wta: Fix one more overflow

src/random-wta/IndexedTransition.hs

@@ -75,9 +75,9 @@ aritySummand spec arity =
 
 transitionsPerState :: WTASpec m -> (Integer, Vector Integer)
 transitionsPerState spec =
-  let n = numStates spec
+  let n :: Integer = fromIntegral $ numStates spec
       tPerSymbol =
-          (V.imap (\i syms -> fromIntegral $ syms * n ^ i) (numSymbols spec))
+          (V.imap (\i syms -> fromIntegral syms * n ^ i) (numSymbols spec))
       runningTotal = V.scanl' (+) 0 tPerSymbol
   in  (V.last runningTotal, runningTotal)
 

src/random-wta/Tests.hs

+{-# OPTIONS_GHC -fno-warn-orphans  #-}
+
 module Main (main) where
 
 import           Test.Hspec
@@ -27,6 +29,11 @@ main = hspec $ do
                 (IndexedTransition.fromIndex wta t)
           == t
 
+    describe "maxIndex" $ do
+      it "doesn't overflow for large values" $ do
+        let wta = WTASpec MaxInt 72000 (V.fromList [0, 0, 0, 0, 4])
+        IndexedTransition.maxIndex wta `shouldSatisfy` (>0)
+
   describe "Generator" $ describe "uniqueTransitions" $ do
     it "generates unique transitions" $ do
       res <- uniqueTransitions 5 (IndexedTransition.Index 10)