Crate lineage 

Lineage<T> is a type of cell that allows replacing the contained value while the current value may still be borrowed. This is safe because old values are stored until explicitly cleared.

let lineage: Lineage<String> = Lineage::new(String::from("ONE"));
let s1 = lineage.get();

lineage.set(String::from("TWO"));
let s2 = lineage.get();

assert_eq!(s1, "ONE");
assert_eq!(s2, "TWO");

The original implementation was essentially a Vec<Box<T>>. The Box ensures that the values are not moved when the Vec needs to reallocate to increase its capacity. The current implementation uses a linked list instead of a Vec to avoid the additional allocations caused by the Vec. Also, the first value is stored inline within the Lineage. Only calling Lineage::set causes a heap allocation.

Structs

Lineage

A type of cell that allows replacing the contained value without invalidating references to the current value.