Raises an exception on mixed Awkward/NumPy slices.

src/awkward/_v2/_slicing.py

@@ -18,13 +18,16 @@ def headtail(oldtail):
 def getitem_broadcast(items):
     lookup = []
     broadcastable = []
+    awkward_items = 0
     for item in items:
+        if isinstance(item, ak._v2.contents.Content):
+            awkward_items += 1
         if (
             isinstance(
                 item,
                 (
                     slice,
-                    list,
+                    list,  # of strings
                     ak._v2.contents.ListOffsetArray,
                     ak._v2.contents.IndexedOptionArray,
                 ),
@@ -35,9 +38,17 @@ def getitem_broadcast(items):
         ):
             lookup.append(None)
         else:
+            # this includes integers (which broadcast to arrays)
             lookup.append(len(broadcastable))
             broadcastable.append(item)
 
+    if awkward_items > 1 or (awkward_items == 1 and len(broadcastable) != 0):
+        raise ak._v2._util.error(
+            TypeError(
+                "cannot mix Awkward slicing (using an array with missing or variable-length lists in the slice) with NumPy advanced slicing (using more than one broadcastable array or integer in the slice), though you can perform multiple slices"
+            )
+        )
+
     nplike = ak.nplike.of(*broadcastable)
 
     broadcasted = nplike.broadcast_arrays(*broadcastable)
@@ -354,7 +365,7 @@ def prepare_tuple_bool_to_int(item):
             if item.content.content.data.shape[0] > 0:
                 expanded = item.content.content.data[safeindex]
             else:
-                expanded = item.content.content.data.nplike.ones(
+                expanded = item.content.content.nplike.ones(
                     safeindex.shape[0], np.bool_
                 )
 
@@ -423,9 +434,7 @@ def prepare_tuple_bool_to_int(item):
                 if item.content.data.shape[0] > 0:
                     expanded = item.content.data[safeindex]
                 else:
-                    expanded = item.content.data.nplike.ones(
-                        safeindex.shape[0], np.bool_
-                    )
+                    expanded = item.content.nplike.ones(safeindex.shape[0], np.bool_)
 
                 # nextcontent does not include missing values
                 expanded[isnegative] = False
@@ -448,7 +457,7 @@ def prepare_tuple_bool_to_int(item):
                 )
 
             return ak._v2.contents.IndexedOptionArray(
-                ak._v2.index.Index(outindex, item.nplike),
+                ak._v2.index.Index(outindex, nplike=item.nplike),
                 ak._v2.contents.NumpyArray(nextcontent, nplike=item.nplike),
             )
 

src/awkward/_v2/contents/unionarray.py

@@ -291,7 +291,9 @@ def project(self, index):
                 index,
             )
         )
-        nextcarry = ak._v2.index.Index64(tmpcarry.data[: lenout[0]], self._nplike)
+        nextcarry = ak._v2.index.Index64(
+            tmpcarry.data[: lenout[0]], nplike=self._nplike
+        )
         return self._contents[index]._carry(nextcarry, False)
 
     @staticmethod

src/awkward/_v2/index.py

@@ -20,6 +20,8 @@ def __init__(self, data, metadata=None, nplike=None):
         if nplike is None:
             nplike = ak.nplike.of(data)
         self._nplike = nplike
+        if metadata is not None and not isinstance(metadata, dict):
+            raise ak._v2._util.error(TypeError("Index metadata must be None or a dict"))
         self._metadata = metadata
         self._data = self._nplike.index_nplike.asarray(
             data, dtype=self._expected_dtype, order="C"

tests/v2/test_1305-mixed-awkward-numpy-slicing.py

@@ -0,0 +1,13 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/awkward-1.0/blob/main/LICENSE
+
+import pytest  # noqa: F401
+import numpy as np  # noqa: F401
+import awkward as ak  # noqa: F401
+
+
+def test():
+    array = ak._v2.Array([[3.14]])
+    first_slice = ak._v2.Array([True, None])[:1]  # type is 1 * ?bool
+    second_slice = 0
+    with pytest.raises(TypeError):
+        array[first_slice, second_slice]