From a1e51d125944ad840a306d0cddec681848808f4c Mon Sep 17 00:00:00 2001
From: Hans Bolinder <hasse@erlang.org>
Date: Mon, 22 Apr 2019 13:54:12 +0200
Subject: dialyzer: Add parentheses around annotated union elements

In contracts, annotated elements of unions are printed with
parentheses around them. They are not parseable otherwise.
---
 .../test/small_SUITE_data/results/union_paren      |  7 +++++++
 .../test/small_SUITE_data/src/union_paren.erl      | 24 ++++++++++++++++++++++
 lib/hipe/cerl/erl_types.erl                        | 10 ++++++++-
 3 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 lib/dialyzer/test/small_SUITE_data/results/union_paren
 create mode 100644 lib/dialyzer/test/small_SUITE_data/src/union_paren.erl

diff --git a/lib/dialyzer/test/small_SUITE_data/results/union_paren b/lib/dialyzer/test/small_SUITE_data/results/union_paren
new file mode 100644
index 0000000000..3a3526df89
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/results/union_paren
@@ -0,0 +1,7 @@
+
+union_paren.erl:12: Function t2/0 has no local return
+union_paren.erl:13: The call union_paren:t2(3.14) breaks the contract (integer() | atom()) -> integer()
+union_paren.erl:19: Function t3/0 has no local return
+union_paren.erl:20: The pattern 3.14 can never match the type atom() | integer()
+union_paren.erl:5: Function t1/0 has no local return
+union_paren.erl:6: The call union_paren:t1(3.14) breaks the contract ((A::integer()) | (B::atom())) -> integer()
diff --git a/lib/dialyzer/test/small_SUITE_data/src/union_paren.erl b/lib/dialyzer/test/small_SUITE_data/src/union_paren.erl
new file mode 100644
index 0000000000..4691a57d98
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/union_paren.erl
@@ -0,0 +1,24 @@
+-module(union_paren).
+
+-compile(export_all).
+
+t1() ->
+    t1(3.14).
+
+-spec t1((A :: integer()) | (B :: atom())) -> integer().
+t1(A) ->
+    fy:bar(A).
+
+t2() ->
+    t2(3.14).
+
+-spec t2(integer() | atom()) -> integer().
+t2(A) ->
+    fy:bar(A).
+
+t3() ->
+    3.14 = t3(foo).
+
+-spec t3(_) -> (I :: integer()) | (A :: atom()).
+t3(A) when is_atom(A) -> A;
+t3(I) when is_integer(I) -> I.
diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index d61cd8664c..badf58936f 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -5338,7 +5338,15 @@ t_form_to_string({type, _L, tuple, any}) -> "tuple()";
 t_form_to_string({type, _L, tuple, Args}) ->
   "{" ++ flat_join(t_form_to_string_list(Args), ",") ++ "}";
 t_form_to_string({type, _L, union, Args}) ->
-  flat_join(t_form_to_string_list(Args), " | ");
+  flat_join(lists:map(fun(Arg) ->
+                          case Arg of
+                            {ann_type, _AL, _} ->
+                              "(" ++ t_form_to_string(Arg) ++ ")";
+                            _ ->
+                              t_form_to_string(Arg)
+                          end
+                      end, Args),
+            " | ");
 t_form_to_string({type, _L, Name, []} = T) ->
    try
      M = mod,
-- 
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