Merge branch 'bg/compiler-suppress-result-ignored' into dev

* bg/compiler-suppress-result-ignored:
  compiler tests: Eliminate "result of expression is ignored" warnings
  Silence warnings for expressions that are assigned to "_"

OTP-8602 bg/compiler-suppress-result-ignored

It is now possible to suppress the warning in code such as
"list_to_integer(S), ok" by assigning the ignored value "_" like this: "_ =
list_to_integer(S), ok".

1 files changed, 19 insertions, 7 deletions

diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl
index 20969c0b26..9c4687efa1 100644
--- a/lib/compiler/test/match_SUITE.erl
+++ b/lib/compiler/test/match_SUITE.erl
@@ -1,19 +1,19 @@
 %%
 %% %CopyrightBegin%
-%% 
-%% Copyright Ericsson AB 2004-2009. All Rights Reserved.
-%% 
+%%
+%% Copyright Ericsson AB 2004-2010. All Rights Reserved.
+%%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
 %% compliance with the License. You should have received a copy of the
 %% Erlang Public License along with this software. If not, it can be
 %% retrieved online at http://www.erlang.org/.
-%% 
+%%
 %% Software distributed under the License is distributed on an "AS IS"
 %% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 %% the License for the specific language governing rights and limitations
 %% under the License.
-%% 
+%%
 %% %CopyrightEnd%
 %%
 -module(match_SUITE).
@@ -21,14 +21,14 @@
 -export([all/1,
 	 pmatch/1,mixed/1,aliases/1,match_in_call/1,
 	 untuplify/1,shortcut_boolean/1,letify_guard/1,
-	 selectify/1]).
+	 selectify/1,underscore/1]).
 	 
 -include("test_server.hrl").
 
 all(suite) ->
     test_lib:recompile(?MODULE),
     [pmatch,mixed,aliases,match_in_call,untuplify,shortcut_boolean,
-     letify_guard,selectify].
+     letify_guard,selectify,underscore].
 
 pmatch(Config) when is_list(Config) ->
     ?line ok = doit(1),
@@ -352,4 +352,16 @@ sel_same_value2(V) when V =:= 42; V =:= 43 ->
 sel_same_value2(_) ->
     error.
 
+underscore(Config) when is_list(Config) ->
+    case Config of
+	[] ->
+	    %% Assignment to _ at the end of a construct.
+	    _ = length(Config);
+	[_|_] ->
+	    %% Assignment to _ at the end of a construct.
+	    _ = list_to_tuple(Config)
+    end,
+    _ = is_list(Config),
+    ok.
+
 id(I) -> I.