Split implied and super predicate queries, then allow elaborator to filter only supertraits

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1663,39 +1663,45 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
  })
  });
 
- let existential_projections = projection_bounds.iter().map(|(bound, _)| {
- bound.map_bound(|mut b| {
- assert_eq!(b.projection_ty.self_ty(), dummy_self);
-
- // Like for trait refs, verify that `dummy_self` did not leak inside default type
- // parameters.
- let references_self = b.projection_ty.substs.iter().skip(1).any(|arg| {
- if arg.walk().any(|arg| arg == dummy_self.into()) {
- return true;
+ let existential_projections = projection_bounds
+ .iter()
+ // We filter out traits that don't have `Self` as their self type above,
+ // we need to do the same for projections.
+ .filter(|(bound, _)| bound.skip_binder().self_ty() == dummy_self)
+ .map(|(bound, _)| {
+ bound.map_bound(|mut b| {
+ assert_eq!(b.projection_ty.self_ty(), dummy_self);
+
+ // Like for trait refs, verify that `dummy_self` did not leak inside default type
+ // parameters.
+ let references_self = b.projection_ty.substs.iter().skip(1).any(|arg| {
+ if arg.walk().any(|arg| arg == dummy_self.into()) {
+ return true;
+ }
+ false
+ });
+ if references_self {
+ let guar = tcx.sess.delay_span_bug(
+ span,
+ "trait object projection bounds reference `Self`",
+ );
+ let substs: Vec<_> = b
+ .projection_ty
+ .substs
+ .iter()
+ .map(|arg| {
+ if arg.walk().any(|arg| arg == dummy_self.into()) {
+ return tcx.ty_error(guar).into();
+ }
+ arg
+ })
+ .collect();
+ b.projection_ty.substs = tcx.mk_substs(&substs);
  }
- false
- });
- if references_self {
- let guar = tcx
- .sess
- .delay_span_bug(span, "trait object projection bounds reference `Self`");
- let substs: Vec<_> = b
- .projection_ty
- .substs
- .iter()
- .map(|arg| {
- if arg.walk().any(|arg| arg == dummy_self.into()) {
- return tcx.ty_error(guar).into();
- }
- arg
- })
- .collect();
- b.projection_ty.substs = tcx.mk_substs(&substs);
- }
 
- ty::ExistentialProjection::erase_self_ty(tcx, b)
- })
- });
+  ty::ExistentialProjection::erase_self_ty(tcx, b)
+  })
+  });
 
  let regular_trait_predicates = existential_trait_refs
  .map(|trait_ref| trait_ref.map_bound(ty::ExistentialPredicate::Trait));

compiler/rustc_hir_analysis/src/collect.rs

@@ -64,6 +64,7 @@ pub fn provide(providers: &mut Providers) {
  predicates_defined_on,
  explicit_predicates_of: predicates_of::explicit_predicates_of,
  super_predicates_of: predicates_of::super_predicates_of,
+ implied_predicates_of: predicates_of::implied_predicates_of,
  super_predicates_that_define_assoc_type:
  predicates_of::super_predicates_that_define_assoc_type,
  trait_explicit_predicates_and_bounds: predicates_of::trait_explicit_predicates_and_bounds,
@@ -596,6 +597,7 @@ fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
  }
  hir::ItemKind::TraitAlias(..) => {
  tcx.ensure().generics_of(def_id);
+ tcx.at(it.span).implied_predicates_of(def_id);
  tcx.at(it.span).super_predicates_of(def_id);
  tcx.ensure().predicates_of(def_id);
  }

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -125,7 +125,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
  // on a trait we need to add in the supertrait bounds and bounds found on
  // associated types.
  if let Some(_trait_ref) = is_trait {
- predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
+ predicates.extend(tcx.implied_predicates_of(def_id).predicates.iter().cloned());
  }
 
  // In default impls, we can assume that the self type implements
@@ -534,31 +534,62 @@ pub(super) fn explicit_predicates_of<'tcx>(
  }
 }
 
+#[derive(Copy, Clone, Debug)]
+pub enum PredicateFilter {
+ /// All predicates may be implied by the trait
+ All,
+
+ /// Only traits that reference `Self: ..` are implied by the trait
+ SelfOnly,
+
+ /// Only traits that reference `Self: ..` and define an associated type
+ /// with the given ident are implied by the trait
+ SelfThatDefines(Ident),
+}
+
 /// Ensures that the super-predicates of the trait with a `DefId`
 /// of `trait_def_id` are converted and stored. This also ensures that
 /// the transitive super-predicates are converted.
 pub(super) fn super_predicates_of(
  tcx: TyCtxt<'_>,
  trait_def_id: LocalDefId,
 ) -> ty::GenericPredicates<'_> {
- tcx.super_predicates_that_define_assoc_type((trait_def_id.to_def_id(), None))
+ implied_predicates_with_filter(tcx, trait_def_id.to_def_id(), PredicateFilter::SelfOnly)
+}
+
+pub(super) fn super_predicates_that_define_assoc_type(
+ tcx: TyCtxt<'_>,
+ (trait_def_id, assoc_name): (DefId, Ident),
+) -> ty::GenericPredicates<'_> {
+ implied_predicates_with_filter(tcx, trait_def_id, PredicateFilter::SelfThatDefines(assoc_name))
+}
+
+pub(super) fn implied_predicates_of(
+ tcx: TyCtxt<'_>,
+ trait_def_id: LocalDefId,
+) -> ty::GenericPredicates<'_> {
+ if tcx.is_trait_alias(trait_def_id.to_def_id()) {
+ implied_predicates_with_filter(tcx, trait_def_id.to_def_id(), PredicateFilter::All)
+ } else {
+ tcx.super_predicates_of(trait_def_id)
+ }
 }
 
 /// Ensures that the super-predicates of the trait with a `DefId`
 /// of `trait_def_id` are converted and stored. This also ensures that
 /// the transitive super-predicates are converted.
-pub(super) fn super_predicates_that_define_assoc_type(
+pub(super) fn implied_predicates_with_filter(
  tcx: TyCtxt<'_>,
- (trait_def_id, assoc_name): (DefId, Option<Ident>),
+ trait_def_id: DefId,
+ filter: PredicateFilter,
 ) -> ty::GenericPredicates<'_> {
  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!(assoc_name.is_some());
+ assert!(matches!(filter, PredicateFilter::SelfThatDefines(_)));
  return tcx.super_predicates_of(trait_def_id);
  };
 
- debug!("local trait");
  let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id);
 
  let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
@@ -573,48 +604,66 @@ pub(super) fn super_predicates_that_define_assoc_type(
 
  let icx = ItemCtxt::new(tcx, trait_def_id);
 
- // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
  let self_param_ty = tcx.types.self_param;
- let superbounds1 = if let Some(assoc_name) = assoc_name {
- icx.astconv().compute_bounds_that_match_assoc_type(self_param_ty, bounds, assoc_name)
- } else {
- icx.astconv().compute_bounds(self_param_ty, bounds)
+ let (superbounds, where_bounds_that_match) = match filter {
+ PredicateFilter::All => (
+ // Convert the bounds that follow the colon (or equal in trait aliases)
+ icx.astconv().compute_bounds(self_param_ty, bounds),
+ // Also include all where clause bounds
+ icx.type_parameter_bounds_in_generics(
+ generics,
+ item.owner_id.def_id,
+ self_param_ty,
+ OnlySelfBounds(false),
+ None,
+ ),
+ ),
+ PredicateFilter::SelfOnly => (
+ // Convert the bounds that follow the colon (or equal in trait aliases)
+ icx.astconv().compute_bounds(self_param_ty, bounds),
+ // Include where clause bounds for `Self`
+ icx.type_parameter_bounds_in_generics(
+ generics,
+ item.owner_id.def_id,
+ self_param_ty,
+ OnlySelfBounds(true),
+ None,
+ ),
+ ),
+ PredicateFilter::SelfThatDefines(assoc_name) => (
+ // Convert the bounds that follow the colon (or equal) that reference the associated name
+ icx.astconv().compute_bounds_that_match_assoc_type(self_param_ty, bounds, assoc_name),
+ // Include where clause bounds for `Self` that reference the associated name
+ icx.type_parameter_bounds_in_generics(
+ generics,
+ item.owner_id.def_id,
+ self_param_ty,
+ OnlySelfBounds(true),
+ Some(assoc_name),
+ ),
+ ),
  };
 
- let superbounds1 = superbounds1.predicates();
-
- // Convert any explicit superbounds in the where-clause,
- // e.g., `trait Foo where Self: Bar`.
- // In the case of trait aliases, however, we include all bounds in the where-clause,
- // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
- // as one of its "superpredicates".
- let is_trait_alias = tcx.is_trait_alias(trait_def_id.to_def_id());
- let superbounds2 = icx.type_parameter_bounds_in_generics(
- generics,
- item.owner_id.def_id,
- self_param_ty,
- OnlySelfBounds(!is_trait_alias),
- assoc_name,
- );
-
  // Combine the two lists to form the complete set of superbounds:
- let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
- debug!(?superbounds);
+ let implied_bounds = &*tcx
+ .arena
+ .alloc_from_iter(superbounds.predicates().into_iter().chain(where_bounds_that_match));
+ debug!(?implied_bounds);
 
  // Now require that immediate supertraits are converted,
  // which will, in turn, reach indirect supertraits.
- if assoc_name.is_none() {
+ if matches!(filter, PredicateFilter::SelfOnly) {
  // Now require that immediate supertraits are converted,
  // which will, in turn, reach indirect supertraits.
- for &(pred, span) in superbounds {
+ for &(pred, span) in implied_bounds {
  debug!("superbound: {:?}", pred);
  if let ty::PredicateKind::Clause(ty::Clause::Trait(bound)) = pred.kind().skip_binder() {
  tcx.at(span).super_predicates_of(bound.def_id());
  }
  }
  }
 
- ty::GenericPredicates { parent: None, predicates: superbounds }
+ ty::GenericPredicates { parent: None, predicates: implied_bounds }
 }
 
 /// Returns the predicates defined on `item_def_id` of the form

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -1749,8 +1749,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
  if trait_defines_associated_type_named(def_id) {
  break Some(bound_vars.into_iter().collect());
  }
- let predicates =
- tcx.super_predicates_that_define_assoc_type((def_id, Some(assoc_name)));
+ let predicates = tcx.super_predicates_that_define_assoc_type((def_id, assoc_name));
  let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| {
  let bound_predicate = pred.kind();
  match bound_predicate.skip_binder() {

compiler/rustc_hir_typeck/src/closure.rs

@@ -210,7 +210,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  // and we want to keep inference generally in the same order of
  // the registered obligations.
  predicates.rev(),
- ) {
+ )
+ // We only care about self bounds
+ .filter_only_self()
+ {
  debug!(?pred);
  let bound_predicate = pred.kind();
 

compiler/rustc_infer/src/traits/util.rs

@@ -69,6 +69,7 @@ impl<'tcx> Extend<ty::Predicate<'tcx>> for PredicateSet<'tcx> {
 pub struct Elaborator<'tcx, O> {
  stack: Vec<O>,
  visited: PredicateSet<'tcx>,
+ only_self: bool,
 }
 
 /// Describes how to elaborate an obligation into a sub-obligation.
@@ -170,7 +171,8 @@ pub fn elaborate<'tcx, O: Elaboratable<'tcx>>(
  tcx: TyCtxt<'tcx>,
  obligations: impl IntoIterator<Item = O>,
 ) -> Elaborator<'tcx, O> {
- let mut elaborator = Elaborator { stack: Vec::new(), visited: PredicateSet::new(tcx) };
+ let mut elaborator =
+ Elaborator { stack: Vec::new(), visited: PredicateSet::new(tcx), only_self: false };
  elaborator.extend_deduped(obligations);
  elaborator
 }
@@ -185,14 +187,25 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
  self.stack.extend(obligations.into_iter().filter(|o| self.visited.insert(o.predicate())));
  }
 
+ /// Filter to only the supertraits of trait predicates, i.e. only the predicates
+ /// that have `Self` as their self type, instead of all implied predicates.
+ pub fn filter_only_self(mut self) -> Self {
+ self.only_self = true;
+ self
+ }
+
  fn elaborate(&mut self, elaboratable: &O) {
  let tcx = self.visited.tcx;
 
  let bound_predicate = elaboratable.predicate().kind();
  match bound_predicate.skip_binder() {
  ty::PredicateKind::Clause(ty::Clause::Trait(data)) => {
- // Get predicates declared on the trait.
- let predicates = tcx.super_predicates_of(data.def_id());
+ // Get predicates implied by the trait, or only super predicates if we only care about self predicates.
+ let predicates = if self.only_self {
+ tcx.super_predicates_of(data.def_id())
+ } else {
+ tcx.implied_predicates_of(data.def_id())
+ };
 
  let obligations =
  predicates.predicates.iter().enumerate().map(|(index, &(mut pred, span))| {
@@ -350,18 +363,16 @@ pub fn supertraits<'tcx>(
  tcx: TyCtxt<'tcx>,
  trait_ref: ty::PolyTraitRef<'tcx>,
 ) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> {
- let pred: ty::Predicate<'tcx> = trait_ref.to_predicate(tcx);
- FilterToTraits::new(elaborate(tcx, [pred]))
+ elaborate(tcx, [trait_ref.to_predicate(tcx)]).filter_only_self().filter_to_traits()
 }
 
 pub fn transitive_bounds<'tcx>(
  tcx: TyCtxt<'tcx>,
  trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
 ) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> {
- FilterToTraits::new(elaborate(
- tcx,
- trait_refs.map(|trait_ref| -> ty::Predicate<'tcx> { trait_ref.to_predicate(tcx) }),
- ))
+ elaborate(tcx, trait_refs.map(|trait_ref| trait_ref.to_predicate(tcx)))
+ .filter_only_self()
+ .filter_to_traits()
 }
 
 /// A specialized variant of `elaborate` that only elaborates trait references that may
@@ -381,10 +392,8 @@ pub fn transitive_bounds_that_define_assoc_type<'tcx>(
  while let Some(trait_ref) = stack.pop() {
  let anon_trait_ref = tcx.anonymize_bound_vars(trait_ref);
  if visited.insert(anon_trait_ref) {
- let super_predicates = tcx.super_predicates_that_define_assoc_type((
- trait_ref.def_id(),
- Some(assoc_name),
- ));
+ let super_predicates =
+ tcx.super_predicates_that_define_assoc_type((trait_ref.def_id(), assoc_name));
  for (super_predicate, _) in super_predicates.predicates {
  let subst_predicate = super_predicate.subst_supertrait(tcx, &trait_ref);
  if let Some(binder) = subst_predicate.to_opt_poly_trait_pred() {
@@ -404,18 +413,18 @@ pub fn transitive_bounds_that_define_assoc_type<'tcx>(
 // Other
 ///////////////////////////////////////////////////////////////////////////
 
+impl<'tcx> Elaborator<'tcx, ty::Predicate<'tcx>> {
+ fn filter_to_traits(self) -> FilterToTraits<Self> {
+ FilterToTraits { base_iterator: self }
+ }
+}
+
 /// A filter around an iterator of predicates that makes it yield up
 /// just trait references.
 pub struct FilterToTraits<I> {
  base_iterator: I,
 }
 
-impl<I> FilterToTraits<I> {
- fn new(base: I) -> FilterToTraits<I> {
- FilterToTraits { base_iterator: base }
- }
-}
-
 impl<'tcx, I: Iterator<Item = ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> {
  type Item = ty::PolyTraitRef<'tcx>;