patch 8.0.0645: no error for illegal back reference in NFA engine commit https://github.com/vim/vim/commit/1ef9bbe215e13a273e74fccaddd8fc5a42c76b6e Author: Bram Moolenaar <Bram@vim.org> Date: Sat Jun 17 20:08:20 2017 +0200 patch 8.0.0645: no error for illegal back reference in NFA engine Problem: The new regexp engine does not give an error for using a back reference where it is not allowed. (Dominique Pelle) Solution: Check the back reference like the old engine. (closes #1774)

TYPEMAP
VIWIN	T_VIOBJNOMUNGE
VIBUF	T_VIOBJNOMUNGE

INPUT
T_VIOBJNOMUNGE
	if (sv_isa($arg, \"${ntype}\")) {
	    IV tmp = SvIV((SV*)SvRV($arg));
	    $var = INT2PTR($type, tmp);
	    if (!tmp)
		croak(\"$ntype no longer exists\");
	}
	else
	    croak(\"$var is not of type ${ntype}\")