Merge branch 'master' of https://git.cduce.org/cduce into typing/polymorphic-recursive-types

tests/poly/red-black.cd

@@ -81,10 +81,11 @@ let balance ( Unbalanced('a) -> Rtree('a) ; 'b\UTree -> 'b\UTree )
 
 
 
+
 (* Here we start the definition of         *)
 (* standard operations for red-black trees *)
 
-let insert (x : 'a) (t : Btree('a)) : Btree('a) =
+let insert (x : 'a) (t : Btree('a)) : Btree('a)\[]=
   let ins_aux ( [] -> Rtree('a);
                 Btree('a)\[] -> RBtree('a)\[];
                 Rtree('a) -> Rtree('a)|Wrongtree('a) )