restore positive Decimal invariant

src/Convert/SeverityTask.hs

@@ -23,7 +23,7 @@ convert = map $ traverseDescriptions traverseDescription
 elaborationFatalIdent :: Identifier
 elaborationFatalIdent = "_sv2v_elaboration_fatal"
 elaborationFatalCancelCode :: Expr
-elaborationFatalCancelCode = RawNum (-1)
+elaborationFatalCancelCode = UniOp UniSub $ RawNum 1
 
 -- Checker for fatal elaboration
 elaborationFatalDecl :: ModuleItem

src/Language/SystemVerilog/AST/Number.hs

@@ -322,7 +322,7 @@ numberBitLength (Based size _ _ _ _) =
         then max 32 $ negate size
         else size
 
--- get whether or not a number is sized
+-- get whether or not a number is signed
 numberIsSized :: Number -> Bool
 numberIsSized UnbasedUnsized{} = False
 numberIsSized (Decimal size _ _) = size > 0
@@ -359,7 +359,9 @@ instance Show Number where
     show (UnbasedUnsized bit) =
         '\'' : show bit
     show (Decimal (-32) True value) =
-        show value
+        if value < 0
+            then error $ "illegal decimal: " ++ show value
+            else show value
     show (Decimal size signed value) =
         if size == 0
             then error $ "illegal decimal literal: "