luau/Analysis/include/Luau/TxnLog.h

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#pragma once

#include "Luau/TypeVar.h"

LUAU_FASTFLAG(LuauShareTxnSeen);

namespace Luau
{

// Log of where what TypeIds we are rebinding and what they used to be
struct TxnLog
{
    TxnLog()
        : originalSeenSize(0)
        , ownedSeen()
        , sharedSeen(&ownedSeen)
    {
    }

    explicit TxnLog(std::vector<std::pair<TypeId, TypeId>>* sharedSeen)
        : originalSeenSize(sharedSeen->size())
        , ownedSeen()
        , sharedSeen(sharedSeen)
    {
    }

    explicit TxnLog(const std::vector<std::pair<TypeId, TypeId>>& ownedSeen)
        : originalSeenSize(ownedSeen.size())
        , ownedSeen(ownedSeen)
        , sharedSeen(nullptr)
    {
        // This is deprecated!
        LUAU_ASSERT(!FFlag::LuauShareTxnSeen);
    }

    TxnLog(const TxnLog&) = delete;
    TxnLog& operator=(const TxnLog&) = delete;

    TxnLog(TxnLog&&) = default;
    TxnLog& operator=(TxnLog&&) = default;

    void operator()(TypeId a);
    void operator()(TypePackId a);
    void operator()(TableTypeVar* a);

    void rollback();

    void concat(TxnLog rhs);

    bool haveSeen(TypeId lhs, TypeId rhs);
    void pushSeen(TypeId lhs, TypeId rhs);
    void popSeen(TypeId lhs, TypeId rhs);

private:
    std::vector<std::pair<TypeId, TypeVar>> typeVarChanges;
    std::vector<std::pair<TypePackId, TypePackVar>> typePackChanges;
    std::vector<std::pair<TableTypeVar*, std::optional<TypeId>>> tableChanges;
    size_t originalSeenSize;

public:
    std::vector<std::pair<TypeId, TypeId>> ownedSeen;   // used to avoid infinite recursion when types are cyclic
    std::vector<std::pair<TypeId, TypeId>>* sharedSeen; // shared with all the descendent logs
};

} // namespace Luau