3 files changed, 28 insertions, 3 deletions
diff --git a/lib/dialyzer/src/dialyzer_utils.erl b/lib/dialyzer/src/dialyzer_utils.erl
index 8046b48838..dc8e825199 100644
--- a/lib/dialyzer/src/dialyzer_utils.erl
+++ b/lib/dialyzer/src/dialyzer_utils.erl
@@ -219,15 +219,18 @@ get_record_and_type_info([], _Module, Records, RecDict) ->
   end.
 
 add_new_type(TypeOrOpaque, Name, TypeForm, ArgForms, Module, RecDict) ->
-  case erl_types:type_is_defined(TypeOrOpaque, Name, RecDict) of
+  Arity = length(ArgForms),
+  case erl_types:type_is_defined(TypeOrOpaque, Name, Arity, RecDict) of
     true ->
-      throw({error, flat_format("Type ~s already defined\n", [Name])});
+      Msg = flat_format("Type ~s/~w already defined\n", [Name, Arity]),
+      throw({error, Msg});
     false ->
       ArgTypes = [erl_types:t_from_form(X) || X <- ArgForms],
       case lists:all(fun erl_types:t_is_var/1, ArgTypes) of
 	true ->
 	  ArgNames = [erl_types:t_var_name(X) || X <- ArgTypes],
-	  dict:store({TypeOrOpaque, Name}, {Module, TypeForm, ArgNames}, RecDict);
+	  dict:store({TypeOrOpaque, Name, Arity},
+                     {Module, TypeForm, ArgNames}, RecDict);
 	false ->
 	  throw({error, flat_format("Type declaration for ~w does not "
 				    "have variables as parameters", [Name])})
diff --git a/lib/dialyzer/test/small_SUITE_data/results/types_arity b/lib/dialyzer/test/small_SUITE_data/results/types_arity
new file mode 100644
index 0000000000..02641bd167
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/results/types_arity
@@ -0,0 +1,2 @@
+
+types_arity.erl:16: Invalid type specification for function types_arity:test2/0. The success typing is () -> {'node','a','nil','nil'}
diff --git a/lib/dialyzer/test/small_SUITE_data/src/types_arity.erl b/lib/dialyzer/test/small_SUITE_data/src/types_arity.erl
new file mode 100644
index 0000000000..4ddc986ea8
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/types_arity.erl
@@ -0,0 +1,20 @@
+-module(types_arity).
+
+-export([ test1/0
+        , test2/0
+        , test3/0
+        ]).
+
+-export_type([tree/0, tree/1]).
+
+-type tree(T) :: 'nil' | {'node', T, tree(T), tree(T)}.
+-type tree()  :: tree(integer()).
+
+-spec test1() -> tree().
+test1() -> {node, 7, nil, nil}.
+
+-spec test2() -> tree().
+test2() -> {node, a, nil, nil}.
+
+-spec test3() -> tree(atom()).
+test3() -> {node, a, nil, nil}.