RT #124207: assert failure in ck_stringify()

v5.21.4-416-g73f4c4f converted (among other things) stringify(join(...))
into just join(...).  It asserted that the stringify didn't have any extra
children, which it won't normally do, since in something like "@a-" the
elements of the stringify get bundled up into a single tree of concats
etc, and stringify just sees a single top-level join or concat or
whatever. However during error recovery weird stuff can get left on the
stack.

So rather than asserting no more kids, skip the optimisation if there are
more kids.

1 files changed, 4 insertions, 4 deletions

diff --git a/op.c b/op.c
index 4e8f5a4b56..afaae61c75 100644
--- a/op.c
+++ b/op.c
@@ -11118,11 +11118,11 @@ Perl_ck_stringify(pTHX_ OP *o)
 {
     OP * const kid = OpSIBLING(cUNOPo->op_first);
     PERL_ARGS_ASSERT_CK_STRINGIFY;
-    if (kid->op_type == OP_JOIN || kid->op_type == OP_QUOTEMETA
-     || kid->op_type == OP_LC   || kid->op_type == OP_LCFIRST
-     || kid->op_type == OP_UC   || kid->op_type == OP_UCFIRST)
+    if ((   kid->op_type == OP_JOIN || kid->op_type == OP_QUOTEMETA
+         || kid->op_type == OP_LC   || kid->op_type == OP_LCFIRST
+         || kid->op_type == OP_UC   || kid->op_type == OP_UCFIRST)
+	&& !OpHAS_SIBLING(kid)) /* syntax errs can leave extra children */
     {
-	assert(!OpHAS_SIBLING(kid));
 	op_sibling_splice(o, cUNOPo->op_first, -1, NULL);
 	op_free(o);
 	return kid;