Support multiple stability attributes on items #131824
Open
+1,552
−657
Commits on Nov 6, 2024
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This moves stability structs' `feature` fields into `StabilityLevel::Unstable` and `ConstStabilityLevel::Unstable`, in preparation to support multiple unstable attributes on items. Seemingly, the `feature` field isn't used with the `StabilityLevel::Stable` variant, so I haven't included it. `rustc_passes::lib_features` uses the 'feature' meta-item for 'stable' attributes, but it extracts them itself, rather than relying on `rustc_attr`. In order to support the new const stability check rules, this additionally introduces `ConstStabilityLevel` and moves the case of `feature` being `None` to the `Implicit` variant for clarity; having it correspond to an empty `unstables` vec seems like it would be a footgun.
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factor out some commonalities in the
find_stabilityfamily of funct……ions the logic for adding unstable attrs gets a bit messier when supporting multiple instances thereof. this keeps that from being duplicated in 3 places.
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find_stability: don't give up when emitting "multiple stability lev……els" errors this makes things a little cleaner. since multiple stability levels are allowed, I think it makes sense too.
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support multiple stability attributes (a mix of stable and unstable)
An item is unstable if it has any unstable attributes, to make it easier to track which features library items depended on as they stabilize. This changes the text for E0544. Unfortunately, the example doesn't make much sense anymore. The way this merges stability levels together is made to work for stability-checking and rustdoc; as far as I can tell, only `rustc_passes::lib_features` needs them separate, and it extracts them itself.
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Improve diagnostics for the use of unstable library features
- only emits one error/lint (instead of one per missing feature) per usage of unstable and body-unstable items - only emits one future-name-collision lint (instead of one per missing feature) for unstable trait items - makes diagnostics for unstable, soft-unstable, const-unstable, and body-unstable library features translatable, using common subdiagnostic structs. - adds notes with features, reasons, and issue links to const-unstability errors - adds notes with issue links to soft_unstable lints - on nightly, adds `#![feature]` crate attr help to soft_unstable lints - on nightly, adds compiler-upgrade-suggestion notes to const-unstable and soft_unstable diagnostics
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Simplify unstable language feature use diagnostics
Reasons provided on `#[unstable]` attributes are now per-item rather than per-feature. This is how they mostly are used anyway, and it simplifies both the implementation and the diagnostics themselves.
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Add sanity check for inconsistent
softusage on soft-unstable itemsIt doesn't make sense for something to be partially soft, and allowing inconsistent softness markers would risk an item accidentally becoming properly unstable as its features stabilize.
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Suppress redundant listing of unstable library features used on nightly
On nightly, there's a suggestion/help containing the `#![feature(..)]` attribute required to enable any required unstable features, so the note listing the features is unnecessary. This only applies to const-unstable and default-body-unstable errors. Normal "use of unstable library feature" errors list the features in the error message, so it doesn't feel redundant.
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