Good name for f.byLine.map!(x => x.idup)?

[Timon Gehr]

On 03/16/2014 08:27 PM, monarch_dodra wrote:
>>
>> f.byLine.map!idup
>
> Indeed, I've been wanting to write this before. IMO, not being able to
> write it is a serious inconsistency.

What is it inconsistent with?