diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/solve/assembly/mod.rs')
| -rw-r--r-- | compiler/rustc_trait_selection/src/solve/assembly/mod.rs | 161 |
1 files changed, 26 insertions, 135 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs index caf9470b4c6..915d722dd02 100644 --- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs +++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs @@ -253,17 +253,6 @@ pub(super) trait GoalKind<'tcx>: ecx: &mut EvalCtxt<'_, 'tcx>, goal: Goal<'tcx, Self>, ) -> Vec<(CanonicalResponse<'tcx>, BuiltinImplSource)>; - - /// Consider the `Unsize` candidate corresponding to coercing a sized type - /// into a `dyn Trait`. - /// - /// This is computed separately from the rest of the `Unsize` candidates - /// since it is only done once per self type, and not once per - /// *normalization step* (in `assemble_candidates_via_self_ty`). - fn consider_unsize_to_dyn_candidate( - ecx: &mut EvalCtxt<'_, 'tcx>, - goal: Goal<'tcx, Self>, - ) -> QueryResult<'tcx>; } impl<'tcx> EvalCtxt<'_, 'tcx> { @@ -271,64 +260,32 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { &mut self, goal: Goal<'tcx, G>, ) -> Vec<Candidate<'tcx>> { - debug_assert_eq!(goal, self.resolve_vars_if_possible(goal)); - if let Some(ambig) = self.assemble_self_ty_infer_ambiguity_response(goal) { - return vec![ambig]; - } - - let mut candidates = self.assemble_candidates_via_self_ty(goal, 0); - - self.assemble_unsize_to_dyn_candidate(goal, &mut candidates); - - self.assemble_blanket_impl_candidates(goal, &mut candidates); - - self.assemble_param_env_candidates(goal, &mut candidates); - - self.assemble_coherence_unknowable_candidates(goal, &mut candidates); - - candidates - } - - /// `?0: Trait` is ambiguous, because it may be satisfied via a builtin rule, - /// object bound, alias bound, etc. We are unable to determine this until we can at - /// least structurally resolve the type one layer. - /// - /// It would also require us to consider all impls of the trait, which is both pretty - /// bad for perf and would also constrain the self type if there is just a single impl. - fn assemble_self_ty_infer_ambiguity_response<G: GoalKind<'tcx>>( - &mut self, - goal: Goal<'tcx, G>, - ) -> Option<Candidate<'tcx>> { - if goal.predicate.self_ty().is_ty_var() { - debug!("adding self_ty_infer_ambiguity_response"); + let dummy_candidate = |this: &mut EvalCtxt<'_, 'tcx>, certainty| { let source = CandidateSource::BuiltinImpl(BuiltinImplSource::Misc); - let result = self - .evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) - .unwrap(); - let mut dummy_probe = self.inspect.new_probe(); + let result = this.evaluate_added_goals_and_make_canonical_response(certainty).unwrap(); + let mut dummy_probe = this.inspect.new_probe(); dummy_probe.probe_kind(ProbeKind::TraitCandidate { source, result: Ok(result) }); - self.inspect.finish_probe(dummy_probe); - Some(Candidate { source, result }) - } else { - None + this.inspect.finish_probe(dummy_probe); + vec![Candidate { source, result }] + }; + + let Some(normalized_self_ty) = + self.try_normalize_ty(goal.param_env, goal.predicate.self_ty()) + else { + debug!("overflow while evaluating self type"); + return dummy_candidate(self, Certainty::OVERFLOW); + }; + + if normalized_self_ty.is_ty_var() { + debug!("self type has been normalized to infer"); + return dummy_candidate(self, Certainty::AMBIGUOUS); } - } - /// Assemble candidates which apply to the self type. This only looks at candidate which - /// apply to the specific self type and ignores all others. - /// - /// Returns `None` if the self type is still ambiguous. - fn assemble_candidates_via_self_ty<G: GoalKind<'tcx>>( - &mut self, - goal: Goal<'tcx, G>, - num_steps: usize, - ) -> Vec<Candidate<'tcx>> { + let goal = + goal.with(self.tcx(), goal.predicate.with_self_ty(self.tcx(), normalized_self_ty)); debug_assert_eq!(goal, self.resolve_vars_if_possible(goal)); - if let Some(ambig) = self.assemble_self_ty_infer_ambiguity_response(goal) { - return vec![ambig]; - } - let mut candidates = Vec::new(); + let mut candidates = vec![]; self.assemble_non_blanket_impl_candidates(goal, &mut candidates); @@ -338,61 +295,13 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { self.assemble_object_bound_candidates(goal, &mut candidates); - self.assemble_candidates_after_normalizing_self_ty(goal, &mut candidates, num_steps); - candidates - } + self.assemble_blanket_impl_candidates(goal, &mut candidates); - /// If the self type of a goal is an alias we first try to normalize the self type - /// and compute the candidates for the normalized self type in case that succeeds. - /// - /// These candidates are used in addition to the ones with the alias as a self type. - /// We do this to simplify both builtin candidates and for better performance. - /// - /// We generate the builtin candidates on the fly by looking at the self type, e.g. - /// add `FnPtr` candidates if the self type is a function pointer. Handling builtin - /// candidates while the self type is still an alias seems difficult. This is similar - /// to `try_structurally_resolve_type` during hir typeck (FIXME once implemented). - /// - /// Looking at all impls for some trait goal is prohibitively expensive. We therefore - /// only look at implementations with a matching self type. Because of this function, - /// we can avoid looking at all existing impls if the self type is an alias. - #[instrument(level = "debug", skip_all)] - fn assemble_candidates_after_normalizing_self_ty<G: GoalKind<'tcx>>( - &mut self, - goal: Goal<'tcx, G>, - candidates: &mut Vec<Candidate<'tcx>>, - num_steps: usize, - ) { - let tcx = self.tcx(); - let &ty::Alias(_, alias) = goal.predicate.self_ty().kind() else { return }; - - candidates.extend(self.probe(|_| ProbeKind::NormalizedSelfTyAssembly).enter(|ecx| { - if tcx.recursion_limit().value_within_limit(num_steps) { - let normalized_ty = ecx.next_ty_infer(); - let normalizes_to_goal = - goal.with(tcx, ty::NormalizesTo { alias, term: normalized_ty.into() }); - ecx.add_goal(GoalSource::Misc, normalizes_to_goal); - if let Err(NoSolution) = ecx.try_evaluate_added_goals() { - debug!("self type normalization failed"); - return vec![]; - } - let normalized_ty = ecx.resolve_vars_if_possible(normalized_ty); - debug!(?normalized_ty, "self type normalized"); - // NOTE: Alternatively we could call `evaluate_goal` here and only - // have a `Normalized` candidate. This doesn't work as long as we - // use `CandidateSource` in winnowing. - let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty)); - ecx.assemble_candidates_via_self_ty(goal, num_steps + 1) - } else { - match ecx.evaluate_added_goals_and_make_canonical_response(Certainty::OVERFLOW) { - Ok(result) => vec![Candidate { - source: CandidateSource::BuiltinImpl(BuiltinImplSource::Misc), - result, - }], - Err(NoSolution) => vec![], - } - } - })); + self.assemble_param_env_candidates(goal, &mut candidates); + + self.assemble_coherence_unknowable_candidates(goal, &mut candidates); + + candidates } #[instrument(level = "debug", skip_all)] @@ -501,24 +410,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> { } #[instrument(level = "debug", skip_all)] - fn assemble_unsize_to_dyn_candidate<G: GoalKind<'tcx>>( - &mut self, - goal: Goal<'tcx, G>, - candidates: &mut Vec<Candidate<'tcx>>, - ) { - let tcx = self.tcx(); - if tcx.lang_items().unsize_trait() == Some(goal.predicate.trait_def_id(tcx)) { - match G::consider_unsize_to_dyn_candidate(self, goal) { - Ok(result) => candidates.push(Candidate { - source: CandidateSource::BuiltinImpl(BuiltinImplSource::Misc), - result, - }), - Err(NoSolution) => (), - } - } - } - - #[instrument(level = "debug", skip_all)] fn assemble_blanket_impl_candidates<G: GoalKind<'tcx>>( &mut self, goal: Goal<'tcx, G>, |