os: fix stat_result test

Implement tp_new for `stat_result`

To unpack args, this PR implement a `flatten_args` closure to
unpack args like
```
args = (1, 2, 3, 4, 5)
args = ((1, 2, 3, 4, 5))
args = (((1, 2, 3, 4, 5)))  # from pickle load
```

Lib/test/test_os.py

@@ -443,13 +443,9 @@ class StatAttributeTests(unittest.TestCase):
         except TypeError:
             pass
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_stat_attributes(self):
         self.check_stat_attributes(self.fname)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_stat_attributes_bytes(self):
         try:
             fname = self.fname.encode(sys.getfilesystemencoding())

vm/src/builtins/int.rs

@@ -118,6 +118,12 @@ impl_try_from_object_int!(
     (u64, to_u64),
 );
 
+impl TryFromBorrowedObject for BigInt {
+    fn try_from_borrowed_object(vm: &VirtualMachine, obj: &PyObjectRef) -> PyResult<Self> {
+        try_value_from_borrowed_object(vm, obj, |int: &PyInt| Ok(int.as_bigint().clone()))
+    }
+}
+
 // _PyLong_AsUnsignedLongMask
 pub fn bigint_unsigned_mask(v: &BigInt) -> u32 {
     v.to_u32()

vm/src/stdlib/os.rs

@@ -9,6 +9,7 @@ use std::{env, fs};
 
 use crate::crt_fd::Fd;
 use crossbeam_utils::atomic::AtomicCell;
+use itertools::Itertools;
 use num_bigint::BigInt;
 #[cfg(unix)]
 use strum_macros::EnumString;
@@ -1042,24 +1043,40 @@ mod _os {
 
     #[pyattr]
     #[pyclass(module = "os", name = "stat_result")]
-    #[derive(Debug, PyStructSequence)]
+    #[derive(Debug, PyStructSequence, FromArgs)]
     struct StatResult {
+        #[pyarg(any)]
         pub st_mode: BigInt,
+        #[pyarg(any)]
         pub st_ino: BigInt,
+        #[pyarg(any)]
         pub st_dev: BigInt,
+        #[pyarg(any)]
         pub st_nlink: BigInt,
+        #[pyarg(any)]
         pub st_uid: BigInt,
+        #[pyarg(any)]
         pub st_gid: BigInt,
+        #[pyarg(any)]
         pub st_size: BigInt,
         // TODO: unnamed structsequence fields
+        #[pyarg(positional, default)]
         pub __st_atime_int: BigInt,
+        #[pyarg(positional, default)]
         pub __st_mtime_int: BigInt,
+        #[pyarg(positional, default)]
         pub __st_ctime_int: BigInt,
+        #[pyarg(any, default)]
         pub st_atime: f64,
+        #[pyarg(any, default)]
         pub st_mtime: f64,
+        #[pyarg(any, default)]
         pub st_ctime: f64,
+        #[pyarg(any, default)]
         pub st_atime_ns: BigInt,
+        #[pyarg(any, default)]
         pub st_mtime_ns: BigInt,
+        #[pyarg(any, default)]
         pub st_ctime_ns: BigInt,
     }
 
@@ -1102,6 +1119,32 @@ mod _os {
                 st_ctime_ns: to_ns(ctime).into(),
             }
         }
+
+        #[pyslot]
+        fn tp_new(_cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+            let flatten_args = |r: &[PyObjectRef]| {
+                let mut vec_args = Vec::from(r);
+                loop {
+                    if let Ok(obj) = vec_args.iter().exactly_one() {
+                        match obj.payload::<PyTuple>() {
+                            Some(t) => {
+                                vec_args = Vec::from(t.as_slice());
+                            }
+                            None => {
+                                return vec_args;
+                            }
+                        }
+                    } else {
+                        return vec_args;
+                    }
+                }
+            };
+
+            let args: FuncArgs = flatten_args(args.args.as_slice()).into();
+
+            let stat: StatResult = args.bind(vm)?;
+            Ok(stat.into_pyobject(vm))
+        }
     }
 
     #[cfg(not(windows))]