diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/traits/project.rs')
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/project.rs | 180 |
1 files changed, 170 insertions, 10 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs index ea45412e47f..8e684b7ac23 100644 --- a/compiler/rustc_trait_selection/src/traits/project.rs +++ b/compiler/rustc_trait_selection/src/traits/project.rs @@ -16,6 +16,7 @@ use super::{ }; use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey}; +use crate::errors::InherentProjectionNormalizationOverflow; use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime}; use crate::traits::error_reporting::TypeErrCtxtExt as _; @@ -370,10 +371,14 @@ pub(crate) fn needs_normalization<'tcx, T: TypeVisitable<TyCtxt<'tcx>>>( reveal: Reveal, ) -> bool { match reveal { - Reveal::UserFacing => value - .has_type_flags(ty::TypeFlags::HAS_TY_PROJECTION | ty::TypeFlags::HAS_CT_PROJECTION), + Reveal::UserFacing => value.has_type_flags( + ty::TypeFlags::HAS_TY_PROJECTION + | ty::TypeFlags::HAS_TY_INHERENT + | ty::TypeFlags::HAS_CT_PROJECTION, + ), Reveal::All => value.has_type_flags( ty::TypeFlags::HAS_TY_PROJECTION + | ty::TypeFlags::HAS_TY_INHERENT | ty::TypeFlags::HAS_TY_OPAQUE | ty::TypeFlags::HAS_CT_PROJECTION, ), @@ -616,6 +621,51 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx ); normalized_ty } + + ty::Inherent if !data.has_escaping_bound_vars() => { + // This branch is *mostly* just an optimization: when we don't + // have escaping bound vars, we don't need to replace them with + // placeholders (see branch below). *Also*, we know that we can + // register an obligation to *later* project, since we know + // there won't be bound vars there. + + let data = data.fold_with(self); + + // FIXME(inherent_associated_types): Do we need to honor `self.eager_inference_replacement` + // here like `ty::Projection`? + normalize_inherent_projection( + self.selcx, + self.param_env, + data, + self.cause.clone(), + self.depth, + &mut self.obligations, + ) + } + + ty::Inherent => { + let infcx = self.selcx.infcx; + let (data, mapped_regions, mapped_types, mapped_consts) = + BoundVarReplacer::replace_bound_vars(infcx, &mut self.universes, data); + let data = data.fold_with(self); + let ty = normalize_inherent_projection( + self.selcx, + self.param_env, + data, + self.cause.clone(), + self.depth, + &mut self.obligations, + ); + + PlaceholderReplacer::replace_placeholders( + infcx, + mapped_regions, + mapped_types, + mapped_consts, + &self.universes, + ty, + ) + } } } @@ -1204,6 +1254,115 @@ fn normalize_to_error<'a, 'tcx>( Normalized { value: new_value, obligations: vec![trait_obligation] } } +/// Confirm and normalize the given inherent projection. +#[instrument(level = "debug", skip(selcx, param_env, cause, obligations))] +pub fn normalize_inherent_projection<'a, 'b, 'tcx>( + selcx: &'a mut SelectionContext<'b, 'tcx>, + param_env: ty::ParamEnv<'tcx>, + alias_ty: ty::AliasTy<'tcx>, + cause: ObligationCause<'tcx>, + depth: usize, + obligations: &mut Vec<PredicateObligation<'tcx>>, +) -> Ty<'tcx> { + let tcx = selcx.tcx(); + + if !tcx.recursion_limit().value_within_limit(depth) { + // Halt compilation because it is important that overflows never be masked. + tcx.sess.emit_fatal(InherentProjectionNormalizationOverflow { + span: cause.span, + ty: alias_ty.to_string(), + }); + } + + let substs = compute_inherent_assoc_ty_substs( + selcx, + param_env, + alias_ty, + cause.clone(), + depth, + obligations, + ); + + // Register the obligations arising from the impl and from the associated type itself. + let predicates = tcx.predicates_of(alias_ty.def_id).instantiate(tcx, substs); + for (predicate, span) in predicates { + let predicate = normalize_with_depth_to( + selcx, + param_env, + cause.clone(), + depth + 1, + predicate, + obligations, + ); + + let nested_cause = ObligationCause::new( + cause.span, + cause.body_id, + // FIXME(inherent_associated_types): Since we can't pass along the self type to the + // cause code, inherent projections will be printed with identity substitutions in + // diagnostics which is not ideal. + // Consider creating separate cause codes for this specific situation. + if span.is_dummy() { + super::ItemObligation(alias_ty.def_id) + } else { + super::BindingObligation(alias_ty.def_id, span) + }, + ); + + obligations.push(Obligation::with_depth( + tcx, + nested_cause, + depth + 1, + param_env, + predicate, + )); + } + + let ty = tcx.type_of(alias_ty.def_id).subst(tcx, substs); + + let mut ty = selcx.infcx.resolve_vars_if_possible(ty); + if ty.has_projections() { + ty = normalize_with_depth_to(selcx, param_env, cause.clone(), depth + 1, ty, obligations); + } + + ty +} + +pub fn compute_inherent_assoc_ty_substs<'a, 'b, 'tcx>( + selcx: &'a mut SelectionContext<'b, 'tcx>, + param_env: ty::ParamEnv<'tcx>, + alias_ty: ty::AliasTy<'tcx>, + cause: ObligationCause<'tcx>, + depth: usize, + obligations: &mut Vec<PredicateObligation<'tcx>>, +) -> ty::SubstsRef<'tcx> { + let tcx = selcx.tcx(); + + let impl_def_id = tcx.parent(alias_ty.def_id); + let impl_substs = selcx.infcx.fresh_substs_for_item(cause.span, impl_def_id); + + let impl_ty = tcx.type_of(impl_def_id).subst(tcx, impl_substs); + let impl_ty = + normalize_with_depth_to(selcx, param_env, cause.clone(), depth + 1, impl_ty, obligations); + + // Infer the generic parameters of the impl by unifying the + // impl type with the self type of the projection. + let self_ty = alias_ty.self_ty(); + match selcx.infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, impl_ty, self_ty) { + Ok(mut ok) => obligations.append(&mut ok.obligations), + Err(_) => { + tcx.sess.delay_span_bug( + cause.span, + format!( + "{self_ty:?} was a subtype of {impl_ty:?} during selection but now it is not" + ), + ); + } + } + + alias_ty.rebase_substs_onto_impl(impl_substs, tcx) +} + enum Projected<'tcx> { Progress(Progress<'tcx>), NoProgress(ty::Term<'tcx>), @@ -1319,7 +1478,7 @@ fn assemble_candidate_for_impl_trait_in_trait<'cx, 'tcx>( let trait_substs = obligation.predicate.substs.truncate_to(tcx, tcx.generics_of(trait_def_id)); // FIXME(named-returns): Binders - let trait_predicate = ty::Binder::dummy(tcx.mk_trait_ref(trait_def_id, trait_substs)); + let trait_predicate = ty::TraitRef::new(tcx, trait_def_id, trait_substs); let _ = selcx.infcx.commit_if_ok(|_| { match selcx.select(&obligation.with(tcx, trait_predicate)) { @@ -1682,10 +1841,8 @@ fn assemble_candidates_from_impls<'cx, 'tcx>( if selcx.infcx.predicate_must_hold_modulo_regions( &obligation.with( selcx.tcx(), - ty::Binder::dummy( - selcx.tcx().at(obligation.cause.span()).mk_trait_ref(LangItem::Sized, [self_ty]), - ) - .without_const(), + ty::TraitRef::from_lang_item(selcx.tcx(), LangItem::Sized, obligation.cause.span(),[self_ty]) + .without_const(), ), ) => { @@ -1749,7 +1906,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>( // These traits have no associated types. selcx.tcx().sess.delay_span_bug( obligation.cause.span, - &format!("Cannot project an associated type from `{:?}`", impl_source), + format!("Cannot project an associated type from `{:?}`", impl_source), ); return Err(()); } @@ -1948,8 +2105,11 @@ fn confirm_builtin_candidate<'cx, 'tcx>( ) }); if check_is_sized { - let sized_predicate = ty::Binder::dummy( - tcx.at(obligation.cause.span()).mk_trait_ref(LangItem::Sized, [self_ty]), + let sized_predicate = ty::TraitRef::from_lang_item( + tcx, + LangItem::Sized, + obligation.cause.span(), + [self_ty], ) .without_const(); obligations.push(obligation.with(tcx, sized_predicate)); |