How to construct a TransparentKeyBuilder?

[sourcefrog]

This looks nice!

I'm trying this code:

        let cache = stretto::Cache::new_with_key_builder(
            max_counters,
            MAX_CACHE_BYTES as i64,
            stretto::TransparentKeyBuilder::default(),
        )
        .expect("Create blockdir cache");

However, it complains that my key type doesn't implement Default, which it doesn't, and I don't really want to since there is no sensible default

error[E0277]: the trait bound `blockhash::BlockHash: std::default::Default` is not satisfied
   --> src/blockdir.rs:109:13
    |
109 |             stretto::TransparentKeyBuilder::default(),
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::default::Default` is not implemented for `blockhash::BlockHash`
    |
    = help: the trait `std::default::Default` is implemented for `stretto::TransparentKeyBuilder<K>`
    = note: required for `stretto::TransparentKeyBuilder<blockhash::BlockHash>` to implement `std::default::Default`

It doesn't seem inherently necessary that the key has a default? Could we just add a new method?

[al8n]

Hi, TransparentKeyBuilder only supports types which implement TransparentKey trait, if you want to use it, you must implement TransparentKey for your key type first.

[sourcefrog]

I think the problem I hit was connected to this:

https://github.com/al8n/stretto/blob/cccb12b14fc612a5e8f2ac595e04c995036d4212/src/lib.rs#L457-L461

I tried implementing TransparentKey, but the problem is that the derive(Default) implies that my key type K must also implement Default. I feel like for many keys, at least for my key, there is no very meaningful defaulti

[sourcefrog]

I tried to make a small repro, but it seems to work OK when the key type is !Default. Perhaps I was just confused.