>> Shouldn't goto-line use the same function to read a number?
>> The first version of your patch used the code similar to
>> goto-line-read-args, so wouldn't it make sense to use the
>> new function in goto-line-read-args as well?
>
> Reusing it directly would be awkward, but goto-line-read-args could
> indeed use number-at-point.

Here's a patch where it uses number-at-point: