1 files changed, 12 insertions, 6 deletions
diff --git a/lib/dialyzer/src/dialyzer_contracts.erl b/lib/dialyzer/src/dialyzer_contracts.erl
index 7251de8b10..83b3ef72f2 100644
--- a/lib/dialyzer/src/dialyzer_contracts.erl
+++ b/lib/dialyzer/src/dialyzer_contracts.erl
@@ -126,13 +126,19 @@ butlast([H|T]) -> [H|butlast(T)].
 
 constraints_to_string([]) ->
   "";
-constraints_to_string([{type, _, constraint, [{atom, _, What}, Types]}]) ->
-  atom_to_list(What) ++ "(" ++
-    sequence([erl_types:t_form_to_string(T) || T <- Types], ",") ++ ")";
 constraints_to_string([{type, _, constraint, [{atom, _, What}, Types]}|Rest]) ->
-  atom_to_list(What) ++ "(" ++
-    sequence([erl_types:t_form_to_string(T) || T <- Types], ",")
-    ++ "), " ++ constraints_to_string(Rest).
+  S = constraint_to_string(What, Types),
+  case Rest of
+    [] -> S;
+    _ -> S ++ ", " ++ constraints_to_string(Rest)
+  end.
+
+constraint_to_string(is_subtype, [{var, _, Var}, T]) ->
+  atom_to_list(Var) ++ " :: " ++ erl_types:t_form_to_string(T);
+constraint_to_string(What, Types) ->
+  atom_to_list(What) ++ "("
+    ++ sequence([erl_types:t_form_to_string(T) || T <- Types], ",")
+    ++ ")".
 
 sequence([], _Delimiter) -> "";
 sequence([H], _Delimiter) -> H;