From b4243128452036945a6168ab994528050b318528 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 30 Jan 2015 07:07:01 +0100
Subject: v3_core: Suppress compiler-generated calls in guards

Compiling the following function:

  f(V) when not (bar and V) -> true;   %Line 4
  f(_) -> false.

would produce the following warnings:

  no_file: Warning: the call to is_boolean/1 has no effect
  t.erl:4: Warning: the guard for this clause evaluates to 'false'
  t.erl:4: Warning: use of operator '=:=' has no effect

Two of the warnings refer to calls to is_boolean/1 and '=:='/2 which
v3_core added when translating the code to Core Erlang. The only
relevant warning is:

  t.erl:4: Warning: the guard for this clause evaluates to 'false'

Suppress the other two warning by marking the compiler-generated
calls with a 'compiler_generated' annotation.
---
 lib/compiler/src/v3_core.erl | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

(limited to 'lib')

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index c997c77587..7ab14cfffa 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -387,33 +387,30 @@ gexpr_test(E0, Bools0, St0) ->
 		    Lanno = Anno#a.anno,
 		    {New,St2} = new_var(Lanno, St1),
 		    Bools = [New|Bools0],
-		    {#icall{anno=Anno,	%Must have an #a{}
-			    module=#c_literal{anno=Lanno,val=erlang},
-			    name=#c_literal{anno=Lanno,val='=:='},
-			    args=[New,#c_literal{anno=Lanno,val=true}]},
+		    {icall_eq_true(New),
 		     Eps0 ++ [#iset{anno=Anno,var=New,arg=E1}],Bools,St2}
 	    end;
 	_ ->
-	    Anno = get_ianno(E1),
 	    Lanno = get_lineno_anno(E1),
+	    ACompGen = #a{anno=[compiler_generated]},
 	    case is_simple(E1) of
 		true ->
 		    Bools = [E1|Bools0],
-		    {#icall{anno=Anno,	%Must have an #a{}
-			    module=#c_literal{anno=Lanno,val=erlang},
-			    name=#c_literal{anno=Lanno,val='=:='},
-			    args=[E1,#c_literal{anno=Lanno,val=true}]},Eps0,Bools,St1};
+		    {icall_eq_true(E1),Eps0,Bools,St1};
 		false ->
 		    {New,St2} = new_var(Lanno, St1),
 		    Bools = [New|Bools0],
-		    {#icall{anno=Anno,	%Must have an #a{}
-			    module=#c_literal{anno=Lanno,val=erlang},
-			    name=#c_literal{anno=Lanno,val='=:='},
-			    args=[New,#c_literal{anno=Lanno,val=true}]},
-		     Eps0 ++ [#iset{anno=Anno,var=New,arg=E1}],Bools,St2}
+		    {icall_eq_true(New),
+		     Eps0 ++ [#iset{anno=ACompGen,var=New,arg=E1}],Bools,St2}
 	    end
     end.
 
+icall_eq_true(Arg) ->
+    #icall{anno=#a{anno=[compiler_generated]},
+	   module=#c_literal{val=erlang},
+	   name=#c_literal{val='=:='},
+	   args=[Arg,#c_literal{val=true}]}.
+
 force_booleans(Vs0, E, Eps, St) ->
     Vs1 = [set_anno(V, []) || V <- Vs0],
     Vs = unforce(E, Eps, Vs1),
@@ -423,16 +420,15 @@ force_booleans_1([], E, Eps, St) ->
     {E,Eps,St};
 force_booleans_1([V|Vs], E0, Eps0, St0) ->
     {E1,Eps1,St1} = force_safe(E0, St0),
-    Lanno = element(2, V),
-    Anno = #a{anno=Lanno},
-    Call = #icall{anno=Anno,module=#c_literal{anno=Lanno,val=erlang},
-		  name=#c_literal{anno=Lanno,val=is_boolean},
+    ACompGen = #a{anno=[compiler_generated]},
+    Call = #icall{anno=ACompGen,module=#c_literal{val=erlang},
+		  name=#c_literal{val=is_boolean},
 		  args=[V]},
-    {New,St} = new_var(Lanno, St1),
-    Iset = #iset{anno=Anno,var=New,arg=Call},
+    {New,St} = new_var([], St1),
+    Iset = #iset{var=New,arg=Call},
     Eps = Eps0 ++ Eps1 ++ [Iset],
-    E = #icall{anno=Anno,
-	       module=#c_literal{anno=Lanno,val=erlang},name=#c_literal{anno=Lanno,val='and'},
+    E = #icall{anno=ACompGen,
+	       module=#c_literal{val=erlang},name=#c_literal{val='and'},
 	       args=[E1,New]},
     force_booleans_1(Vs, E, Eps, St).
 
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