Merge pull request #1378 from crytic/fix-1321

shrink: consider empty reproducers when removing reverts

Author: elopez

lib/Echidna/Shrink.hs

@@ -72,6 +72,7 @@ removeUselessNoCalls = mapMaybe f
 -- If a transaction reverts, replace it by a "NoCall" with the same parameters as the original call
 -- (e.g. same block increment timestamp and number)
 removeReverts :: (MonadIO m, MonadReader Env m, MonadThrow m) => VM Concrete RealWorld -> [Tx] -> m [Tx]
+removeReverts _ [] = return []
 removeReverts vm txs = do
   let (itxs, le) = (init txs, last txs)
   ftxs <- removeReverts' vm itxs []

src/test/Tests/Optimization.hs

@@ -9,5 +9,8 @@ optimizationTests = testGroup "Optimization-based Integration Testing"
   [ 
     testContract "optimize/linear.sol"   (Just "optimize/config.yaml")
       [ ("Max value found in echidna_opt_linear",  optimized "echidna_opt_linear" 4000)
+      ],
+    testContract "optimize/zero.sol"   (Just "optimize/config.yaml")
+      [ ("Max value found in echidna_opt_zero",  optimized "echidna_opt_zero" 0)
       ]
   ]

tests/solidity/optimize/zero.sol

@@ -0,0 +1,5 @@
+contract Test {
+  function echidna_opt_zero() public returns (int256) {
+      return 0;
+  }
+}