From 6d9d4af8725f26972481b2e997c54ee5b3eafb29 Mon Sep 17 00:00:00 2001
From: Hans Bolinder <hasse@erlang.org>
Date: Wed, 24 Apr 2019 09:52:54 +0200
Subject: dialyzer: Improve the warning tagged 'fun_app_args'

The mismatching argument positions are included.
---
 lib/dialyzer/src/dialyzer.erl          | 7 +++++--
 lib/dialyzer/src/dialyzer_dataflow.erl | 7 ++++++-
 2 files changed, 11 insertions(+), 3 deletions(-)

(limited to 'lib/dialyzer/src')

diff --git a/lib/dialyzer/src/dialyzer.erl b/lib/dialyzer/src/dialyzer.erl
index 185c8c9ae6..a168b3c8c5 100644
--- a/lib/dialyzer/src/dialyzer.erl
+++ b/lib/dialyzer/src/dialyzer.erl
@@ -320,9 +320,12 @@ message_to_string({call_to_missing, [M, F, A]}) ->
 message_to_string({exact_eq, [Type1, Op, Type2]}) ->
   io_lib:format("The test ~ts ~s ~ts can never evaluate to 'true'\n",
 		[Type1, Op, Type2]);
-message_to_string({fun_app_args, [Args, Type]}) ->
+message_to_string({fun_app_args, [ArgNs, Args, Type]}) ->
+  PositionString = form_position_string(ArgNs),
   io_lib:format("Fun application with arguments ~ts will fail"
-		" since the function has type ~ts\n", [Args, Type]);
+		" since the function has type ~ts,"
+                " which differs in the ~s argument\n",
+                [Args, Type, PositionString]);
 message_to_string({fun_app_no_fun, [Op, Type, Arity]}) ->
   io_lib:format("Fun application will fail since ~ts :: ~ts"
 		" is not a function of arity ~w\n", [Op, Type, Arity]);
diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index 45b4abb253..f7aa167f5c 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -405,8 +405,13 @@ handle_apply(Tree, Map, State) ->
                                     t_fun_args(OpType1, 'universe')),
 	      case any_none(NewArgs) of
 		true ->
+                  EnumNewArgs = lists:zip(lists:seq(1, length(NewArgs)),
+                                          NewArgs),
+                  ArgNs = [Arg ||
+                            {Arg, Type} <- EnumNewArgs, t_is_none(Type)],
 		  Msg = {fun_app_args,
-			 [format_args(Args, ArgTypes, State),
+			 [ArgNs,
+			  format_args(Args, ArgTypes, State),
 			  format_type(OpType, State)]},
 		  State3 = state__add_warning(State2, ?WARN_FAILING_CALL,
 					      Tree, Msg),
-- 
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