Raise NotImplementedError for boolean scalar indexing

This is a special-edge case that behaves differently than other boolean indexing. It adds a new dimension (either empty or with one entry). The logic in `make_node` and `infer_shape` don't handle this.

pytensor/tensor/subtensor.py

@@ -2627,6 +2627,11 @@ def as_index_variable(idx):
     idx = as_tensor_variable(idx)
     if idx.type.dtype not in discrete_dtypes:
         raise TypeError("index must be integers or a boolean mask")
+    if idx.type.dtype == "bool" and idx.type.ndim == 0:
+        raise NotImplementedError(
+            "Boolean scalar indexing not implemented. "
+            "Open an issue in https://github.com/pymc-devs/pytensor/issues if you need this behavior."
+        )
     return idx
 
 

tests/tensor/test_subtensor.py

@@ -2228,6 +2228,11 @@ def fun(x, y):
             mode=self.mode,
         )
 
+    def test_boolean_scalar_raises(self):
+        x = vector("x")
+        with pytest.raises(NotImplementedError):
+            x[np.array(True)]
+
 
 class TestInferShape(utt.InferShapeTester):
     @staticmethod