profiles/lib/guidance.lua throwing error trying to call trimLaneString

[danpat]

While trying to replicate #2832, I'm hitting this error using the current master (bb244e2):

$ ./osrm-extract -p ../profiles/car.lua ../../unprocessed-osm.pbf
[info] input file generated by Osmium (http://wiki.openstreetmap.org/wiki/Osmium)
[info] timestamp: 2015-11-11T22:22:02Z
[info] Found 3 exceptions to turn restrictions:
[info]   motorcar
[info]   motor_vehicle
[info]   vehicle
[New Thread 0x7fffbf7fe700 (LWP 73528)]
[New Thread 0x7fffbeffd700 (LWP 73529)]
[New Thread 0x7fffbe7fc700 (LWP 73530)]
[New Thread 0x7fffc47f8700 (LWP 73531)]
[New Thread 0x7fffbdffb700 (LWP 73532)]
[New Thread 0x7fffbdbfa700 (LWP 73533)]
[New Thread 0x7fffbd3f8700 (LWP 73534)]
[New Thread 0x7fffbd7f9700 (LWP 73535)]
[New Thread 0x7fffbcbf5700 (LWP 73536)]
[New Thread 0x7fffbc7f4700 (LWP 73537)]
[New Thread 0x7fff97bfe700 (LWP 73539)]
[New Thread 0x7fff973fc700 (LWP 73541)]
[New Thread 0x7fff977fd700 (LWP 73540)]
[New Thread 0x7fff97fff700 (LWP 73538)]
[New Thread 0x7fff96bfa700 (LWP 73543)]
[New Thread 0x7fff967f9700 (LWP 73544)]
[New Thread 0x7fff96ffb700 (LWP 73542)]
[New Thread 0x7fff963f8700 (LWP 73545)]
[New Thread 0x7fff95ff7700 (LWP 73546)]
terminate called after throwing an instance of 'osrm::util::exception'
  what():  ERROR occurred in profile script:
No matching overload found, candidates:
std::string trimLaneString(std::string,int,int)

It looks like the problem might lie here:

https://github.com/Project-OSRM/osrm-backend/blob/master/profiles/lib/guidance.lua#L99

Something about the (17GB) EU extract linked in #2832 that I'm using is causing one of the parameters to trimLaneString to be nil (I think), and luabind is not finding a matching function call (it's expecting to find a string,int,int function, and because Lua has no types, nil is neither string or int).

Without digging too deep here, I tried applying this change:

diff --git a/profiles/lib/guidance.lua b/profiles/lib/guidance.lua
index 3a4106e..d39d438 100644
--- a/profiles/lib/guidance.lua
+++ b/profiles/lib/guidance.lua
@@ -95,7 +95,7 @@ local function process_lanes(turn_lane,vehicle_lane,first_count,second_count)
     if turn_lane and turn_lane ~= "" then
         if vehicle_lane and vehicle_lane ~= "" then
             turn_lane = applyAccessTokens(turn_lane,vehicle_lane)
-        elseif fw_count ~= 0 or bw_count ~= 0 then
+        elseif first_count ~= 0 or second_count ~= 0 then
             turn_lane = trimLaneString(turn_lane, first_count, second_count)
         end
     end

but that wasn't sufficient, the same error is still being thrown.

/cc @MoKob @daniel-j-h