diff options
Diffstat (limited to 'compiler/rustc_trait_selection')
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/project.rs | 58 | ||||
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/select/confirmation.rs | 74 |
2 files changed, 131 insertions, 1 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs index 49c34550f8e..9b8317fda75 100644 --- a/compiler/rustc_trait_selection/src/traits/project.rs +++ b/compiler/rustc_trait_selection/src/traits/project.rs @@ -7,8 +7,8 @@ use rustc_data_structures::stack::ensure_sufficient_stack; use rustc_errors::ErrorGuaranteed; use rustc_hir::def::DefKind; use rustc_hir::lang_items::LangItem; -use rustc_infer::infer::DefineOpaqueTypes; use rustc_infer::infer::resolve::OpportunisticRegionResolver; +use rustc_infer::infer::{DefineOpaqueTypes, RegionVariableOrigin}; use rustc_infer::traits::{ObligationCauseCode, PredicateObligations}; use rustc_middle::traits::select::OverflowError; use rustc_middle::traits::{BuiltinImplSource, ImplSource, ImplSourceUserDefinedData}; @@ -18,6 +18,7 @@ use rustc_middle::ty::visit::TypeVisitableExt; use rustc_middle::ty::{self, Term, Ty, TyCtxt, TypingMode, Upcast}; use rustc_middle::{bug, span_bug}; use rustc_span::symbol::sym; +use thin_vec::thin_vec; use tracing::{debug, instrument}; use super::{ @@ -61,6 +62,9 @@ enum ProjectionCandidate<'tcx> { /// Bounds specified on an object type Object(ty::PolyProjectionPredicate<'tcx>), + /// Built-in bound for a dyn async fn in trait + ObjectRpitit, + /// From an "impl" (or a "pseudo-impl" returned by select) Select(Selection<'tcx>), } @@ -827,6 +831,17 @@ fn assemble_candidates_from_object_ty<'cx, 'tcx>( env_predicates, false, ); + + // `dyn Trait` automagically project their AFITs to `dyn* Future`. + if tcx.is_impl_trait_in_trait(obligation.predicate.def_id) + && let Some(out_trait_def_id) = data.principal_def_id() + && let rpitit_trait_def_id = tcx.parent(obligation.predicate.def_id) + && tcx + .supertrait_def_ids(out_trait_def_id) + .any(|trait_def_id| trait_def_id == rpitit_trait_def_id) + { + candidate_set.push_candidate(ProjectionCandidate::ObjectRpitit); + } } #[instrument( @@ -1247,6 +1262,8 @@ fn confirm_candidate<'cx, 'tcx>( ProjectionCandidate::Select(impl_source) => { confirm_select_candidate(selcx, obligation, impl_source) } + + ProjectionCandidate::ObjectRpitit => confirm_object_rpitit_candidate(selcx, obligation), }; // When checking for cycle during evaluation, we compare predicates with @@ -2034,6 +2051,45 @@ fn confirm_impl_candidate<'cx, 'tcx>( } } +fn confirm_object_rpitit_candidate<'cx, 'tcx>( + selcx: &mut SelectionContext<'cx, 'tcx>, + obligation: &ProjectionTermObligation<'tcx>, +) -> Progress<'tcx> { + let tcx = selcx.tcx(); + let mut obligations = thin_vec![]; + + // Compute an intersection lifetime for all the input components of this GAT. + let intersection = + selcx.infcx.next_region_var(RegionVariableOrigin::MiscVariable(obligation.cause.span)); + for component in obligation.predicate.args { + match component.unpack() { + ty::GenericArgKind::Lifetime(lt) => { + obligations.push(obligation.with(tcx, ty::OutlivesPredicate(lt, intersection))); + } + ty::GenericArgKind::Type(ty) => { + obligations.push(obligation.with(tcx, ty::OutlivesPredicate(ty, intersection))); + } + ty::GenericArgKind::Const(_ct) => { + // Consts have no outlives... + } + } + } + + Progress { + term: Ty::new_dynamic( + tcx, + tcx.item_bounds_to_existential_predicates( + obligation.predicate.def_id, + obligation.predicate.args, + ), + intersection, + ty::DynStar, + ) + .into(), + obligations, + } +} + // Get obligations corresponding to the predicates from the where-clause of the // associated type itself. fn assoc_ty_own_obligations<'cx, 'tcx>( diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs index 2fbe2e1e323..3664121ac4b 100644 --- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs +++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs @@ -19,6 +19,7 @@ use rustc_middle::traits::{BuiltinImplSource, SignatureMismatchData}; use rustc_middle::ty::{self, GenericArgsRef, ToPolyTraitRef, Ty, TyCtxt, Upcast}; use rustc_middle::{bug, span_bug}; use rustc_span::def_id::DefId; +use rustc_type_ir::elaborate; use tracing::{debug, instrument}; use super::SelectionCandidate::{self, *}; @@ -624,6 +625,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { for assoc_type in assoc_types { let defs: &ty::Generics = tcx.generics_of(assoc_type); + // When `async_fn_in_dyn_trait` is enabled, we don't need to check the + // RPITIT for compatibility, since it's not provided by the user. + if tcx.features().async_fn_in_dyn_trait() && tcx.is_impl_trait_in_trait(assoc_type) { + continue; + } + if !defs.own_params.is_empty() { tcx.dcx().span_delayed_bug( obligation.cause.span, @@ -1175,6 +1182,33 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { ty::ClauseKind::TypeOutlives(outlives).upcast(tcx), )); + // Require that all AFIT will return something that can be coerced into `dyn*` + // -- a shim will be responsible for doing the actual coercion to `dyn*`. + if let Some(principal) = data.principal() { + for supertrait in + elaborate::supertraits(tcx, principal.with_self_ty(tcx, source)) + { + if tcx.is_trait_alias(supertrait.def_id()) { + continue; + } + + for &assoc_item in tcx.associated_item_def_ids(supertrait.def_id()) { + if !tcx.is_impl_trait_in_trait(assoc_item) { + continue; + } + + let pointer_like_goal = pointer_like_goal_for_rpitit( + tcx, + supertrait, + assoc_item, + &obligation.cause, + ); + + nested.push(predicate_to_obligation(pointer_like_goal.upcast(tcx))); + } + } + } + ImplSource::Builtin(BuiltinImplSource::Misc, nested) } @@ -1280,3 +1314,43 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { }) } } + +/// Compute a goal that some RPITIT (right now, only RPITITs corresponding to Futures) +/// implements the `PointerLike` trait, which is a requirement for the RPITIT to be +/// coercible to `dyn* Future`, which is itself a requirement for the RPITIT's parent +/// trait to be coercible to `dyn Trait`. +/// +/// We do this given a supertrait's substitutions, and then augment the substitutions +/// with bound variables to compute the goal universally. Given that `PointerLike` has +/// no region requirements (at least for the built-in pointer types), this shouldn't +/// *really* matter, but it is the best choice for soundness. +fn pointer_like_goal_for_rpitit<'tcx>( + tcx: TyCtxt<'tcx>, + supertrait: ty::PolyTraitRef<'tcx>, + rpitit_item: DefId, + cause: &ObligationCause<'tcx>, +) -> ty::PolyTraitRef<'tcx> { + let mut bound_vars = supertrait.bound_vars().to_vec(); + + let args = supertrait.skip_binder().args.extend_to(tcx, rpitit_item, |arg, _| match arg.kind { + ty::GenericParamDefKind::Lifetime => { + let kind = ty::BoundRegionKind::Named(arg.def_id, tcx.item_name(arg.def_id)); + bound_vars.push(ty::BoundVariableKind::Region(kind)); + ty::Region::new_bound(tcx, ty::INNERMOST, ty::BoundRegion { + var: ty::BoundVar::from_usize(bound_vars.len() - 1), + kind, + }) + .into() + } + ty::GenericParamDefKind::Type { .. } | ty::GenericParamDefKind::Const { .. } => { + unreachable!() + } + }); + + ty::Binder::bind_with_vars( + ty::TraitRef::new(tcx, tcx.require_lang_item(LangItem::PointerLike, Some(cause.span)), [ + Ty::new_projection_from_args(tcx, rpitit_item, args), + ]), + tcx.mk_bound_variable_kinds(&bound_vars), + ) +} |