Vyper fixes (#645)

* Workaround to run vyper contracts without slither

* More vyper fixes

* fix

lib/Echidna/Exec.hs

@@ -11,7 +11,7 @@ import Control.Lens
 import Control.Monad.Catch (Exception, MonadThrow(..))
 import Control.Monad.State.Strict (MonadState, execState)
 import Data.Has (Has(..))
-import Data.Maybe (fromMaybe, fromJust)
+import Data.Maybe (fromMaybe)
 import EVM
 import EVM.Op (Op(..))
 import EVM.Exec (exec, vmForEthrunCreation)
@@ -106,7 +106,7 @@ usingCoverage cov = maybe (cov >> liftSH exec1 >> usingCoverage cov) pure =<< us
 pointCoverage :: (MonadState x m, Has VM x) => Lens' x CoverageMap -> m ()
 pointCoverage l = do
   v <- use hasLens
-  l %= M.insertWith (const . S.insert $ (v ^. state . pc, fromJust $ vmOpIx v, Success))
+  l %= M.insertWith (const . S.insert $ (v ^. state . pc, fromMaybe 0 $ vmOpIx v, Success))
                     (fromMaybe (error "no contract information on coverage") $ h v)
                     mempty
   where

lib/Echidna/Processor.hs

@@ -12,6 +12,7 @@ import Data.Aeson             ((.:), decode, parseJSON, withEmbeddedJSON, withOb
 import Data.Aeson.Types       (FromJSON, Parser, Value(String))
 import Data.List              (nub)
 import Data.Maybe             (catMaybes)
+import Data.Text              (pack, isSuffixOf)
 import Text.Read              (readMaybe)
 import System.Directory       (findExecutable)
 import System.Process         (StdStream(..), readCreateProcessWithExitCode, proc, std_err)
@@ -67,6 +68,9 @@ data SlitherInfo = SlitherInfo
   , generationGraph :: M.HashMap ContractName (M.HashMap FunctionName [FunctionName])
   } deriving (Show)
 
+noInfo :: SlitherInfo
+noInfo = SlitherInfo mempty mempty mempty mempty mempty
+
 instance FromJSON SlitherInfo where
   parseJSON = withObject "slitherOutput" $ \o -> do
     -- take the value under 'description' through the path - $['results']['printers'][0]['description']
@@ -119,7 +123,7 @@ instance FromJSON SlitherInfo where
 
 -- Slither processing
 runSlither :: (MonadIO m, MonadThrow m) => FilePath -> [String] -> m SlitherInfo
-runSlither fp extraArgs = do
+runSlither fp extraArgs = if ".vy" `isSuffixOf` pack fp then return noInfo else do
   mp <- liftIO $ findExecutable "slither"
   case mp of
     Nothing -> throwM $ ProcessorNotFound "slither" "You should install it using 'pip3 install slither-analyzer --user'"

lib/Echidna/Types/Signature.hs

@@ -36,7 +36,7 @@ getBytecodeMetadata :: ByteString -> ByteString
 getBytecodeMetadata bs =
   let stripCandidates = flip BS.breakSubstring bs <$> knownBzzrPrefixes in
     case find ((/= mempty) . snd) stripCandidates of
-      Nothing -> mempty
+      Nothing     -> bs -- if no metadata is found, return the complete bytecode
       Just (_, m) -> m
 
 knownBzzrPrefixes :: [ByteString]