Two things:
1) Verified this has always been a problem and still is in the development branch, so I added 2.7 and 3.6 to the versions list.
2) Couldn't tolerate the duplicate code handling the extended args operator, so in the interests of DRY, I moved the code scanner to a generator function (see attached dis_with_code_scanner.diff).
The patch is definitely not required to fix this bug, but it does isolate the original problem area to just one piece of code.
Could we get a get a quick review from a core dev saying either "go with Barun's less invasive preliminarypatch.diff" or "go with Eric's greater-churn dis_with_code_scanner.diff patch?"
(We still need to flesh out the testing a bit, so don't call us, we'll call you. :) )