src/Pure/type_infer.ML

   let
 
     (* adjust sorts of parameters *)
 
     fun not_in_sort x S' S =
-      "Type variable " ^ x ^ "::" ^ Sorts.str_of_sort S' ^ " not in sort " ^
+      "Variable " ^ x ^ "::" ^ Sorts.str_of_sort S' ^ " not of sort " ^
         Sorts.str_of_sort S ^ ".";
 
     fun meet _ [] = ()
       | meet (Link (r as (ref (Param S')))) S =
           if Sorts.sort_le classrel (S', S) then ()