Rollup merge of #99212 - davidtwco:partial-stability-implies, r=michaelwoerister
introduce `implied_by` in `#[unstable]` attribute Requested by the library team [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/better.20support.20for.20partial.20stabilizations/near/285581519). If part of a feature is stabilized and a new feature is added for the remaining parts, then the `implied_by` meta-item can be added to `#[unstable]` to indicate which now-stable feature was used previously. ```diagnostic error: the feature `foo` has been partially stabilized since 1.62.0 and is succeeded by the feature `foobar` --> $DIR/stability-attribute-implies-using-unstable.rs:3:12 | LL | #![feature(foo)] | ^^^ | note: the lint level is defined here --> $DIR/stability-attribute-implies-using-stable.rs:2:9 | LL | #![deny(stable_features)] | ^^^^^^^^^^^^^^^ help: if you are using features which are still unstable, change to using `foobar` | LL | #![feature(foobar)] | ~~~~~~ help: if you are using features which are now stable, remove this line | LL - #![feature(foo)] | ``` When a `#![feature(..)]` attribute still exists for the now-stable attribute, then there this has two effects: - There will not be an stability error for uses of items from the implied feature which are still unstable (until the `#![feature(..)]` is removed or updated to the new feature). - There will be an improved diagnostic for the remaining use of the feature attribute for the now-stable feature. ```rust /// If part of a feature is stabilized and a new feature is added for the remaining parts, /// then the `implied_by` attribute is used to indicate which now-stable feature previously /// contained a item. /// /// ```pseudo-Rust /// #[unstable(feature = "foo", issue = "...")] /// fn foo() {} /// #[unstable(feature = "foo", issue = "...")] /// fn foobar() {} /// ``` /// /// ...becomes... /// /// ```pseudo-Rust /// #[stable(feature = "foo", since = "1.XX.X")] /// fn foo() {} /// #[unstable(feature = "foobar", issue = "...", implied_by = "foo")] /// fn foobar() {} /// ``` ``` In the Zulip discussion, this was envisioned as `implies` on `#[stable]` but I went with `implied_by` on `#[unstable]` because it means that only the unstable attribute needs to be changed in future, not the new stable attribute, which seems less error-prone. It also isn't particularly feasible for me to detect whether items from the implied feature are used and then only suggest updating _or_ removing the `#![feature(..)]` as appropriate, so I always do both. There's some new information in the cross-crate metadata as a result of this change, that's a little unfortunate, but without requiring that the `#[unstable]` and `#[stable]` attributes both contain the implication information, it's necessary: ```rust /// This mapping is necessary unless both the `#[stable]` and `#[unstable]` attributes should /// specify their implications (both `implies` and `implied_by`). If only one of the two /// attributes do (as in the current implementation, `implied_by` in `#[unstable]`), then this /// mapping is necessary for diagnostics. When a "unnecessary feature attribute" error is /// reported, only the `#[stable]` attribute information is available, so the map is necessary /// to know that the feature implies another feature. If it were reversed, and the `#[stable]` /// attribute had an `implies` meta item, then a map would be necessary when avoiding a "use of /// unstable feature" error for a feature that was implied. ``` I also change some comments to documentation comments in the compiler, add a helper for going from a `Span` to a `Span` for the entire line, and fix a incorrect part of the pre-existing stability attribute diagnostics. cc `@yaahc`
This commit is contained in:
Matthias Krüger
GitHub
commit
857afc75e6
24 changed files with 357 additions and 62 deletions
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#![feature(staged_api)]
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#![stable(feature = "stability_attribute_implies", since = "1.0.0")]
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#[stable(feature = "foo", since = "1.62.0")]
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pub fn foo() {}
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#[unstable(feature = "foobar", issue = "1", implied_by = "foo")]
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pub fn foobar() {}
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@ -0,0 +1,10 @@
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#![feature(staged_api)]
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#![stable(feature = "stability_attribute_implies", since = "1.0.0")]
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// Tests that `implied_by = "bar"` results in an error being emitted if `bar` does not exist.
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#[unstable(feature = "foobar", issue = "1", implied_by = "bar")]
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//~^ ERROR feature `bar` implying `foobar` does not exist
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pub fn foobar() {}
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fn main() {}
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error: feature `bar` implying `foobar` does not exist
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--> $DIR/stability-attribute-implies-missing.rs:6:1
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LL | #[unstable(feature = "foobar", issue = "1", implied_by = "bar")]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to previous error
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// aux-build:stability-attribute-implies.rs
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// Tests that despite the `foobar` feature being implied by now-stable feature `foo`, if `foobar`
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// isn't allowed in this crate then an error will be emitted.
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extern crate stability_attribute_implies;
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use stability_attribute_implies::{foo, foobar};
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//~^ ERROR use of unstable library feature 'foobar'
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fn main() {
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foo(); // no error - stable
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foobar(); //~ ERROR use of unstable library feature 'foobar'
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}
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error[E0658]: use of unstable library feature 'foobar'
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--> $DIR/stability-attribute-implies-no-feature.rs:7:40
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LL | use stability_attribute_implies::{foo, foobar};
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| ^^^^^^
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= note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
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= help: add `#![feature(foobar)]` to the crate attributes to enable
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error[E0658]: use of unstable library feature 'foobar'
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--> $DIR/stability-attribute-implies-no-feature.rs:12:5
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LL | foobar();
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| ^^^^^^
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= note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
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= help: add `#![feature(foobar)]` to the crate attributes to enable
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0658`.
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// aux-build:stability-attribute-implies.rs
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#![deny(stable_features)]
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#![feature(foo)]
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//~^ ERROR the feature `foo` has been partially stabilized since 1.62.0 and is succeeded by the feature `foobar`
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// Tests that the use of `implied_by` in the `#[unstable]` attribute results in a diagnostic
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// mentioning partial stabilization, and that given the implied unstable feature is unused (there
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// is no `foobar` call), that the compiler suggests removing the flag.
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extern crate stability_attribute_implies;
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use stability_attribute_implies::foo;
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fn main() {
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foo();
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}
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error: the feature `foo` has been partially stabilized since 1.62.0 and is succeeded by the feature `foobar`
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--> $DIR/stability-attribute-implies-using-stable.rs:3:12
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LL | #![feature(foo)]
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| ^^^
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note: the lint level is defined here
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--> $DIR/stability-attribute-implies-using-stable.rs:2:9
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LL | #![deny(stable_features)]
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| ^^^^^^^^^^^^^^^
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help: if you are using features which are still unstable, change to using `foobar`
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LL | #![feature(foobar)]
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| ~~~~~~
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help: if you are using features which are now stable, remove this line
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LL - #![feature(foo)]
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error: aborting due to previous error
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// aux-build:stability-attribute-implies.rs
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#![deny(stable_features)]
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#![feature(foo)]
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//~^ ERROR the feature `foo` has been partially stabilized since 1.62.0 and is succeeded by the feature `foobar`
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// Tests that the use of `implied_by` in the `#[unstable]` attribute results in a diagnostic
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// mentioning partial stabilization and that given the implied unstable feature is used (there is a
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// `foobar` call), that the compiler suggests changing to that feature and doesn't error about its
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// use.
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extern crate stability_attribute_implies;
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use stability_attribute_implies::{foo, foobar};
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fn main() {
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foo();
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foobar(); // no error!
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}
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error: the feature `foo` has been partially stabilized since 1.62.0 and is succeeded by the feature `foobar`
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--> $DIR/stability-attribute-implies-using-unstable.rs:3:12
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LL | #![feature(foo)]
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| ^^^
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note: the lint level is defined here
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--> $DIR/stability-attribute-implies-using-unstable.rs:2:9
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LL | #![deny(stable_features)]
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| ^^^^^^^^^^^^^^^
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help: if you are using features which are still unstable, change to using `foobar`
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LL | #![feature(foobar)]
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| ~~~~~~
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help: if you are using features which are now stable, remove this line
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LL - #![feature(foo)]
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error: aborting due to previous error
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@ -8,7 +8,7 @@ error[E0541]: unknown meta item 'sinse'
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--> $DIR/stability-attribute-sanity-2.rs:10:25
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LL | #[stable(feature = "a", sinse = "1.0.0")]
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| ^^^^^^^^^^^^^^^ expected one of `since`, `note`
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| ^^^^^^^^^^^^^^^ expected one of `feature`, `since`
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error[E0545]: `issue` must be a non-zero numeric string or "none"
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--> $DIR/stability-attribute-sanity-2.rs:13:27
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@ -14,7 +14,7 @@ error[E0541]: unknown meta item 'reason'
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--> $DIR/stability-attribute-sanity.rs:8:42
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LL | #[stable(feature = "a", since = "b", reason)]
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| ^^^^^^ expected one of `since`, `note`
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| ^^^^^^ expected one of `feature`, `since`
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error[E0539]: incorrect meta item
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--> $DIR/stability-attribute-sanity.rs:11:29
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