Exotic Examples for Field Projections

This is a list of ideas that require more work on our proposal to integrate, these have not been fleshed out yet and might not make it into the final design. Nevertheless, they enable interesting use-cases and we’ll try to integrate them.

FileSlice<T> (Alice)

• Have a type FileSlice<T> type that points at a T: FromBytes inside of a file with a file-offset that’s u64.
  • Projections require that P::Target: FromBytes (we already support this with a where bound on the PlaceBorrow impl).
  • We also want to use PlaceRead to perform a read_at call and extract the contents of a T. But that call can not only fail, but also not read enough bytes, because the file is too short. Our current PlaceRead::read function must return a <Self as HasPlace>::Target, which we want to be T for FileSlice in order to support projecting to subfields.
• Needs to have custom projections that allow for u64 instead of usize offsets.

HashMap<K, V> (Alice & Benno)

• With custom projections, we could allow map["key"] = value; to mean map.insert("key", value);.
• Needs to have custom projections that allow for &'static str (or any Sized value in general) instead of usize.
• We would also need to coordinate with Index[Mut], since we’re now generalizing it too (maybe we need to do that already).