Make keys $scalar an lvalue

This does a run-time check to see whether $scalar is a hash ref, and
dies if it is not.

This is to keep keys \@_ consistent with keys @_.

I cannot simply use OPf_MOD, since that indicates *potential* lvalue
context (including subroutine args).

So, instead, I take advantage of the fact that OPf_SPECIAL is always
set on the LHS of an assignment (usually to indicate that local()
should not erase the value).

1 files changed, 8 insertions, 0 deletions

diff --git a/t/op/smartkve.t b/t/op/smartkve.t
index 7c57e7bba4..ad56e6a9c4 100644
--- a/t/op/smartkve.t
+++ b/t/op/smartkve.t
@@ -131,6 +131,14 @@ ok(defined $empty,
   'Vivify: $empty (after keys $empty->{hash}) is HASHREF');
 ok(!defined $empty->{hash}      ,   'Vivify: $empty->{hash} is undef');
 
+# Keys -- lvalue
+$_{foo} = "bar";
+keys \%_ = 65;
+is scalar %_, '1/128', 'keys $hashref as lvalue';
+eval 'keys \@_ = 65';
+like $@, qr/Can't modify keys on reference in scalar assignment/,
+  'keys $arrayref as lvalue dies';
+
 # Keys -- errors
 $errpat = qr/
  (?-x:Type of argument to keys on reference must be unblessed hashref or)