I was downloading a big .dmg file, half way through it got interrupted and in the Downloads window the said 'failed', I clicked retry but somehow it didn't work, and the 'retry' option was no longer available, though the .part file was still on my desktop. I clicked 'Copy download link' and started over again, now a new file appeared named (1).dmg.part ... Trying to solve the problem, I paused the download and deleted the new (1).dmg.part file and renamed the old one (1).dmg.part and clicked Resume, and it resumed from where it had failed earlier, so I didn't lose the previous download.

Can FireFox, in case it detects a file with a similar name, try to continue the download instead of creating a new file and starting over again?