Move around ammo source checks

src/Dodge/HeldUse.hs

@@ -459,15 +459,25 @@ overNozzle eff it cr w nz =
     maxa = _nzMaxWalkAngle nz
     wa = min maxa $ max (negate maxa) (_nzCurrentWalkAngle nz + walkamount)
 
+getAmmoMagazine :: Item -> Creature -> Maybe ItemUse
+getAmmoMagazine itm cr = do
+    invid <- itm ^? itLocation . ipInvID
+    amtype <- itm ^? itUse . heldConsumption . ix 0
+    mag <- cr ^? crInv . ix (invid + 1) . itUse
+    magtype <- mag ^? amagType
+    guard $ amtype == magtype
+    return mag
+
 useGasParams :: Nozzle -> Item -> Creature -> World -> World
 useGasParams nz it cr =
     createGas
-        (_amCreateGas (_laAmmoType (_heldConsumption (_itUse it))))
+        (_ampCreateGas (_amagParams amag))
         (_nzPressure nz)
         pos
         dir
         cr
   where
+    amag = fromMaybe (error "cannot find gas ammo") $ getAmmoMagazine it cr
     dir = _crDir cr
     pos = _crPos cr +.+ (_nzLength nz *.* unitVectorAtAngle (_crDir cr))