Support slice hash (RustPython#5123)

* make slice object hashable

* Update test_slice.py from CPython v3.12

* remove TODO

* remove outdated tests

Author: cygao90

Lib/test/test_slice.py

@@ -5,6 +5,7 @@
 import sys
 import unittest
 import weakref
+import copy
 
 from pickle import loads, dumps
 from test import support
@@ -79,10 +80,16 @@ def test_repr(self):
         self.assertEqual(repr(slice(1, 2, 3)), "slice(1, 2, 3)")
 
     def test_hash(self):
-        # Verify clearing of SF bug #800796
-        self.assertRaises(TypeError, hash, slice(5))
+        self.assertEqual(hash(slice(5)), slice(5).__hash__())
+        self.assertEqual(hash(slice(1, 2)), slice(1, 2).__hash__())
+        self.assertEqual(hash(slice(1, 2, 3)), slice(1, 2, 3).__hash__())
+        self.assertNotEqual(slice(5), slice(6))
+
+        with self.assertRaises(TypeError):
+            hash(slice(1, 2, []))
+
         with self.assertRaises(TypeError):
-            slice(5).__hash__()
+            hash(slice(4, {}))
 
     def test_cmp(self):
         s1 = slice(1, 2, 3)
@@ -235,13 +242,50 @@ def __setitem__(self, i, k):
         self.assertEqual(tmp, [(slice(1, 2), 42)])
 
     def test_pickle(self):
+        import pickle
+
         s = slice(10, 20, 3)
-        for protocol in (0,1,2):
+        for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
             t = loads(dumps(s, protocol))
             self.assertEqual(s, t)
             self.assertEqual(s.indices(15), t.indices(15))
             self.assertNotEqual(id(s), id(t))
 
+    def test_copy(self):
+        s = slice(1, 10)
+        c = copy.copy(s)
+        self.assertIs(s, c)
+
+        s = slice(1, 10, 2)
+        c = copy.copy(s)
+        self.assertIs(s, c)
+
+        # Corner case for mutable indices:
+        s = slice([1, 2], [3, 4], [5, 6])
+        c = copy.copy(s)
+        self.assertIs(s, c)
+        self.assertIs(s.start, c.start)
+        self.assertIs(s.stop, c.stop)
+        self.assertIs(s.step, c.step)
+
+    def test_deepcopy(self):
+        s = slice(1, 10)
+        c = copy.deepcopy(s)
+        self.assertEqual(s, c)
+
+        s = slice(1, 10, 2)
+        c = copy.deepcopy(s)
+        self.assertEqual(s, c)
+
+        # Corner case for mutable indices:
+        s = slice([1, 2], [3, 4], [5, 6])
+        c = copy.deepcopy(s)
+        self.assertIsNot(s, c)
+        self.assertEqual(s, c)
+        self.assertIsNot(s.start, c.start)
+        self.assertIsNot(s.stop, c.stop)
+        self.assertIsNot(s.step, c.step)
+
     # TODO: RUSTPYTHON
     @unittest.expectedFailure
     def test_cycle(self):

extra_tests/snippets/builtin_slice.py

@@ -82,16 +82,6 @@
 assert_raises(TypeError, lambda: slice(0) <= 3)
 assert_raises(TypeError, lambda: slice(0) >= 3)
 
-# TODO: slice is hashable in CPython 3.12
-# assert_raises(TypeError, hash, slice(0))
-# assert_raises(TypeError, hash, slice(None))
-#
-# def dict_slice():
-#     d = {}
-#     d[slice(0)] = 3
-#
-# assert_raises(TypeError, dict_slice)
-
 assert slice(None           ).indices(10) == (0, 10,  1)
 assert slice(None,  None,  2).indices(10) == (0, 10,  2)
 assert slice(1,     None,  2).indices(10) == (1, 10,  2)

vm/src/builtins/slice.rs

@@ -3,10 +3,11 @@
 use super::{PyStrRef, PyTupleRef, PyType, PyTypeRef};
 use crate::{
     class::PyClassImpl,
+    common::hash::{PyHash, PyUHash},
     convert::ToPyObject,
     function::{ArgIndex, FuncArgs, OptionalArg, PyComparisonValue},
     sliceable::SaturatedSlice,
-    types::{Comparable, Constructor, PyComparisonOp, Representable},
+    types::{Comparable, Constructor, Hashable, PyComparisonOp, Representable},
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
 };
 use malachite_bigint::{BigInt, ToBigInt};
@@ -26,7 +27,7 @@ impl PyPayload for PySlice {
     }
 }
 
-#[pyclass(with(Comparable, Representable))]
+#[pyclass(with(Comparable, Representable, Hashable))]
 impl PySlice {
     #[pygetset]
     fn start(&self, vm: &VirtualMachine) -> PyObjectRef {
@@ -197,6 +198,47 @@ impl PySlice {
     }
 }
 
+impl Hashable for PySlice {
+    #[inline]
+    fn hash(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyHash> {
+        const XXPRIME_1: PyUHash = if cfg!(target_pointer_width = "64") {
+            11400714785074694791
+        } else {
+            2654435761
+        };
+        const XXPRIME_2: PyUHash = if cfg!(target_pointer_width = "64") {
+            14029467366897019727
+        } else {
+            2246822519
+        };
+        const XXPRIME_5: PyUHash = if cfg!(target_pointer_width = "64") {
+            2870177450012600261
+        } else {
+            374761393
+        };
+        const ROTATE: u32 = if cfg!(target_pointer_width = "64") {
+            31
+        } else {
+            13
+        };
+
+        let mut acc = XXPRIME_5;
+        for part in [zelf.start_ref(vm), &zelf.stop, zelf.step_ref(vm)].iter() {
+            let lane = part.hash(vm)? as PyUHash;
+            if lane == u64::MAX as PyUHash {
+                return Ok(-1 as PyHash);
+            }
+            acc = acc.wrapping_add(lane.wrapping_mul(XXPRIME_2));
+            acc = acc.rotate_left(ROTATE);
+            acc = acc.wrapping_mul(XXPRIME_1);
+        }
+        if acc == u64::MAX as PyUHash {
+            return Ok(1546275796 as PyHash);
+        }
+        Ok(acc as PyHash)
+    }
+}
+
 impl Comparable for PySlice {
     fn cmp(
         zelf: &Py<Self>,