Default auto traits: revert to the default supertraits
This commit is contained in:
Bryanskiy
@@ -174,12 +174,6 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
|
||||
}
|
||||
};
|
||||
|
||||
if let Node::TraitItem(item) = node {
|
||||
let mut bounds = Vec::new();
|
||||
icx.lowerer().add_default_trait_item_bounds(item, &mut bounds);
|
||||
predicates.extend(bounds);
|
||||
}
|
||||
|
||||
let generics = tcx.generics_of(def_id);
|
||||
|
||||
// Below we'll consider the bounds on the type parameters (including `Self`)
|
||||
|
||||
@@ -1,12 +1,13 @@
|
||||
use std::assert_matches::assert_matches;
|
||||
use std::ops::ControlFlow;
|
||||
|
||||
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
|
||||
use rustc_errors::codes::*;
|
||||
use rustc_errors::struct_span_code_err;
|
||||
use rustc_hir as hir;
|
||||
use rustc_hir::PolyTraitRef;
|
||||
use rustc_hir::def::{DefKind, Res};
|
||||
use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
|
||||
use rustc_hir::{AmbigArg, PolyTraitRef};
|
||||
use rustc_middle::bug;
|
||||
use rustc_middle::ty::{
|
||||
self as ty, IsSuggestable, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
|
||||
@@ -230,122 +231,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
|
||||
}
|
||||
}
|
||||
|
||||
/// Checks whether `Self: DefaultAutoTrait` bounds should be added on trait super bounds
|
||||
/// or associated items.
|
||||
///
|
||||
/// To keep backward compatibility with existing code, `experimental_default_bounds` bounds
|
||||
/// should be added everywhere, including super bounds. However this causes a huge performance
|
||||
/// costs. For optimization purposes instead of adding default supertraits, bounds
|
||||
/// are added to the associated items:
|
||||
///
|
||||
/// ```ignore(illustrative)
|
||||
/// // Default bounds are generated in the following way:
|
||||
/// trait Trait {
|
||||
/// fn foo(&self) where Self: Leak {}
|
||||
/// }
|
||||
///
|
||||
/// // instead of this:
|
||||
/// trait Trait: Leak {
|
||||
/// fn foo(&self) {}
|
||||
/// }
|
||||
/// ```
|
||||
/// It is not always possible to do this because of backward compatibility:
|
||||
///
|
||||
/// ```ignore(illustrative)
|
||||
/// pub trait Trait<Rhs = Self> {}
|
||||
/// pub trait Trait1 : Trait {}
|
||||
/// //~^ ERROR: `Rhs` requires `DefaultAutoTrait`, but `Self` is not `DefaultAutoTrait`
|
||||
/// ```
|
||||
///
|
||||
/// or:
|
||||
///
|
||||
/// ```ignore(illustrative)
|
||||
/// trait Trait {
|
||||
/// type Type where Self: Sized;
|
||||
/// }
|
||||
/// trait Trait2<T> : Trait<Type = T> {}
|
||||
/// //~^ ERROR: `DefaultAutoTrait` required for `Trait2`, by implicit `Self: DefaultAutoTrait` in `Trait::Type`
|
||||
/// ```
|
||||
///
|
||||
/// Therefore, `experimental_default_bounds` are still being added to supertraits if
|
||||
/// the `SelfTyParam` or `AssocItemConstraint` were found in a trait header.
|
||||
fn requires_default_supertraits(
|
||||
&self,
|
||||
hir_bounds: &'tcx [hir::GenericBound<'tcx>],
|
||||
hir_generics: &'tcx hir::Generics<'tcx>,
|
||||
) -> bool {
|
||||
struct TraitInfoCollector;
|
||||
|
||||
impl<'tcx> hir::intravisit::Visitor<'tcx> for TraitInfoCollector {
|
||||
type Result = ControlFlow<()>;
|
||||
|
||||
fn visit_assoc_item_constraint(
|
||||
&mut self,
|
||||
_constraint: &'tcx hir::AssocItemConstraint<'tcx>,
|
||||
) -> Self::Result {
|
||||
ControlFlow::Break(())
|
||||
}
|
||||
|
||||
fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx, AmbigArg>) -> Self::Result {
|
||||
if matches!(
|
||||
&t.kind,
|
||||
hir::TyKind::Path(hir::QPath::Resolved(
|
||||
_,
|
||||
hir::Path { res: hir::def::Res::SelfTyParam { .. }, .. },
|
||||
))
|
||||
) {
|
||||
return ControlFlow::Break(());
|
||||
}
|
||||
hir::intravisit::walk_ty(self, t)
|
||||
}
|
||||
}
|
||||
|
||||
let mut found = false;
|
||||
for bound in hir_bounds {
|
||||
found |= hir::intravisit::walk_param_bound(&mut TraitInfoCollector, bound).is_break();
|
||||
}
|
||||
found |= hir::intravisit::walk_generics(&mut TraitInfoCollector, hir_generics).is_break();
|
||||
found
|
||||
}
|
||||
|
||||
/// Implicitly add `Self: DefaultAutoTrait` clauses on trait associated items if
|
||||
/// they are not added as super trait bounds to the trait itself. See
|
||||
/// `requires_default_supertraits` for more information.
|
||||
pub(crate) fn add_default_trait_item_bounds(
|
||||
&self,
|
||||
trait_item: &hir::TraitItem<'tcx>,
|
||||
bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
|
||||
) {
|
||||
let tcx = self.tcx();
|
||||
if !tcx.sess.opts.unstable_opts.experimental_default_bounds {
|
||||
return;
|
||||
}
|
||||
|
||||
let parent = tcx.local_parent(trait_item.hir_id().owner.def_id);
|
||||
let hir::Node::Item(parent_trait) = tcx.hir_node_by_def_id(parent) else {
|
||||
unreachable!();
|
||||
};
|
||||
|
||||
let (trait_generics, trait_bounds) = match parent_trait.kind {
|
||||
hir::ItemKind::Trait(_, _, _, _, generics, supertraits, _) => (generics, supertraits),
|
||||
hir::ItemKind::TraitAlias(_, generics, supertraits) => (generics, supertraits),
|
||||
_ => unreachable!(),
|
||||
};
|
||||
|
||||
if !self.requires_default_supertraits(trait_bounds, trait_generics) {
|
||||
let self_ty_where_predicates = (parent, trait_item.generics.predicates);
|
||||
self.add_default_traits(
|
||||
bounds,
|
||||
tcx.types.self_param,
|
||||
&[],
|
||||
Some(self_ty_where_predicates),
|
||||
trait_item.span,
|
||||
);
|
||||
}
|
||||
}
|
||||
|
||||
/// Lazily sets `experimental_default_bounds` to true on trait super bounds.
|
||||
/// See `requires_default_supertraits` for more information.
|
||||
/// Adds `experimental_default_bounds` bounds to the supertrait bounds.
|
||||
pub(crate) fn add_default_super_traits(
|
||||
&self,
|
||||
trait_def_id: LocalDefId,
|
||||
@@ -354,21 +240,21 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
|
||||
hir_generics: &'tcx hir::Generics<'tcx>,
|
||||
span: Span,
|
||||
) {
|
||||
if !self.tcx().sess.opts.unstable_opts.experimental_default_bounds {
|
||||
assert_matches!(self.tcx().def_kind(trait_def_id), DefKind::Trait | DefKind::TraitAlias);
|
||||
|
||||
// Supertraits for auto trait are unsound according to the unstable book:
|
||||
// https://doc.rust-lang.org/beta/unstable-book/language-features/auto-traits.html#supertraits
|
||||
if self.tcx().trait_is_auto(trait_def_id.to_def_id()) {
|
||||
return;
|
||||
}
|
||||
|
||||
assert!(matches!(self.tcx().def_kind(trait_def_id), DefKind::Trait | DefKind::TraitAlias));
|
||||
if self.requires_default_supertraits(hir_bounds, hir_generics) {
|
||||
let self_ty_where_predicates = (trait_def_id, hir_generics.predicates);
|
||||
self.add_default_traits(
|
||||
bounds,
|
||||
self.tcx().types.self_param,
|
||||
hir_bounds,
|
||||
Some(self_ty_where_predicates),
|
||||
span,
|
||||
);
|
||||
}
|
||||
self.add_default_traits(
|
||||
bounds,
|
||||
self.tcx().types.self_param,
|
||||
hir_bounds,
|
||||
Some((trait_def_id, hir_generics.predicates)),
|
||||
span,
|
||||
);
|
||||
}
|
||||
|
||||
pub(crate) fn add_default_traits(
|
||||
|
||||
Reference in New Issue
Block a user