2 use crate::astconv::{AstConv, SizedByDefault};
4 use rustc_infer::traits::util;
5 use rustc_middle::ty::subst::InternalSubsts;
6 use rustc_middle::ty::{self, TyCtxt};
7 use rustc_span::def_id::DefId;
10 /// For associated types we include both bounds written on the type
11 /// (`type X: Trait`) and predicates from the trait: `where Self::X: Trait`.
13 /// Note that this filtering is done with the items identity substs to
14 /// simplify checking that these bounds are met in impls. This means that
15 /// a bound such as `for<'b> <Self as X<'b>>::U: Clone` can't be used, as in
16 /// `hr-associated-type-bound-1.rs`.
17 fn associated_type_bounds<'tcx>(
19 assoc_item_def_id: DefId,
20 bounds: &'tcx [hir::GenericBound<'tcx>],
22 ) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
23 let item_ty = tcx.mk_projection(
25 InternalSubsts::identity_for_item(tcx, assoc_item_def_id),
28 let bounds = AstConv::compute_bounds(
29 &ItemCtxt::new(tcx, assoc_item_def_id),
36 let trait_def_id = tcx.associated_item(assoc_item_def_id).container.id();
37 let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id.expect_local());
39 let bounds_from_parent =
40 trait_predicates.predicates.iter().copied().filter(|(pred, _)| match pred.skip_binders() {
41 ty::PredicateAtom::Trait(tr, _) => tr.self_ty() == item_ty,
42 ty::PredicateAtom::Projection(proj) => proj.projection_ty.self_ty() == item_ty,
43 ty::PredicateAtom::TypeOutlives(outlives) => outlives.0 == item_ty,
49 .alloc_from_iter(bounds.predicates(tcx, item_ty).into_iter().chain(bounds_from_parent));
50 debug!("associated_type_bounds({}) = {:?}", tcx.def_path_str(assoc_item_def_id), all_bounds);
54 /// Opaque types don't inherit bounds from their parent: for return position
55 /// impl trait it isn't possible to write a suitable predicate on the
56 /// containing function and for type-alias impl trait we don't have a backwards
57 /// compatibility issue.
58 fn opaque_type_bounds<'tcx>(
61 bounds: &'tcx [hir::GenericBound<'tcx>],
63 ) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
64 ty::print::with_no_queries(|| {
66 tcx.mk_opaque(opaque_def_id, InternalSubsts::identity_for_item(tcx, opaque_def_id));
68 let bounds = AstConv::compute_bounds(
69 &ItemCtxt::new(tcx, opaque_def_id),
75 .predicates(tcx, item_ty);
77 debug!("opaque_type_bounds({}) = {:?}", tcx.def_path_str(opaque_def_id), bounds);
79 tcx.arena.alloc_slice(&bounds)
83 pub(super) fn explicit_item_bounds(
86 ) -> &'_ [(ty::Predicate<'_>, Span)] {
87 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
88 match tcx.hir().get(hir_id) {
89 hir::Node::TraitItem(hir::TraitItem {
90 kind: hir::TraitItemKind::Type(bounds, _),
93 }) => associated_type_bounds(tcx, def_id, bounds, *span),
94 hir::Node::Item(hir::Item {
95 kind: hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds, .. }),
98 }) => opaque_type_bounds(tcx, def_id, bounds, *span),
99 _ => bug!("item_bounds called on {:?}", def_id),
103 pub(super) fn item_bounds(tcx: TyCtxt<'_>, def_id: DefId) -> &'_ ty::List<ty::Predicate<'_>> {
105 util::elaborate_predicates(
107 tcx.explicit_item_bounds(def_id).iter().map(|&(bound, _span)| bound),
109 .map(|obligation| obligation.predicate),