I converted my (macOS) project to Swift 3 in Xcode 8 and I get the following warnings with several delegate methods I implement in swift classes:
Instance me
Here's what fixed it for me.
I was getting the same warning in some code that I was sure that I typed into the editor initially and allowed it to autocomplete. I subsequently went back and re-visted the warning and tried to just type the same function over again right after my existing function. When I entered the function name over again, my function signature changed and the parms matched up exactly with what Xcode expected and the warning was suppressed.
So if you want to do a quick sanity check, do yourself a favor and try typing in the function one more time and see if the parm types change. That might be all you need.