# Description
In this PR I replaced most of the raw usize IDs with
[newtypes](https://doc.rust-lang.org/rust-by-example/generics/new_types.html).
Some other IDs already started using new types and in this PR I did not
want to touch them. To make the implementation less repetitive, I made
use of a generic `Id<T>` with marker structs. If this lands I would try
to move make other IDs also in this pattern.
Also at some places I needed to use `cast`, I'm not sure if the type was
incorrect and therefore casting not needed or if actually different ID
types intermingle sometimes.
# User-Facing Changes
Probably few, if you got a `DeclId` via a function and placed it later
again it will still work.
f0c83a4459