From 29c2de1044d25c5ae641797e527ca72df8495355 Mon Sep 17 00:00:00 2001
From: Anthony Ramine <n.oxyde@gmail.com>
Date: Thu, 6 Jun 2013 22:25:07 +0200
Subject: Silence a misleading warning with some comprehensions

When compiling comprehensions with generators which are foldable to
'true', a misleading warning is emitted by sys_core_fold because a
clause resulting from the compilation of the comprehension to Core
Erlang is not marked as generated by the compiler.

An example of such a comprehension is [ true || true ].
---
 lib/compiler/src/v3_core.erl         |  6 ++++--
 lib/compiler/test/warnings_SUITE.erl | 14 ++++++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

(limited to 'lib/compiler')

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index eea54b30a2..f243127b66 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -956,7 +956,8 @@ lc_tq(Line, E, [Fil0|Qs0], Mc, St0) ->
 		    args=[],
 		    clauses=[#iclause{anno=LAnno,pats=[],
 				      guard=Gs,body=Lps ++ [Lc]}],
-		    fc=#iclause{anno=LAnno,pats=[],guard=[],body=[Mc]}},
+		    fc=#iclause{anno=LAnno#a{anno=[compiler_generated|LA]},
+				pats=[],guard=[],body=[Mc]}},
 	     [],St2};
 	false ->
 	    {Lc,Lps,St1} = lc_tq(Line, E, Qs0, Mc, St0),
@@ -1101,7 +1102,8 @@ bc_tq1(Line, E, [Fil0|Qs0], AccVar, St0) ->
 		    clauses=[#iclause{anno=LAnno,
 				      pats=[],
 				      guard=Gs,body=Bps ++ [Bc]}],
-		    fc=#iclause{anno=LAnno,pats=[],guard=[],body=[AccVar]}},
+		    fc=#iclause{anno=LAnno#a{anno=[compiler_generated|LA]},
+				pats=[],guard=[],body=[AccVar]}},
 	     [],St};
 	false ->
 	    {Bc,Bps,St1} = bc_tq1(Line, E, Qs0, AccVar, St0),
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index f00bfe663b..810b2b48c9 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -37,7 +37,7 @@
 
 -export([pattern/1,pattern2/1,pattern3/1,pattern4/1,
 	 guard/1,bad_arith/1,bool_cases/1,bad_apply/1,
-         files/1,effect/1,bin_opt_info/1,bin_construction/1]).
+         files/1,effect/1,bin_opt_info/1,bin_construction/1, comprehensions/1]).
 
 % Default timetrap timeout (set in init_per_testcase).
 -define(default_timeout, ?t:minutes(2)).
@@ -61,7 +61,7 @@ groups() ->
     [{p,test_lib:parallel(),
       [pattern,pattern2,pattern3,pattern4,guard,
        bad_arith,bool_cases,bad_apply,files,effect,
-       bin_opt_info,bin_construction]}].
+       bin_opt_info,bin_construction,comprehensions]}].
 
 init_per_suite(Config) ->
     Config.
@@ -536,6 +536,16 @@ bin_construction(Config) when is_list(Config) ->
     
     ok.
 
+comprehensions(Config) when is_list(Config) ->
+    Ts = [{tautologic_guards,
+           <<"
+             f() -> [ true || true ].
+             g() -> << <<1>> || true >>.
+           ">>,
+           [], []}],
+    run(Config, Ts),
+    ok.
+
 %%%
 %%% End of test cases.
 %%%
-- 
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