Avoid making AdjointField custom if forward field CUSTOM

src/pystencils_autodiff/_adjoint_field.py

@@ -11,7 +11,9 @@ class AdjointField(pystencils.Field):
 
     def __init__(self, forward_field, name_prefix='diff'):
         new_name = name_prefix + forward_field.name
-        super().__init__(new_name, forward_field.field_type, forward_field._dtype,
+        super().__init__(new_name, pystencils.FieldType.GENERIC
+                         if forward_field.field_type != pystencils.FieldType.BUFFER
+                         else pystencils.FieldType.BUFFER, forward_field._dtype,
                          forward_field._layout, forward_field.shape, forward_field.strides)
         self.corresponding_forward_field = forward_field
         self.name_prefix = name_prefix