Add wasm_c_abi future-incompat lint

[daxpedda]

This is a warning that will tell users to update to wasm-bindgen v0.2.88, which supports spec-compliant C ABI.

The idea is to prepare for a future where Rust will switch to the spec-compliant C ABI by default; so not to break everyone's world, this warning is introduced.

Addresses #71871.

[rustbot]

r? @cjgillot

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[daxpedda]

For some reason -Dwasm_c_abi seems to have no effect at all. Neither does -Awasm_c_abi, it will always be on a warning level. Is this intentional because of FutureIncompatibilityReason::FutureReleaseErrorReportInDeps?

[workingjubilee]

Do you mean through cargo? Because when using rustc, it caps lints when compiling dependencies? Though I thought that was just a cap....

[daxpedda]

Do you mean through cargo? Because when using rustc, it caps lints when compiling dependencies? Though I thought that was just a cap....

I used RUSTFLAGS=-Dwasm_c_abi cargo build for example. Maybe it's because it's emitting the lint inside the dependency ... but I don't know what exactly is desirable here.

[workingjubilee]

I used RUSTFLAGS=-Dwasm_c_abi cargo build for example. Maybe it's because it's emitting the lint inside the dependency ... but I don't know what exactly is desirable here.

Hmm, yeah. Yeah, I'm not 100% on exactly how everything has to going to trigger, here. But I'm pretty sure you gotta emit these lints in the crates that are themselves dependent on wasm-bindgen, effectively, and not in wasm-bindgen, or it won't do anything.

[daxpedda]

But I'm pretty sure you gotta emit these lints in the crates that are themselves dependent on wasm-bindgen, effectively, and not in wasm-bindgen, or it won't do anything.

I don't remember exactly where the lint is emitted, but it does work. E.g. it correctly emits a warnings when the root crate or one of it's dependencies depends on wasm-bindgen <v0.2.88.

The problem was that you can't control the lint, e.g. you can't disable it or change the level from warning to deny, but it will trigger correctly at a warning level.

If I remember correctly the unused-crate-dependencies lint stores the warnings somewhere and then emits them later. I could do this as well here? Feels a bit odd to add that much machinery for a lint that AFAIU will be removed at some point. I could turn the part that stores unused-crate-dependencies into something more general that could be used by any lint to justify it.

[workingjubilee]

Oh okay, I misunderstood, sorry!

It does seem silly (not necessarily undesirable, but more Unnecessary Ceremony) as a one-off, but maybe it's possible to generalize the machinery, so it would remain useful for later lints of this nature?

[daxpedda]

Yeah that's what I was proposing here:

I could turn the part that stores unused-crate-dependencies into something more general that could be used by any lint to justify it.

Unfortunately I remembered that this isn't correct, because unused-crate-dependencies does some more things that can't really be generalized like that. E.g. it doesn't actually store warnings to be emitted later, but a list of found dependencies that are checked later against a list of used dependencies.

So any general machinery I would introduce here would only be used by this lint, so as soon as it's removed this machinery will be unused. I'm not really familiar with Rustc's codebase, I could be missing something.

In any case, I'm happy to figure out a one-off implementation as well on consensus.

[bors]

☔ The latest upstream changes (presumably #118324) made this pull request unmergeable. Please resolve the merge conflicts.

[cjgillot]

r? @workingjubilee

[bors]

☔ The latest upstream changes (presumably #120239) made this pull request unmergeable. Please resolve the merge conflicts.

[apiraino]

I'll try to signal that this PR appears to be waiting on T-lang (IIUC by reading the labels)

@rustbot label +S-waiting-on-team -S-waiting-on-review

[workingjubilee]

It seems... inauspicious... to land a lint that ignores a lint, barring reason.

@rustbot author

[workingjubilee]

Thank you.

@bors r+ rollup

[bors]

📌 Commit 873a0f2 has been approved by workingjubilee

It is now in the queue for this repository.