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Do not deduplicate list of associated types provided by dyn principal

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This commit is contained in:
Michael Goulet 2025-02-03 02:38:56 +00:00
parent 71e06b9c59
commit 72bd174c43
18 changed files with 265 additions and 117 deletions
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127
compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
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@ -1,4 +1,4 @@
use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
use rustc_errors::codes::*;
use rustc_errors::struct_span_code_err;
use rustc_hir as hir;
@ -58,9 +58,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
}
}
let (trait_bounds, mut projection_bounds) =
let (elaborated_trait_bounds, elaborated_projection_bounds) =
traits::expand_trait_aliases(tcx, user_written_bounds.iter().copied());
let (regular_traits, mut auto_traits): (Vec<_>, Vec<_>) = trait_bounds
let (regular_traits, mut auto_traits): (Vec<_>, Vec<_>) = elaborated_trait_bounds
.into_iter()
.partition(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()));
@ -103,29 +103,81 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
}
}
// Map the projection bounds onto a key that makes it easy to remove redundant
// bounds that are constrained by supertraits of the principal def id.
//
// Also make sure we detect conflicting bounds from expanding a trait alias and
// also specifying it manually, like:
// ```
// type Alias = Trait<Assoc = i32>;
// let _: &dyn Alias<Assoc = u32> = /* ... */;
// ```
let mut projection_bounds = FxIndexMap::default();
for (proj, proj_span) in elaborated_projection_bounds {
let key = (
proj.skip_binder().projection_term.def_id,
tcx.anonymize_bound_vars(
proj.map_bound(|proj| proj.projection_term.trait_ref(tcx)),
),
);
if let Some((old_proj, old_proj_span)) =
projection_bounds.insert(key, (proj, proj_span))
&& tcx.anonymize_bound_vars(proj) != tcx.anonymize_bound_vars(old_proj)
{
let item = tcx.item_name(proj.item_def_id());
self.dcx()
.struct_span_err(
span,
format!(
"conflicting associated type bounds for `{item}` when \
expanding trait alias"
),
)
.with_span_label(
old_proj_span,
format!("`{item}` is specified to be `{}` here", old_proj.term()),
)
.with_span_label(
proj_span,
format!("`{item}` is specified to be `{}` here", proj.term()),
)
.emit();
}
}
let principal_trait = regular_traits.into_iter().next();
let mut needed_associated_types = FxIndexSet::default();
if let Some((principal_trait, spans)) = &principal_trait {
let pred: ty::Predicate<'tcx> = (*principal_trait).upcast(tcx);
for ClauseWithSupertraitSpan { pred, supertrait_span } in traits::elaborate(
let mut needed_associated_types = vec![];
if let Some((principal_trait, ref spans)) = principal_trait {
let principal_trait = principal_trait.map_bound(|trait_pred| {
assert_eq!(trait_pred.polarity, ty::PredicatePolarity::Positive);
trait_pred.trait_ref
});
for ClauseWithSupertraitSpan { clause, supertrait_span } in traits::elaborate(
tcx,
[ClauseWithSupertraitSpan::new(pred, *spans.last().unwrap())],
[ClauseWithSupertraitSpan::new(
ty::TraitRef::identity(tcx, principal_trait.def_id()).upcast(tcx),
*spans.last().unwrap(),
)],
)
.filter_only_self()
{
debug!("observing object predicate `{pred:?}`");
let clause = clause.instantiate_supertrait(tcx, principal_trait);
debug!("observing object predicate `{clause:?}`");
let bound_predicate = pred.kind();
let bound_predicate = clause.kind();
match bound_predicate.skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => {
ty::ClauseKind::Trait(pred) => {
// FIXME(negative_bounds): Handle this correctly...
let trait_ref =
tcx.anonymize_bound_vars(bound_predicate.rebind(pred.trait_ref));
needed_associated_types.extend(
tcx.associated_items(trait_ref.def_id())
tcx.associated_items(pred.trait_ref.def_id)
.in_definition_order()
// We only care about associated types.
.filter(|item| item.kind == ty::AssocKind::Type)
// No RPITITs -- even with `async_fn_in_dyn_trait`, they are implicit.
.filter(|item| !item.is_impl_trait_in_trait())
// If the associated type has a `where Self: Sized` bound,
// we do not need to constrain the associated type.
@ -133,7 +185,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
.map(|item| (item.def_id, trait_ref)),
);
}
ty::PredicateKind::Clause(ty::ClauseKind::Projection(pred)) => {
ty::ClauseKind::Projection(pred) => {
let pred = bound_predicate.rebind(pred);
// A `Self` within the original bound will be instantiated with a
// `trait_object_dummy_self`, so check for that.
@ -161,8 +213,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
// `dyn MyTrait<MyOutput = X, Output = X>`, which is uglier but works. See
// the discussion in #56288 for alternatives.
if !references_self {
// Include projections defined on supertraits.
projection_bounds.push((pred, supertrait_span));
let key = (
pred.skip_binder().projection_term.def_id,
tcx.anonymize_bound_vars(
pred.map_bound(|proj| proj.projection_term.trait_ref(tcx)),
),
);
if !projection_bounds.contains_key(&key) {
projection_bounds.insert(key, (pred, supertrait_span));
}
}
self.check_elaborated_projection_mentions_input_lifetimes(
@ -182,12 +241,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
// types that we expect to be provided by the user, so the following loop
// removes all the associated types that have a corresponding `Projection`
// clause, either from expanding trait aliases or written by the user.
for &(projection_bound, span) in &projection_bounds {
for &(projection_bound, span) in projection_bounds.values() {
let def_id = projection_bound.item_def_id();
let trait_ref = tcx.anonymize_bound_vars(
projection_bound.map_bound(|p| p.projection_term.trait_ref(tcx)),
);
needed_associated_types.swap_remove(&(def_id, trait_ref));
if tcx.generics_require_sized_self(def_id) {
tcx.emit_node_span_lint(
UNUSED_ASSOCIATED_TYPE_BOUNDS,
@ -198,9 +253,22 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
}
}
let mut missing_assoc_types = FxIndexSet::default();
let projection_bounds: Vec<_> = needed_associated_types
.into_iter()
.filter_map(|key| {
if let Some(assoc) = projection_bounds.get(&key) {
Some(*assoc)
} else {
missing_assoc_types.insert(key);
None
}
})
.collect();
if let Err(guar) = self.check_for_required_assoc_tys(
principal_trait.as_ref().map_or(smallvec![], |(_, spans)| spans.clone()),
needed_associated_types,
missing_assoc_types,
potential_assoc_types,
hir_bounds,
) {
@ -266,7 +334,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
})
});
let existential_projections = projection_bounds.iter().map(|(bound, _)| {
let existential_projections = projection_bounds.into_iter().map(|(bound, _)| {
bound.map_bound(|mut b| {
assert_eq!(b.projection_term.self_ty(), dummy_self);
@ -291,12 +359,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
})
});
let auto_trait_predicates = auto_traits.into_iter().map(|(trait_pred, _)| {
assert_eq!(trait_pred.polarity(), ty::PredicatePolarity::Positive);
assert_eq!(trait_pred.self_ty().skip_binder(), dummy_self);
let mut auto_trait_predicates: Vec<_> = auto_traits
.into_iter()
.map(|(trait_pred, _)| {
assert_eq!(trait_pred.polarity(), ty::PredicatePolarity::Positive);
assert_eq!(trait_pred.self_ty().skip_binder(), dummy_self);
ty::Binder::dummy(ty::ExistentialPredicate::AutoTrait(trait_pred.def_id()))
});
ty::Binder::dummy(ty::ExistentialPredicate::AutoTrait(trait_pred.def_id()))
})
.collect();
auto_trait_predicates.dedup();
// N.b. principal, projections, auto traits
// FIXME: This is actually wrong with multiple principals in regards to symbol mangling
@ -306,7 +378,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
.chain(auto_trait_predicates)
.collect::<SmallVec<[_; 8]>>();
v.sort_by(|a, b| a.skip_binder().stable_cmp(tcx, &b.skip_binder()));
v.dedup();
let existential_predicates = tcx.mk_poly_existential_predicates(&v);
// Use explicitly-specified region bound, unless the bound is missing.