Make frozenset idempotent and unskip some set tests

Lib/test/test_set.py

@@ -315,6 +315,7 @@ class TestJointOps:
             self.assertRaises(RuntimeError, s.discard, BadCmp())
             self.assertRaises(RuntimeError, s.remove, BadCmp())
 
+    @unittest.skip("TODO: RUSTPYTHON")
     def test_cyclical_repr(self):
         w = ReprWrapper()
         s = self.thetype([w])
@@ -676,7 +677,6 @@ class TestSet(TestJointOps, unittest.TestCase):
 class SetSubclass(set):
     pass
 
-@unittest.skip("TODO: RUSTPYTHON")
 class TestSetSubclass(TestSet):
     thetype = SetSubclass
     basetype = set
@@ -685,9 +685,9 @@ class SetSubclassWithKeywordArgs(set):
     def __init__(self, iterable=[], newarg=None):
         set.__init__(self, iterable)
 
-@unittest.skip("TODO: RUSTPYTHON")
 class TestSetSubclassWithKeywordArgs(TestSet):
-
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
     def test_keywords_in_subclass(self):
         'SF bug #1486663 -- this used to erroneously raise a TypeError'
         SetSubclassWithKeywordArgs(newarg=1)
@@ -712,8 +712,6 @@ class TestFrozenSet(TestJointOps, unittest.TestCase):
         # All of the empty frozensets should have just one id()
         self.assertEqual(len(set(map(id, efs))), 1)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_constructor_identity(self):
         s = self.thetype(range(3))
         t = self.thetype(s)

vm/src/builtins/set.rs

@@ -5,10 +5,11 @@ use super::pytype::PyTypeRef;
 use crate::common::hash::PyHash;
 use crate::common::rc::PyRc;
 use crate::dictdatatype;
+use crate::function::OptionalArg::{Missing, Present};
 use crate::function::{Args, OptionalArg};
 use crate::pyobject::{
-    self, BorrowValue, PyClassImpl, PyComparisonValue, PyContext, PyIterable, PyObjectRef, PyRef,
-    PyResult, PyValue, TryFromObject, TypeProtocol,
+    self, BorrowValue, IdProtocol, PyClassImpl, PyComparisonValue, PyContext, PyIterable,
+    PyObjectRef, PyRef, PyResult, PyValue, TryFromObject, TypeProtocol,
 };
 use crate::slots::{Comparable, Hashable, Iterable, PyComparisonOp, PyIter, Unhashable};
 use crate::vm::{ReprGuard, VirtualMachine};
@@ -569,9 +570,22 @@ impl PyFrozenSet {
     #[pyslot]
     fn tp_new(
         cls: PyTypeRef,
-        iterable: OptionalArg<PyIterable>,
+        iterable: OptionalArg<PyObjectRef>,
         vm: &VirtualMachine,
     ) -> PyResult<PyRef<Self>> {
+        let iterable = if let Present(iterable) = iterable {
+            if cls.is(&vm.ctx.types.frozenset_type) {
+                match iterable.downcast_exact::<PyFrozenSet>(vm) {
+                    Ok(iter) => return Ok(iter),
+                    Err(iterable) => Present(PyIterable::try_from_object(vm, iterable)?),
+                }
+            } else {
+                Present(PyIterable::try_from_object(vm, iterable)?)
+            }
+        } else {
+            Missing
+        };
+
         Self {
             inner: PySetInner::from_arg(iterable, vm)?,
         }