PyTuple::_new to hide it from public api

derive/src/pystructseq.rs

@@ -36,7 +36,7 @@ pub(crate) fn impl_pystruct_sequence(
                     self.#field_names,
                     vm,
                 )),*];
-                items.into_boxed_slice().into()
+                ::rustpython_vm::obj::objtuple::PyTuple::_new(items.into_boxed_slice())
             }
         }
     };

vm/src/obj/objtuple.rs

@@ -30,12 +30,6 @@ impl fmt::Debug for PyTuple {
     }
 }
 
-impl From<Box<[PyObjectRef]>> for PyTuple {
-    fn from(elements: Box<[PyObjectRef]>) -> Self {
-        PyTuple { elements }
-    }
-}
-
 impl<'a> BorrowValue<'a> for PyTuple {
     type Borrowed = &'a [PyObjectRef];
 
@@ -93,6 +87,13 @@ pub(crate) fn get_value(obj: &PyObjectRef) -> &[PyObjectRef] {
 
 #[pyimpl(flags(BASETYPE), with(Hashable, Comparable))]
 impl PyTuple {
+    /// Creating a new tuple with given boxed slice.
+    /// NOTE: for usual case, you probably want to use PyTupleRef::with_elements.
+    /// Calling this function implies trying micro optimization for non-zero-sized tuple.
+    pub(crate) fn _new(elements: Box<[PyObjectRef]>) -> Self {
+        Self { elements }
+    }
+
     #[pymethod(name = "__add__")]
     fn add(
         zelf: PyRef<Self>,

vm/src/obj/objtype.rs

@@ -184,7 +184,7 @@ impl PyClass {
     #[pyproperty(name = "__mro__")]
     fn get_mro(zelf: PyRef<Self>) -> PyTuple {
         let elements: Vec<PyObjectRef> = zelf.iter_mro().map(|x| x.as_object().clone()).collect();
-        elements.into_boxed_slice().into()
+        PyTuple::_new(elements.into_boxed_slice())
     }
 
     #[pyproperty(magic)]

vm/src/pyobject.rs

@@ -140,7 +140,7 @@ impl PyContext {
         let false_value = create_object(PyInt::from(0), &types.bool_type);
 
         let empty_tuple = create_object(
-            PyTuple::from(Vec::new().into_boxed_slice()),
+            PyTuple::_new(Vec::new().into_boxed_slice()),
             &types.tuple_type,
         );