[improve pretty printing of wildcards
Helmut Grohne <grohne@cs.uni-bonn.de>**20150217143213
 Ignore-this: e0aa9284e9302ebdeaead04bfd53e064
 
 The current way of transforming TWildEs into TH.Exp, is not valid Haskell as an
 unbound identifier prefixed with a question mark is used. If a wildcard shows
 up in a final hypothesis, it cannot be compiled. Thus changing the
 representation of wildcards to calls of error with the wildcard name attached.
 
 While this is not relevant here, it becomes relevant once igor can create
 hypotheses containing wildcards.
] hunk ./src/Syntax/Name.hs 4
-    arrowName, isTuple, isAnyTuple, isCons, isNil, listTypeName,
+    arrowName, errorName, isTuple, isAnyTuple, isCons, isNil, listTypeName,
hunk ./src/Syntax/Name.hs 15
+errorName :: Name
+errorName = 'error
+
hunk ./src/Syntax/Ppr.hs 117
-    stripFrom s p = maybe s id (stripPrefix p s)
-    qualifiers    = ["Data.Either.","Data.Maybe.","GHC.Bool."
-                    ,"GHC.Base.","GHC.Types.", "GHC.List."
-                    ,"Generics.Pointless.Combinators."
-                    ,"Generics.Pointless.RecursionPatterns."]
+    stripFrom s p = fromMaybe s (stripPrefix p s)
+    qualifiers    = ["Data.Either.", "Data.Maybe.", "GHC.Bool."
+                    , "GHC.Base.", "GHC.Err.", "GHC.Types.", "GHC.List."
+                    , "Generics.Pointless.Combinators."
+                    , "Generics.Pointless.RecursionPatterns."]
hunk ./src/Syntax/Ppr.hs 170
-toExp (TWildE n _)        = TH.VarE (mkName ('?':(show n))) -- shouldn' occur in body
+toExp (TWildE n _)        = TH.AppE (TH.ConE errorName) . TH.LitE $ TH.StringL ('?':show n) -- shouldn' occur in body