From 5e7f2a62546398dc87e4fa01ac43800dc462e539 Mon Sep 17 00:00:00 2001
From: Ed J <mohawk2@users.noreply.github.com>
Date: Wed, 18 Dec 2024 18:11:43 +0000
Subject: [PATCH] prevent type-conversion of output ndarray with parent already

---
 lib/PDL/Core/pdlapi.c |  5 +++--
 t/core.t              | 10 ++++++++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/PDL/Core/pdlapi.c b/lib/PDL/Core/pdlapi.c
index c31e3d8bb..78c39d15d 100644
--- a/lib/PDL/Core/pdlapi.c
+++ b/lib/PDL/Core/pdlapi.c
@@ -1081,14 +1081,13 @@ pdl_trans *pdl_create_trans(pdl_transvtable *vtable) {
 
 pdl_error pdl_type_coerce(pdl_trans *trans) {
   pdl_error PDL_err = {0, NULL, 0};
-  PDL_Indx i;
   pdl_transvtable *vtable = trans->vtable;
   pdl **pdls = trans->pdls;
   trans->__datatype = -1;
   char p2child_has_badvalue = (vtable->npdls == 2 && pdls[0]->has_badvalue
       && (vtable->par_flags[1] & PDL_PARAM_ISCREATEALWAYS));
   PDL_Anyval parent_badvalue = p2child_has_badvalue ? pdls[0]->badvalue : (PDL_Anyval){PDL_INVALID, {0}};
-  PDL_Indx nchildren = vtable->npdls - vtable->nparents;
+  PDL_Indx i, nparents = vtable->nparents, nchildren = vtable->npdls - nparents;
   /* copy the "real" (passed-in) outputs to the end-area to use as actual
     outputs, possibly after being converted, leaving the passed-in ones
     alone to be picked up for use in CopyBadStatusCode */
@@ -1132,6 +1131,8 @@ pdl_error pdl_type_coerce(pdl_trans *trans) {
       pdl->datatype = new_dtype;
     } else if (new_dtype != pdl->datatype) {
       PDLDEBUG_f(printf("pdl_type_coerce (%s) pdl=%"IND_FLAG" from %d to %d\n", vtable->name, i, pdl->datatype, new_dtype));
+      if (i >= nparents && pdl->trans_parent && pdl->trans_parent != trans)
+        return pdl_make_error(PDL_EFATAL, "%s: cannot convert output ndarray %s from type %d to %d with parent", vtable->name, vtable->par_names[i], pdl->datatype, new_dtype);
       pdl = pdl_get_convertedpdl(pdl, new_dtype);
       if (!pdl)
         return pdl_make_error(PDL_EFATAL, "%s got NULL pointer from get_convertedpdl on param %s", vtable->name, vtable->par_names[i]);
diff --git a/t/core.t b/t/core.t
index 8aa22c950..658f85110 100644
--- a/t/core.t
+++ b/t/core.t
@@ -803,8 +803,14 @@ my $oneway_slice = $y->slice('0:1');
 is_pdl $oneway_slice, pdl '[4 5]';
 eval {$oneway_slice .= 11};
 isnt $@, '', 'error on assigning into one-way slice';
-my $c = $y->flowing->_convert_int(cdouble->enum);
-ok $c->fflows, 'flowing -> converted has "flowing" on';
+ok $y->flowing->_convert_int(cdouble->enum)->fflows, 'flowing -> converted has "flowing" on';
+}
+
+{
+eval {czip(float(3), float(2), cdouble(0)->slice(''))};
+like $@, qr/convert output ndarray.*with.*parent/;
+czip(float(3), float(2), my $out_cd = cdouble(0));
+is_pdl $out_cd, cdouble('3+2i');
 }
 
 {