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Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_typeck/src/collect/item_bounds.rs | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/collect/item_bounds.rs b/compiler/rustc_typeck/src/collect/item_bounds.rs new file mode 100644 index 000000000..0d2b75d33 --- /dev/null +++ b/compiler/rustc_typeck/src/collect/item_bounds.rs @@ -0,0 +1,102 @@ +use super::ItemCtxt; +use crate::astconv::AstConv; +use rustc_hir as hir; +use rustc_infer::traits::util; +use rustc_middle::ty::subst::InternalSubsts; +use rustc_middle::ty::{self, DefIdTree, TyCtxt}; +use rustc_span::def_id::DefId; +use rustc_span::Span; + +/// For associated types we include both bounds written on the type +/// (`type X: Trait`) and predicates from the trait: `where Self::X: Trait`. +/// +/// Note that this filtering is done with the items identity substs to +/// simplify checking that these bounds are met in impls. This means that +/// a bound such as `for<'b> <Self as X<'b>>::U: Clone` can't be used, as in +/// `hr-associated-type-bound-1.rs`. +fn associated_type_bounds<'tcx>( + tcx: TyCtxt<'tcx>, + assoc_item_def_id: DefId, + ast_bounds: &'tcx [hir::GenericBound<'tcx>], + span: Span, +) -> &'tcx [(ty::Predicate<'tcx>, Span)] { + let item_ty = tcx.mk_projection( + assoc_item_def_id, + InternalSubsts::identity_for_item(tcx, assoc_item_def_id), + ); + + let icx = ItemCtxt::new(tcx, assoc_item_def_id); + let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, item_ty, ast_bounds); + // Associated types are implicitly sized unless a `?Sized` bound is found + <dyn AstConv<'_>>::add_implicitly_sized(&icx, &mut bounds, ast_bounds, None, span); + + let trait_def_id = tcx.parent(assoc_item_def_id); + let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id.expect_local()); + + let bounds_from_parent = trait_predicates.predicates.iter().copied().filter(|(pred, _)| { + match pred.kind().skip_binder() { + ty::PredicateKind::Trait(tr) => tr.self_ty() == item_ty, + ty::PredicateKind::Projection(proj) => proj.projection_ty.self_ty() == item_ty, + ty::PredicateKind::TypeOutlives(outlives) => outlives.0 == item_ty, + _ => false, + } + }); + + let all_bounds = tcx + .arena + .alloc_from_iter(bounds.predicates(tcx, item_ty).into_iter().chain(bounds_from_parent)); + debug!("associated_type_bounds({}) = {:?}", tcx.def_path_str(assoc_item_def_id), all_bounds); + all_bounds +} + +/// Opaque types don't inherit bounds from their parent: for return position +/// impl trait it isn't possible to write a suitable predicate on the +/// containing function and for type-alias impl trait we don't have a backwards +/// compatibility issue. +fn opaque_type_bounds<'tcx>( + tcx: TyCtxt<'tcx>, + opaque_def_id: DefId, + ast_bounds: &'tcx [hir::GenericBound<'tcx>], + span: Span, +) -> &'tcx [(ty::Predicate<'tcx>, Span)] { + ty::print::with_no_queries!({ + let item_ty = + tcx.mk_opaque(opaque_def_id, InternalSubsts::identity_for_item(tcx, opaque_def_id)); + + let icx = ItemCtxt::new(tcx, opaque_def_id); + let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, item_ty, ast_bounds); + // Opaque types are implicitly sized unless a `?Sized` bound is found + <dyn AstConv<'_>>::add_implicitly_sized(&icx, &mut bounds, ast_bounds, None, span); + tcx.arena.alloc_from_iter(bounds.predicates(tcx, item_ty)) + }) +} + +pub(super) fn explicit_item_bounds( + tcx: TyCtxt<'_>, + def_id: DefId, +) -> &'_ [(ty::Predicate<'_>, Span)] { + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); + match tcx.hir().get(hir_id) { + hir::Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Type(bounds, _), + span, + .. + }) => associated_type_bounds(tcx, def_id, bounds, *span), + hir::Node::Item(hir::Item { + kind: hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds, .. }), + span, + .. + }) => opaque_type_bounds(tcx, def_id, bounds, *span), + _ => bug!("item_bounds called on {:?}", def_id), + } +} + +pub(super) fn item_bounds(tcx: TyCtxt<'_>, def_id: DefId) -> &'_ ty::List<ty::Predicate<'_>> { + tcx.mk_predicates( + util::elaborate_predicates( + tcx, + tcx.explicit_item_bounds(def_id).iter().map(|&(bound, _span)| bound), + ) + .map(|obligation| obligation.predicate), + ) +} |