) -> Vec<ObjectSafetyViolation> {
debug_assert!(self.generics_of(trait_def_id).has_self);
let violations = traits::supertrait_def_ids(self, trait_def_id)
- .filter(|&def_id| self.predicates_reference_self(def_id, true))
+ .filter(|&def_id| predicates_reference_self(self, def_id, true))
.map(|_| ObjectSafetyViolation::SupertraitSelf)
.collect();
debug!("object_safety_violations: {:?}", trait_def_id);
traits::supertrait_def_ids(self, trait_def_id)
- .flat_map(|def_id| self.object_safety_violations_for_trait(def_id))
+ .flat_map(|def_id| object_safety_violations_for_trait(self, def_id))
.collect()
}
debug_assert!(self.generics_of(trait_def_id).has_self);
debug!("is_vtable_safe_method({:?}, {:?})", trait_def_id, method);
// Any method that has a `Self: Sized` bound cannot be called.
- if self.generics_require_sized_self(method.def_id) {
+ if generics_require_sized_self(self, method.def_id) {
return false;
}
- match self.virtual_call_violation_for_method(trait_def_id, method) {
+ match virtual_call_violation_for_method(self, trait_def_id, method) {
None | Some(MethodViolationCode::WhereClauseReferencesSelf) => true,
Some(_) => false,
}
}
+}
- fn object_safety_violations_for_trait(self, trait_def_id: DefId) -> Vec<ObjectSafetyViolation> {
- // Check methods for violations.
- let mut violations: Vec<_> = self
- .associated_items(trait_def_id)
- .filter(|item| item.kind == ty::AssocKind::Method)
- .filter_map(|item| {
- self.object_safety_violation_for_method(trait_def_id, &item).map(|code| {
- ObjectSafetyViolation::Method(item.ident.name, code, item.ident.span)
- })
- })
- .filter(|violation| {
- if let ObjectSafetyViolation::Method(
- _,
- MethodViolationCode::WhereClauseReferencesSelf,
- span,
- ) = violation
- {
- // Using `CRATE_NODE_ID` is wrong, but it's hard to get a more precise id.
- // It's also hard to get a use site span, so we use the method definition span.
- self.lint_node_note(
- lint::builtin::WHERE_CLAUSES_OBJECT_SAFETY,
- hir::CRATE_HIR_ID,
- *span,
- &format!(
- "the trait `{}` cannot be made into an object",
- self.def_path_str(trait_def_id)
- ),
- &violation.error_msg(),
- );
- false
- } else {
- true
- }
- })
- .collect();
-
- // Check the trait itself.
- if self.trait_has_sized_self(trait_def_id) {
- violations.push(ObjectSafetyViolation::SizedSelf);
- }
- if self.predicates_reference_self(trait_def_id, false) {
- violations.push(ObjectSafetyViolation::SupertraitSelf);
- }
-
- violations.extend(
- self.associated_items(trait_def_id)
- .filter(|item| item.kind == ty::AssocKind::Const)
- .map(|item| ObjectSafetyViolation::AssocConst(item.ident.name, item.ident.span)),
- );
-
- debug!(
- "object_safety_violations_for_trait(trait_def_id={:?}) = {:?}",
- trait_def_id, violations
- );
+fn object_safety_violations_for_trait(
+ tcx: TyCtxt<'_>,
+ trait_def_id: DefId,
+) -> Vec<ObjectSafetyViolation> {
+ // Check methods for violations.
+ let mut violations: Vec<_> = tcx
+ .associated_items(trait_def_id)
+ .filter(|item| item.kind == ty::AssocKind::Method)
+ .filter_map(|item| {
+ object_safety_violation_for_method(tcx, trait_def_id, &item)
+ .map(|code| ObjectSafetyViolation::Method(item.ident.name, code, item.ident.span))
+ })
+ .filter(|violation| {
+ if let ObjectSafetyViolation::Method(
+ _,
+ MethodViolationCode::WhereClauseReferencesSelf,
+ span,
+ ) = violation
+ {
+ // Using `CRATE_NODE_ID` is wrong, but it's hard to get a more precise id.
+ // It's also hard to get a use site span, so we use the method definition span.
+ tcx.lint_node_note(
+ lint::builtin::WHERE_CLAUSES_OBJECT_SAFETY,
+ hir::CRATE_HIR_ID,
+ *span,
+ &format!(
+ "the trait `{}` cannot be made into an object",
+ tcx.def_path_str(trait_def_id)
+ ),
+ &violation.error_msg(),
+ );
+ false
+ } else {
+ true
+ }
+ })
+ .collect();
- violations
+ // Check the trait itself.
+ if trait_has_sized_self(tcx, trait_def_id) {
+ violations.push(ObjectSafetyViolation::SizedSelf);
}
-
- fn predicates_reference_self(self, trait_def_id: DefId, supertraits_only: bool) -> bool {
- let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(self, trait_def_id));
- let predicates = if supertraits_only {
- self.super_predicates_of(trait_def_id)
- } else {
- self.predicates_of(trait_def_id)
- };
- let self_ty = self.types.self_param;
- let has_self_ty = |t: Ty<'tcx>| t.walk().any(|t| t == self_ty);
- predicates
- .predicates
- .iter()
- .map(|(predicate, _)| predicate.subst_supertrait(self, &trait_ref))
- .any(|predicate| {
- match predicate {
- ty::Predicate::Trait(ref data) => {
- // In the case of a trait predicate, we can skip the "self" type.
- data.skip_binder().input_types().skip(1).any(has_self_ty)
- }
- ty::Predicate::Projection(ref data) => {
- // And similarly for projections. This should be redundant with
- // the previous check because any projection should have a
- // matching `Trait` predicate with the same inputs, but we do
- // the check to be safe.
- //
- // Note that we *do* allow projection *outputs* to contain
- // `self` (i.e., `trait Foo: Bar<Output=Self::Result> { type Result; }`),
- // we just require the user to specify *both* outputs
- // in the object type (i.e., `dyn Foo<Output=(), Result=()>`).
- //
- // This is ALT2 in issue #56288, see that for discussion of the
- // possible alternatives.
- data.skip_binder()
- .projection_ty
- .trait_ref(self)
- .input_types()
- .skip(1)
- .any(has_self_ty)
- }
- ty::Predicate::WellFormed(..)
- | ty::Predicate::ObjectSafe(..)
- | ty::Predicate::TypeOutlives(..)
- | ty::Predicate::RegionOutlives(..)
- | ty::Predicate::ClosureKind(..)
- | ty::Predicate::Subtype(..)
- | ty::Predicate::ConstEvaluatable(..) => false,
- }
- })
+ if predicates_reference_self(tcx, trait_def_id, false) {
+ violations.push(ObjectSafetyViolation::SupertraitSelf);
}
- fn trait_has_sized_self(self, trait_def_id: DefId) -> bool {
- self.generics_require_sized_self(trait_def_id)
- }
+ violations.extend(
+ tcx.associated_items(trait_def_id)
+ .filter(|item| item.kind == ty::AssocKind::Const)
+ .map(|item| ObjectSafetyViolation::AssocConst(item.ident.name, item.ident.span)),
+ );
- fn generics_require_sized_self(self, def_id: DefId) -> bool {
- let sized_def_id = match self.lang_items().sized_trait() {
- Some(def_id) => def_id,
- None => {
- return false; /* No Sized trait, can't require it! */
- }
- };
+ debug!(
+ "object_safety_violations_for_trait(trait_def_id={:?}) = {:?}",
+ trait_def_id, violations
+ );
- // Search for a predicate like `Self : Sized` amongst the trait bounds.
- let predicates = self.predicates_of(def_id);
- let predicates = predicates.instantiate_identity(self).predicates;
- elaborate_predicates(self, predicates).any(|predicate| match predicate {
- ty::Predicate::Trait(ref trait_pred) => {
- trait_pred.def_id() == sized_def_id
- && trait_pred.skip_binder().self_ty().is_param(0)
+ violations
+}
+
+fn predicates_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId, supertraits_only: bool) -> bool {
+ let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(tcx, trait_def_id));
+ let predicates = if supertraits_only {
+ tcx.super_predicates_of(trait_def_id)
+ } else {
+ tcx.predicates_of(trait_def_id)
+ };
+ let self_ty = tcx.types.self_param;
+ let has_self_ty = |t: Ty<'_>| t.walk().any(|t| t == self_ty);
+ predicates
+ .predicates
+ .iter()
+ .map(|(predicate, _)| predicate.subst_supertrait(tcx, &trait_ref))
+ .any(|predicate| {
+ match predicate {
+ ty::Predicate::Trait(ref data) => {
+ // In the case of a trait predicate, we can skip the "self" type.
+ data.skip_binder().input_types().skip(1).any(has_self_ty)
+ }
+ ty::Predicate::Projection(ref data) => {
+ // And similarly for projections. This should be redundant with
+ // the previous check because any projection should have a
+ // matching `Trait` predicate with the same inputs, but we do
+ // the check to be safe.
+ //
+ // Note that we *do* allow projection *outputs* to contain
+ // `self` (i.e., `trait Foo: Bar<Output=Self::Result> { type Result; }`),
+ // we just require the user to specify *both* outputs
+ // in the object type (i.e., `dyn Foo<Output=(), Result=()>`).
+ //
+ // This is ALT2 in issue #56288, see that for discussion of the
+ // possible alternatives.
+ data.skip_binder()
+ .projection_ty
+ .trait_ref(tcx)
+ .input_types()
+ .skip(1)
+ .any(has_self_ty)
+ }
+ ty::Predicate::WellFormed(..)
+ | ty::Predicate::ObjectSafe(..)
+ | ty::Predicate::TypeOutlives(..)
+ | ty::Predicate::RegionOutlives(..)
+ | ty::Predicate::ClosureKind(..)
+ | ty::Predicate::Subtype(..)
+ | ty::Predicate::ConstEvaluatable(..) => false,
}
- ty::Predicate::Projection(..)
- | ty::Predicate::Subtype(..)
- | ty::Predicate::RegionOutlives(..)
- | ty::Predicate::WellFormed(..)
- | ty::Predicate::ObjectSafe(..)
- | ty::Predicate::ClosureKind(..)
- | ty::Predicate::TypeOutlives(..)
- | ty::Predicate::ConstEvaluatable(..) => false,
})
- }
+}
- /// Returns `Some(_)` if this method makes the containing trait not object safe.
- fn object_safety_violation_for_method(
- self,
- trait_def_id: DefId,
- method: &ty::AssocItem,
- ) -> Option<MethodViolationCode> {
- debug!("object_safety_violation_for_method({:?}, {:?})", trait_def_id, method);
- // Any method that has a `Self : Sized` requisite is otherwise
- // exempt from the regulations.
- if self.generics_require_sized_self(method.def_id) {
- return None;
+fn trait_has_sized_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool {
+ generics_require_sized_self(tcx, trait_def_id)
+}
+
+fn generics_require_sized_self(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
+ let sized_def_id = match tcx.lang_items().sized_trait() {
+ Some(def_id) => def_id,
+ None => {
+ return false; /* No Sized trait, can't require it! */
+ }
+ };
+
+ // Search for a predicate like `Self : Sized` amongst the trait bounds.
+ let predicates = tcx.predicates_of(def_id);
+ let predicates = predicates.instantiate_identity(tcx).predicates;
+ elaborate_predicates(tcx, predicates).any(|predicate| match predicate {
+ ty::Predicate::Trait(ref trait_pred) => {
+ trait_pred.def_id() == sized_def_id && trait_pred.skip_binder().self_ty().is_param(0)
}
+ ty::Predicate::Projection(..)
+ | ty::Predicate::Subtype(..)
+ | ty::Predicate::RegionOutlives(..)
+ | ty::Predicate::WellFormed(..)
+ | ty::Predicate::ObjectSafe(..)
+ | ty::Predicate::ClosureKind(..)
+ | ty::Predicate::TypeOutlives(..)
+ | ty::Predicate::ConstEvaluatable(..) => false,
+ })
+}
- self.virtual_call_violation_for_method(trait_def_id, method)
+/// Returns `Some(_)` if this method makes the containing trait not object safe.
+fn object_safety_violation_for_method(
+ tcx: TyCtxt<'_>,
+ trait_def_id: DefId,
+ method: &ty::AssocItem,
+) -> Option<MethodViolationCode> {
+ debug!("object_safety_violation_for_method({:?}, {:?})", trait_def_id, method);
+ // Any method that has a `Self : Sized` requisite is otherwise
+ // exempt from the regulations.
+ if generics_require_sized_self(tcx, method.def_id) {
+ return None;
}
- /// Returns `Some(_)` if this method cannot be called on a trait
- /// object; this does not necessarily imply that the enclosing trait
- /// is not object safe, because the method might have a where clause
- /// `Self:Sized`.
- fn virtual_call_violation_for_method(
- self,
- trait_def_id: DefId,
- method: &ty::AssocItem,
- ) -> Option<MethodViolationCode> {
- // The method's first parameter must be named `self`
- if !method.method_has_self_argument {
- return Some(MethodViolationCode::StaticMethod);
- }
+ virtual_call_violation_for_method(tcx, trait_def_id, method)
+}
- let sig = self.fn_sig(method.def_id);
+/// Returns `Some(_)` if this method cannot be called on a trait
+/// object; this does not necessarily imply that the enclosing trait
+/// is not object safe, because the method might have a where clause
+/// `Self:Sized`.
+fn virtual_call_violation_for_method<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ trait_def_id: DefId,
+ method: &ty::AssocItem,
+) -> Option<MethodViolationCode> {
+ // The method's first parameter must be named `self`
+ if !method.method_has_self_argument {
+ return Some(MethodViolationCode::StaticMethod);
+ }
- for input_ty in &sig.skip_binder().inputs()[1..] {
- if self.contains_illegal_self_type_reference(trait_def_id, input_ty) {
- return Some(MethodViolationCode::ReferencesSelf);
- }
- }
- if self.contains_illegal_self_type_reference(trait_def_id, sig.output().skip_binder()) {
+ let sig = tcx.fn_sig(method.def_id);
+
+ for input_ty in &sig.skip_binder().inputs()[1..] {
+ if contains_illegal_self_type_reference(tcx, trait_def_id, input_ty) {
return Some(MethodViolationCode::ReferencesSelf);
}
+ }
+ if contains_illegal_self_type_reference(tcx, trait_def_id, sig.output().skip_binder()) {
+ return Some(MethodViolationCode::ReferencesSelf);
+ }
-
// We can't monomorphize things like `fn foo<A>(...)`.
- let own_counts = self.generics_of(method.def_id).own_counts();
- if own_counts.types + own_counts.consts != 0 {
- return Some(MethodViolationCode::Generic);
- }
+ // We can't monomorphize things like `fn foo<A>(...)`.
+ let own_counts = tcx.generics_of(method.def_id).own_counts();
+ if own_counts.types + own_counts.consts != 0 {
+ return Some(MethodViolationCode::Generic);
+ }
- if self
- .predicates_of(method.def_id)
- .predicates
- .iter()
- // A trait object can't claim to live more than the concrete type,
- // so outlives predicates will always hold.
- .cloned()
- .filter(|(p, _)| p.to_opt_type_outlives().is_none())
- .collect::<Vec<_>>()
- // Do a shallow visit so that `contains_illegal_self_type_reference`
- // may apply it's custom visiting.
- .visit_tys_shallow(|t| self.contains_illegal_self_type_reference(trait_def_id, t))
- {
- return Some(MethodViolationCode::WhereClauseReferencesSelf);
- }
+ if tcx
+ .predicates_of(method.def_id)
+ .predicates
+ .iter()
+ // A trait object can't claim to live more than the concrete type,
+ // so outlives predicates will always hold.
+ .cloned()
+ .filter(|(p, _)| p.to_opt_type_outlives().is_none())
+ .collect::<Vec<_>>()
+ // Do a shallow visit so that `contains_illegal_self_type_reference`
+ // may apply it's custom visiting.
+ .visit_tys_shallow(|t| contains_illegal_self_type_reference(tcx, trait_def_id, t))
+ {
+ return Some(MethodViolationCode::WhereClauseReferencesSelf);
+ }
- let receiver_ty =
- self.liberate_late_bound_regions(method.def_id, &sig.map_bound(|sig| sig.inputs()[0]));
+ let receiver_ty =
+ tcx.liberate_late_bound_regions(method.def_id, &sig.map_bound(|sig| sig.inputs()[0]));
- // Until `unsized_locals` is fully implemented, `self: Self` can't be dispatched on.
- // However, this is already considered object-safe. We allow it as a special case here.
- // FIXME(mikeyhew) get rid of this `if` statement once `receiver_is_dispatchable` allows
- // `Receiver: Unsize<Receiver[Self => dyn Trait]>`.
- if receiver_ty != self.types.self_param {
- if !self.receiver_is_dispatchable(method, receiver_ty) {
- return Some(MethodViolationCode::UndispatchableReceiver);
- } else {
- // Do sanity check to make sure the receiver actually has the layout of a pointer.
+ // Until `unsized_locals` is fully implemented, `self: Self` can't be dispatched on.
+ // However, this is already considered object-safe. We allow it as a special case here.
+ // FIXME(mikeyhew) get rid of this `if` statement once `receiver_is_dispatchable` allows
+ // `Receiver: Unsize<Receiver[Self => dyn Trait]>`.
+ if receiver_ty != tcx.types.self_param {
+ if !receiver_is_dispatchable(tcx, method, receiver_ty) {
+ return Some(MethodViolationCode::UndispatchableReceiver);
+ } else {
+ // Do sanity check to make sure the receiver actually has the layout of a pointer.
- use crate::ty::layout::Abi;
+ use crate::ty::layout::Abi;
- let param_env = self.param_env(method.def_id);
+ let param_env = tcx.param_env(method.def_id);
- let abi_of_ty = |ty: Ty<'tcx>| -> &Abi {
- match self.layout_of(param_env.and(ty)) {
- Ok(layout) => &layout.abi,
- Err(err) => {
- bug!("error: {}\n while computing layout for type {:?}", err, ty)
- }
- }
- };
-
- // e.g., `Rc<()>`
- let unit_receiver_ty =
- self.receiver_for_self_ty(receiver_ty, self.mk_unit(), method.def_id);
-
- match abi_of_ty(unit_receiver_ty) {
- &Abi::Scalar(..) => (),
- abi => {
- self.sess.delay_span_bug(
- self.def_span(method.def_id),
- &format!(
- "receiver when `Self = ()` should have a Scalar ABI; found {:?}",
- abi
- ),
- );
- }
+ let abi_of_ty = |ty: Ty<'tcx>| -> &Abi {
+ match tcx.layout_of(param_env.and(ty)) {
+ Ok(layout) => &layout.abi,
+ Err(err) => bug!("error: {}\n while computing layout for type {:?}", err, ty),
+ }
+ };
+
+ // e.g., `Rc<()>`
+ let unit_receiver_ty =
+ receiver_for_self_ty(tcx, receiver_ty, tcx.mk_unit(), method.def_id);
+
+ match abi_of_ty(unit_receiver_ty) {
+ &Abi::Scalar(..) => (),
+ abi => {
+ tcx.sess.delay_span_bug(
+ tcx.def_span(method.def_id),
+ &format!(
+ "receiver when `Self = ()` should have a Scalar ABI; found {:?}",
+ abi
+ ),
+ );
}
+ }
- let trait_object_ty =
- self.object_ty_for_trait(trait_def_id, self.mk_region(ty::ReStatic));
+ let trait_object_ty =
+ object_ty_for_trait(tcx, trait_def_id, tcx.mk_region(ty::ReStatic));
- // e.g., `Rc<dyn Trait>`
- let trait_object_receiver =
- self.receiver_for_self_ty(receiver_ty, trait_object_ty, method.def_id);
+ // e.g., `Rc<dyn Trait>`
+ let trait_object_receiver =
+ receiver_for_self_ty(tcx, receiver_ty, trait_object_ty, method.def_id);
- match abi_of_ty(trait_object_receiver) {
- &Abi::ScalarPair(..) => (),
- abi => {
- self.sess.delay_span_bug(
- self.def_span(method.def_id),
- &format!(
- "receiver when `Self = {}` should have a ScalarPair ABI; \
+ match abi_of_ty(trait_object_receiver) {
+ &Abi::ScalarPair(..) => (),
+ abi => {
+ tcx.sess.delay_span_bug(
+ tcx.def_span(method.def_id),
+ &format!(
+ "receiver when `Self = {}` should have a ScalarPair ABI; \
found {:?}",
- trait_object_ty, abi
- ),
- );
- }
+ trait_object_ty, abi
+ ),
+ );
}
}
}
-
- None
}
- /// Performs a type substitution to produce the version of `receiver_ty` when `Self = self_ty`.
- /// For example, for `receiver_ty = Rc<Self>` and `self_ty = Foo`, returns `Rc<Foo>`.
- fn receiver_for_self_ty(
- self,
- receiver_ty: Ty<'tcx>,
- self_ty: Ty<'tcx>,
- method_def_id: DefId,
- ) -> Ty<'tcx> {
- debug!("receiver_for_self_ty({:?}, {:?}, {:?})", receiver_ty, self_ty, method_def_id);
- let substs = InternalSubsts::for_item(self, method_def_id, |param, _| {
- if param.index == 0 { self_ty.into() } else { self.mk_param_from_def(param) }
- });
-
- let result = receiver_ty.subst(self, substs);
- debug!(
- "receiver_for_self_ty({:?}, {:?}, {:?}) = {:?}",
- receiver_ty, self_ty, method_def_id, result
- );
- result
- }
+ None
+}
- /// Creates the object type for the current trait. For example,
- /// if the current trait is `Deref`, then this will be
- /// `dyn Deref<Target = Self::Target> + 'static`.
- fn object_ty_for_trait(self, trait_def_id: DefId, lifetime: ty::Region<'tcx>) -> Ty<'tcx> {
- debug!("object_ty_for_trait: trait_def_id={:?}", trait_def_id);
+/// Performs a type substitution to produce the version of `receiver_ty` when `Self = self_ty`.
+/// For example, for `receiver_ty = Rc<Self>` and `self_ty = Foo`, returns `Rc<Foo>`.
+fn receiver_for_self_ty<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ receiver_ty: Ty<'tcx>,
+ self_ty: Ty<'tcx>,
+ method_def_id: DefId,
+) -> Ty<'tcx> {
+ debug!("receiver_for_self_ty({:?}, {:?}, {:?})", receiver_ty, self_ty, method_def_id);
+ let substs = InternalSubsts::for_item(tcx, method_def_id, |param, _| {
+ if param.index == 0 { self_ty.into() } else { tcx.mk_param_from_def(param) }
+ });
+
+ let result = receiver_ty.subst(tcx, substs);
+ debug!(
+ "receiver_for_self_ty({:?}, {:?}, {:?}) = {:?}",
+ receiver_ty, self_ty, method_def_id, result
+ );
+ result
+}
- let trait_ref = ty::TraitRef::identity(self, trait_def_id);
+/// Creates the object type for the current trait. For example,
+/// if the current trait is `Deref`, then this will be
+/// `dyn Deref<Target = Self::Target> + 'static`.
+fn object_ty_for_trait<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ trait_def_id: DefId,
+ lifetime: ty::Region<'tcx>,
+) -> Ty<'tcx> {
+ debug!("object_ty_for_trait: trait_def_id={:?}", trait_def_id);
- let trait_predicate = ty::ExistentialPredicate::Trait(
- ty::ExistentialTraitRef::erase_self_ty(self, trait_ref),
- );
+ let trait_ref = ty::TraitRef::identity(tcx, trait_def_id);
- let mut associated_types = traits::supertraits(self, ty::Binder::dummy(trait_ref))
- .flat_map(|super_trait_ref| {
- self.associated_items(super_trait_ref.def_id())
- .map(move |item| (super_trait_ref, item))
- })
- .filter(|(_, item)| item.kind == ty::AssocKind::Type)
- .collect::<Vec<_>>();
-
- // existential predicates need to be in a specific order
- associated_types.sort_by_cached_key(|(_, item)| self.def_path_hash(item.def_id));
-
- let projection_predicates = associated_types.into_iter().map(|(super_trait_ref, item)| {
- // We *can* get bound lifetimes here in cases like
- // `trait MyTrait: for<'s> OtherTrait<&'s T, Output=bool>`.
- //
- // binder moved to (*)...
- let super_trait_ref = super_trait_ref.skip_binder();
- ty::ExistentialPredicate::Projection(ty::ExistentialProjection {
- ty: self.mk_projection(item.def_id, super_trait_ref.substs),
- item_def_id: item.def_id,
- substs: super_trait_ref.substs,
- })
- });
-
- let existential_predicates = self
- .mk_existential_predicates(iter::once(trait_predicate).chain(projection_predicates));
-
- let object_ty = self.mk_dynamic(
- // (*) ... binder re-introduced here
- ty::Binder::bind(existential_predicates),
- lifetime,
- );
+ let trait_predicate =
+ ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref));
- debug!("object_ty_for_trait: object_ty=`{}`", object_ty);
+ let mut associated_types = traits::supertraits(tcx, ty::Binder::dummy(trait_ref))
+ .flat_map(|super_trait_ref| {
+ tcx.associated_items(super_trait_ref.def_id()).map(move |item| (super_trait_ref, item))
+ })
+ .filter(|(_, item)| item.kind == ty::AssocKind::Type)
+ .collect::<Vec<_>>();
- object_ty
- }
+ // existential predicates need to be in a specific order
+ associated_types.sort_by_cached_key(|(_, item)| tcx.def_path_hash(item.def_id));
- /// Checks the method's receiver (the `self` argument) can be dispatched on when `Self` is a
- /// trait object. We require that `DispatchableFromDyn` be implemented for the receiver type
- /// in the following way:
- /// - let `Receiver` be the type of the `self` argument, i.e `Self`, `&Self`, `Rc<Self>`,
- /// - require the following bound:
- ///
- /// ```
- /// Receiver[Self => T]: DispatchFromDyn<Receiver[Self => dyn Trait]>
- /// ```
- ///
- /// where `Foo[X => Y]` means "the same type as `Foo`, but with `X` replaced with `Y`"
- /// (substitution notation).
- ///
- /// Some examples of receiver types and their required obligation:
- /// - `&'a mut self` requires `&'a mut Self: DispatchFromDyn<&'a mut dyn Trait>`,
- /// - `self: Rc<Self>` requires `Rc<Self>: DispatchFromDyn<Rc<dyn Trait>>`,
- /// - `self: Pin<Box<Self>>` requires `Pin<Box<Self>>: DispatchFromDyn<Pin<Box<dyn Trait>>>`.
- ///
- /// The only case where the receiver is not dispatchable, but is still a valid receiver
- /// type (just not object-safe), is when there is more than one level of pointer indirection.
- /// E.g., `self: &&Self`, `self: &Rc<Self>`, `self: Box<Box<Self>>`. In these cases, there
- /// is no way, or at least no inexpensive way, to coerce the receiver from the version where
- /// `Self = dyn Trait` to the version where `Self = T`, where `T` is the unknown erased type
- /// contained by the trait object, because the object that needs to be coerced is behind
- /// a pointer.
- ///
- /// In practice, we cannot use `dyn Trait` explicitly in the obligation because it would result
- /// in a new check that `Trait` is object safe, creating a cycle (until object_safe_for_dispatch
- /// is stabilized, see tracking issue https://github.com/rust-lang/rust/issues/43561).
- /// Instead, we fudge a little by introducing a new type parameter `U` such that
- /// `Self: Unsize<U>` and `U: Trait + ?Sized`, and use `U` in place of `dyn Trait`.
- /// Written as a chalk-style query:
- ///
- /// forall (U: Trait + ?Sized) {
- /// if (Self: Unsize<U>) {
- /// Receiver: DispatchFromDyn<Receiver[Self => U]>
- /// }
- /// }
- ///
- /// for `self: &'a mut Self`, this means `&'a mut Self: DispatchFromDyn<&'a mut U>`
- /// for `self: Rc<Self>`, this means `Rc<Self>: DispatchFromDyn<Rc<U>>`
- /// for `self: Pin<Box<Self>>`, this means `Pin<Box<Self>>: DispatchFromDyn<Pin<Box<U>>>`
- //
- // FIXME(mikeyhew) when unsized receivers are implemented as part of unsized rvalues, add this
- // fallback query: `Receiver: Unsize<Receiver[Self => U]>` to support receivers like
- // `self: Wrapper<Self>`.
- #[allow(dead_code)]
- fn receiver_is_dispatchable(self, method: &ty::AssocItem, receiver_ty: Ty<'tcx>) -> bool {
- debug!("receiver_is_dispatchable: method = {:?}, receiver_ty = {:?}", method, receiver_ty);
-
- let traits =
- (self.lang_items().unsize_trait(), self.lang_items().dispatch_from_dyn_trait());
- let (unsize_did, dispatch_from_dyn_did) = if let (Some(u), Some(cu)) = traits {
- (u, cu)
- } else {
- debug!("receiver_is_dispatchable: Missing Unsize or DispatchFromDyn traits");
- return false;
- };
+ let projection_predicates = associated_types.into_iter().map(|(super_trait_ref, item)| {
+ // We *can* get bound lifetimes here in cases like
+ // `trait MyTrait: for<'s> OtherTrait<&'s T, Output=bool>`.
+ //
+ // binder moved to (*)...
+ let super_trait_ref = super_trait_ref.skip_binder();
+ ty::ExistentialPredicate::Projection(ty::ExistentialProjection {
+ ty: tcx.mk_projection(item.def_id, super_trait_ref.substs),
+ item_def_id: item.def_id,
+ substs: super_trait_ref.substs,
+ })
+ });
- // the type `U` in the query
- // use a bogus type parameter to mimick a forall(U) query using u32::MAX for now.
- // FIXME(mikeyhew) this is a total hack. Once object_safe_for_dispatch is stabilized, we can
- // replace this with `dyn Trait`
- let unsized_self_ty: Ty<'tcx> =
- self.mk_ty_param(::std::u32::MAX, Symbol::intern("RustaceansAreAwesome"));
-
- // `Receiver[Self => U]`
- let unsized_receiver_ty =
- self.receiver_for_self_ty(receiver_ty, unsized_self_ty, method.def_id);
-
- // create a modified param env, with `Self: Unsize<U>` and `U: Trait` added to caller bounds
- // `U: ?Sized` is already implied here
- let param_env = {
- let mut param_env = self.param_env(method.def_id);
-
- // Self: Unsize<U>
- let unsize_predicate = ty::TraitRef {
- def_id: unsize_did,
- substs: self.mk_substs_trait(self.types.self_param, &[unsized_self_ty.into()]),
- }
- .to_predicate();
-
- // U: Trait<Arg1, ..., ArgN>
- let trait_predicate = {
- let substs =
- InternalSubsts::for_item(self, method.container.assert_trait(), |param, _| {
- if param.index == 0 {
- unsized_self_ty.into()
- } else {
- self.mk_param_from_def(param)
- }
- });
-
- ty::TraitRef { def_id: unsize_did, substs }.to_predicate()
- };
+ let existential_predicates =
+ tcx.mk_existential_predicates(iter::once(trait_predicate).chain(projection_predicates));
- let caller_bounds: Vec<Predicate<'tcx>> = param_env
- .caller_bounds
- .iter()
- .cloned()
- .chain(iter::once(unsize_predicate))
- .chain(iter::once(trait_predicate))
- .collect();
+ let object_ty = tcx.mk_dynamic(
+ // (*) ... binder re-introduced here
+ ty::Binder::bind(existential_predicates),
+ lifetime,
+ );
- param_env.caller_bounds = self.intern_predicates(&caller_bounds);
+ debug!("object_ty_for_trait: object_ty=`{}`", object_ty);
- param_env
- };
+ object_ty
+}
- // Receiver: DispatchFromDyn<Receiver[Self => U]>
- let obligation = {
- let predicate = ty::TraitRef {
- def_id: dispatch_from_dyn_did,
- substs: self.mk_substs_trait(receiver_ty, &[unsized_receiver_ty.into()]),
- }
- .to_predicate();
+/// Checks the method's receiver (the `self` argument) can be dispatched on when `Self` is a
+/// trait object. We require that `DispatchableFromDyn` be implemented for the receiver type
+/// in the following way:
+/// - let `Receiver` be the type of the `self` argument, i.e `Self`, `&Self`, `Rc<Self>`,
+/// - require the following bound:
+///
+/// ```
+/// Receiver[Self => T]: DispatchFromDyn<Receiver[Self => dyn Trait]>
+/// ```
+///
+/// where `Foo[X => Y]` means "the same type as `Foo`, but with `X` replaced with `Y`"
+/// (substitution notation).
+///
+/// Some examples of receiver types and their required obligation:
+/// - `&'a mut self` requires `&'a mut Self: DispatchFromDyn<&'a mut dyn Trait>`,
+/// - `self: Rc<Self>` requires `Rc<Self>: DispatchFromDyn<Rc<dyn Trait>>`,
+/// - `self: Pin<Box<Self>>` requires `Pin<Box<Self>>: DispatchFromDyn<Pin<Box<dyn Trait>>>`.
+///
+/// The only case where the receiver is not dispatchable, but is still a valid receiver
+/// type (just not object-safe), is when there is more than one level of pointer indirection.
+/// E.g., `self: &&Self`, `self: &Rc<Self>`, `self: Box<Box<Self>>`. In these cases, there
+/// is no way, or at least no inexpensive way, to coerce the receiver from the version where
+/// `Self = dyn Trait` to the version where `Self = T`, where `T` is the unknown erased type
+/// contained by the trait object, because the object that needs to be coerced is behind
+/// a pointer.
+///
+/// In practice, we cannot use `dyn Trait` explicitly in the obligation because it would result
+/// in a new check that `Trait` is object safe, creating a cycle (until object_safe_for_dispatch
+/// is stabilized, see tracking issue https://github.com/rust-lang/rust/issues/43561).
+/// Instead, we fudge a little by introducing a new type parameter `U` such that
+/// `Self: Unsize<U>` and `U: Trait + ?Sized`, and use `U` in place of `dyn Trait`.
+/// Written as a chalk-style query:
+///
+/// forall (U: Trait + ?Sized) {
+/// if (Self: Unsize<U>) {
+/// Receiver: DispatchFromDyn<Receiver[Self => U]>
+/// }
+/// }
+///
+/// for `self: &'a mut Self`, this means `&'a mut Self: DispatchFromDyn<&'a mut U>`
+/// for `self: Rc<Self>`, this means `Rc<Self>: DispatchFromDyn<Rc<U>>`
+/// for `self: Pin<Box<Self>>`, this means `Pin<Box<Self>>: DispatchFromDyn<Pin<Box<U>>>`
+//
+// FIXME(mikeyhew) when unsized receivers are implemented as part of unsized rvalues, add this
+// fallback query: `Receiver: Unsize<Receiver[Self => U]>` to support receivers like
+// `self: Wrapper<Self>`.
+#[allow(dead_code)]
+fn receiver_is_dispatchable<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ method: &ty::AssocItem,
+ receiver_ty: Ty<'tcx>,
+) -> bool {
+ debug!("receiver_is_dispatchable: method = {:?}, receiver_ty = {:?}", method, receiver_ty);
+
+ let traits = (tcx.lang_items().unsize_trait(), tcx.lang_items().dispatch_from_dyn_trait());
+ let (unsize_did, dispatch_from_dyn_did) = if let (Some(u), Some(cu)) = traits {
+ (u, cu)
+ } else {
+ debug!("receiver_is_dispatchable: Missing Unsize or DispatchFromDyn traits");
+ return false;
+ };
+
+ // the type `U` in the query
+ // use a bogus type parameter to mimick a forall(U) query using u32::MAX for now.
+ // FIXME(mikeyhew) this is a total hack. Once object_safe_for_dispatch is stabilized, we can
+ // replace this with `dyn Trait`
+ let unsized_self_ty: Ty<'tcx> =
+ tcx.mk_ty_param(::std::u32::MAX, Symbol::intern("RustaceansAreAwesome"));
+
+ // `Receiver[Self => U]`
+ let unsized_receiver_ty =
+ receiver_for_self_ty(tcx, receiver_ty, unsized_self_ty, method.def_id);
+
+ // create a modified param env, with `Self: Unsize<U>` and `U: Trait` added to caller bounds
+ // `U: ?Sized` is already implied here
+ let param_env = {
+ let mut param_env = tcx.param_env(method.def_id);
+
+ // Self: Unsize<U>
+ let unsize_predicate = ty::TraitRef {
+ def_id: unsize_did,
+ substs: tcx.mk_substs_trait(tcx.types.self_param, &[unsized_self_ty.into()]),
+ }
+ .to_predicate();
+
+ // U: Trait<Arg1, ..., ArgN>
+ let trait_predicate = {
+ let substs =
+ InternalSubsts::for_item(tcx, method.container.assert_trait(), |param, _| {
+ if param.index == 0 {
+ unsized_self_ty.into()
+ } else {
+ tcx.mk_param_from_def(param)
+ }
+ });
- Obligation::new(ObligationCause::dummy(), param_env, predicate)
+ ty::TraitRef { def_id: unsize_did, substs }.to_predicate()
};
- self.infer_ctxt().enter(|ref infcx| {
- // the receiver is dispatchable iff the obligation holds
- infcx.predicate_must_hold_modulo_regions(&obligation)
- })
- }
+ let caller_bounds: Vec<Predicate<'tcx>> = param_env
+ .caller_bounds
+ .iter()
+ .cloned()
+ .chain(iter::once(unsize_predicate))
+ .chain(iter::once(trait_predicate))
+ .collect();
- fn contains_illegal_self_type_reference(self, trait_def_id: DefId, ty: Ty<'tcx>) -> bool {
- // This is somewhat subtle. In general, we want to forbid
- // references to `Self` in the argument and return types,
- // since the value of `Self` is erased. However, there is one
- // exception: it is ok to reference `Self` in order to access
- // an associated type of the current trait, since we retain
- // the value of those associated types in the object type
- // itself.
- //
- // ```rust
- // trait SuperTrait {
- // type X;
- // }
- //
- // trait Trait : SuperTrait {
- // type Y;
- // fn foo(&self, x: Self) // bad
- // fn foo(&self) -> Self // bad
- // fn foo(&self) -> Option<Self> // bad
- // fn foo(&self) -> Self::Y // OK, desugars to next example
- // fn foo(&self) -> <Self as Trait>::Y // OK
- // fn foo(&self) -> Self::X // OK, desugars to next example
- // fn foo(&self) -> <Self as SuperTrait>::X // OK
- // }
- // ```
- //
- // However, it is not as simple as allowing `Self` in a projected
- // type, because there are illegal ways to use `Self` as well:
- //
- // ```rust
- // trait Trait : SuperTrait {
- // ...
- // fn foo(&self) -> <Self as SomeOtherTrait>::X;
- // }
- // ```
- //
- // Here we will not have the type of `X` recorded in the
- // object type, and we cannot resolve `Self as SomeOtherTrait`
- // without knowing what `Self` is.
-
- let mut supertraits: Option<Vec<ty::PolyTraitRef<'tcx>>> = None;
- let mut error = false;
- let self_ty = self.types.self_param;
- ty.maybe_walk(|ty| {
- match ty.kind {
- ty::Param(_) => {
- if ty == self_ty {
- error = true;
- }
+ param_env.caller_bounds = tcx.intern_predicates(&caller_bounds);
+
+ param_env
+ };
+
+ // Receiver: DispatchFromDyn<Receiver[Self => U]>
+ let obligation = {
+ let predicate = ty::TraitRef {
+ def_id: dispatch_from_dyn_did,
+ substs: tcx.mk_substs_trait(receiver_ty, &[unsized_receiver_ty.into()]),
+ }
+ .to_predicate();
+
+ Obligation::new(ObligationCause::dummy(), param_env, predicate)
+ };
- false // no contained types to walk
+ tcx.infer_ctxt().enter(|ref infcx| {
+ // the receiver is dispatchable iff the obligation holds
+ infcx.predicate_must_hold_modulo_regions(&obligation)
+ })
+}
+
+fn contains_illegal_self_type_reference<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ trait_def_id: DefId,
+ ty: Ty<'tcx>,
+) -> bool {
+ // This is somewhat subtle. In general, we want to forbid
+ // references to `Self` in the argument and return types,
+ // since the value of `Self` is erased. However, there is one
+ // exception: it is ok to reference `Self` in order to access
+ // an associated type of the current trait, since we retain
+ // the value of those associated types in the object type
+ // itself.
+ //
+ // ```rust
+ // trait SuperTrait {
+ // type X;
+ // }
+ //
+ // trait Trait : SuperTrait {
+ // type Y;
+ // fn foo(&self, x: Self) // bad
+ // fn foo(&self) -> Self // bad
+ // fn foo(&self) -> Option<Self> // bad
+ // fn foo(&self) -> Self::Y // OK, desugars to next example
+ // fn foo(&self) -> <Self as Trait>::Y // OK
+ // fn foo(&self) -> Self::X // OK, desugars to next example
+ // fn foo(&self) -> <Self as SuperTrait>::X // OK
+ // }
+ // ```
+ //
+ // However, it is not as simple as allowing `Self` in a projected
+ // type, because there are illegal ways to use `Self` as well:
+ //
+ // ```rust
+ // trait Trait : SuperTrait {
+ // ...
+ // fn foo(&self) -> <Self as SomeOtherTrait>::X;
+ // }
+ // ```
+ //
+ // Here we will not have the type of `X` recorded in the
+ // object type, and we cannot resolve `Self as SomeOtherTrait`
+ // without knowing what `Self` is.
+
+ let mut supertraits: Option<Vec<ty::PolyTraitRef<'tcx>>> = None;
+ let mut error = false;
+ let self_ty = tcx.types.self_param;
+ ty.maybe_walk(|ty| {
+ match ty.kind {
+ ty::Param(_) => {
+ if ty == self_ty {
+ error = true;
}
- ty::Projection(ref data) => {
- // This is a projected type `<Foo as SomeTrait>::X`.
+ false // no contained types to walk
+ }
- // Compute supertraits of current trait lazily.
- if supertraits.is_none() {
- let trait_ref =
- ty::Binder::bind(ty::TraitRef::identity(self, trait_def_id));
- supertraits = Some(traits::supertraits(self, trait_ref).collect());
- }
+ ty::Projection(ref data) => {
+ // This is a projected type `<Foo as SomeTrait>::X`.
- // Determine whether the trait reference `Foo as
- // SomeTrait` is in fact a supertrait of the
- // current trait. In that case, this type is
- // legal, because the type `X` will be specified
- // in the object type. Note that we can just use
- // direct equality here because all of these types
- // are part of the formal parameter listing, and
- // hence there should be no inference variables.
- let projection_trait_ref = ty::Binder::bind(data.trait_ref(self));
- let is_supertrait_of_current_trait =
- supertraits.as_ref().unwrap().contains(&projection_trait_ref);
-
- if is_supertrait_of_current_trait {
- false // do not walk contained types, do not report error, do collect $200
- } else {
- true // DO walk contained types, POSSIBLY reporting an error
- }
+ // Compute supertraits of current trait lazily.
+ if supertraits.is_none() {
+ let trait_ref = ty::Binder::bind(ty::TraitRef::identity(tcx, trait_def_id));
+ supertraits = Some(traits::supertraits(tcx, trait_ref).collect());
}
- _ => true, // walk contained types, if any
+ // Determine whether the trait reference `Foo as
+ // SomeTrait` is in fact a supertrait of the
+ // current trait. In that case, this type is
+ // legal, because the type `X` will be specified
+ // in the object type. Note that we can just use
+ // direct equality here because all of these types
+ // are part of the formal parameter listing, and
+ // hence there should be no inference variables.
+ let projection_trait_ref = ty::Binder::bind(data.trait_ref(tcx));
+ let is_supertrait_of_current_trait =
+ supertraits.as_ref().unwrap().contains(&projection_trait_ref);
+
+ if is_supertrait_of_current_trait {
+ false // do not walk contained types, do not report error, do collect $200
+ } else {
+ true // DO walk contained types, POSSIBLY reporting an error
+ }
}
- });
- error
- }
+ _ => true, // walk contained types, if any
+ }
+ });
+
+ error
}
pub(super) fn is_object_safe_provider(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool {
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