digest: reduce the number of required methods in `Digest`?

[fjarri]

It seems that a number of currently required methods in Digest can be expressed via other methods, for example:

• chain_update via update
• finalize via finalize_into
• finalize_reset via reset and finalize
• finalize_into_reset via reset and finalize_into
• possibly, new via new_with_prefix with an empty slice

Is there a reason it's not currently done?

[newpavlov]

You mean why those methods don't have blanket impls? It's because those implementations reside in the blanket impl of the trait itself. It uses the underlying traits directly without adding a layer of indirection (i.e. we use Update::update directly instead of using Digest::update which in turn uses Update::update). We could've used blanket methods implementations, but it's a very minor implementation detail considering that Digest should not be directly implemented by user crates.

[fjarri]

Ah, I see, that makes sense. I don't think it would hurt adding the blanket impls still, but I don't insist on it. Closing.