Warn when list-assigning to TEMP

2 files changed, 13 insertions, 1 deletions

diff --git a/ext/XS-APItest/t/lvalue.t b/ext/XS-APItest/t/lvalue.t
index 718507a402..d348ea6bbc 100644
--- a/ext/XS-APItest/t/lvalue.t
+++ b/ext/XS-APItest/t/lvalue.t
@@ -3,7 +3,7 @@
 use warnings;
 use strict;
 
-use Test::More tests => 3;
+use Test::More tests => 4;
 
 use XS::APItest 'lv_temp_object';
 
@@ -16,6 +16,10 @@ use XS::APItest 'lv_temp_object';
     lv_temp_object() = 75;
     like $w, qr/Useless assignment to a temporary at/,
 	'warning when assigning to temp returned from XS lv sub';
+    undef $w;
+    (lv_temp_object()) = 75;
+    like $w, qr/Useless assignment to a temporary at/,
+	'warning when list-assigning to temp returned from XS lv sub';
 
     $w = undef;
     {
diff --git a/pp_hot.c b/pp_hot.c
index bb0f20517b..9dffb988ff 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1112,6 +1112,14 @@ PP(pp_aassign)
 		break;
 	    }
 	    if (relem <= lastrelem) {
+		if (
+		  SvTEMP(sv) && !SvSMAGICAL(sv) && SvREFCNT(sv) == 1 &&
+		  (!isGV_with_GP(sv) || SvFAKE(sv)) && ckWARN(WARN_MISC)
+		)
+		    Perl_warner(aTHX_
+		       packWARN(WARN_MISC),
+		      "Useless assignment to a temporary"
+		    );
 		sv_setsv(sv, *relem);
 		*(relem++) = sv;
 	    }