public EncVariableSlotAllocator(
            SymbolMatcher symbolMap,
            Func<SyntaxNode, SyntaxNode> syntaxMapOpt,
            IMethodSymbolInternal previousTopLevelMethod,
            DebugId methodId,
            ImmutableArray<EncLocalInfo> previousLocals,
            IReadOnlyDictionary<int, KeyValuePair<DebugId, int>> lambdaMapOpt,
            IReadOnlyDictionary<int, DebugId> closureMapOpt,
            string stateMachineTypeNameOpt,
            int hoistedLocalSlotCount,
            IReadOnlyDictionary<EncHoistedLocalInfo, int> hoistedLocalSlotsOpt,
            int awaiterCount,
            IReadOnlyDictionary<Cci.ITypeReference, int> awaiterMapOpt,
            LambdaSyntaxFacts lambdaSyntaxFacts)
        {
            Debug.Assert(symbolMap != null);
            Debug.Assert(previousTopLevelMethod != null);
            Debug.Assert(!previousLocals.IsDefault);

            _symbolMap = symbolMap;
            _syntaxMapOpt = syntaxMapOpt;
            _previousLocals = previousLocals;
            _previousTopLevelMethod = previousTopLevelMethod;
            _methodId = methodId;
            _hoistedLocalSlotsOpt = hoistedLocalSlotsOpt;
            _hoistedLocalSlotCount = hoistedLocalSlotCount;
            _stateMachineTypeNameOpt = stateMachineTypeNameOpt;
            _awaiterCount = awaiterCount;
            _awaiterMapOpt = awaiterMapOpt;
            _lambdaMapOpt = lambdaMapOpt;
            _closureMapOpt = closureMapOpt;
            _lambdaSyntaxFacts = lambdaSyntaxFacts;

            // Create a map from local info to slot.
            var previousLocalInfoToSlot = new Dictionary<EncLocalInfo, int>();
            for (int slot = 0; slot < previousLocals.Length; slot++)
            {
                var localInfo = previousLocals[slot];
                Debug.Assert(!localInfo.IsDefault);
                if (localInfo.IsUnused)
                {
                    // Unrecognized or deleted local.
                    continue;
                }

                previousLocalInfoToSlot.Add(localInfo, slot);
            }

            _previousLocalSlots = previousLocalInfoToSlot;
        }