tuple internal to Box<[PyObjectRef]>

it will use 16bytes instead of 24bytes

derive/src/pystructseq.rs

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

vm/src/obj/objtuple.rs

@@ -6,9 +6,8 @@ use super::objsequence::get_item;
 use super::objtype::PyClassRef;
 use crate::function::OptionalArg;
 use crate::pyobject::{
-    self, BorrowValue, Either, IdProtocol, IntoPyObject,
-    PyArithmaticValue::{self, *},
-    PyClassImpl, PyComparisonValue, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TypeProtocol,
+    self, BorrowValue, Either, IdProtocol, IntoPyObject, PyArithmaticValue, PyClassImpl,
+    PyComparisonValue, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TypeProtocol,
 };
 use crate::sequence::{self, SimpleSeq};
 use crate::slots::{Comparable, Hashable, PyComparisonOp};
@@ -21,7 +20,7 @@ use rustpython_common::hash::PyHash;
 /// If the argument is a tuple, the return value is the same object.
 #[pyclass(module = false, name = "tuple")]
 pub struct PyTuple {
-    elements: Vec<PyObjectRef>,
+    elements: Box<[PyObjectRef]>,
 }
 
 impl fmt::Debug for PyTuple {
@@ -31,6 +30,12 @@ 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];
 
@@ -64,12 +69,6 @@ impl_intopyobj_tuple!((A, 0), (B, 1), (C, 2), (D, 3), (E, 4), (F, 5));
 impl_intopyobj_tuple!((A, 0), (B, 1), (C, 2), (D, 3), (E, 4), (F, 5), (G, 6));
 
 impl PyTuple {
-    // this is designed to be only used to skip empty tuple optimization
-    // not unsafe as meaning of rust, but a warning because this is performance critical
-    pub(crate) unsafe fn _new(elements: Vec<PyObjectRef>) -> Self {
-        Self { elements }
-    }
-
     pub(crate) fn fast_getitem(&self, idx: usize) -> PyObjectRef {
         self.elements[idx].clone()
     }
@@ -82,6 +81,7 @@ impl PyTupleRef {
         if elements.is_empty() {
             ctx.empty_tuple.clone()
         } else {
+            let elements = elements.into_boxed_slice();
             Self::new_ref(PyTuple { elements }, ctx.types.tuple_type.clone(), None)
         }
     }
@@ -110,7 +110,8 @@ impl PyTuple {
                     .boxed_iter()
                     .chain(other.borrow_value().boxed_iter())
                     .cloned()
-                    .collect::<Vec<_>>();
+                    .collect::<Vec<_>>()
+                    .into_boxed_slice();
                 Self { elements }.into_ref(vm)
             }
         });
@@ -172,9 +173,10 @@ impl PyTuple {
         if self.elements.is_empty() || counter == 0 {
             vm.ctx.empty_tuple.clone()
         } else {
-            let elements: Vec<_> = sequence::seq_mul(&self.elements, counter)
+            let elements = sequence::seq_mul(&self.elements, counter)
                 .cloned()
-                .collect();
+                .collect::<Vec<_>>()
+                .into_boxed_slice();
             Self { elements }.into_ref(vm)
         }
     }
@@ -227,7 +229,8 @@ impl PyTuple {
             vm.extract_elements(&iterable)?
         } else {
             vec![]
-        };
+        }
+        .into_boxed_slice();
 
         Self { elements }.into_ref_with_type(vm, cls)
     }

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();
-        unsafe { PyTuple::_new(elements) }
+        elements.into_boxed_slice().into()
     }
 
     #[pyproperty(magic)]

vm/src/pyobject.rs

@@ -139,7 +139,10 @@ impl PyContext {
         let true_value = create_object(PyInt::from(1), &types.bool_type);
         let false_value = create_object(PyInt::from(0), &types.bool_type);
 
-        let empty_tuple = create_object(unsafe { PyTuple::_new(Vec::new()) }, &types.tuple_type);
+        let empty_tuple = create_object(
+            PyTuple::from(Vec::new().into_boxed_slice()),
+            &types.tuple_type,
+        );
 
         let tp_new_wrapper = create_object(
             PyFuncDef::from(objtype::tp_new_wrapper.into_func()).into_function(),