repr(align(...)) added or removed on struct, enum, or union

[obi1kenobi]

Breaking because of:
https://jack.wrenn.fyi/blog/semver-snares-alignment/
https://old.reddit.com/r/rust/comments/kr41sq/semver_snares_sizedness_and_size/

Now documented at:
https://doc.rust-lang.org/cargo/reference/semver.html#type-layout

[max-heller]

I'm interested in working on this!

[obi1kenobi]

Awesome! Here are the most-related lints we have right now:

• repr(C) removed from struct: https://github.com/obi1kenobi/cargo-semver-check/blob/main/src/queries/struct_repr_c_removed.ron
• repr(C) removed from enum: https://github.com/obi1kenobi/cargo-semver-check/blob/main/src/queries/enum_repr_c_removed.ron

I put a little syntax explainer in this sibling issue, it covers most of the concepts this lint will need as well so please check it out:
#73 (comment)

Let's focus on writing the query we'll need first, and then we can pretty straightforwardly add the test cases, error messages, etc.

In addition to the information in the link above:

• We'll need a regex filter operator instead of the contains / not_contains filter operators in the repr(C) lints I linked above.
• We'll need to say "none of the current attributes match this regex" instead of "the list doesn't contain this element." This will require the @fold @transform(...) @filter(...) construct ("no such neighbors exist" construct) as in the link above.
• For that construct, we'll need to refer to the attributes as neighboring vertices (attribute edge) of the item, rather than just a list of strings that's a property of the item (attrs property). Check out the schema: https://github.com/obi1kenobi/cargo-semver-check/blob/main/src/rustdoc_schema.graphql

It's totally fine if the new lint runs into bug #104 as well, that's on me for not representing attributes better in the schema. Whenever we fix #104, we can do a pass through all the affected lints as well, and in the meantime we'll just bear with the extra false-negatives. In this project, false negatives are unfortunate, but false positives are deal-breakers.

Ping me with any questions! Happy to hop on a video call if that would make it easier to get started, and I'm also in the rust-lang zulip if you'd prefer more interactive text chat.

I'm also working with a few friends on a WASM-powered web editor for Trustfall queries with all the modern conveniences (autocomplete, syntax highlighting, etc.), stay tuned! 🤞