This PR introduces a new `CacheKey` trait for types that can be used as a cache key.
I'm not entirely sure if this is worth the "overhead", but I was surprised to find `HashableHashSet` and got scared when I looked at the time complexity of the `hash` function. These implementations must be extremely slow in hashed collections.
I then searched for usages and quickly realized that only the cache uses these `Hash` implementations, where performance is less sensitive.
This PR introduces a new `CacheKey` trait to communicate the difference between a hash and computing a key for the cache. The new trait can be implemented for types that don't implement `Hash` for performance reasons, and we can define additional constraints on the implementation: For example, we'll want to enforce portability when we add remote caching support. Using a different trait further allows us not to implement it for types without stable identities (e.g. pointers) or use other implementations than the standard hash function.
```console
❯ cargo run rule B017
Finished dev [unoptimized + debuginfo] target(s) in 0.13s
Running `target/debug/ruff rule B017`
no-assert-raises-exception
Code: B017 (flake8-bugbear)
### What it does
Checks for `self.assertRaises(Exception)`.
## Why is this bad?
`assertRaises(Exception)` can lead to your test passing even if the
code being tested is never executed due to a typo.
Either assert for a more specific exception (builtin or custom), use
`assertRaisesRegex` or the context manager form of `assertRaises`.
```
Micha Reiser
Charlie Marsh
Jonathan Plasse
Martin Fischer