From fad7d220fd2daefe8ee778b8cafbbeaf2dda4fc5 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Sat, 19 Aug 2023 23:27:50 +0000 Subject: [PATCH] Warn on elided lifetimes in associated constants --- compiler/rustc_lint/src/context.rs | 8 ++ compiler/rustc_lint_defs/src/builtin.rs | 42 ++++++++++ compiler/rustc_lint_defs/src/lib.rs | 4 + compiler/rustc_resolve/src/late.rs | 79 +++++++++++++------ ...nfer-placeholder-in-non-suggestable-pos.rs | 2 + ...-placeholder-in-non-suggestable-pos.stderr | 16 +++- .../ui/consts/assoc-const-elided-lifetime.rs | 19 +++++ .../consts/assoc-const-elided-lifetime.stderr | 33 ++++++++ 8 files changed, 178 insertions(+), 25 deletions(-) create mode 100644 tests/ui/consts/assoc-const-elided-lifetime.rs create mode 100644 tests/ui/consts/assoc-const-elided-lifetime.stderr diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs index f73797415bc..aabefb729f3 100644 --- a/compiler/rustc_lint/src/context.rs +++ b/compiler/rustc_lint/src/context.rs @@ -966,6 +966,14 @@ fn lookup_with_diagnostics( Applicability::MachineApplicable ); } + BuiltinLintDiagnostics::AssociatedConstElidedLifetime { elided, span } => { + db.span_suggestion_verbose( + if elided { span.shrink_to_hi() } else { span }, + "use the `'static` lifetime", + if elided { "'static " } else { "'static" }, + Applicability::MachineApplicable + ); + } } // Rewrap `db`, and pass control to the user. decorate(db) diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs index 96c31a90da8..0aa37642b74 100644 --- a/compiler/rustc_lint_defs/src/builtin.rs +++ b/compiler/rustc_lint_defs/src/builtin.rs @@ -3376,6 +3376,7 @@ DEPRECATED_IN_FUTURE, DEPRECATED_WHERE_CLAUSE_LOCATION, DUPLICATE_MACRO_ATTRIBUTES, + ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT, ELIDED_LIFETIMES_IN_PATHS, EXPORTED_PRIVATE_DEPENDENCIES, FFI_UNWIND_CALLS, @@ -4527,3 +4528,44 @@ reference: "issue #114095 ", }; } + +declare_lint! { + /// The `elided_lifetimes_in_associated_constant` lint detects elided lifetimes + /// that were erroneously allowed in associated constants. + /// + /// ### Example + /// + /// ```rust,compile_fail + /// #![deny(elided_lifetimes_in_associated_constant)] + /// + /// struct Foo; + /// + /// impl Foo { + /// const STR: &str = "hello, world"; + /// } + /// ``` + /// + /// {{produces}} + /// + /// ### Explanation + /// + /// Previous version of Rust + /// + /// Implicit static-in-const behavior was decided [against] for associated + /// constants because of ambiguity. This, however, regressed and the compiler + /// erroneously treats elided lifetimes in associated constants as lifetime + /// parameters on the impl. + /// + /// This is a [future-incompatible] lint to transition this to a + /// hard error in the future. + /// + /// [against]: https://github.com/rust-lang/rust/issues/38831 + /// [future-incompatible]: ../index.md#future-incompatible-lints + pub ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT, + Warn, + "elided lifetimes cannot be used in associated constants in impls", + @future_incompatible = FutureIncompatibleInfo { + reason: FutureIncompatibilityReason::FutureReleaseError, + reference: "issue #115010 ", + }; +} diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs index f350957f72f..d68d0847254 100644 --- a/compiler/rustc_lint_defs/src/lib.rs +++ b/compiler/rustc_lint_defs/src/lib.rs @@ -572,6 +572,10 @@ pub enum BuiltinLintDiagnostics { /// The span of the unnecessarily-qualified path to remove. removal_span: Span, }, + AssociatedConstElidedLifetime { + elided: bool, + span: Span, + }, } /// Lints that are buffered up early on in the `Session` before the diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs index c87db96a5dd..22d084c8e0b 100644 --- a/compiler/rustc_resolve/src/late.rs +++ b/compiler/rustc_resolve/src/late.rs @@ -311,6 +311,10 @@ enum LifetimeRibKind { /// error on default object bounds (e.g., `Box`). AnonymousReportError, + /// Resolves elided lifetimes to `'static`, but gives a warning that this behavior + /// is a bug and will be reverted soon. + AnonymousWarnToStatic(NodeId), + /// Signal we cannot find which should be the anonymous lifetime. ElisionFailure, @@ -1148,6 +1152,7 @@ fn visit_path_segment(&mut self, path_segment: &'ast PathSegment) { } LifetimeRibKind::AnonymousCreateParameter { .. } | LifetimeRibKind::AnonymousReportError + | LifetimeRibKind::AnonymousWarnToStatic(_) | LifetimeRibKind::Elided(_) | LifetimeRibKind::ElisionFailure | LifetimeRibKind::ConcreteAnonConst(_) @@ -1515,6 +1520,7 @@ fn resolve_lifetime(&mut self, lifetime: &'ast Lifetime, use_ctxt: visit::Lifeti // lifetime would be illegal. LifetimeRibKind::Item | LifetimeRibKind::AnonymousReportError + | LifetimeRibKind::AnonymousWarnToStatic(_) | LifetimeRibKind::ElisionFailure => Some(LifetimeUseSet::Many), // An anonymous lifetime is legal here, and bound to the right // place, go ahead. @@ -1576,7 +1582,8 @@ fn resolve_lifetime(&mut self, lifetime: &'ast Lifetime, use_ctxt: visit::Lifeti | LifetimeRibKind::Elided(_) | LifetimeRibKind::Generics { .. } | LifetimeRibKind::ElisionFailure - | LifetimeRibKind::AnonymousReportError => {} + | LifetimeRibKind::AnonymousReportError + | LifetimeRibKind::AnonymousWarnToStatic(_) => {} } } @@ -1616,6 +1623,25 @@ fn resolve_anonymous_lifetime(&mut self, lifetime: &Lifetime, elided: bool) { self.record_lifetime_res(lifetime.id, res, elision_candidate); return; } + LifetimeRibKind::AnonymousWarnToStatic(node_id) => { + self.record_lifetime_res(lifetime.id, LifetimeRes::Static, elision_candidate); + let msg = if elided { + "`&` without an explicit lifetime name cannot be used here" + } else { + "`'_` cannot be used here" + }; + self.r.lint_buffer.buffer_lint_with_diagnostic( + lint::builtin::ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT, + node_id, + lifetime.ident.span, + msg, + lint::BuiltinLintDiagnostics::AssociatedConstElidedLifetime { + elided, + span: lifetime.ident.span, + }, + ); + return; + } LifetimeRibKind::AnonymousReportError => { let (msg, note) = if elided { ( @@ -1811,7 +1837,8 @@ fn resolve_elided_lifetimes_in_path( // // impl Foo for std::cell::Ref // note lack of '_ // async fn foo(_: std::cell::Ref) { ... } - LifetimeRibKind::AnonymousCreateParameter { report_in_path: true, .. } => { + LifetimeRibKind::AnonymousCreateParameter { report_in_path: true, .. } + | LifetimeRibKind::AnonymousWarnToStatic(_) => { let sess = self.r.tcx.sess; let mut err = rustc_errors::struct_span_err!( sess, @@ -2898,7 +2925,6 @@ fn resolve_impl_item( match &item.kind { AssocItemKind::Const(box ast::ConstItem { generics, ty, expr, .. }) => { debug!("resolve_implementation AssocItemKind::Const"); - self.with_generic_param_rib( &generics.params, RibKind::AssocItem, @@ -2908,28 +2934,33 @@ fn resolve_impl_item( kind: LifetimeBinderKind::ConstItem, }, |this| { - // If this is a trait impl, ensure the const - // exists in trait - this.check_trait_item( - item.id, - item.ident, - &item.kind, - ValueNS, - item.span, - seen_trait_items, - |i, s, c| ConstNotMemberOfTrait(i, s, c), - ); + this.with_lifetime_rib( + LifetimeRibKind::AnonymousWarnToStatic(item.id), + |this| { + // If this is a trait impl, ensure the const + // exists in trait + this.check_trait_item( + item.id, + item.ident, + &item.kind, + ValueNS, + item.span, + seen_trait_items, + |i, s, c| ConstNotMemberOfTrait(i, s, c), + ); - this.visit_generics(generics); - this.visit_ty(ty); - if let Some(expr) = expr { - // We allow arbitrary const expressions inside of associated consts, - // even if they are potentially not const evaluatable. - // - // Type parameters can already be used and as associated consts are - // not used as part of the type system, this is far less surprising. - this.resolve_const_body(expr, None); - } + this.visit_generics(generics); + this.visit_ty(ty); + if let Some(expr) = expr { + // We allow arbitrary const expressions inside of associated consts, + // even if they are potentially not const evaluatable. + // + // Type parameters can already be used and as associated consts are + // not used as part of the type system, this is far less surprising. + this.resolve_const_body(expr, None); + } + }, + ); }, ); } diff --git a/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.rs b/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.rs index 40896c32e11..1e0b77b0d3b 100644 --- a/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.rs +++ b/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.rs @@ -5,6 +5,8 @@ trait Trait { impl Trait for () { const ASSOC: &dyn Fn(_) = 1i32; //~^ ERROR the placeholder `_` is not allowed within types on item signatures for associated constants + //~| WARN `&` without an explicit lifetime name cannot be used here + //~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! } fn main() {} diff --git a/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.stderr b/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.stderr index 993a08faba9..f8c02420f96 100644 --- a/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.stderr +++ b/tests/ui/associated-consts/infer-placeholder-in-non-suggestable-pos.stderr @@ -1,9 +1,23 @@ +warning: `&` without an explicit lifetime name cannot be used here + --> $DIR/infer-placeholder-in-non-suggestable-pos.rs:6:18 + | +LL | const ASSOC: &dyn Fn(_) = 1i32; + | ^ + | + = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! + = note: for more information, see issue #115010 + = note: `#[warn(elided_lifetimes_in_associated_constant)]` on by default +help: use the `'static` lifetime + | +LL | const ASSOC: &'static dyn Fn(_) = 1i32; + | +++++++ + error[E0121]: the placeholder `_` is not allowed within types on item signatures for associated constants --> $DIR/infer-placeholder-in-non-suggestable-pos.rs:6:26 | LL | const ASSOC: &dyn Fn(_) = 1i32; | ^ not allowed in type signatures -error: aborting due to previous error +error: aborting due to previous error; 1 warning emitted For more information about this error, try `rustc --explain E0121`. diff --git a/tests/ui/consts/assoc-const-elided-lifetime.rs b/tests/ui/consts/assoc-const-elided-lifetime.rs new file mode 100644 index 00000000000..10cd33a8fed --- /dev/null +++ b/tests/ui/consts/assoc-const-elided-lifetime.rs @@ -0,0 +1,19 @@ +#![deny(elided_lifetimes_in_associated_constant)] + +use std::marker::PhantomData; + +struct Foo<'a> { + x: PhantomData<&'a ()>, +} + +impl<'a> Foo<'a> { + const FOO: Foo<'_> = Foo { x: PhantomData::<&()> }; + //~^ ERROR `'_` cannot be used here + //~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! + + const BAR: &() = &(); + //~^ ERROR `&` without an explicit lifetime name cannot be used here + //~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! +} + +fn main() {} diff --git a/tests/ui/consts/assoc-const-elided-lifetime.stderr b/tests/ui/consts/assoc-const-elided-lifetime.stderr new file mode 100644 index 00000000000..a1eeaff4ba8 --- /dev/null +++ b/tests/ui/consts/assoc-const-elided-lifetime.stderr @@ -0,0 +1,33 @@ +error: `'_` cannot be used here + --> $DIR/assoc-const-elided-lifetime.rs:10:20 + | +LL | const FOO: Foo<'_> = Foo { x: PhantomData::<&()> }; + | ^^ + | + = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! + = note: for more information, see issue #115010 +note: the lint level is defined here + --> $DIR/assoc-const-elided-lifetime.rs:1:9 + | +LL | #![deny(elided_lifetimes_in_associated_constant)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +help: use the `'static` lifetime + | +LL | const FOO: Foo<'static> = Foo { x: PhantomData::<&()> }; + | ~~~~~~~ + +error: `&` without an explicit lifetime name cannot be used here + --> $DIR/assoc-const-elided-lifetime.rs:14:16 + | +LL | const BAR: &() = &(); + | ^ + | + = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! + = note: for more information, see issue #115010 +help: use the `'static` lifetime + | +LL | const BAR: &'static () = &(); + | +++++++ + +error: aborting due to 2 previous errors +