[WIP] Add @box(slice)

numba/core/boxing.py

@@ -377,6 +377,15 @@ def unbox_slice(typ, obj, c):
     return NativeValue(sli._getvalue(), is_error=c.builder.not_(ok))
 
 
+@box(types.SliceType)
+def box_slice(typ, val, c):
+    sli = c.context.make_helper(c.builder, typ, val)
+    start = c.box(types.int64, sli.start)
+    stop = c.box(types.int64, sli.stop)
+    step = c.box(types.int64, sli.step)
+    return c.pyapi.slice_new(start, stop, step)
+
+
 @unbox(types.StringLiteral)
 def unbox_string_literal(typ, obj, c):
     # A string literal is a dummy value

numba/core/pythonapi.py

@@ -683,6 +683,11 @@ def slice_as_ints(self, obj):
         stop = self.builder.load(pstop)
         step = self.builder.load(pstep)
         return cgutils.is_null(self.builder, res), start, stop, step
+
+    def slice_new(self, start, stop, step):
+        fnty = Type.function(self.pyobj, [self.pyobj, self.pyobj, self.pyobj])
+        fn = self._get_function(fnty, name="PySlice_New")
+        return self.builder.call(fn, (start, stop, step))
 
     #
     # List and sequence APIs

numba/tests/test_slices.py

@@ -19,6 +19,9 @@ def slice_constructor(*args):
     sl = slice(*args)
     return sl.start, sl.stop, sl.step
 
+def slice_return(*args):
+    return slice(*args)
+
 def slice_construct_and_use(args, l):
     sl = slice(*args)
     return l[sl]
@@ -63,6 +66,37 @@ def check(a, b, c, d, e, f):
         # Some member is neither integer nor None
         with self.assertRaises(TypeError):
             cfunc(slice(1.5, 1, 1))
+
+    def test_slice_return(self):
+        pyfunc = slice_return
+        cfunc = jit(nopython=True)(pyfunc)
+
+        # Positive steps
+        cases = (
+            # (None, None, None),
+            (None, None, 12),
+            # (None, 9, None),
+            # (None, 9, 12),
+            # (None, -11, None),
+            # (None, -11, 12),
+            # (42, None, None),
+            # (42, None, 12),
+            # (42, 9, None),
+            # (42, 9, 12),
+            # (42, -11, None),
+            # (42, -11, 12),
+            # (-1, None, None),
+            # (-1, None, 12),
+            # (-1, 9, None),
+            # (-1, 9, 12),
+            # (-1, -11, None),
+            (-1, -11, 12),
+        )
+        for start, stop, step in cases:
+            expected = pyfunc(start, stop, step)
+            result = cfunc(start, stop, step)
+            print(result)
+            # self.assertEqual(expected, result)
 
     def test_slice_constructor(self):
         """