protected void FindDestinationFullName()

in tools/AutoMapper/XpressionMapper/XpressionMapperVisitor.cs [192:265]
64 lines of code
15 McCabe index (conditional complexity)

        protected void FindDestinationFullName(Type typeSource, Type typeDestination, string sourceFullName, List<PropertyMapInfo> propertyMapInfoList)
        {
            const string period = ".";
            if (typeSource == typeDestination)
            {
                var sourceFullNameArray = sourceFullName.Split(new[] { period[0] }, StringSplitOptions.RemoveEmptyEntries);
                sourceFullNameArray.Aggregate(propertyMapInfoList, (list, next) =>
                {

                    if (list.Count == 0)
                    {
                        AddPropertyMapInfo(typeSource,  next, list);
                    }
                    else
                    {
                        var last = list[list.Count - 1];
                        AddPropertyMapInfo(last.CustomExpression == null
                            ? last.DestinationPropertyInfos[last.DestinationPropertyInfos.Count - 1].GetMemberType()
                            : last.CustomExpression.ReturnType, next, list);
                    }
                    return list;
                });
                return;
            }

            var typeMap = ConfigurationProvider.CheckIfMapExists(sourceType: typeDestination, destinationType: typeSource);//The destination becomes the source because to map a source expression to a destination expression,
            //we need the expressions used to create the source from the destination 

            PathMap pathMap = typeMap.FindPathMapByDestinationPath(destinationFullPath: sourceFullName);
            if (pathMap != null)
            {
                propertyMapInfoList.Add(new PropertyMapInfo(pathMap.SourceExpression, new List<MemberInfo>()));
                return;
            }


            if (sourceFullName.IndexOf(period, StringComparison.OrdinalIgnoreCase) < 0)
            {
                var propertyMap = typeMap.GetPropertyMapByDestinationProperty(sourceFullName);
                var sourceMemberInfo = typeSource.GetFieldOrProperty(propertyMap.DestinationProperty.Name);
                if (propertyMap.ValueResolverConfig != null)
                {
                    throw new InvalidOperationException(Resource.customResolversNotSupported);
                }
                if (propertyMap.CustomExpression != null)
                {
                    if (propertyMap.CustomExpression.ReturnType.IsValueType() && sourceMemberInfo.GetMemberType() != propertyMap.CustomExpression.ReturnType)
                        throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, Resource.expressionMapValueTypeMustMatchFormat, propertyMap.CustomExpression.ReturnType.Name, propertyMap.CustomExpression.ToString(), sourceMemberInfo.GetMemberType().Name, propertyMap.DestinationProperty.Name));
                }
                else
                {
                    if (propertyMap.SourceMember.GetMemberType().IsValueType() && sourceMemberInfo.GetMemberType() != propertyMap.SourceMember.GetMemberType())
                        throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, Resource.expressionMapValueTypeMustMatchFormat, propertyMap.SourceMember.GetMemberType().Name, propertyMap.SourceMember.Name, sourceMemberInfo.GetMemberType().Name, propertyMap.DestinationProperty.Name));
                }

                propertyMapInfoList.Add(new PropertyMapInfo(propertyMap.CustomExpression, propertyMap.SourceMembers.ToList()));
            }
            else
            {
                var propertyName = sourceFullName.Substring(0, sourceFullName.IndexOf(period, StringComparison.OrdinalIgnoreCase));
                var propertyMap = typeMap.GetPropertyMapByDestinationProperty(propertyName);

                var sourceMemberInfo = typeSource.GetFieldOrProperty(propertyMap.DestinationProperty.Name);
                if (propertyMap.CustomExpression == null && propertyMap.SourceMember == null)//If sourceFullName has a period then the SourceMember cannot be null.  The SourceMember is required to find the ProertyMap of its child object.
                    throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, Resource.srcMemberCannotBeNullFormat, typeSource.Name, typeDestination.Name, propertyName));

                propertyMapInfoList.Add(new PropertyMapInfo(propertyMap.CustomExpression, propertyMap.SourceMembers.ToList()));
                var childFullName = sourceFullName.Substring(sourceFullName.IndexOf(period, StringComparison.OrdinalIgnoreCase) + 1);

                FindDestinationFullName(sourceMemberInfo.GetMemberType(), propertyMap.CustomExpression == null
                    ? propertyMap.SourceMember.GetMemberType()
                    : propertyMap.CustomExpression.ReturnType, childFullName, propertyMapInfoList);
            }
        }