Sealing Slice

This crate impements a slice that can seal parts of itself off from mutability, and hand out the sealed parts as immutable references.

Crate dimensions

This is a very small crate, with only about a dozen lines of effective code.

It is still provided in a dedicated crate to clearly encapsulate the guarantees of this crate from whatever uses it, and to provide some testing and stability, as opposed to ad-hoc implementations of the same concept.

Roadmap

This crate should be versioned as 1.0 soon, given there's not much interface that can change.

One thing that should still be considered before making it 1.0 is whether it might be more intuitive to implement access via the core Index/IndexMut traits rather than having accessor methods to always changing subslices.