Method promote

crates/vm/src/object/core.rs:1943–1950

(&mut self)

    /// clears the borrow tag).  No-op if already owned.
    #[inline(always)]
    pub fn promote(&mut self) {
        if self.is_borrowed() {
            self.as_object().0.ref_count.inc();
            // SAFETY: clearing the low bit of a non-null pointer keeps it non-zero
            self.bits =
                unsafe { NonZeroUsize::new_unchecked(self.bits.get() & !STACKREF_BORROW_TAG) };
        }
    }
}

impl Drop for PyStackRef {