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Rollup merge of #152698 - Zalathar:zforce, r=jieyouxu
Suppress unstable-trait notes under `-Zforce-unstable-if-unmarked` - Fixes #152692. --- #151036 adds extra diagnostic text (“the nightly-only, unstable trait”) to note when a not-implemented trait is unstable. However, that extra text is usually unhelpful when building a crate graph with `-Zforce-unstable-if-unmarked` (such as the compiler or stdlib), because *any* trait not explicitly marked stable will be treated as unstable. (For typical compiler contributors using the stage0 compiler, this fix won't take effect until the next bootstrap beta bump.)
2 parents 7ab22cd + 125e69e commit dc77672

5 files changed

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‎compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs‎

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@@ -5608,15 +5608,17 @@ pub(super) fn get_explanation_based_on_obligation<'tcx>(
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None => String::new(),
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};
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if let ty::PredicatePolarity::Positive = trait_predicate.polarity() {
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// If the trait in question is unstable, mention that fact in the diagnostic.
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// But if we're building with `-Zforce-unstable-if-unmarked` then _any_ trait
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// not explicitly marked stable is considered unstable, so the extra text is
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// unhelpful noise. See <https://github.com/rust-lang/rust/issues/152692>.
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let mention_unstable = !tcx.sess.opts.unstable_opts.force_unstable_if_unmarked
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&& try { tcx.lookup_stability(trait_predicate.def_id())?.level.is_stable() }
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== Some(false);
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let unstable = if mention_unstable { "nightly-only, unstable " } else { "" };
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format!(
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"{pre_message}the {}trait `{}` is not implemented for{desc} `{}`",
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if tcx.lookup_stability(trait_predicate.def_id()).map(|s| s.level.is_stable())
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== Some(false)
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{
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"nightly-only, unstable "
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} else {
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""
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},
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"{pre_message}the {unstable}trait `{}` is not implemented for{desc} `{}`",
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trait_predicate.print_modifiers_and_trait_path(),
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tcx.short_string(trait_predicate.self_ty().skip_binder(), long_ty_path),
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)

‎tests/ui/traits/auxiliary/force_unstable.rs‎

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//@ edition: 2024
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//@ compile-flags: -Zforce-unstable-if-unmarked
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// Auxiliary crate that uses `-Zforce-unstable-if-unmarked` to export an
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// "unstable" trait.
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pub trait ForeignTrait {}

‎tests/ui/traits/nightly-only-unstable.force.stderr‎

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error[E0277]: the trait bound `(): LocalTrait` is not satisfied
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--> $DIR/nightly-only-unstable.rs:25:21
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|
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LL | use_local_trait(());
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| --------------- ^^ the trait `LocalTrait` is not implemented for `()`
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| |
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| required by a bound introduced by this call
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|
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help: this trait has no implementations, consider adding one
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--> $DIR/nightly-only-unstable.rs:14:1
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|
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LL | trait LocalTrait {}
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| ^^^^^^^^^^^^^^^^
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note: required by a bound in `use_local_trait`
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--> $DIR/nightly-only-unstable.rs:16:28
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|
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LL | fn use_local_trait(_: impl LocalTrait) {}
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| ^^^^^^^^^^ required by this bound in `use_local_trait`
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error[E0277]: the trait bound `(): ForeignTrait` is not satisfied
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--> $DIR/nightly-only-unstable.rs:31:23
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|
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LL | use_foreign_trait(());
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| ----------------- ^^ the trait `ForeignTrait` is not implemented for `()`
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| |
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| required by a bound introduced by this call
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|
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note: required by a bound in `use_foreign_trait`
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--> $DIR/nightly-only-unstable.rs:20:30
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|
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LL | fn use_foreign_trait(_: impl force_unstable::ForeignTrait) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `use_foreign_trait`
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.

‎tests/ui/traits/nightly-only-unstable.normal.stderr‎

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error[E0277]: the trait bound `(): LocalTrait` is not satisfied
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--> $DIR/nightly-only-unstable.rs:25:21
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|
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LL | use_local_trait(());
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| --------------- ^^ the trait `LocalTrait` is not implemented for `()`
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| |
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| required by a bound introduced by this call
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|
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help: this trait has no implementations, consider adding one
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--> $DIR/nightly-only-unstable.rs:14:1
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|
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LL | trait LocalTrait {}
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| ^^^^^^^^^^^^^^^^
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note: required by a bound in `use_local_trait`
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--> $DIR/nightly-only-unstable.rs:16:28
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|
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LL | fn use_local_trait(_: impl LocalTrait) {}
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| ^^^^^^^^^^ required by this bound in `use_local_trait`
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error[E0277]: the trait bound `(): ForeignTrait` is not satisfied
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--> $DIR/nightly-only-unstable.rs:31:23
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|
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LL | use_foreign_trait(());
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| ----------------- ^^ the nightly-only, unstable trait `ForeignTrait` is not implemented for `()`
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| |
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| required by a bound introduced by this call
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|
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note: required by a bound in `use_foreign_trait`
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--> $DIR/nightly-only-unstable.rs:20:30
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|
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LL | fn use_foreign_trait(_: impl force_unstable::ForeignTrait) {}
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `use_foreign_trait`
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.

‎tests/ui/traits/nightly-only-unstable.rs‎

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//@ revisions: normal force
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//@ edition: 2024
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//@ aux-crate: force_unstable=force_unstable.rs
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//@[force] compile-flags: -Zforce-unstable-if-unmarked
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#![feature(rustc_private)]
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// Regression test for <https://github.com/rust-lang/rust/issues/152692>.
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//
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// When building a crate with `-Zforce-unstable-if-unmarked` (e.g. the compiler or stdlib),
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// it's unhelpful to mention that a not-implemented trait is unstable, because that will
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// be true of every local and foreign trait that isn't explicitly marked stable.
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trait LocalTrait {}
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fn use_local_trait(_: impl LocalTrait) {}
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//~^ NOTE required by a bound in `use_local_trait`
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//~| NOTE required by this bound in `use_local_trait`
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fn use_foreign_trait(_: impl force_unstable::ForeignTrait) {}
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//~^ NOTE required by a bound in `use_foreign_trait`
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//~| NOTE required by this bound in `use_foreign_trait`
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fn main() {
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use_local_trait(());
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//~^ ERROR the trait bound `(): LocalTrait` is not satisfied
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//[normal]~| NOTE the trait `LocalTrait` is not implemented for `()`
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//[force]~| NOTE the trait `LocalTrait` is not implemented for `()`
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//~| NOTE required by a bound introduced by this call
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use_foreign_trait(());
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//~^ ERROR the trait bound `(): ForeignTrait` is not satisfied
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//[normal]~| NOTE the nightly-only, unstable trait `ForeignTrait` is not implemented for `()`
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//[force]~| NOTE the trait `ForeignTrait` is not implemented for `()`
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//~| NOTE required by a bound introduced by this call
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}

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