System.Linq.Expressions.Expression.ValidateIndexedProperty C# (CSharp) Method

        private static void ValidateIndexedProperty(Expression instance, PropertyInfo indexer, ref ReadOnlyCollection<Expression> argList)
        {
            // If both getter and setter specified, all their parameter types
            // should match, with exception of the last setter parameter which
            // should match the type returned by the get method.
            // Accessor parameters cannot be ByRef.

            ContractUtils.RequiresNotNull(indexer, nameof(indexer));
            if (indexer.PropertyType.IsByRef)
            {
                throw Error.PropertyCannotHaveRefType(nameof(indexer));
            }
            if (indexer.PropertyType == typeof(void))
            {
                throw Error.PropertyTypeCannotBeVoid(nameof(indexer));
            }

            ParameterInfo[] getParameters = null;
            MethodInfo getter = indexer.GetGetMethod(nonPublic: true);
            if (getter != null)
            {
                getParameters = getter.GetParametersCached();
                ValidateAccessor(instance, getter, getParameters, ref argList, nameof(indexer));
            }

            MethodInfo setter = indexer.GetSetMethod(nonPublic: true);
            if (setter != null)
            {
                ParameterInfo[] setParameters = setter.GetParametersCached();
                if (setParameters.Length == 0)
                {
                    throw Error.SetterHasNoParams(nameof(indexer));
                }

                // valueType is the type of the value passed to the setter (last parameter)
                Type valueType = setParameters[setParameters.Length - 1].ParameterType;
                if (valueType.IsByRef)
                {
                    throw Error.PropertyCannotHaveRefType(nameof(indexer));
                }
                if (setter.ReturnType != typeof(void))
                {
                    throw Error.SetterMustBeVoid(nameof(indexer));
                }
                if (indexer.PropertyType != valueType)
                {
                    throw Error.PropertyTypeMustMatchSetter(nameof(indexer));
                }

                if (getter != null)
                {
                    if (getter.IsStatic ^ setter.IsStatic)
                    {
                        throw Error.BothAccessorsMustBeStatic(nameof(indexer));
                    }
                    if (getParameters.Length != setParameters.Length - 1)
                    {
                        throw Error.IndexesOfSetGetMustMatch(nameof(indexer));
                    }

                    for (int i = 0; i < getParameters.Length; i++)
                    {
                        if (getParameters[i].ParameterType != setParameters[i].ParameterType)
                        {
                            throw Error.IndexesOfSetGetMustMatch(nameof(indexer));
                        }
                    }
                }
                else
                {
                    ValidateAccessor(instance, setter, setParameters.RemoveLast(), ref argList, nameof(indexer));
                }
            }

            if (getter == null && setter == null)
            {
                throw Error.PropertyDoesNotHaveAccessor(indexer, nameof(indexer));
            }
        }