Make HASH/HASHXOF types immutable (#7131)

Lib/test/test_hashlib.py

@@ -992,8 +992,6 @@ class HashLibTestCase(unittest.TestCase):
         support.check_disallow_instantiation(self, HASH)
         support.check_disallow_instantiation(self, HASHXOF)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_readonly_types(self):
         for algorithm, constructors in self.constructors_to_test.items():
             # all other types have DISALLOW_INSTANTIATION

crates/stdlib/src/hashlib.rs

@@ -110,7 +110,7 @@ pub mod _hashlib {
         }
     }
 
-    #[pyclass(with(Representable))]
+    #[pyclass(with(Representable), flags(IMMUTABLETYPE))]
     impl PyHasher {
         fn new(name: &str, d: HashWrapper) -> Self {
             Self {
@@ -183,7 +183,7 @@ pub mod _hashlib {
         }
     }
 
-    #[pyclass]
+    #[pyclass(flags(IMMUTABLETYPE))]
     impl PyHasherXof {
         fn new(name: &str, d: HashXofWrapper) -> Self {
             Self {