Fix bug with generated default implementations of nullary class methods

CHANGELOG.md

@@ -5,6 +5,7 @@ Version 1.0.2 (under development)
 =============
 
   * Fixed bug with wrong type of free variables in the intermediate language.
+  * Fixed bug with generated default implementations of nullary class methods.
 
 Version 1.0.1
 =============

src/Transformations/Dictionary.hs

@@ -413,10 +413,12 @@ defaultClassMethodDecl :: QualIdent -> Ident -> DTM (Decl PredType)
 defaultClassMethodDecl cls f = do
   pty@(PredType _ ty) <- getClassMethodType cls f
   augEnv <- getAugEnv
-  let pats = if isAugmented augEnv (qualifyLike cls f)
+  let augmented = isAugmented augEnv (qualifyLike cls f)
+      pats = if augmented
                then [ConstructorPattern predUnitType qUnitId []]
                else []
-  return $ funDecl NoPos pty f pats $ preludeError (instType ty) $
+      ty' = if augmented then arrowBase ty else ty
+  return $ funDecl NoPos pty f pats $ preludeError (instType ty') $
     "No instance or default method for class operation " ++ escName f
 
 getClassMethodType :: QualIdent -> Ident -> DTM PredType