From f58af9ba28f1bb49f880da43227c65cc10673be2 Mon Sep 17 00:00:00 2001 From: Oli Scherer Date: Tue, 9 Jan 2024 11:12:30 +0000 Subject: [PATCH] Add a simpler and more targetted code path for impl trait in assoc items --- .../rustc_hir_analysis/src/collect/type_of.rs | 6 +- .../src/collect/type_of/opaque.rs | 71 +++++++++++++++++-- compiler/rustc_middle/src/query/mod.rs | 9 +++ compiler/rustc_ty_utils/src/opaque_types.rs | 10 ++- 4 files changed, 88 insertions(+), 8 deletions(-) diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs index bfa9dc42422..3674a760cbf 100644 --- a/compiler/rustc_hir_analysis/src/collect/type_of.rs +++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs @@ -530,9 +530,13 @@ pub(super) fn type_of_opaque( Ok(ty::EarlyBinder::bind(match tcx.hir_node_by_def_id(def_id) { Node::Item(item) => match item.kind { ItemKind::OpaqueTy(OpaqueTy { - origin: hir::OpaqueTyOrigin::TyAlias { .. }, + origin: hir::OpaqueTyOrigin::TyAlias { in_assoc_ty: false }, .. }) => opaque::find_opaque_ty_constraints_for_tait(tcx, def_id), + ItemKind::OpaqueTy(OpaqueTy { + origin: hir::OpaqueTyOrigin::TyAlias { in_assoc_ty: true }, + .. + }) => opaque::find_opaque_ty_constraints_for_impl_trait_in_assoc_type(tcx, def_id), // Opaque types desugared from `impl Trait`. ItemKind::OpaqueTy(&OpaqueTy { origin: diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs index 85093bc12b3..51b2401531c 100644 --- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs +++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs @@ -23,6 +23,60 @@ pub fn test_opaque_hidden_types(tcx: TyCtxt<'_>) -> Result<(), ErrorGuaranteed> res } +/// Checks "defining uses" of opaque `impl Trait` in associated types. +/// These can only be defined by associated items of the same trait. +#[instrument(skip(tcx), level = "debug")] +pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type( + tcx: TyCtxt<'_>, + def_id: LocalDefId, +) -> Ty<'_> { + let mut parent_def_id = def_id; + while tcx.def_kind(parent_def_id) == def::DefKind::OpaqueTy { + // Account for `type Alias = impl Trait;` (#116031) + parent_def_id = tcx.local_parent(parent_def_id); + } + let impl_def_id = tcx.local_parent(parent_def_id); + match tcx.def_kind(impl_def_id) { + DefKind::Impl { .. } => {} + other => bug!("invalid impl trait in assoc type parent: {other:?}"), + } + + let mut locator = TaitConstraintLocator { def_id, tcx, found: None, typeck_types: vec![] }; + + for &assoc_id in tcx.associated_item_def_ids(impl_def_id) { + let assoc = tcx.associated_item(assoc_id); + match assoc.kind { + ty::AssocKind::Const | ty::AssocKind::Fn => { + locator.check(assoc_id.expect_local(), true) + } + // Associated types don't have bodies, so they can't constrain hidden types + ty::AssocKind::Type => {} + } + } + + if let Some(hidden) = locator.found { + // Only check against typeck if we didn't already error + if !hidden.ty.references_error() { + for concrete_type in locator.typeck_types { + if concrete_type.ty != tcx.erase_regions(hidden.ty) + && !(concrete_type, hidden).references_error() + { + hidden.report_mismatch(&concrete_type, def_id, tcx).emit(); + } + } + } + + hidden.ty + } else { + let reported = tcx.dcx().emit_err(UnconstrainedOpaqueType { + span: tcx.def_span(def_id), + name: tcx.item_name(parent_def_id.to_def_id()), + what: "impl", + }); + Ty::new_error(tcx, reported) + } +} + /// Checks "defining uses" of opaque `impl Trait` types to ensure that they meet the restrictions /// laid for "higher-order pattern unification". /// This ensures that inference is tractable. @@ -130,7 +184,7 @@ struct TaitConstraintLocator<'tcx> { impl TaitConstraintLocator<'_> { #[instrument(skip(self), level = "debug")] - fn check(&mut self, item_def_id: LocalDefId) { + fn check(&mut self, item_def_id: LocalDefId, impl_trait_in_assoc_type: bool) { // Don't try to check items that cannot possibly constrain the type. if !self.tcx.has_typeck_results(item_def_id) { debug!("no constraint: no typeck results"); @@ -182,7 +236,12 @@ impl TaitConstraintLocator<'_> { continue; } constrained = true; - if !self.tcx.opaque_types_defined_by(item_def_id).contains(&self.def_id) { + let opaque_types_defined_by = if impl_trait_in_assoc_type { + self.tcx.impl_trait_in_assoc_types_defined_by(item_def_id) + } else { + self.tcx.opaque_types_defined_by(item_def_id) + }; + if !opaque_types_defined_by.contains(&self.def_id) { self.tcx.dcx().emit_err(TaitForwardCompat { span: hidden_type.span, item_span: self @@ -240,7 +299,7 @@ impl<'tcx> intravisit::Visitor<'tcx> for TaitConstraintLocator<'tcx> { } fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) { if let hir::ExprKind::Closure(closure) = ex.kind { - self.check(closure.def_id); + self.check(closure.def_id, false); } intravisit::walk_expr(self, ex); } @@ -248,7 +307,7 @@ impl<'tcx> intravisit::Visitor<'tcx> for TaitConstraintLocator<'tcx> { trace!(?it.owner_id); // The opaque type itself or its children are not within its reveal scope. if it.owner_id.def_id != self.def_id { - self.check(it.owner_id.def_id); + self.check(it.owner_id.def_id, false); intravisit::walk_item(self, it); } } @@ -256,13 +315,13 @@ impl<'tcx> intravisit::Visitor<'tcx> for TaitConstraintLocator<'tcx> { trace!(?it.owner_id); // The opaque type itself or its children are not within its reveal scope. if it.owner_id.def_id != self.def_id { - self.check(it.owner_id.def_id); + self.check(it.owner_id.def_id, false); intravisit::walk_impl_item(self, it); } } fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) { trace!(?it.owner_id); - self.check(it.owner_id.def_id); + self.check(it.owner_id.def_id, false); intravisit::walk_trait_item(self, it); } fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) { diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs index a9dc7f5d11a..23daefd5a65 100644 --- a/compiler/rustc_middle/src/query/mod.rs +++ b/compiler/rustc_middle/src/query/mod.rs @@ -343,6 +343,15 @@ rustc_queries! { } } + query impl_trait_in_assoc_types_defined_by( + key: LocalDefId + ) -> &'tcx ty::List { + desc { + |tcx| "computing the opaque types defined by `{}`", + tcx.def_path_str(key.to_def_id()) + } + } + /// Returns the list of bounds that can be used for /// `SelectionCandidate::ProjectionCandidate(_)` and /// `ProjectionTyCandidate::TraitDef`. diff --git a/compiler/rustc_ty_utils/src/opaque_types.rs b/compiler/rustc_ty_utils/src/opaque_types.rs index 0bb833c66fa..eae4c57fc99 100644 --- a/compiler/rustc_ty_utils/src/opaque_types.rs +++ b/compiler/rustc_ty_utils/src/opaque_types.rs @@ -272,6 +272,13 @@ impl<'tcx> TypeVisitor> for OpaqueTypeCollector<'tcx> { } } +fn impl_trait_in_assoc_types_defined_by<'tcx>( + tcx: TyCtxt<'tcx>, + item: LocalDefId, +) -> &'tcx ty::List { + opaque_types_defined_by(tcx, item) +} + fn opaque_types_defined_by<'tcx>( tcx: TyCtxt<'tcx>, item: LocalDefId, @@ -321,5 +328,6 @@ fn opaque_types_defined_by<'tcx>( } pub(super) fn provide(providers: &mut Providers) { - *providers = Providers { opaque_types_defined_by, ..*providers }; + *providers = + Providers { opaque_types_defined_by, impl_trait_in_assoc_types_defined_by, ..*providers }; }