From ee96ae0a32d35b81103f666ea5ebd898714fa433 Mon Sep 17 00:00:00 2001 From: Deadbeef Date: Sun, 18 Sep 2022 17:38:18 +0000 Subject: [PATCH] make projection bounds with const bounds satisfy const --- compiler/rustc_middle/src/traits/select.rs | 5 +++-- .../src/traits/select/candidate_assembly.rs | 4 +++- .../src/traits/select/confirmation.rs | 5 ++--- .../src/traits/select/mod.rs | 20 ++++++++++--------- .../assoc-type-const-bound-usage.rs | 14 +++++++++++++ 5 files changed, 33 insertions(+), 15 deletions(-) create mode 100644 src/test/ui/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.rs diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs index 53af3e9053419..6bcdfd6394a94 100644 --- a/compiler/rustc_middle/src/traits/select.rs +++ b/compiler/rustc_middle/src/traits/select.rs @@ -119,8 +119,9 @@ pub enum SelectionCandidate<'tcx> { /// This is a trait matching with a projected type as `Self`, and we found /// an applicable bound in the trait definition. The `usize` is an index - /// into the list returned by `tcx.item_bounds`. - ProjectionCandidate(usize), + /// into the list returned by `tcx.item_bounds`. The constness is the + /// constness of the bound in the trait. + ProjectionCandidate(usize, ty::BoundConstness), /// Implementation of a `Fn`-family trait by one of the anonymous types /// generated for an `||` expression. diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs index a80527f63a004..451427a69807d 100644 --- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs +++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs @@ -362,7 +362,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { .infcx .probe(|_| self.match_projection_obligation_against_definition_bounds(obligation)); - candidates.vec.extend(result.into_iter().map(ProjectionCandidate)); + candidates + .vec + .extend(result.into_iter().map(|(idx, constness)| ProjectionCandidate(idx, constness))); } /// Given an obligation like ``, searches the obligations that the caller diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs index d1deef7840710..15d8205e15784 100644 --- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs +++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs @@ -68,10 +68,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { ImplSource::AutoImpl(data) } - ProjectionCandidate(idx) => { + ProjectionCandidate(idx, constness) => { let obligations = self.confirm_projection_candidate(obligation, idx)?; - // FIXME(jschievink): constness - ImplSource::Param(obligations, ty::BoundConstness::NotConst) + ImplSource::Param(obligations, constness) } ObjectCandidate(idx) => { diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs index 75bd2c89f54e4..0a802184bb802 100644 --- a/compiler/rustc_trait_selection/src/traits/select/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs @@ -1192,6 +1192,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { ImplCandidate(def_id) if tcx.constness(def_id) == hir::Constness::Const => {} // const param ParamCandidate(trait_pred) if trait_pred.is_const_if_const() => {} + // const projection + ProjectionCandidate(_, ty::BoundConstness::ConstIfConst) => {} // auto trait impl AutoImplCandidate(..) => {} // generator, this will raise error in other places @@ -1399,7 +1401,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { fn match_projection_obligation_against_definition_bounds( &mut self, obligation: &TraitObligation<'tcx>, - ) -> smallvec::SmallVec<[usize; 2]> { + ) -> smallvec::SmallVec<[(usize, ty::BoundConstness); 2]> { let poly_trait_predicate = self.infcx().resolve_vars_if_possible(obligation.predicate); let placeholder_trait_predicate = self.infcx().replace_bound_vars_with_placeholders(poly_trait_predicate); @@ -1447,7 +1449,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { _ => false, } }) { - return Some(idx); + return Some((idx, pred.constness)); } } None @@ -1683,9 +1685,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { | BuiltinCandidate { .. } | TraitAliasCandidate(..) | ObjectCandidate(_) - | ProjectionCandidate(_), + | ProjectionCandidate(..), ) => !is_global(cand), - (ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(ref cand)) => { + (ObjectCandidate(_) | ProjectionCandidate(..), ParamCandidate(ref cand)) => { // Prefer these to a global where-clause bound // (see issue #50825). is_global(cand) @@ -1707,20 +1709,20 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { is_global(cand) && other.evaluation.must_apply_modulo_regions() } - (ProjectionCandidate(i), ProjectionCandidate(j)) + (ProjectionCandidate(i, _), ProjectionCandidate(j, _)) | (ObjectCandidate(i), ObjectCandidate(j)) => { // Arbitrarily pick the lower numbered candidate for backwards // compatibility reasons. Don't let this affect inference. i < j && !needs_infer } - (ObjectCandidate(_), ProjectionCandidate(_)) - | (ProjectionCandidate(_), ObjectCandidate(_)) => { + (ObjectCandidate(_), ProjectionCandidate(..)) + | (ProjectionCandidate(..), ObjectCandidate(_)) => { bug!("Have both object and projection candidate") } // Arbitrarily give projection and object candidates priority. ( - ObjectCandidate(_) | ProjectionCandidate(_), + ObjectCandidate(_) | ProjectionCandidate(..), ImplCandidate(..) | ClosureCandidate | GeneratorCandidate @@ -1742,7 +1744,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { | TraitUpcastingUnsizeCandidate(_) | BuiltinCandidate { .. } | TraitAliasCandidate(..), - ObjectCandidate(_) | ProjectionCandidate(_), + ObjectCandidate(_) | ProjectionCandidate(..), ) => false, (&ImplCandidate(other_def), &ImplCandidate(victim_def)) => { diff --git a/src/test/ui/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.rs b/src/test/ui/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.rs new file mode 100644 index 0000000000000..780a510c500dc --- /dev/null +++ b/src/test/ui/rfc-2632-const-trait-impl/assoc-type-const-bound-usage.rs @@ -0,0 +1,14 @@ +// check-pass +#![feature(const_trait_impl)] + +#[const_trait] +trait Foo { + type Assoc: ~const Foo; + fn foo() {} +} + +const fn foo() { + ::Assoc::foo(); +} + +fn main() {}