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108 lines
3.6 KiB
Rust
108 lines
3.6 KiB
Rust
//! Bounds are restrictions applied to some types after they've been converted into the
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//! `ty` form from the HIR.
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use rustc_hir::LangItem;
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use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
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use rustc_span::Span;
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/// Collects together a list of type bounds. These lists of bounds occur in many places
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/// in Rust's syntax:
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///
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/// ```text
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/// trait Foo: Bar + Baz { }
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/// ^^^^^^^^^ supertrait list bounding the `Self` type parameter
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///
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/// fn foo<T: Bar + Baz>() { }
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/// ^^^^^^^^^ bounding the type parameter `T`
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///
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/// impl dyn Bar + Baz
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/// ^^^^^^^^^ bounding the type-erased dynamic type
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/// ```
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///
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/// Our representation is a bit mixed here -- in some cases, we
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/// include the self type (e.g., `trait_bounds`) but in others we do not
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#[derive(Default, PartialEq, Eq, Clone, Debug)]
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pub struct Bounds<'tcx> {
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pub clauses: Vec<(ty::Clause<'tcx>, Span)>,
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}
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impl<'tcx> Bounds<'tcx> {
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pub fn push_region_bound(
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&mut self,
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tcx: TyCtxt<'tcx>,
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region: ty::PolyTypeOutlivesPredicate<'tcx>,
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span: Span,
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) {
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self.clauses
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.push((region.map_bound(|p| ty::ClauseKind::TypeOutlives(p)).to_predicate(tcx), span));
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}
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pub fn push_trait_bound(
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&mut self,
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tcx: TyCtxt<'tcx>,
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trait_ref: ty::PolyTraitRef<'tcx>,
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span: Span,
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polarity: ty::ImplPolarity,
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) {
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self.push_trait_bound_inner(tcx, trait_ref, span, polarity);
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// push a non-const (`host = true`) version of the bound if it is `~const`.
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if tcx.features().effects
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&& let Some(host_effect_idx) = tcx.generics_of(trait_ref.def_id()).host_effect_index
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&& trait_ref.skip_binder().args.const_at(host_effect_idx) != tcx.consts.true_
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{
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let generics = tcx.generics_of(trait_ref.def_id());
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let Some(host_index) = generics.host_effect_index else { return };
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let trait_ref = trait_ref.map_bound(|mut trait_ref| {
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trait_ref.args =
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tcx.mk_args_from_iter(trait_ref.args.iter().enumerate().map(|(n, arg)| {
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if host_index == n { tcx.consts.true_.into() } else { arg }
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}));
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trait_ref
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});
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self.push_trait_bound_inner(tcx, trait_ref, span, polarity);
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}
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}
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fn push_trait_bound_inner(
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&mut self,
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tcx: TyCtxt<'tcx>,
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trait_ref: ty::PolyTraitRef<'tcx>,
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span: Span,
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polarity: ty::ImplPolarity,
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) {
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self.clauses.push((
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trait_ref
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.map_bound(|trait_ref| {
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ty::ClauseKind::Trait(ty::TraitPredicate { trait_ref, polarity })
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})
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.to_predicate(tcx),
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span,
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));
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}
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pub fn push_projection_bound(
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&mut self,
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tcx: TyCtxt<'tcx>,
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projection: ty::PolyProjectionPredicate<'tcx>,
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span: Span,
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) {
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self.clauses.push((
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projection.map_bound(|proj| ty::ClauseKind::Projection(proj)).to_predicate(tcx),
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span,
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));
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}
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pub fn push_sized(&mut self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, span: Span) {
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let sized_def_id = tcx.require_lang_item(LangItem::Sized, Some(span));
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let trait_ref = ty::TraitRef::new(tcx, sized_def_id, [ty]);
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// Preferable to put this obligation first, since we report better errors for sized ambiguity.
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self.clauses.insert(0, (trait_ref.to_predicate(tcx), span));
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}
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pub fn clauses(&self) -> impl Iterator<Item = (ty::Clause<'tcx>, Span)> + '_ {
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self.clauses.iter().cloned()
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}
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}
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