[perl #81290] assertion failure with lock &lvsub

With this commit, locking an lvalue subroutine no longer tries to lock
the subroutine itself (triggering an assertion in pp_lock).  Instead,
the &foo syntax is treated as a scalar lvalue expression, as with tie,
so the return value gets locked.  Non-lvalue sub calls still produce a
‘Can't modify’ error, as they are not modifiable.

This also stops lock from trying to return a sub as though it were a
scalar, thereby breaking this JAPH I’ve just written:-)

sub _:lvalue{$x}for(lock&_){$_
="Just another Perl hacker,\n"}
print+prototype"_"

1 files changed, 1 insertions, 1 deletions

diff --git a/op.c b/op.c
index ab65490bc9..1ff086bac3 100644
--- a/op.c
+++ b/op.c
@@ -1878,7 +1878,7 @@ Perl_doref(pTHX_ OP *o, I32 type, bool set_op_ref)
 
     switch (o->op_type) {
     case OP_ENTERSUB:
-	if ((type == OP_EXISTS || type == OP_DEFINED || type == OP_LOCK) &&
+	if ((type == OP_EXISTS || type == OP_DEFINED) &&
 	    !(o->op_flags & OPf_STACKED)) {
 	    o->op_type = OP_RV2CV;             /* entersub => rv2cv */
 	    o->op_ppaddr = PL_ppaddr[OP_RV2CV];