Rollup merge of #97875 - JohnTitor:rm-infer-static-outlives-requirements, r=pnkfelix
Remove the `infer_static_outlives_requirements` feature Closes #54185 r? ``@pnkfelix``
This commit is contained in:
Matthias Krüger
GitHub
commit
89249b199e
11 changed files with 13 additions and 123 deletions
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@ -409,8 +409,6 @@ declare_features! (
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(active, if_let_guard, "1.47.0", Some(51114), None),
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/// Allows using imported `main` function
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(active, imported_main, "1.53.0", Some(28937), None),
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/// Allows inferring `'static` outlives requirements (RFC 2093).
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(active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
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/// Allows associated types in inherent impls.
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(incomplete, inherent_associated_types, "1.52.0", Some(8995), None),
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/// Allow anonymous constants from an inline `const` block
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@ -109,6 +109,9 @@ declare_features! (
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/// Allows in-band quantification of lifetime bindings (e.g., `fn foo(x: &'a u8) -> &'a u8`).
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(removed, in_band_lifetimes, "1.23.0", Some(44524), None,
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Some("removed due to unsolved ergonomic questions and added lifetime resolution complexity")),
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/// Allows inferring `'static` outlives requirements (RFC 2093).
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(removed, infer_static_outlives_requirements, "1.63.0", Some(54185), None,
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Some("removed as it caused some confusion and discussion was inactive for years")),
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/// Lazily evaluate constants. This allows constants to depend on type parameters.
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(removed, lazy_normalization_consts, "1.46.0", Some(72219), None, Some("superseded by `generic_const_exprs`")),
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/// Allows using the `#[link_args]` attribute.
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@ -2113,7 +2113,6 @@ impl ExplicitOutlivesRequirements {
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tcx: TyCtxt<'tcx>,
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bounds: &hir::GenericBounds<'_>,
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inferred_outlives: &[ty::Region<'tcx>],
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infer_static: bool,
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) -> Vec<(usize, Span)> {
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use rustc_middle::middle::resolve_lifetime::Region;
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@ -2123,9 +2122,6 @@ impl ExplicitOutlivesRequirements {
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.filter_map(|(i, bound)| {
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if let hir::GenericBound::Outlives(lifetime) = bound {
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let is_inferred = match tcx.named_region(lifetime.hir_id) {
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Some(Region::Static) if infer_static => {
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inferred_outlives.iter().any(|r| matches!(**r, ty::ReStatic))
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}
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Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
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if let ty::ReEarlyBound(ebr) = **r { ebr.index == index } else { false }
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}),
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@ -2201,7 +2197,6 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
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use rustc_middle::middle::resolve_lifetime::Region;
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let infer_static = cx.tcx.features().infer_static_outlives_requirements;
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let def_id = item.def_id;
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if let hir::ItemKind::Struct(_, ref hir_generics)
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| hir::ItemKind::Enum(_, ref hir_generics)
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@ -2262,12 +2257,8 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
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continue;
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}
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let bound_spans = self.collect_outlives_bound_spans(
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cx.tcx,
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bounds,
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&relevant_lifetimes,
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infer_static,
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);
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let bound_spans =
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self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
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bound_count += bound_spans.len();
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let drop_predicate = bound_spans.len() == bounds.len();
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@ -21,7 +21,7 @@ pub fn insert_outlives_predicate<'tcx>(
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) {
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// If the `'a` region is bound within the field type itself, we
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// don't want to propagate this constraint to the header.
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if !is_free_region(tcx, outlived_region) {
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if !is_free_region(outlived_region) {
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return;
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}
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@ -119,7 +119,7 @@ pub fn insert_outlives_predicate<'tcx>(
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}
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GenericArgKind::Lifetime(r) => {
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if !is_free_region(tcx, r) {
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if !is_free_region(r) {
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return;
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}
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required_predicates.entry(ty::OutlivesPredicate(kind, outlived_region)).or_insert(span);
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@ -131,7 +131,7 @@ pub fn insert_outlives_predicate<'tcx>(
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}
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}
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fn is_free_region(tcx: TyCtxt<'_>, region: Region<'_>) -> bool {
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fn is_free_region(region: Region<'_>) -> bool {
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// First, screen for regions that might appear in a type header.
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match *region {
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// These correspond to `T: 'a` relationships:
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@ -144,13 +144,12 @@ fn is_free_region(tcx: TyCtxt<'_>, region: Region<'_>) -> bool {
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ty::ReEarlyBound(_) => true,
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// These correspond to `T: 'static` relationships which can be
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// rather surprising. We are therefore putting this behind a
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// feature flag:
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// rather surprising.
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//
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// struct Foo<'a, T> {
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// field: &'static T, // this would generate a ReStatic
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// }
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ty::ReStatic => tcx.sess.features_untracked().infer_static_outlives_requirements,
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ty::ReStatic => false,
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// Late-bound regions can appear in `fn` types:
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//
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@ -1,44 +0,0 @@
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# `infer_static_outlives_requirements`
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The tracking issue for this feature is: [#54185]
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[#54185]: https://github.com/rust-lang/rust/issues/54185
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------------------------
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The `infer_static_outlives_requirements` feature indicates that certain
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`'static` outlives requirements can be inferred by the compiler rather than
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stating them explicitly.
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Note: It is an accompanying feature to `infer_outlives_requirements`,
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which must be enabled to infer outlives requirements.
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For example, currently generic struct definitions that contain
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references, require where-clauses of the form T: 'static. By using
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this feature the outlives predicates will be inferred, although
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they may still be written explicitly.
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```rust,ignore (pseudo-Rust)
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struct Foo<U> where U: 'static { // <-- currently required
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bar: Bar<U>
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}
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struct Bar<T: 'static> {
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x: T,
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}
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```
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## Examples:
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```rust,ignore (pseudo-Rust)
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#![feature(infer_outlives_requirements)]
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#![feature(infer_static_outlives_requirements)]
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#[rustc_outlives]
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// Implicitly infer U: 'static
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struct Foo<U> {
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bar: Bar<U>
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}
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struct Bar<T: 'static> {
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x: T,
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}
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```
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@ -1,12 +0,0 @@
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// Needs an explicit where clause stating outlives condition. (RFC 2093)
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// Type T needs to outlive lifetime 'static.
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struct Foo<U> {
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bar: Bar<U> //~ ERROR the parameter type `U` may not live long enough [E0310]
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}
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struct Bar<T: 'static> {
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x: T,
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}
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fn main() { }
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@ -1,19 +0,0 @@
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error[E0310]: the parameter type `U` may not live long enough
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--> $DIR/feature-gate-infer_static_outlives_requirements.rs:5:10
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LL | bar: Bar<U>
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| ^^^^^^ ...so that the type `U` will meet its required lifetime bounds...
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note: ...that is required by this bound
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--> $DIR/feature-gate-infer_static_outlives_requirements.rs:7:15
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LL | struct Bar<T: 'static> {
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| ^^^^^^^
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help: consider adding an explicit lifetime bound...
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LL | struct Foo<U: 'static> {
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| +++++++++
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0310`.
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@ -1,7 +1,5 @@
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/*
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* We don't infer `T: 'static` outlives relationships by default.
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* Instead an additional feature gate `infer_static_outlives_requirements`
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* is required.
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* We don't infer `T: 'static` outlives relationships.
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*/
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struct Foo<U> {
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@ -1,11 +1,11 @@
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error[E0310]: the parameter type `U` may not live long enough
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--> $DIR/dont-infer-static.rs:8:10
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--> $DIR/dont-infer-static.rs:6:10
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LL | bar: Bar<U>
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| ^^^^^^ ...so that the type `U` will meet its required lifetime bounds...
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note: ...that is required by this bound
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--> $DIR/dont-infer-static.rs:10:15
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--> $DIR/dont-infer-static.rs:8:15
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LL | struct Bar<T: 'static> {
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| ^^^^^^^
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@ -1,12 +0,0 @@
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#![feature(rustc_attrs)]
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#![feature(infer_static_outlives_requirements)]
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#[rustc_outlives]
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struct Foo<U> { //~ ERROR rustc_outlives
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bar: Bar<U>
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}
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struct Bar<T: 'static> {
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x: T,
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}
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fn main() {}
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@ -1,12 +0,0 @@
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error: rustc_outlives
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--> $DIR/infer-static.rs:5:1
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LL | / struct Foo<U> {
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LL | | bar: Bar<U>
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LL | | }
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| |_^
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= note: U: 'static
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error: aborting due to previous error
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