Remove unnecessary lifetimes of CRC digest

[cdunster]

The CRC digest lifetime is set to the same as the provided buffer lifetime which means that the CRC has to live as long as the buffer which I don't think is necessary as the finalize() method is called on the digest. This strictness of the lifetime meant that I couldn't create a Crc in the local scope i.e. a method and then just return the bytes (see the new unit test for an example of what I mean).

Clippy suggests this change and to remove a few other lifetimes too so I think this should be a low risk change 🙂

Thanks for the great crate!

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[jamesmunns]

CC @huntc - do you know if these lifetimes were chosen intentionally?

[jamesmunns]

Also, I need to figure out if removing a lifetime like this is a breaking API change. If yes, it might need to wait for #128, but I don't think it is?

[cdunster]

Also, I need to figure out if removing a lifetime like this is a breaking API change. If yes, it might need to wait for #128, but I don't think it is?

I would assume that removing a lifetime like this is not breaking because '_ could still live as long as 'a but it no longer has to, right? Maybe going the other way would be
a breaking change as the public interface would become more strict.

That's just my thought though and I'm not 100% sure 😅

[huntc]

I've just pulled down the latest commit on main, updated my toolchain to the latest (rustc 1.75.0 (82e1608df 2023-12-21) ), and performed a cargo clippy.

All I see that clippy recommends is the following:

warning: use of `default` to create a unit struct
   --> src/ser/serializer.rs:377:50
    |
377 |                     .map_err(|_| core::fmt::Error::default())
    |                                                  ^^^^^^^^^^^ help: remove this call to `default`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#default_constructed_unit_structs
    = note: `#[warn(clippy::default_constructed_unit_structs)]` on by default

warning: the following explicit lifetimes could be elided: 'a
   --> src/ser/mod.rs:269:18
    |
269 | pub fn to_extend<'a, T, W>(value: &'a T, writer: W) -> Result<W>
    |                  ^^                ^^
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_lifetimes
    = note: `#[warn(clippy::needless_lifetimes)]` on by default
help: elide the lifetimes
    |
269 - pub fn to_extend<'a, T, W>(value: &'a T, writer: W) -> Result<W>
269 + pub fn to_extend<T, W>(value: &T, writer: W) -> Result<W>

The explicit lifetime for to_extend is not required. However, I don't see that in this PR.

Regarding the lifetimes on Digest, the _ lifetime should be fine. I don't think this would be a breaking a change as the lifetime there relates to the Crc. I'm not sure why I originally associated the lifetime with the buffer.

[huntc]

Should we progress this pull request?

[jamesmunns]

Thank you all!