Expose the inner value of Unalign as public

[kupiakos]

This enables full field reference projection for fields that are sufficiently aligned and field read/write access for all fields and subfields. This must be done through direct struct field access for the compiler to accept it.

Sample use case

Say the input buffer you receive has bytes in the format of BigStruct, and our function reads specific fields out of those bytes based on a struct layout defined by bindgen. There are too many unread fields to reasonably copy it. However, the input buffer may be unaligned. So, you first access the prefix as a &Unalign<BigStruct>.

In order to access specific unaligned fields safely, you need one of the following:

• Field projection
• To copy the whole struct
• To use unsafe
• Have field access to the contents of the Unalign.

Currently, the workaround is to declare your own repr(packed) newtype that has an accessible inner value. But honestly, I should be able to use the built-in Unalign newtype for this. Rust will guard against an accidental reference to an unaligned field.

[kupiakos]

It might be worth gating the inner pub field based on Rust version since the lint producing a hard error for referencing an underaligned field was introduced in 1.69.

Additionally, if we add T: ?Sized to Unalign, then only in 1.76 was this lint fixed for unsized fields.

[joshlf]

Merging this into #836 (comment)