--- /dev/null
+use crate::astconv::AstConv;
+use crate::bounds::Bounds;
+use crate::collect::ItemCtxt;
+use crate::constrained_generic_params as cgp;
+use hir::{HirId, Node};
+use rustc_data_structures::fx::FxIndexSet;
+use rustc_hir as hir;
+use rustc_hir::def::DefKind;
+use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::intravisit::{self, Visitor};
+use rustc_middle::ty::subst::InternalSubsts;
+use rustc_middle::ty::ToPredicate;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::symbol::{sym, Ident};
+use rustc_span::{Span, DUMMY_SP};
+
+#[derive(Debug)]
+struct OnlySelfBounds(bool);
+
+/// Returns a list of all type predicates (explicit and implicit) for the definition with
+/// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
+/// `Self: Trait` predicates for traits.
+pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
+ let mut result = tcx.predicates_defined_on(def_id);
+
+ if tcx.is_trait(def_id) {
+ // For traits, add `Self: Trait` predicate. This is
+ // not part of the predicates that a user writes, but it
+ // is something that one must prove in order to invoke a
+ // method or project an associated type.
+ //
+ // In the chalk setup, this predicate is not part of the
+ // "predicates" for a trait item. But it is useful in
+ // rustc because if you directly (e.g.) invoke a trait
+ // method like `Trait::method(...)`, you must naturally
+ // prove that the trait applies to the types that were
+ // used, and adding the predicate into this list ensures
+ // that this is done.
+ //
+ // We use a DUMMY_SP here as a way to signal trait bounds that come
+ // from the trait itself that *shouldn't* be shown as the source of
+ // an obligation and instead be skipped. Otherwise we'd use
+ // `tcx.def_span(def_id);`
+
+ let constness = if tcx.has_attr(def_id, sym::const_trait) {
+ ty::BoundConstness::ConstIfConst
+ } else {
+ ty::BoundConstness::NotConst
+ };
+
+ let span = rustc_span::DUMMY_SP;
+ result.predicates =
+ tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
+ ty::TraitRef::identity(tcx, def_id).with_constness(constness).to_predicate(tcx),
+ span,
+ ))));
+ }
+ debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
+ result
+}
+
+/// Returns a list of user-specified type predicates for the definition with ID `def_id`.
+/// N.B., this does not include any implied/inferred constraints.
+#[instrument(level = "trace", skip(tcx), ret)]
+fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
+ use rustc_hir::*;
+
+ let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
+ let node = tcx.hir().get(hir_id);
+
+ let mut is_trait = None;
+ let mut is_default_impl_trait = None;
+
+ let icx = ItemCtxt::new(tcx, def_id);
+
+ const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty();
+
+ // We use an `IndexSet` to preserves order of insertion.
+ // Preserving the order of insertion is important here so as not to break UI tests.
+ let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
+
+ let ast_generics = match node {
+ Node::TraitItem(item) => item.generics,
+
+ Node::ImplItem(item) => item.generics,
+
+ Node::Item(item) => {
+ match item.kind {
+ ItemKind::Impl(ref impl_) => {
+ if impl_.defaultness.is_default() {
+ is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
+ }
+ &impl_.generics
+ }
+ ItemKind::Fn(.., ref generics, _)
+ | ItemKind::TyAlias(_, ref generics)
+ | ItemKind::Enum(_, ref generics)
+ | ItemKind::Struct(_, ref generics)
+ | ItemKind::Union(_, ref generics) => *generics,
+
+ ItemKind::Trait(_, _, ref generics, ..) => {
+ is_trait = Some(ty::TraitRef::identity(tcx, def_id));
+ *generics
+ }
+ ItemKind::TraitAlias(ref generics, _) => {
+ is_trait = Some(ty::TraitRef::identity(tcx, def_id));
+ *generics
+ }
+ ItemKind::OpaqueTy(OpaqueTy {
+ origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
+ ..
+ }) => {
+ // return-position impl trait
+ //
+ // We don't inherit predicates from the parent here:
+ // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
+ // then the return type is `f::<'static, T>::{{opaque}}`.
+ //
+ // If we inherited the predicates of `f` then we would
+ // require that `T: 'static` to show that the return
+ // type is well-formed.
+ //
+ // The only way to have something with this opaque type
+ // is from the return type of the containing function,
+ // which will ensure that the function's predicates
+ // hold.
+ return ty::GenericPredicates { parent: None, predicates: &[] };
+ }
+ ItemKind::OpaqueTy(OpaqueTy {
+ ref generics,
+ origin: hir::OpaqueTyOrigin::TyAlias,
+ ..
+ }) => {
+ // type-alias impl trait
+ generics
+ }
+
+ _ => NO_GENERICS,
+ }
+ }
+
+ Node::ForeignItem(item) => match item.kind {
+ ForeignItemKind::Static(..) => NO_GENERICS,
+ ForeignItemKind::Fn(_, _, ref generics) => *generics,
+ ForeignItemKind::Type => NO_GENERICS,
+ },
+
+ _ => NO_GENERICS,
+ };
+
+ let generics = tcx.generics_of(def_id);
+ let parent_count = generics.parent_count as u32;
+ let has_own_self = generics.has_self && parent_count == 0;
+
+ // Below we'll consider the bounds on the type parameters (including `Self`)
+ // and the explicit where-clauses, but to get the full set of predicates
+ // 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());
+ }
+
+ // In default impls, we can assume that the self type implements
+ // the trait. So in:
+ //
+ // default impl Foo for Bar { .. }
+ //
+ // we add a default where clause `Foo: Bar`. We do a similar thing for traits
+ // (see below). Recall that a default impl is not itself an impl, but rather a
+ // set of defaults that can be incorporated into another impl.
+ if let Some(trait_ref) = is_default_impl_trait {
+ predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
+ }
+
+ // Collect the region predicates that were declared inline as
+ // well. In the case of parameters declared on a fn or method, we
+ // have to be careful to only iterate over early-bound regions.
+ let mut index = parent_count
+ + has_own_self as u32
+ + super::early_bound_lifetimes_from_generics(tcx, ast_generics).count() as u32;
+
+ trace!(?predicates);
+ trace!(?ast_generics);
+
+ // Collect the predicates that were written inline by the user on each
+ // type parameter (e.g., `<T: Foo>`).
+ for param in ast_generics.params {
+ match param.kind {
+ // We already dealt with early bound lifetimes above.
+ GenericParamKind::Lifetime { .. } => (),
+ GenericParamKind::Type { .. } => {
+ let name = param.name.ident().name;
+ let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
+ index += 1;
+
+ let mut bounds = Bounds::default();
+ // Params are implicitly sized unless a `?Sized` bound is found
+ <dyn AstConv<'_>>::add_implicitly_sized(
+ &icx,
+ &mut bounds,
+ &[],
+ Some((param.hir_id, ast_generics.predicates)),
+ param.span,
+ );
+ trace!(?bounds);
+ predicates.extend(bounds.predicates(tcx, param_ty));
+ trace!(?predicates);
+ }
+ GenericParamKind::Const { .. } => {
+ // Bounds on const parameters are currently not possible.
+ index += 1;
+ }
+ }
+ }
+
+ trace!(?predicates);
+ // Add in the bounds that appear in the where-clause.
+ for predicate in ast_generics.predicates {
+ match predicate {
+ hir::WherePredicate::BoundPredicate(bound_pred) => {
+ let ty = icx.to_ty(bound_pred.bounded_ty);
+ let bound_vars = icx.tcx.late_bound_vars(bound_pred.hir_id);
+
+ // Keep the type around in a dummy predicate, in case of no bounds.
+ // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
+ // is still checked for WF.
+ if bound_pred.bounds.is_empty() {
+ if let ty::Param(_) = ty.kind() {
+ // This is a `where T:`, which can be in the HIR from the
+ // transformation that moves `?Sized` to `T`'s declaration.
+ // We can skip the predicate because type parameters are
+ // trivially WF, but also we *should*, to avoid exposing
+ // users who never wrote `where Type:,` themselves, to
+ // compiler/tooling bugs from not handling WF predicates.
+ } else {
+ let span = bound_pred.bounded_ty.span;
+ let predicate = ty::Binder::bind_with_vars(
+ ty::PredicateKind::WellFormed(ty.into()),
+ bound_vars,
+ );
+ predicates.insert((predicate.to_predicate(tcx), span));
+ }
+ }
+
+ let mut bounds = Bounds::default();
+ <dyn AstConv<'_>>::add_bounds(
+ &icx,
+ ty,
+ bound_pred.bounds.iter(),
+ &mut bounds,
+ bound_vars,
+ );
+ predicates.extend(bounds.predicates(tcx, ty));
+ }
+
+ hir::WherePredicate::RegionPredicate(region_pred) => {
+ let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, ®ion_pred.lifetime, None);
+ predicates.extend(region_pred.bounds.iter().map(|bound| {
+ let (r2, span) = match bound {
+ hir::GenericBound::Outlives(lt) => {
+ (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
+ }
+ _ => bug!(),
+ };
+ let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
+ ty::OutlivesPredicate(r1, r2),
+ ))
+ .to_predicate(icx.tcx);
+
+ (pred, span)
+ }))
+ }
+
+ hir::WherePredicate::EqPredicate(..) => {
+ // FIXME(#20041)
+ }
+ }
+ }
+
+ if tcx.features().generic_const_exprs {
+ predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
+ }
+
+ let mut predicates: Vec<_> = predicates.into_iter().collect();
+
+ // Subtle: before we store the predicates into the tcx, we
+ // sort them so that predicates like `T: Foo<Item=U>` come
+ // before uses of `U`. This avoids false ambiguity errors
+ // in trait checking. See `setup_constraining_predicates`
+ // for details.
+ if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
+ let self_ty = tcx.type_of(def_id);
+ let trait_ref = tcx.impl_trait_ref(def_id);
+ cgp::setup_constraining_predicates(
+ tcx,
+ &mut predicates,
+ trait_ref,
+ &mut cgp::parameters_for_impl(self_ty, trait_ref),
+ );
+ }
+
+ ty::GenericPredicates {
+ parent: generics.parent,
+ predicates: tcx.arena.alloc_from_iter(predicates),
+ }
+}
+
+fn const_evaluatable_predicates_of<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ def_id: LocalDefId,
+) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
+ struct ConstCollector<'tcx> {
+ tcx: TyCtxt<'tcx>,
+ preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
+ }
+
+ impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
+ fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
+ let def_id = self.tcx.hir().local_def_id(c.hir_id);
+ let ct = ty::Const::from_anon_const(self.tcx, def_id);
+ if let ty::ConstKind::Unevaluated(_) = ct.kind() {
+ let span = self.tcx.hir().span(c.hir_id);
+ self.preds.insert((
+ ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(ct))
+ .to_predicate(self.tcx),
+ span,
+ ));
+ }
+ }
+
+ fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
+ // Do not look into const param defaults,
+ // these get checked when they are actually instantiated.
+ //
+ // We do not want the following to error:
+ //
+ // struct Foo<const N: usize, const M: usize = { N + 1 }>;
+ // struct Bar<const N: usize>(Foo<N, 3>);
+ }
+ }
+
+ let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
+ let node = tcx.hir().get(hir_id);
+
+ let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
+ if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
+ if let Some(of_trait) = &impl_.of_trait {
+ debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
+ collector.visit_trait_ref(of_trait);
+ }
+
+ debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
+ collector.visit_ty(impl_.self_ty);
+ }
+
+ if let Some(generics) = node.generics() {
+ debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
+ collector.visit_generics(generics);
+ }
+
+ if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
+ debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
+ collector.visit_fn_decl(fn_sig.decl);
+ }
+ debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
+
+ collector.preds
+}
+
+pub(super) fn trait_explicit_predicates_and_bounds(
+ tcx: TyCtxt<'_>,
+ def_id: LocalDefId,
+) -> ty::GenericPredicates<'_> {
+ assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
+ gather_explicit_predicates_of(tcx, def_id.to_def_id())
+}
+
+pub(super) fn explicit_predicates_of<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ def_id: DefId,
+) -> ty::GenericPredicates<'tcx> {
+ let def_kind = tcx.def_kind(def_id);
+ if let DefKind::Trait = def_kind {
+ // Remove bounds on associated types from the predicates, they will be
+ // returned by `explicit_item_bounds`.
+ let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
+ let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
+
+ let is_assoc_item_ty = |ty: Ty<'tcx>| {
+ // For a predicate from a where clause to become a bound on an
+ // associated type:
+ // * It must use the identity substs of the item.
+ // * Since any generic parameters on the item are not in scope,
+ // this means that the item is not a GAT, and its identity
+ // substs are the same as the trait's.
+ // * It must be an associated type for this trait (*not* a
+ // supertrait).
+ if let ty::Projection(projection) = ty.kind() {
+ projection.substs == trait_identity_substs
+ && tcx.associated_item(projection.item_def_id).container_id(tcx) == def_id
+ } else {
+ false
+ }
+ };
+
+ let predicates: Vec<_> = predicates_and_bounds
+ .predicates
+ .iter()
+ .copied()
+ .filter(|(pred, _)| match pred.kind().skip_binder() {
+ ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
+ ty::PredicateKind::Projection(proj) => {
+ !is_assoc_item_ty(proj.projection_ty.self_ty())
+ }
+ ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
+ _ => true,
+ })
+ .collect();
+ if predicates.len() == predicates_and_bounds.predicates.len() {
+ predicates_and_bounds
+ } else {
+ ty::GenericPredicates {
+ parent: predicates_and_bounds.parent,
+ predicates: tcx.arena.alloc_slice(&predicates),
+ }
+ }
+ } else {
+ if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
+ let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
+ if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
+ // In `generics_of` we set the generics' parent to be our parent's parent which means that
+ // we lose out on the predicates of our actual parent if we dont return those predicates here.
+ // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
+ //
+ // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
+ // ^^^ ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
+ // ^^^ explicit_predicates_of on
+ // parent item we dont have set as the
+ // parent of generics returned by `generics_of`
+ //
+ // In the above code we want the anon const to have predicates in its param env for `T: Trait`
+ let item_def_id = tcx.hir().get_parent_item(hir_id);
+ // In the above code example we would be calling `explicit_predicates_of(Foo)` here
+ return tcx.explicit_predicates_of(item_def_id);
+ }
+ }
+ gather_explicit_predicates_of(tcx, 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_of(
+ tcx: TyCtxt<'_>,
+ trait_def_id: DefId,
+) -> ty::GenericPredicates<'_> {
+ tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
+}
+
+/// 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(
+ tcx: TyCtxt<'_>,
+ (trait_def_id, assoc_name): (DefId, Option<Ident>),
+) -> ty::GenericPredicates<'_> {
+ if trait_def_id.is_local() {
+ debug!("local trait");
+ let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
+
+ let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
+ bug!("trait_node_id {} is not an item", trait_hir_id);
+ };
+
+ let (generics, bounds) = match item.kind {
+ hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
+ hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
+ _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
+ };
+
+ 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 {
+ <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
+ &icx,
+ self_param_ty,
+ bounds,
+ assoc_name,
+ )
+ } else {
+ <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
+ };
+
+ let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
+
+ // 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);
+ let superbounds2 = icx.type_parameter_bounds_in_generics(
+ generics,
+ item.hir_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);
+
+ // Now require that immediate supertraits are converted,
+ // which will, in turn, reach indirect supertraits.
+ if assoc_name.is_none() {
+ // Now require that immediate supertraits are converted,
+ // which will, in turn, reach indirect supertraits.
+ for &(pred, span) in superbounds {
+ debug!("superbound: {:?}", pred);
+ if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
+ tcx.at(span).super_predicates_of(bound.def_id());
+ }
+ }
+ }
+
+ ty::GenericPredicates { parent: None, predicates: superbounds }
+ } else {
+ // if `assoc_name` is None, then the query should've been redirected to an
+ // external provider
+ assert!(assoc_name.is_some());
+ tcx.super_predicates_of(trait_def_id)
+ }
+}
+
+/// Returns the predicates defined on `item_def_id` of the form
+/// `X: Foo` where `X` is the type parameter `def_id`.
+#[instrument(level = "trace", skip(tcx))]
+pub(super) fn type_param_predicates(
+ tcx: TyCtxt<'_>,
+ (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
+) -> ty::GenericPredicates<'_> {
+ use rustc_hir::*;
+
+ // In the AST, 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.hir().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 = tcx.mk_ty_param(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.to_def_id() {
+ None
+ } else {
+ tcx.generics_of(item_def_id).parent
+ };
+
+ let mut result = parent
+ .map(|parent| {
+ let icx = ItemCtxt::new(tcx, parent);
+ icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
+ })
+ .unwrap_or_default();
+ let mut extend = None;
+
+ let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
+ let ast_generics = match tcx.hir().get(item_hir_id) {
+ Node::TraitItem(item) => &item.generics,
+
+ Node::ImplItem(item) => &item.generics,
+
+ Node::Item(item) => {
+ match item.kind {
+ ItemKind::Fn(.., ref generics, _)
+ | ItemKind::Impl(hir::Impl { ref generics, .. })
+ | ItemKind::TyAlias(_, ref generics)
+ | ItemKind::OpaqueTy(OpaqueTy {
+ ref generics,
+ origin: hir::OpaqueTyOrigin::TyAlias,
+ ..
+ })
+ | ItemKind::Enum(_, ref generics)
+ | ItemKind::Struct(_, ref generics)
+ | ItemKind::Union(_, ref generics) => generics,
+ ItemKind::Trait(_, _, ref generics, ..) => {
+ // Implied `Self: Trait` and supertrait bounds.
+ if param_id == item_hir_id {
+ let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
+ extend =
+ Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
+ }
+ generics
+ }
+ _ => return result,
+ }
+ }
+
+ Node::ForeignItem(item) => match item.kind {
+ ForeignItemKind::Fn(_, _, ref generics) => generics,
+ _ => return result,
+ },
+
+ _ => return result,
+ };
+
+ let icx = ItemCtxt::new(tcx, item_def_id);
+ let extra_predicates = extend.into_iter().chain(
+ icx.type_parameter_bounds_in_generics(
+ ast_generics,
+ param_id,
+ ty,
+ OnlySelfBounds(true),
+ Some(assoc_name),
+ )
+ .into_iter()
+ .filter(|(predicate, _)| match predicate.kind().skip_binder() {
+ ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
+ _ => false,
+ }),
+ );
+ result.predicates =
+ tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
+ result
+}
+
+impl<'tcx> ItemCtxt<'tcx> {
+ /// Finds bounds from `hir::Generics`. This requires scanning through the
+ /// AST. We do this to avoid having to convert *all* the bounds, which
+ /// would create artificial cycles. Instead, we can only convert the
+ /// bounds for a type parameter `X` if `X::Foo` is used.
+ #[instrument(level = "trace", skip(self, ast_generics))]
+ fn type_parameter_bounds_in_generics(
+ &self,
+ ast_generics: &'tcx hir::Generics<'tcx>,
+ param_id: hir::HirId,
+ ty: Ty<'tcx>,
+ only_self_bounds: OnlySelfBounds,
+ assoc_name: Option<Ident>,
+ ) -> Vec<(ty::Predicate<'tcx>, Span)> {
+ let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
+ trace!(?param_def_id);
+ ast_generics
+ .predicates
+ .iter()
+ .filter_map(|wp| match *wp {
+ hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
+ _ => None,
+ })
+ .flat_map(|bp| {
+ let bt = if bp.is_param_bound(param_def_id) {
+ Some(ty)
+ } else if !only_self_bounds.0 {
+ Some(self.to_ty(bp.bounded_ty))
+ } else {
+ None
+ };
+ let bvars = self.tcx.late_bound_vars(bp.hir_id);
+
+ bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b, bvars))).filter(
+ |(_, b, _)| match assoc_name {
+ Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
+ None => true,
+ },
+ )
+ })
+ .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars))
+ .collect()
+ }
+
+ #[instrument(level = "trace", skip(self))]
+ fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
+ match b {
+ hir::GenericBound::Trait(poly_trait_ref, _) => {
+ let trait_ref = &poly_trait_ref.trait_ref;
+ if let Some(trait_did) = trait_ref.trait_def_id() {
+ self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
+ } else {
+ false
+ }
+ }
+ _ => false,
+ }
+ }
+}
+
+/// Converts a specific `GenericBound` from the AST into a set of
+/// predicates that apply to the self type. A vector is returned
+/// because this can be anywhere from zero predicates (`T: ?Sized` adds no
+/// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
+/// and `<T as Bar>::X == i32`).
+fn predicates_from_bound<'tcx>(
+ astconv: &dyn AstConv<'tcx>,
+ param_ty: Ty<'tcx>,
+ bound: &'tcx hir::GenericBound<'tcx>,
+ bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
+) -> Vec<(ty::Predicate<'tcx>, Span)> {
+ let mut bounds = Bounds::default();
+ astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
+ bounds.predicates(astconv.tcx(), param_ty).collect()
+}
projects / rustc.git / blobdiff