In sixth, split_before / split_after may return illegal empty linked list in some corner cases.

[makisevon]

For example:

    pub fn split_before(&mut self) -> LinkedList<T> {
        // We have this:
        //
        //     list.front -> A <-> B <- list.back
        //                   ^
        //                  cur
        //
        //
        // And we want to produce this:
        //
        //     list.front -> A <-> B <- list.back
        //                   ^
        //                  cur
        //
        //
        //     return.front -> None <- return.back
        //
        if let Some(cur) = self.cur {
            unsafe {
                let old_len = self.list.len;        // 2
                let old_idx = self.index.unwrap();  // 0
                let prev = (*cur.as_ptr()).front;   // None

                let new_len = old_len - old_idx;    // 2
                let new_front = self.cur;
                let new_back = self.list.back;
                let new_idx = Some(0);

                let output_len = old_len - new_len; // 0
                // oops...
                let output_front = self.list.front; // -> A
                let output_back = prev;             // None

                if let Some(prev) = prev {
                    (*cur.as_ptr()).front = None;
                    (*prev.as_ptr()).back = None;
                }

                self.list.len = new_len;
                self.list.front = new_front;
                self.list.back = new_back;
                self.index = new_idx;

                LinkedList {
                    front: output_front,            // -> A
                    back: output_back,              // None
                    len: output_len,                // 0
                    _boo: PhantomData,
                }
            }
        } else {
            std::mem::replace(self.list, LinkedList::new())
        }
    }

[morlinbrot]

I just found this now where I just opened a PR for this exact issue in the contain-rs/linked-list project.

It is actually quite easily fixed, I'd be happy to open a PR in this project, too. I'm just not sure how exactly the structure of this project works, e.g. how can I run the code part of src/sixth-final.rs? Sixth is also not implemented as a "proper" list in the lists folder, is there a specific reason for that?

I'd be happy to open a PR adding a sixth.rs with the full implementation and all the tests.

[makisevon]

I just found this now where I just opened a PR for this exact issue in the contain-rs/linked-list project.

It is actually quite easily fixed, I'd be happy to open a PR in this project, too. I'm just not sure how exactly the structure of this project works, e.g. how can I run the code part of src/sixth-final.rs? Sixth is also not implemented as a "proper" list in the lists folder, is there a specific reason for that?

I'd be happy to open a PR adding a sixth.rs with the full implementation and all the tests.

Just copy the final code in the src/sixth-final.md, and I think it's equivalent to the lists/src/sixth.rs.