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".

4 files changed, 43 insertions, 26 deletions

diff --git a/lib/compiler/test/float_SUITE.erl b/lib/compiler/test/float_SUITE.erl
index 3d2dbf47e9..07779ddd5a 100644
--- a/lib/compiler/test/float_SUITE.erl
+++ b/lib/compiler/test/float_SUITE.erl
@@ -1,19 +1,19 @@
 %%
 %% %CopyrightBegin%
-%% 
-%% Copyright Ericsson AB 2002-2009. All Rights Reserved.
-%% 
+%%
+%% Copyright Ericsson AB 2002-2010. 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(float_SUITE).
@@ -41,7 +41,7 @@ float_sub(A)->
 float_mul(0, _, _)->
     ok;
 float_mul(Iter, A, B) when is_float(A), is_float(B) ->
-    A*B,
+    _ = A*B,
     float_mul(Iter-1, A, B).
 
 %% Thanks to Mikael Pettersson and Tobias Lindahl (HiPE).
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.
diff --git a/lib/compiler/test/num_bif_SUITE.erl b/lib/compiler/test/num_bif_SUITE.erl
index c246f56611..912f7366dd 100644
--- a/lib/compiler/test/num_bif_SUITE.erl
+++ b/lib/compiler/test/num_bif_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(num_bif_SUITE).
@@ -166,7 +166,7 @@ t_list_to_float_safe(Config) when is_list(Config) ->
 
 t_list_to_float_risky(Config) when is_list(Config) ->
     ?line Many_Ones = lists:duplicate(25000, $1),
-    ?line list_to_float("2."++Many_Ones),
+    ?line _ = list_to_float("2."++Many_Ones),
     ?line {'EXIT', {badarg, _}} = (catch list_to_float("2"++Many_Ones)),
     ok.
 
@@ -186,7 +186,7 @@ t_list_to_integer(Config) when is_list(Config) ->
 
     %% Bignums.
     ?line 123456932798748738738 = list_to_integer("123456932798748738738"),
-    ?line list_to_integer(lists:duplicate(2000, $1)),
+    ?line _ = list_to_integer(lists:duplicate(2000, $1)),
     ok.
 
 %% Tests round/1.
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 6e60ab88cb..5ed8836c70 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -1,19 +1,19 @@
 %%
 %% %CopyrightBegin%
-%% 
-%% Copyright Ericsson AB 2003-2009. All Rights Reserved.
-%% 
+%%
+%% Copyright Ericsson AB 2003-2010. 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(warnings_SUITE).
@@ -375,7 +375,12 @@ effect(Config) when is_list(Config) ->
                 comp_op ->
                     X =:= 2;
                 cookie ->
-                    erlang:get_cookie()
+                    erlang:get_cookie();
+		result_ignore ->
+                    _ = list_to_integer(X);
+                warn_lc_4 ->
+                    %% No warning because of assignment to _.
+                    [_ = abs(Z) || Z <- [1,2,3]]
                end,
                ok.