From 5c906035ffb6b2857a0f941a97ac9e7bb4126275 Mon Sep 17 00:00:00 2001
From: Gerard Goossen <gerard@ggoossen.net>
Date: Sat, 13 Aug 2011 18:38:13 +0200
Subject: [PATCH] Propagate lvalue context only to children of list ops which
 are not in void context.

Children list ops might be in void context because the list is in scalar
context. A test that discarded elements in a list are not assigned lvalue
context is added.
Children of a list op might also be in void context because they are
special entersub ops for attributes. This patch makes the
OPpENTERSUB_NOMOD flag redundant.
---
 op.c        | 7 ++++++-
 t/op/list.t | 9 ++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/op.c b/op.c
index 775705b..c4c0e76 100644
--- a/op.c
+++ b/op.c
@@ -1718,6 +1718,8 @@ Perl_op_lvalue_flags(pTHX_ OP *o, I32 type, U32 flags)
 	return o;
     }
 
+    assert( (o->op_flags & OPf_WANT) != OPf_WANT_VOID );
+
     switch (o->op_type) {
     case OP_UNDEF:
 	localize = 0;
@@ -2016,7 +2018,10 @@ Perl_op_lvalue_flags(pTHX_ OP *o, I32 type, U32 flags)
     case OP_LIST:
 	localize = 0;
 	for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
-	    op_lvalue(kid, type);
+	    /* elements might be in void context because the list is
+	       in scalar context or because they are attribute sub calls */
+	    if ( (kid->op_flags & OPf_WANT) != OPf_WANT_VOID )
+		op_lvalue(kid, type);
 	break;
 
     case OP_RETURN:
diff --git a/t/op/list.t b/t/op/list.t
index c6a0a9a..87045fc 100644
--- a/t/op/list.t
+++ b/t/op/list.t
@@ -6,7 +6,7 @@ BEGIN {
 }
 
 require "test.pl";
-plan( tests => 63 );
+plan( tests => 64 );
 
 @foo = (1, 2, 3, 4);
 cmp_ok($foo[0], '==', 1, 'first elem');
@@ -175,3 +175,10 @@ cmp_ok(join('',(1,2),3,(4,5)),'eq','12345','list (..).(..)');
     my @b = qw();
     is($#b, -1);
 }
+
+{
+    # comma operator with lvalue only propagates the lvalue context to
+    # the last operand.
+    ("const", my $x) ||= 1;
+    is( $x, 1 );
+}
-- 
2.7.4