System.Linq.Expressions.BinaryExpression.ReduceIndex C# (CSharp) Метод

        private Expression ReduceIndex()
        {
            // left[a0, a1, ... aN] (op)= r
            //
            // ... is reduced into ...
            //
            // tempObj = left
            // tempArg0 = a0
            // ...
            // tempArgN = aN
            // tempValue = tempObj[tempArg0, ... tempArgN] (op) r
            // tempObj[tempArg0, ... tempArgN] = tempValue

            var index = (IndexExpression)Left;

            var vars = new ArrayBuilder<ParameterExpression>(index.ArgumentCount + 2);
            var exprs = new ArrayBuilder<Expression>(index.ArgumentCount + 3);

            ParameterExpression tempObj = Expression.Variable(index.Object.Type, "tempObj");
            vars.UncheckedAdd(tempObj);
            exprs.UncheckedAdd(Expression.Assign(tempObj, index.Object));

            int n = index.ArgumentCount;
            var tempArgs = new ArrayBuilder<Expression>(n);
            for (var i = 0; i < n; i++)
            {
                Expression arg = index.GetArgument(i);
                ParameterExpression tempArg = Expression.Variable(arg.Type, "tempArg" + i);
                vars.UncheckedAdd(tempArg);
                tempArgs.UncheckedAdd(tempArg);
                exprs.UncheckedAdd(Expression.Assign(tempArg, arg));
            }

            IndexExpression tempIndex = Expression.MakeIndex(tempObj, index.Indexer, tempArgs.ToReadOnly());

            // tempValue = tempObj[tempArg0, ... tempArgN] (op) r
            ExpressionType binaryOp = GetBinaryOpFromAssignmentOp(NodeType);
            Expression op = Expression.MakeBinary(binaryOp, tempIndex, Right, false, Method);
            LambdaExpression conversion = GetConversion();
            if (conversion != null)
            {
                op = Expression.Invoke(conversion, op);
            }
            ParameterExpression tempValue = Expression.Variable(op.Type, "tempValue");
            vars.UncheckedAdd(tempValue);
            exprs.UncheckedAdd(Expression.Assign(tempValue, op));

            // tempObj[tempArg0, ... tempArgN] = tempValue
            exprs.UncheckedAdd(Expression.Assign(tempIndex, tempValue));

            return Expression.Block(vars.ToReadOnly(), exprs.ToReadOnly());
        }