Didn't, but should have.
I had a partial engine failure in a C150; set up for a glide approach to the nearest field; and had it turn into into a complete power loss on downwind. Put out a call on the Common Traffic Advisory Frequency: something along the lines of "Cessna 12345, partial engine failure; unable to maintain altitude; four miles east of X field at 5,000 descending; all traffic in the area please give way."
To my amazement, that was followed by some genius self-announcing five miles south, telling us all of his intention to enter left downwind at X field. I patiently explained to him that I was stretching my glide into a strong headwind and was not going to be able to avoid him if we arrived at the same time.
He saw the point and agreed to hold until I'd landed. But it was an unnecessary distraction at a time when I had my hands full with more important business. Should it happen again, if I've enough time for radio work, my message will be a lot more unambiguous: "Mayday mayday mayday, Cessna 345 engine failure four miles east X 5,000 descending, everybody keep clear of X until I'm on the ground."