Update slice bounds from data-apis/array-api#138

Author: cr313

array_api_tests/hypothesis_helpers.py

@@ -126,10 +126,13 @@ def integer_indices(draw, sizes):
 def slices(draw, sizes):
     size = draw(sizes)
     # The spec does not specify out of bounds behavior.
-    start = draw(one_of(integers(-size, max(0, size-1)), none()))
-    stop = draw(one_of(integers(-size, size)), none())
     max_step_size = draw(integers(1, max(1, size)))
     step = draw(one_of(integers(-max_step_size, -1), integers(1, max_step_size), none()))
+    start = draw(one_of(integers(-size, max(0, size-1)), none()))
+    if step is None or step > 0:
+        stop = draw(one_of(integers(-size, size)), none())
+    else:
+        stop = draw(one_of(integers(-size - 1, size - 1)), none())
     s = slice(start, stop, step)
     l = list(range(size))
     sliced_list = l[s]

array_api_tests/test_indexing.py

@@ -39,8 +39,10 @@ def test_slicing(size, s):
     if s.start is not None:
         assert -size <= s.start <= max(0, size - 1), "Sanity check failed. This indicates a bug in the test suite"
     if s.stop is not None:
-        assert -size <= s.stop <= size, "Sanity check failed. This indicates a bug in the test suite"
-
+        if s.step is None or s.step > 0:
+            assert -size <= s.stop <= size, "Sanity check failed. This indicates a bug in the test suite"
+        else:
+            assert -size - 1 <= s.stop <= size - 1, "Sanity check failed. This indicates a bug in the test suite"
     a = arange(size)
     l = list(range(size))
     sliced_list = l[s]