error if give null to an [io] Par - #511

Changes

@@ -45,6 +45,7 @@
 - eigens_sym now sorts output like EISPACK
 - Math::isfinite no longer works inplace due to mismatch between Pars (#511)
 - now an error to specify Inplace between differently-typed Pars (#511)
+- now an error to give a null to an [io] Par (#511)
 
 2.095 2024-11-03
 - add PDL_GENTYPE_IS_{REAL,FLOATREAL,COMPLEX,SIGNED,UNSIGNED}_##ppsym (#502)

lib/PDL/Core/pdlapi.c

@@ -685,6 +685,11 @@ static inline pdl_error pdl_trans_flow_null_checks(pdl_trans *trans, char *disab
     pdl *child = trans->pdls[i];
     if (_trans_forward_only(child))
       return pdl_make_error(PDL_EUSERERROR, "%s: cannot output to parameter '%s' with inward but no backward flow", vtable->name, vtable->par_names[i]);
+    if (child->state & PDL_NOMYDIMS && !(vtable->par_flags[i] & PDL_PARAM_ISCREAT))
+      return pdl_make_error(PDL_EUSERERROR,
+	"Error in %s: io parameter '%s' is null",
+	vtable->name, vtable->par_names[i]
+      );
   }
   *disable_back = input_forward_only;
   return PDL_err;

t/core.t

@@ -202,6 +202,9 @@ is_pdl +(5*sequence(5))->maximum_n_ind(3), indx(4,3,2), 'named dim';
 # pptest for dim with fixed value
 is_pdl crossp([1..3],[4..6]), longlong(-3,6,-3), {test_name=>'named dim=3', require_equal_types=>0};
 
+eval {simq(null, zeroes(3), 0)};
+like $@, qr/io.*null/;
+
 subtest 'dim compatibility' => sub {
   for (
     # non-phys params