Deprecate operator dispatch in Var

CHANGELOG.rst

@@ -18,6 +18,10 @@ Change log
 
 - Value propagation of string tensors no longer raises an erroneous ``ValueError`` in some instances.
 
+**Pending breaking changes**
+
+- Usage of ``operator_overloading`` now triggers a ``DeprecationWarning``. This API is scheduled for removal in Spox ``0.14.0``. Consider using ``ndonnx`` as an alternative.
+
 **Other changes**
 
 - The adaption logic is not using inferred values as initializers anymore.

src/spox/_future.py

@@ -3,6 +3,7 @@
 
 """Module containing experimental Spox features that may be standard in the future."""
 
+import warnings
 from collections.abc import Iterable
 from contextlib import contextmanager
 from typing import Optional, Union
@@ -201,6 +202,10 @@ def operator_overloading(
     ...    return x * y
     >>> assert foo()._get_value() == np.array(6)
     """
+    warnings.warn(
+        "using operator_overloading is deprecated, consider using https://github.com/Quantco/ndonnx instead",
+        DeprecationWarning,
+    )
     prev_dispatcher = Var._operator_dispatcher
     Var._operator_dispatcher = _NumpyLikeOperatorDispatcher(
         op, type_promotion, constant_promotion