erl_bif_types: Properly unopaque maps:merge/2 args

erl_bif_types:type/5 was calling erl_types:map_pairwise_merge/3 directly
with its (potentially opaque) arguments, causing Dialyzer crashes.

Bug (ERL-249) reported and minimised test case provided by Felipe
Ripoll.

3 files changed, 36 insertions, 10 deletions

diff --git a/lib/dialyzer/test/map_SUITE_data/src/opaque_bif.erl b/lib/dialyzer/test/map_SUITE_data/src/opaque_bif.erl
new file mode 100644
index 0000000000..40214a1887
--- /dev/null
+++ b/lib/dialyzer/test/map_SUITE_data/src/opaque_bif.erl
@@ -0,0 +1,13 @@
+-module(opaque_bif).
+-export([o1/1]).
+-export_type([opaque_any_map/0]).
+-opaque opaque_any_map() :: map().
+
+%% ERL-249: A bug with opaque arguments to maps:merge/2
+%% Reported by Felipe Ripoll on 6/9/2016
+-spec o1(opaque_any_map()) -> opaque_any_map().
+o1(Map) ->
+    maps:merge(o1_c(), Map).
+
+-spec o1_c() -> opaque_any_map().
+o1_c() -> #{}.
diff --git a/lib/hipe/cerl/erl_bif_types.erl b/lib/hipe/cerl/erl_bif_types.erl
index 9453ca6c6f..230fce2e68 100644
--- a/lib/hipe/cerl/erl_bif_types.erl
+++ b/lib/hipe/cerl/erl_bif_types.erl
@@ -124,7 +124,7 @@
 		    t_map_entries/2,
 		    t_map_put/3,
 		    t_map_update/3,
-		    map_pairwise_merge/3
+		    t_map_pairwise_merge/4
 		   ]).
 
 -ifdef(DO_ERL_BIF_TYPES_TEST).
@@ -1689,10 +1689,10 @@ type(maps, merge, 2, Xs, Opaques) ->
 	     BDefK = t_map_def_key(MapB, Opaques),
 	     ADefV = t_map_def_val(MapA, Opaques),
 	     BDefV = t_map_def_val(MapB, Opaques),
-	     t_map(map_pairwise_merge(
+	     t_map(t_map_pairwise_merge(
 		     fun(K, _,     _,  mandatory, V) -> {K, mandatory, V};
 			(K, MNess, VA, optional, VB) -> {K, MNess, t_sup(VA,VB)}
-		     end, MapA, MapB),
+		     end, MapA, MapB, Opaques),
 		   t_sup(ADefK, BDefK), t_sup(ADefV, BDefV))
 	 end, Opaques);
 type(maps, put, 3, Xs, Opaques) ->
diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index 243bb6e25d..40d7a57952 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -159,6 +159,7 @@
 	 t_map_get/2, t_map_get/3,
 	 t_map_is_key/2, t_map_is_key/3,
 	 t_map_update/2, t_map_update/3,
+	 t_map_pairwise_merge/4,
 	 t_map_put/2, t_map_put/3,
 	 t_matchstate/0,
 	 t_matchstate/2,
@@ -219,8 +220,7 @@
 	 is_erl_type/1,
 	 atom_to_string/1,
 	 var_table__new/0,
-         cache__new/0,
-	 map_pairwise_merge/3
+	 cache__new/0
 	]).
 
 %%-define(DO_ERL_TYPES_TEST, true).
@@ -1768,13 +1768,26 @@ mapdict_insert(E1={K1,_,_}, [E2={K2,_,_}|T]) when K1 > K2 ->
   [E2|mapdict_insert(E1, T)];
 mapdict_insert(E={_,_,_}, T) -> [E|T].
 
+-type map_pairwise_merge_fun() :: fun((erl_type(),
+				       t_map_mandatoriness(), erl_type(),
+				       t_map_mandatoriness(), erl_type())
+				      -> t_map_pair() | false).
+
+-spec t_map_pairwise_merge(map_pairwise_merge_fun(), erl_type(), erl_type(),
+			   opaques()) -> t_map_dict().
+t_map_pairwise_merge(F, MapA, MapB, Opaques) ->
+  do_opaque(MapA, Opaques,
+	    fun(UMapA) ->
+		do_opaque(MapB, Opaques,
+			  fun(UMapB) ->
+			      map_pairwise_merge(F, UMapA, UMapB)
+			  end)
+	    end).
+
 %% Merges the pairs of two maps together. Missing pairs become (?opt, DefV) or
 %% (?opt, ?none), depending on whether K \in DefK.
--spec map_pairwise_merge(fun((erl_type(),
-			      t_map_mandatoriness(), erl_type(),
-			      t_map_mandatoriness(), erl_type())
-			     -> t_map_pair() | false),
-			 erl_type(), erl_type()) -> t_map_dict().
+-spec map_pairwise_merge(map_pairwise_merge_fun(), erl_type(), erl_type())
+			-> t_map_dict().
 map_pairwise_merge(F, ?map(APairs, ADefK, ADefV),
 		       ?map(BPairs, BDefK, BDefV)) ->
   map_pairwise_merge(F, APairs, ADefK, ADefV, BPairs, BDefK, BDefV).