Well, if you run your program, you will get a syntax error and the culprit line will be highlighted.
I tried in an example where I added a ), I got "expecting SEMI, found ')'" error.
Now, if your program isn't finished, you might have much more errors before this one...
The Auto Format algorithm could give a line number, I suppose.

I get this a lot as well. And it is a bug I think (at least if you can compile and run the program but cannot auto-format).

In one particular case I went crazy trying to find it, so used a 'number guessing game' approach by continually copy/pasting half of the code tab to a blank tab and ctrl-t'ing till I found the offending function. When I finally found the offending function, I could not find any mismatching right paranthesis - it was a very short function with only one block (a tiny for loop).
So I just deleted the whole function and re-wrote it, and it worked, copy/pasted all the tabs into one tab and still auto-format works. So at some point the IDE must get confused about something which we cannot see - the question is how did that thing get there! (sometimes invisible characters come when you copy/paste from websites, I hadn't done that). Another weird thing is that the compiler can still compile and run the code, just the auto-formatter gets confused...