Handle oversized __hash__ results without panicking (#6561)

Copilot · youknowone · github-actions[bot] · web-flow · commit 7b36c9e8e0e3 · 2025-12-28T16:27:32.000+09:00
* Initial plan

* Fix hash wrapper overflow handling

Co-authored-by: youknowone &lt;69878+youknowone@users.noreply.github.com&gt;

* Auto-format: cargo fmt --all

* Adjust __hash__ wrapper conversion

Co-authored-by: youknowone &lt;69878+youknowone@users.noreply.github.com&gt;

* Auto-format: cargo fmt --all

---------

Co-authored-by: copilot-swe-agent[bot] &lt;198982749+Copilot@users.noreply.github.com&gt;
Co-authored-by: youknowone &lt;69878+youknowone@users.noreply.github.com&gt;
Co-authored-by: github-actions[bot] &lt;github-actions[bot]@users.noreply.github.com&gt;
diff --git a/crates/vm/src/types/slot.rs b/crates/vm/src/types/slot.rs
@@ -5,7 +5,7 @@ use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
     builtins::{PyInt, PyStr, PyStrInterned, PyStrRef, PyType, PyTypeRef},
     bytecode::ComparisonOperator,
-    common::hash::PyHash,
+    common::hash::{PyHash, fix_sentinel, hash_bigint},
     convert::ToPyObject,
     function::{
         Either, FromArgs, FuncArgs, OptionalArg, PyComparisonValue, PyMethodDef, PySetterValue,
@@ -18,7 +18,6 @@ use crate::{
     vm::Context,
 };
 use crossbeam_utils::atomic::AtomicCell;
-use malachite_bigint::BigInt;
 use num_traits::{Signed, ToPrimitive};
 use std::{any::Any, any::TypeId, borrow::Borrow, cmp::Ordering, ops::Deref};
 
@@ -412,9 +411,10 @@ fn hash_wrapper(zelf: &PyObject, vm: &VirtualMachine) -> PyResult<PyHash> {
         .downcast_ref::<PyInt>()
         .ok_or_else(|| vm.new_type_error("__hash__ method should return an integer"))?;
     let big_int = py_int.as_bigint();
-    let hash: PyHash = big_int
+    let hash = big_int
         .to_i64()
-        .unwrap_or_else(|| (big_int % BigInt::from(u64::MAX)).to_i64().unwrap());
+        .map(fix_sentinel)
+        .unwrap_or_else(|| hash_bigint(big_int));
     Ok(hash)
 }
 
diff --git a/extra_tests/snippets/builtin_hash.py b/extra_tests/snippets/builtin_hash.py
@@ -12,6 +12,14 @@ class A:
 assert type(hash(1.1)) is int
 assert type(hash("")) is int
 
+
+class Evil:
+    def __hash__(self):
+        return 1 << 63
+
+
+assert hash(Evil()) == 4
+
 with assert_raises(TypeError):
     hash({})
 
