Partial reversion of advanced indexing changes

0D array indices are treated as Python scalars and moved to the host when not part of other, consecutive array indices

This means that 0D arrays also can't start a series of consecutive advanced indices

Author: ndgrigorian

dpctl/tensor/_slicing.pxi

@@ -46,7 +46,11 @@ cdef Py_ssize_t _slice_len(
 cdef bint _is_integral(object x) except *:
     """Gives True if x is an integral slice spec"""
     if isinstance(x, usm_ndarray):
-        return False
+        if x.ndim > 0:
+            return False
+        if x.dtype.kind not in "ui":
+            return False
+        return True
     if isinstance(x, bool):
         return False
     if isinstance(x, int):
@@ -194,7 +198,7 @@ def _basic_slice_meta(ind, shape : tuple, strides : tuple, offset : int):
                 dt_k = i.dtype.kind
                 if dt_k == "b" and i.ndim > 0:
                     axes_referenced += i.ndim
-                elif dt_k in "ui":
+                elif dt_k in "ui" and i.ndim > 0:
                     axes_referenced += 1
                 else:
                     raise IndexError(
@@ -266,19 +270,21 @@ def _basic_slice_meta(ind, shape : tuple, strides : tuple, offset : int):
                 if array_streak:
                     array_streak = False
             elif _is_integral(ind_i):
-                ind_i = ind_i.__index__()
                 if array_streak:
-                    # integer will be converted to an array, still raise if OOB
-                    if not (0 <= ind_i < shape[k] or -shape[k] <= ind_i < 0):
-                        raise IndexError(
-                            ("Index {0} is out of range for "
-                            "axes {1} with size {2}").format(ind_i, k, shape[k]))
+                    if not isinstance(ind_i, usm_ndarray):
+                        ind_i = ind_i.__index__()
+                        # integer will be converted to an array, still raise if OOB
+                        if not (0 <= ind_i < shape[k] or -shape[k] <= ind_i < 0):
+                            raise IndexError(
+                                ("Index {0} is out of range for "
+                                "axes {1} with size {2}").format(ind_i, k, shape[k]))
                     new_advanced_ind.append(ind_i)
                     k_new = k + 1
                     new_shape.extend(shape[k:k_new])
                     new_strides.extend(strides[k:k_new])
                     k = k_new
                 else:
+                    ind_i = ind_i.__index__()
                     if 0 <= ind_i < shape[k]:
                         k_new = k + 1
                         if not is_empty: