make a sort with zero args a compile-time err

    @a = sort @empty; # unaffected
    @a = sort;        # now a compile-time error

the main motivation for this is to potentially be able to treat a
colon following the 'sort' keyword as part of the sort expression,
to then be able to add sort attributes at some point, e.g.
    @a = sort :num, 1,2,3;
rather than the colon being seen as part of a ?: conditional.

See http://nntp.perl.org/group/perl.perl5.porters/262425.

1 files changed, 3 insertions, 0 deletions

diff --git a/op.c b/op.c
index 3c119c2133..770b2f949a 100644
--- a/op.c
+++ b/op.c
@@ -14219,6 +14219,9 @@ Perl_ck_sort(pTHX_ OP *o)
         simplify_sort(o);
     firstkid = OpSIBLING(cLISTOPo->op_first);		/* get past pushmark */
 
+    if (!firstkid)
+        return too_few_arguments_pv(o,OP_DESC(o), 0);
+
     if ((stacked = o->op_flags & OPf_STACKED)) {	/* may have been cleared */
         OP *kid = cUNOPx(firstkid)->op_first;		/* get past null */