My partner was just debugging a project that had tried to call a function without arguments in the code but the declaration wasn't declared with a void parameter list. It failed with an assertion that something was trying to ++ past the end of an ilist.
I seem to remember Chris Lattner saying when he made the hand written AsmParser that it wasn't intended to be very robust but, searching the list, I can't find the post where he said it. That being said, is this worthy of a bug report? An error message from the AsmParser would be preferred over a seemingly unrelated assert.