clippy: Raises result_large_err to squelch lint

[brooksprumo]

Problem

Upgrading Rust to 1.87.0¹ is blocked on a new clippy lint², result_large_err³.

Summary of Changes

Raise the threshold for the lint to 265, since the largest size today is 264 bytes.

A subsequent PR can fix the underlying Error type to box the large variant, and remove the custom threshold.

By raising the threshold here, we unblock upgrading Rust, and we don't change any behavior.

Note that annotating the Error enums with #[allow(clippy::result_large_err)] does not squelch the lint unfortunately.

Fixes #6278

Footnotes

1. https://github.com/anza-xyz/agave/issues/6279 ↩

2. https://github.com/anza-xyz/agave/issues/6278 ↩

3. https://rust-lang.github.io/rust-clippy/master/index.html#result_large_err ↩

[yihau]

note: I've tried adding #[allow(clippy::result_large_err)] in several different places before. #5990

I don’t have a preference for any particular solution. just wanted to bring something up: we will allow all new large Result types under 265 bytes if we use this PR.

[brooksprumo]

I implemented boxing the ErrorKind field inside solana_rpc_client_api::client_error::Error here: brooksprumo@36edeac, but it has two problems:

1. solana_rpc_client_api::client_error::Error is public, so changing the type of kind is an API-breaking change. We cannot do this until v3.0.

2. Even if we did change solana_rpc_client_api::client_error::Error, there are still other Result types larger than the default threshold: TpsClientResult is 144 bytes, and storage-bigtable/src/bigtable.rs Error is 176 bytes. So we'd have to change those as well, and changing them is also an API-breaking change.

So, for agave v2.x, I think the only option we have is to bump the threshold.

[brooksprumo]

@steviez / @t-nelson, let me know if you'd like to review before I merge. I'll plan to merge tomorrow otherwise.

[t-nelson]

i'd prefer the explicit allows in offending call sites personally

[brooksprumo]

i'd prefer the explicit allows in offending call sites personally

#5990 is where @yihau tried that previously. Can you take a look? It's a lot of annotations.

[brooksprumo]

Closing. Now that we're on v3.0, we can make API-breaking changes. As such, a real fix (not changing the lint limit) is preferred.