GTK+ save dialog

When you enter an existing filename in a gtk save dialog, you are presented with a pop-up that asks you whether you want to overwrite the existing file or cancel the operation (which is a good and to-be-expected behavior).
However, before you press or click Save, you are given no hint to whether a file of that name might already exist. So i thought the Save dialog could, as-you-type, present you with an unobtrusive warning. Also, it should recognize simple naming patterns. If I'm gonna name this picture "sebastian-in-italy-01" and that one already exists, what would I name it instead? Duh. By using Shift + Enter to accept the naming proposition, you would waste next to no time compared to when your desired file name is free.

This is just one possible solution - please give some ideas as to where the warning message could go, the formatting, etc. I chose the bottom left because I felt like a lot of space was wasted there, anyway (the area was entirely empty in the original screenshot).

The warning triangle i used in this mockup was created by user Zeimusu on openclipart.org. http://openclipart.org/media/files/zeimusu/3235

ps: Nautilus needs something like this, too, and even more badly. If you rename a file to an existing name, it just tells you you can't do that, and then throws you back, canceling the renaming process. This means you have to type in the whole new name _again_, which can be really nerve-boggling. I will create a mockup for a new possible behavior of nautilus in this situation, too, when I find the time.