From e2d0e9a5d1dd29d4005ca9a3e73222eeabd9e2b7 Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Wed, 22 Apr 2020 15:01:40 +1000
Subject: [PATCH] set magic on $lex for $lex = (index(...) == -1) and make it
 an lvalue
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related to #17737 and fixes #17739

re-work of my original patch that only pushes the final result

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 pp.c         | 13 +++++++++----
 t/op/index.t | 28 +++++++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/pp.c b/pp.c
index a061fae363..c3b18b57f8 100644
--- a/pp.c
+++ b/pp.c
@@ -3520,11 +3520,16 @@ PP(pp_index)
   push_result:
     /* OPpTRUEBOOL indicates an '== -1' has been optimised away */
     if (PL_op->op_private & OPpTRUEBOOL) {
-        PUSHs( ((retval != -1) ^ cBOOL(PL_op->op_private & OPpINDEX_BOOLNEG))
-                    ? &PL_sv_yes : &PL_sv_no);
-        if (PL_op->op_private & OPpTARGET_MY)
+        SV *result = ((retval != -1) ^ cBOOL(PL_op->op_private & OPpINDEX_BOOLNEG))
+            ? &PL_sv_yes : &PL_sv_no;
+        if (PL_op->op_private & OPpTARGET_MY) {
             /* $lex = (index() == -1) */
-            sv_setsv(TARG, TOPs);
+            sv_setsv_mg(TARG, result);
+            PUSHs(TARG);
+        }
+        else {
+            PUSHs(result);
+        }
     }
     else
         PUSHi(retval);
diff --git a/t/op/index.t b/t/op/index.t
index 858d03deb4..2f0834e8d1 100644
--- a/t/op/index.t
+++ b/t/op/index.t
@@ -8,7 +8,7 @@ BEGIN {
 }
 
 use strict;
-plan( tests => 412 );
+plan( tests => 414 );
 
 run_tests() unless caller;
 
@@ -332,4 +332,30 @@ sub run_tests {
 
     }
 
+    {
+        my $store = 100;
+        package MyTie {
+            require Tie::Scalar;
+            our @ISA = qw(Tie::StdScalar);
+            sub STORE {
+                my ($self, $value) = @_;
+
+                $store = $value;
+            }
+        };
+        my $x;
+        tie $x, "MyTie";
+        $x = (index("foo", "o") == -1);
+        ok(!$store, 'magic called on $lexical = (index(...) == -1)');
+    }
+    {
+        is(eval <<'EOS', "a", 'optimized $lex = (index(...) == -1) is an lvalue');
+my $y = "foo";
+my $z = "o";
+my $x;
+($x = (index($y, $z) == -1)) =~ s/^/a/;
+$x;
+EOS
+    }
+
 } # end of sub run_tests
-- 
2.25.4