Add a check to verify that the sub-type is "nest", and throw an
exception if no policy could be generated, as a guard to prevent
against generating a bad policy.

This is a trivial patch with no behavioural changes intended.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
---
 tools/net/ynl/pyynl/ynl_gen_c.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/net/ynl/pyynl/ynl_gen_c.py b/tools/net/ynl/pyynl/ynl_gen_c.py
index b7de7f6b1fc7..04c26ed92ca3 100755
--- a/tools/net/ynl/pyynl/ynl_gen_c.py
+++ b/tools/net/ynl/pyynl/ynl_gen_c.py
@@ -826,8 +826,10 @@ class TypeArrayNest(Type):
             return f'.type = YNL_PT_U{c_upper(self.sub_type[1:])}, '
         elif self.attr['sub-type'] == 'binary' and 'exact-len' in self.checks:
             return f'.type = YNL_PT_BINARY, .len = {self.checks["exact-len"]}, '
-        else:
+        elif self.attr['sub-type'] == 'nest':
             return f'.type = YNL_PT_NEST, .nest = &{self.nested_render_name}_nest, '
+        else:
+            raise Exception(f"Typol for ArrayNest sub-type {self.attr['sub-type']} not supported, yet")
 
     def _attr_get(self, ri, var):
         local_vars = ['const struct nlattr *attr2;']
-- 
2.51.0