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Auto merge of rust-lang#132196 - compiler-errors:probe_ty_param_bound…
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…s, r=petrochenkov

Some where clause lowering simplifications

Rename `PredicateFilter::SelfThatDefines` to `PredicateFilter::SelfTraitThatDefines` to make it clear that it's only concerned with converting *traits*, and make it do a bit less work when converting bounds.

Also, make the predicate filter matching in `probe_ty_param_bounds_in_generics` explicit, and simply the args it receives a bit.
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@bors
bors committed Nov 1, 2024
2 parents 145f9cf + 81dba07 commit 5ca0e9f
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Showing 4 changed files with 94 additions and 49 deletions.
6 changes: 3 additions & 3 deletions compiler/rustc_hir_analysis/src/collect/item_bounds.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ fn associated_type_bounds<'tcx>(
match filter {
PredicateFilter::All
| PredicateFilter::SelfOnly
| PredicateFilter::SelfThatDefines(_)
| PredicateFilter::SelfTraitThatDefines(_)
| PredicateFilter::SelfAndAssociatedTypeBounds => {
icx.lowerer().add_sized_bound(&mut bounds, item_ty, hir_bounds, None, span);
}
Expand Down Expand Up @@ -122,7 +122,7 @@ fn remap_gat_vars_and_recurse_into_nested_projections<'tcx>(
PredicateFilter::SelfOnly => {
return None;
}
PredicateFilter::SelfThatDefines(_)
PredicateFilter::SelfTraitThatDefines(_)
| PredicateFilter::SelfConstIfConst
| PredicateFilter::SelfAndAssociatedTypeBounds
| PredicateFilter::ConstIfConst => {
Expand Down Expand Up @@ -329,7 +329,7 @@ fn opaque_type_bounds<'tcx>(
match filter {
PredicateFilter::All
| PredicateFilter::SelfOnly
| PredicateFilter::SelfThatDefines(_)
| PredicateFilter::SelfTraitThatDefines(_)
| PredicateFilter::SelfAndAssociatedTypeBounds => {
// Associated types are implicitly sized unless a `?Sized` bound is found
icx.lowerer().add_sized_bound(&mut bounds, item_ty, hir_bounds, None, span);
Expand Down
121 changes: 81 additions & 40 deletions compiler/rustc_hir_analysis/src/collect/predicates_of.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -557,7 +557,11 @@ pub(super) fn explicit_supertraits_containing_assoc_item<'tcx>(
tcx: TyCtxt<'tcx>,
(trait_def_id, assoc_name): (DefId, Ident),
) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]> {
implied_predicates_with_filter(tcx, trait_def_id, PredicateFilter::SelfThatDefines(assoc_name))
implied_predicates_with_filter(
tcx,
trait_def_id,
PredicateFilter::SelfTraitThatDefines(assoc_name),
)
}

pub(super) fn explicit_implied_predicates_of<'tcx>(
Expand Down Expand Up @@ -586,7 +590,7 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
let Some(trait_def_id) = trait_def_id.as_local() else {
// if `assoc_name` is None, then the query should've been redirected to an
// external provider
assert_matches!(filter, PredicateFilter::SelfThatDefines(_));
assert_matches!(filter, PredicateFilter::SelfTraitThatDefines(_));
return tcx.explicit_super_predicates_of(trait_def_id);
};

Expand All @@ -606,12 +610,8 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
let mut bounds = Bounds::default();
icx.lowerer().lower_bounds(self_param_ty, superbounds, &mut bounds, ty::List::empty(), filter);

let where_bounds_that_match = icx.probe_ty_param_bounds_in_generics(
generics,
item.owner_id.def_id,
self_param_ty,
filter,
);
let where_bounds_that_match =
icx.probe_ty_param_bounds_in_generics(generics, item.owner_id.def_id, filter);

// Combine the two lists to form the complete set of superbounds:
let implied_bounds =
Expand Down Expand Up @@ -652,7 +652,7 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
}

// Make sure when elaborating supertraits, probing for associated types, etc.,
// we really truly are elaborating clauses that have `Self` as their self type.
// we really truly are elaborating clauses that have `ty` as their self type.
// This is very important since downstream code relies on this being correct.
pub(super) fn assert_only_contains_predicates_from<'tcx>(
filter: PredicateFilter,
Expand All @@ -664,7 +664,7 @@ pub(super) fn assert_only_contains_predicates_from<'tcx>(
}

match filter {
PredicateFilter::SelfOnly | PredicateFilter::SelfThatDefines(_) => {
PredicateFilter::SelfOnly => {
for (clause, _) in bounds {
match clause.kind().skip_binder() {
ty::ClauseKind::Trait(trait_predicate) => {
Expand Down Expand Up @@ -704,6 +704,33 @@ pub(super) fn assert_only_contains_predicates_from<'tcx>(
}
}
}
PredicateFilter::SelfTraitThatDefines(_) => {
for (clause, _) in bounds {
match clause.kind().skip_binder() {
ty::ClauseKind::Trait(trait_predicate) => {
assert_eq!(
trait_predicate.self_ty(),
ty,
"expected `Self` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}

ty::ClauseKind::Projection(_)
| ty::ClauseKind::TypeOutlives(_)
| ty::ClauseKind::RegionOutlives(_)
| ty::ClauseKind::ConstArgHasType(_, _)
| ty::ClauseKind::WellFormed(_)
| ty::ClauseKind::ConstEvaluatable(_)
| ty::ClauseKind::HostEffect(..) => {
bug!(
"unexpected non-`Self` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}
}
}
}
PredicateFilter::ConstIfConst => {
for (clause, _) in bounds {
match clause.kind().skip_binder() {
Expand Down Expand Up @@ -767,21 +794,16 @@ pub(super) fn type_param_predicates<'tcx>(
None => {}
}

use rustc_hir::*;
use rustc_middle::ty::Ty;

// In the HIR, bounds can derive from two places. Either
// written inline like `<T: Foo>` or in a where-clause like
// `where T: Foo`.

let param_id = tcx.local_def_id_to_hir_id(def_id);
let param_owner = tcx.hir().ty_param_owner(def_id);
let generics = tcx.generics_of(param_owner);
let index = generics.param_def_id_to_index[&def_id.to_def_id()];
let ty = Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id));

// Don't look for bounds where the type parameter isn't in scope.
let parent = if item_def_id == param_owner {
// FIXME: Shouldn't this be unreachable?
None
} else {
tcx.generics_of(item_def_id).parent.map(|def_id| def_id.expect_local())
Expand All @@ -801,8 +823,9 @@ pub(super) fn type_param_predicates<'tcx>(
let Some(hir_generics) = hir_node.generics() else {
return result;
};

if let Node::Item(item) = hir_node
&& let ItemKind::Trait(..) = item.kind
&& let hir::ItemKind::Trait(..) = item.kind
// Implied `Self: Trait` and supertrait bounds.
&& param_id == item_hir_id
{
Expand All @@ -811,23 +834,34 @@ pub(super) fn type_param_predicates<'tcx>(
}

let icx = ItemCtxt::new(tcx, item_def_id);
let extra_predicates = extend.into_iter().chain(
icx.probe_ty_param_bounds_in_generics(
hir_generics,
def_id,
ty,
PredicateFilter::SelfThatDefines(assoc_name),
)
.into_iter()
.filter(|(predicate, _)| match predicate.kind().skip_binder() {
ty::ClauseKind::Trait(data) => data.self_ty().is_param(index),
_ => false,
}),
let extra_predicates = extend.into_iter().chain(icx.probe_ty_param_bounds_in_generics(
hir_generics,
def_id,
PredicateFilter::SelfTraitThatDefines(assoc_name),
));

let bounds =
&*tcx.arena.alloc_from_iter(result.skip_binder().iter().copied().chain(extra_predicates));

// Double check that the bounds *only* contain `SelfTy: Trait` preds.
let self_ty = match tcx.def_kind(def_id) {
DefKind::TyParam => Ty::new_param(
tcx,
tcx.generics_of(item_def_id)
.param_def_id_to_index(tcx, def_id.to_def_id())
.expect("expected generic param to be owned by item"),
tcx.item_name(def_id.to_def_id()),
),
DefKind::Trait | DefKind::TraitAlias => tcx.types.self_param,
_ => unreachable!(),
};
assert_only_contains_predicates_from(
PredicateFilter::SelfTraitThatDefines(assoc_name),
bounds,
self_ty,
);

ty::EarlyBinder::bind(
tcx.arena.alloc_from_iter(result.skip_binder().iter().copied().chain(extra_predicates)),
)
ty::EarlyBinder::bind(bounds)
}

impl<'tcx> ItemCtxt<'tcx> {
Expand All @@ -841,7 +875,6 @@ impl<'tcx> ItemCtxt<'tcx> {
&self,
hir_generics: &'tcx hir::Generics<'tcx>,
param_def_id: LocalDefId,
ty: Ty<'tcx>,
filter: PredicateFilter,
) -> Vec<(ty::Clause<'tcx>, Span)> {
let mut bounds = Bounds::default();
Expand All @@ -851,13 +884,21 @@ impl<'tcx> ItemCtxt<'tcx> {
continue;
};

let bound_ty = if predicate.is_param_bound(param_def_id.to_def_id()) {
ty
} else if matches!(filter, PredicateFilter::All) {
self.lowerer().lower_ty_maybe_return_type_notation(predicate.bounded_ty)
} else {
continue;
};
match filter {
_ if predicate.is_param_bound(param_def_id.to_def_id()) => {
// Ok
}
PredicateFilter::All => {
// Ok
}
PredicateFilter::SelfOnly
| PredicateFilter::SelfTraitThatDefines(_)
| PredicateFilter::SelfConstIfConst
| PredicateFilter::SelfAndAssociatedTypeBounds => continue,
PredicateFilter::ConstIfConst => unreachable!(),
}

let bound_ty = self.lowerer().lower_ty_maybe_return_type_notation(predicate.bounded_ty);

let bound_vars = self.tcx.late_bound_vars(predicate.hir_id);
self.lowerer().lower_bounds(
Expand Down
9 changes: 5 additions & 4 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -152,9 +152,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
'tcx: 'hir,
{
for hir_bound in hir_bounds {
// In order to avoid cycles, when we're lowering `SelfThatDefines`,
// In order to avoid cycles, when we're lowering `SelfTraitThatDefines`,
// we skip over any traits that don't define the given associated type.
if let PredicateFilter::SelfThatDefines(assoc_name) = predicate_filter {
if let PredicateFilter::SelfTraitThatDefines(assoc_name) = predicate_filter {
if let Some(trait_ref) = hir_bound.trait_ref()
&& let Some(trait_did) = trait_ref.trait_def_id()
&& self.tcx().trait_may_define_assoc_item(trait_did, assoc_name)
Expand Down Expand Up @@ -389,7 +389,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
match predicate_filter {
PredicateFilter::All
| PredicateFilter::SelfOnly
| PredicateFilter::SelfThatDefines(_)
| PredicateFilter::SelfAndAssociatedTypeBounds => {
bounds.push_projection_bound(
tcx,
Expand All @@ -400,6 +399,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
constraint.span,
);
}
// SelfTraitThatDefines is only interested in trait predicates.
PredicateFilter::SelfTraitThatDefines(_) => {}
// `ConstIfConst` is only interested in `~const` bounds.
PredicateFilter::ConstIfConst | PredicateFilter::SelfConstIfConst => {}
}
Expand All @@ -426,7 +427,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
);
}
PredicateFilter::SelfOnly
| PredicateFilter::SelfThatDefines(_)
| PredicateFilter::SelfTraitThatDefines(_)
| PredicateFilter::SelfConstIfConst => {}
}
}
Expand Down
7 changes: 5 additions & 2 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ pub enum PredicateFilter {
/// Only traits that reference `Self: ..` and define an associated type
/// with the given ident are implied by the trait. This mode exists to
/// side-step query cycles when lowering associated types.
SelfThatDefines(Ident),
SelfTraitThatDefines(Ident),

/// Only traits that reference `Self: ..` and their associated type bounds.
/// For example, given `Self: Tr<A: B>`, this would expand to `Self: Tr`
Expand Down Expand Up @@ -730,9 +730,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
}

match predicate_filter {
// This is only concerned with trait predicates.
PredicateFilter::SelfTraitThatDefines(..) => {
bounds.push_trait_bound(tcx, poly_trait_ref, span, polarity);
}
PredicateFilter::All
| PredicateFilter::SelfOnly
| PredicateFilter::SelfThatDefines(..)
| PredicateFilter::SelfAndAssociatedTypeBounds => {
debug!(?poly_trait_ref);
bounds.push_trait_bound(tcx, poly_trait_ref, span, polarity);
Expand Down

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