConstantData(pathFromOwner().appendComponent(c), value, options));
    } else if constexpr (std::is_same_v<DomItem, BaseT>) {
        Q_UNUSED(options);
        return value;
    } else if constexpr (IsList<T>::value && !std::is_convertible_v<BaseT, QStringView>) {
        return subListItem(List::fromQList<typename BaseT::value_type>(
                pathFromOwner().appendComponent(c), value,
                [options](DomItem &list, const PathEls::PathComponent &p,
                          typename T::value_type &v) { return list.subValueItem(p, v, options); }));
    } else if constexpr (IsSharedPointerToDomObject<BaseT>::value) {
        Q_UNUSED(options);
        return subOwnerItem(c, value);
    } else {
        return subDataItem(c, value, options);
    }
}

template<typename T>
DomItem DomItem::subDataItem(const PathEls::PathComponent &c, T value,
                             ConstantData::Options options)
{
    using BaseT = std::remove_cv_t<std::remove_reference_t<T>>;
    if constexpr (std::is_same_v<BaseT, ConstantData>) {
        return this->copy(value);
    } else if constexpr (std::is_base_of_v<QCborValue, BaseT>) {
        return DomItem(m_top, m_owner, m_ownerPath,
                       ConstantData(pathFromOwner().appendComponent(c), value, options));
    } else {
        return DomItem(
                m_top, m_owner, m_ownerPath,
                ConstantData(pathFromOwner().appendComponent(c), QCborValue(value), options));
    }
}

template<typename T>
bool DomItem::dvValue(DirectVisitor visitor, const PathEls::PathComponent &c, T value,
                      ConstantData::Options options)
{
    auto lazyWrap = [this, &c, &value, options]() {
        return this->subValueItem<T>(c, value, options);
    };
    return visitor(c, lazyWrap);
}

template<typename F>
bool DomItem::dvValueLazy(DirectVisitor visitor, const PathEls::PathComponent &c, F valueF,
                          ConstantData::Options options)
{
    auto lazyWrap = [this, &c, &valueF, options]() {
        return this->subValueItem<decltype(valueF())>(c, valueF(), options);
    };
    return visitor(c, lazyWrap);
}

template<typename T>
DomItem DomItem::wrap(const PathEls::PathComponent &c, T &obj)
{
    using BaseT = std::decay_t<T>;
    if constexpr (std::is_same_v<QString, BaseT> || std::is_arithmetic_v<BaseT>) {
        return this->subDataItem(c, QCborValue(obj));
    } else if constexpr (std::is_same_v<SourceLocation, BaseT>) {
        return this->subLocationItem(c, obj);
    } else if constexpr (std::is_same_v<BaseT, Reference>) {
        Q_ASSERT_X(false, "DomItem::wrap",
                   "wrapping a reference object, probably an error (wrap the target path instead)");
        return this->copy(obj);
    } else if constexpr (std::is_same_v<BaseT, ConstantData>) {
        return this->subDataItem(c, obj);
    } else if constexpr (std::is_same_v<BaseT, Map>) {
        return this->subMapItem(obj);
    } else if constexpr (std::is_same_v<BaseT, List>) {
        return this->subListItem(obj);
    } else if constexpr (std::is_base_of_v<ListPBase, BaseT>) {
        return this->subListItem(obj);
    } else if constexpr (std::is_same_v<BaseT, SimpleObjectWrap>) {
        return this->subObjectWrapItem(obj);
    } else if constexpr (IsDomObject<BaseT>::value) {
        if constexpr (domTypeIsObjWrap(BaseT::kindValue) || domTypeIsValueWrap(BaseT::kindValue)) {
            return this->subObjectWrapItem(
                    SimpleObjectWrap::fromObjectRef(this->pathFromOwner().appendComponent(c), obj));
        } else if constexpr (domTypeIsDomElement(BaseT::kindValue)) {
            return this->copy(&obj);
        } else {
            qCWarning(domLog) << "Unhandled object of type " << domTypeToString(BaseT::kindValue)
                              << " in DomItem::wrap, not using a shared_ptr for an "
                              << "OwningItem, or unexpected wrapped object?";
            return DomItem();
        }
    } else if constexpr (IsSharedPointerToDomObject<BaseT>::value) {
        if constexpr (domTypeIsOwningItem(BaseT::element_type::kindValue)) {
            return this->subOwnerItem(c, obj);
        } else {
            Q_ASSERT_X(false, "DomItem::wrap", "shared_ptr with non owning item");
            return DomItem();
        }
    } else if constexpr (IsMultiMap<BaseT>::value) {
        if constexpr (std::is_same_v<typename BaseT::key_type, QString>) {
            return subMapItem(Map::fromMultiMapRef<typename BaseT::mapped_type>(
                    pathFromOwner().appendComponent(c), obj,
                    [](DomItem &map, const PathEls::PathComponent &p,
                       typename BaseT::mapped_type &el) { return map.wrap(p, el); }));
        } else {
            Q_ASSERT_X(false, "DomItem::wrap", "non string keys not supported (try .toString()?)");
        }
    } else if constexpr (IsMap<BaseT>::value) {
        if constexpr (std::is_same_v<typename BaseT::key_type, QString>) {
            return subMapItem(Map::fromMapRef<typename BaseT::mapped_type>(
                    pathFromOwner().appendComponent(c), obj,
                    [](DomItem &map, const PathEls::PathComponent &p,
                       typename BaseT::mapped_type &el) { return map.wrap(p, el); }));
        } else {
            Q_ASSERT_X(false, "DomItem::wrap", "non string keys not supported (try .toString()?)");
        }
    } else if constexpr (IsList<BaseT>::value) {
        if constexpr (IsDomObject<typename BaseT::value_type>::value) {
            return subListItem(List::fromQListRef<typename BaseT::value_type>(
                    pathFromOwner().appendComponent(c), obj,
                    [](DomItem &list, const PathEls::PathComponent &p,
                       typename BaseT::value_type &el) { return list.wrap(p, el); }));
        } else {
            Q_ASSERT_X(false, "DomItem::wrap", "Unsupported list type T");
            return DomItem();
        }
    } else {
        qCWarning(domLog) << "Cannot wrap " << typeid(BaseT).name();
        Q_ASSERT_X(false, "DomItem::wrap", "Do not know how to wrap type T");
        return DomItem();
    }
}

template<typename T>
bool DomItem::dvWrap(DirectVisitor visitor, const PathEls::PathComponent &c, T &obj)
{
    auto lazyWrap = [this, &c, &obj]() { return this->wrap<T>(c, obj); };
    return visitor(c, lazyWrap);
}

template<typename T>
bool ListPT<T>::iterateDirectSubpaths(DomItem &self, DirectVisitor v)
{
    index_type len = index_type(m_pList.size());
    for (index_type i = 0; i < len; ++i) {
        if (!v(PathEls::Index(i), [this, &self, i] { return this->index(self, i); }))
            return false;
    }
    return true;
}

template<typename T>
DomItem ListPT<T>::index(DomItem &self, index_type index) const
{
    if (index >= 0 && index < m_pList.length())
        return self.wrap(PathEls::Index(index), *reinterpret_cast<T *>(m_pList.value(index)));
    return DomItem();
}

// allow inlining of DomBase
inline DomKind DomBase::domKind() const
{
    return kind2domKind(kind());
}

inline bool DomBase::iterateDirectSubpathsConst(DomItem &self, DirectVisitor visitor) const
{
    Q_ASSERT(self.base() == this);
    return self.iterateDirectSubpaths(visitor);
}

inline DomItem DomBase::containingObject(DomItem &self) const
{
    Path path = pathFromOwner(self);
    DomItem base = self.owner();
    if (!path) {
        path = canonicalPath(self);
        base = self;
    }
    Source source = path.split();
    return base.path(source.pathToSource);
}

inline quintptr DomBase::id() const
{
    return quintptr(this);
}

inline QString DomBase::typeName() const
{
    return domTypeToString(kind());
}

inline QList<QString> DomBase::fields(DomItem &self) const
{
    QList<QString> res;
    self.iterateDirectSubpaths([&res](const PathEls::PathComponent &c, function_ref<DomItem()>) {
        if (c.kind() == Path::Kind::Field)
            res.append(c.name());
        return true;
    });
    return res;
}

inline DomItem DomBase::field(DomItem &self, QStringView name) const
{
    DomItem res;
    self.iterateDirectSubpaths(
            [&res, name](const PathEls::PathComponent &c, function_ref<DomItem()> obj) {
                if (c.kind() == Path::Kind::Field && c.checkName(name)) {
                    res = obj();
                    return false;
                }
                return true;
            });
    return res;
}

inline index_type DomBase::indexes(DomItem &self) const
{
    index_type res = 0;
    self.iterateDirectSubpaths([&res](const PathEls::PathComponent &c, function_ref<DomItem()>) {
        if (c.kind() == Path::Kind::Index) {
            index_type i = c.index() + 1;
            if (res < i)
                res = i;
        }
        return true;
    });
    return res;
}

inline DomItem DomBase::index(DomItem &self, qint64 index) const
{
    DomItem res;
    self.iterateDirectSubpaths(
            [&res, index](const PathEls::PathComponent &c, function_ref<DomItem()> obj) {
                if (c.kind() == Path::Kind::Index && c.index() == index) {
                    res = obj();
                    return false;
                }
                return true;
            });
    return res;
}

inline QSet<QString> const DomBase::keys(DomItem &self) const
{
    QSet<QString> res;
    self.iterateDirectSubpaths([&res](const PathEls::PathComponent &c, function_ref<DomItem()>) {
        if (c.kind() == Path::Kind::Key)
            res.insert(c.name());
        return true;
    });
    return res;
}

inline DomItem DomBase::key(DomItem &self, QString name) const
{
    DomItem res;
    self.iterateDirectSubpaths(
            [&res, name](const PathEls::PathComponent &c, function_ref<DomItem()> obj) {
                if (c.kind() == Path::Kind::Key && c.checkName(name)) {
                    res = obj();
                    return false;
                }
                return true;
            });
    return res;
}

inline DomItem DomItem::subReferencesItem(const PathEls::PathComponent &c, QList<Path> paths)
{
    return subListItem(
            List::fromQList<Path>(pathFromOwner().appendComponent(c), paths,
                                  [](DomItem &list, const PathEls::PathComponent &p, Path &el) {
                                      return list.subReferenceItem(p, el);
                                  }));
}

inline DomItem DomItem::subReferenceItem(const PathEls::PathComponent &c, Path referencedObject)
{
    if (domTypeIsOwningItem(internalKind()))
        return DomItem(m_top, m_owner, m_ownerPath, Reference(referencedObject, Path(c)));
    else
        return DomItem(m_top, m_owner, m_ownerPath,
                       Reference(referencedObject, pathFromOwner().appendComponent(c)));
}

inline DomItem DomItem::subListItem(const List &list)
{
    return DomItem(m_top, m_owner, m_ownerPath, list);
}

inline DomItem DomItem::subMapItem(const Map &map)
{
    return DomItem(m_top, m_owner, m_ownerPath, map);
}

} // end namespace Dom
} // end namespace QQmlJS

QT_END_NAMESPACE
#endif // QMLDOMITEM_H