pass regression test by modifying 'SearchList.backtrackRange' function. The modification that worked was swapping two if-statements around: first we check if the string position is 0 (and loop to check the previous string if so); in the else case, we check if the searchPos <= 1 (which signals for us to exit backtracking). Swapping the order of the if-statements means that, when we exit the loop, we always exit with string that is at this position.

test/regression.sml

@@ -64,10 +64,6 @@ struct
 
              (* move and then delete twice *)
              val app = TestUtils.updateMany (app, "edede")
-
-             val s = LineGap.toString (#buffer app)
-             val s = String.toCString s ^ "\n"
-             val () = print s
            in
              Expect.isTrue true
            end)