diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs index fb3e9cb1263..833402abfc4 100644 --- a/compiler/rustc_middle/src/traits/mod.rs +++ b/compiler/rustc_middle/src/traits/mod.rs @@ -897,6 +897,9 @@ pub enum ObjectSafetyViolation { /// (e.g., `trait Foo : Bar`). SupertraitSelf(SmallVec<[Span; 1]>), + // Supertrait has a non-lifetime `for` binder. + SupertraitNonLifetimeBinder(SmallVec<[Span; 1]>), + /// Method has something illegal. Method(Symbol, MethodViolationCode, Span), @@ -919,6 +922,9 @@ pub fn error_msg(&self) -> Cow<'static, str> { .into() } } + ObjectSafetyViolation::SupertraitNonLifetimeBinder(_) => { + format!("where clause cannot reference non-lifetime `for<...>` variables").into() + } ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(_), _) => { format!("associated function `{}` has no `self` parameter", name).into() } @@ -969,7 +975,9 @@ pub fn error_msg(&self) -> Cow<'static, str> { pub fn solution(&self, err: &mut Diagnostic) { match self { - ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf(_) => {} + ObjectSafetyViolation::SizedSelf(_) + | ObjectSafetyViolation::SupertraitSelf(_) + | ObjectSafetyViolation::SupertraitNonLifetimeBinder(..) => {} ObjectSafetyViolation::Method( name, MethodViolationCode::StaticMethod(Some((add_self_sugg, make_sized_sugg))), @@ -1023,7 +1031,8 @@ trait objects", // diagnostics use a `note` instead of a `span_label`. match self { ObjectSafetyViolation::SupertraitSelf(spans) - | ObjectSafetyViolation::SizedSelf(spans) => spans.clone(), + | ObjectSafetyViolation::SizedSelf(spans) + | ObjectSafetyViolation::SupertraitNonLifetimeBinder(spans) => spans.clone(), ObjectSafetyViolation::AssocConst(_, span) | ObjectSafetyViolation::GAT(_, span) | ObjectSafetyViolation::Method(_, _, span) diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs index a5def4151bf..038f8964471 100644 --- a/compiler/rustc_trait_selection/src/traits/object_safety.rs +++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs @@ -17,10 +17,10 @@ use rustc_hir as hir; use rustc_hir::def_id::DefId; use rustc_middle::ty::subst::{GenericArg, InternalSubsts}; -use rustc_middle::ty::ToPredicate; use rustc_middle::ty::{ self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, }; +use rustc_middle::ty::{ToPredicate, TypeVisitableExt}; use rustc_session::lint::builtin::WHERE_CLAUSES_OBJECT_SAFETY; use rustc_span::symbol::Symbol; use rustc_span::Span; @@ -139,6 +139,10 @@ fn object_safety_violations_for_trait( if !spans.is_empty() { violations.push(ObjectSafetyViolation::SupertraitSelf(spans)); } + let spans = super_predicates_have_non_lifetime_binders(tcx, trait_def_id); + if !spans.is_empty() { + violations.push(ObjectSafetyViolation::SupertraitNonLifetimeBinder(spans)); + } violations.extend( tcx.associated_items(trait_def_id) @@ -348,6 +352,21 @@ fn predicate_references_self<'tcx>( } } +fn super_predicates_have_non_lifetime_binders( + tcx: TyCtxt<'_>, + trait_def_id: DefId, +) -> SmallVec<[Span; 1]> { + // If non_lifetime_binders is disabled, then exit early + if !tcx.features().non_lifetime_binders { + return SmallVec::new(); + } + tcx.super_predicates_of(trait_def_id) + .predicates + .iter() + .filter_map(|(pred, span)| pred.has_non_region_late_bound().then_some(*span)) + .collect() +} + fn trait_has_sized_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool { generics_require_sized_self(tcx, trait_def_id) } diff --git a/tests/ui/traits/non_lifetime_binders/supertrait-object-safety.rs b/tests/ui/traits/non_lifetime_binders/supertrait-object-safety.rs new file mode 100644 index 00000000000..a635edb4485 --- /dev/null +++ b/tests/ui/traits/non_lifetime_binders/supertrait-object-safety.rs @@ -0,0 +1,24 @@ +#![feature(non_lifetime_binders)] +//~^ WARN the feature `non_lifetime_binders` is incomplete + +trait Foo: for Bar {} + +trait Bar { + fn method(&self) {} +} + +fn needs_bar(x: &(impl Bar + ?Sized)) { + x.method(); +} + +impl Foo for () {} + +impl Bar for () {} + +fn main() { + let x: &dyn Foo = &(); + //~^ ERROR the trait `Foo` cannot be made into an object + //~| ERROR the trait `Foo` cannot be made into an object + needs_bar(x); + //~^ ERROR the trait `Foo` cannot be made into an object +} diff --git a/tests/ui/traits/non_lifetime_binders/supertrait-object-safety.stderr b/tests/ui/traits/non_lifetime_binders/supertrait-object-safety.stderr new file mode 100644 index 00000000000..47fa29b6648 --- /dev/null +++ b/tests/ui/traits/non_lifetime_binders/supertrait-object-safety.stderr @@ -0,0 +1,56 @@ +warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes + --> $DIR/supertrait-object-safety.rs:1:12 + | +LL | #![feature(non_lifetime_binders)] + | ^^^^^^^^^^^^^^^^^^^^ + | + = note: see issue #108185 for more information + = note: `#[warn(incomplete_features)]` on by default + +error[E0038]: the trait `Foo` cannot be made into an object + --> $DIR/supertrait-object-safety.rs:19:23 + | +LL | let x: &dyn Foo = &(); + | ^^^ `Foo` cannot be made into an object + | +note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit + --> $DIR/supertrait-object-safety.rs:4:12 + | +LL | trait Foo: for Bar {} + | --- ^^^^^^^^^^^^^ ...because where clause cannot reference non-lifetime `for<...>` variables + | | + | this trait cannot be made into an object... + = note: required for `&()` to implement `CoerceUnsized<&dyn Foo>` + = note: required by cast to type `&dyn Foo` + +error[E0038]: the trait `Foo` cannot be made into an object + --> $DIR/supertrait-object-safety.rs:19:12 + | +LL | let x: &dyn Foo = &(); + | ^^^^^^^^ `Foo` cannot be made into an object + | +note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit + --> $DIR/supertrait-object-safety.rs:4:12 + | +LL | trait Foo: for Bar {} + | --- ^^^^^^^^^^^^^ ...because where clause cannot reference non-lifetime `for<...>` variables + | | + | this trait cannot be made into an object... + +error[E0038]: the trait `Foo` cannot be made into an object + --> $DIR/supertrait-object-safety.rs:22:5 + | +LL | needs_bar(x); + | ^^^^^^^^^ `Foo` cannot be made into an object + | +note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit + --> $DIR/supertrait-object-safety.rs:4:12 + | +LL | trait Foo: for Bar {} + | --- ^^^^^^^^^^^^^ ...because where clause cannot reference non-lifetime `for<...>` variables + | | + | this trait cannot be made into an object... + +error: aborting due to 3 previous errors; 1 warning emitted + +For more information about this error, try `rustc --explain E0038`.