diff options
Diffstat (limited to 'compiler/rustc_next_trait_solver')
5 files changed, 111 insertions, 14 deletions
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs index ecb57cc0ad7..381a732b8de 100644 --- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs @@ -10,6 +10,7 @@ use rustc_type_ir::{ }; use tracing::{debug, instrument}; +use super::has_only_region_constraints; use super::trait_goals::TraitGoalProvenVia; use crate::delegate::SolverDelegate; use crate::solve::inspect::ProbeKind; @@ -771,6 +772,69 @@ where } }) } +} + +pub(super) enum AllowInferenceConstraints { + Yes, + No, +} + +impl<D, I> EvalCtxt<'_, D> +where + D: SolverDelegate<Interner = I>, + I: Interner, +{ + /// Check whether we can ignore impl candidates due to specialization. + /// + /// This is only necessary for `feature(specialization)` and seems quite ugly. + pub(super) fn filter_specialized_impls( + &mut self, + allow_inference_constraints: AllowInferenceConstraints, + candidates: &mut Vec<Candidate<I>>, + ) { + match self.typing_mode() { + TypingMode::Coherence => return, + TypingMode::Analysis { .. } + | TypingMode::Borrowck { .. } + | TypingMode::PostBorrowckAnalysis { .. } + | TypingMode::PostAnalysis => {} + } + + let mut i = 0; + 'outer: while i < candidates.len() { + let CandidateSource::Impl(victim_def_id) = candidates[i].source else { + i += 1; + continue; + }; + + for (j, c) in candidates.iter().enumerate() { + if i == j { + continue; + } + + let CandidateSource::Impl(other_def_id) = c.source else { + continue; + }; + + // See if we can toss out `victim` based on specialization. + // + // While this requires us to know *for sure* that the `lhs` impl applies + // we still use modulo regions here. This is fine as specialization currently + // assumes that specializing impls have to be always applicable, meaning that + // the only allowed region constraints may be constraints also present on the default impl. + if matches!(allow_inference_constraints, AllowInferenceConstraints::Yes) + || has_only_region_constraints(c.result) + { + if self.cx().impl_specializes(other_def_id, victim_def_id) { + candidates.remove(i); + continue 'outer; + } + } + } + + i += 1; + } + } /// Assemble and merge candidates for goals which are related to an underlying trait /// goal. Right now, this is normalizes-to and host effect goals. @@ -857,7 +921,7 @@ where } } TraitGoalProvenVia::Misc => { - let candidates = + let mut candidates = self.assemble_and_evaluate_candidates(goal, AssembleCandidatesFrom::All); // Prefer "orphaned" param-env normalization predicates, which are used @@ -871,6 +935,13 @@ where return Ok(response); } + // We drop specialized impls to allow normalization via a final impl here. In case + // the specializing impl has different inference constraints from the specialized + // impl, proving the trait goal is already ambiguous, so we never get here. This + // means we can just ignore inference constraints and don't have to special-case + // constraining the normalized-to `term`. + self.filter_specialized_impls(AllowInferenceConstraints::Yes, &mut candidates); + let responses: Vec<_> = candidates.iter().map(|c| c.result).collect(); if let Some(response) = self.try_merge_responses(&responses) { Ok(response) diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs index 27ca8787db5..19fb2b00fcb 100644 --- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs @@ -16,6 +16,7 @@ use rustc_type_ir::{ }; use tracing::{instrument, trace}; +use super::has_only_region_constraints; use crate::coherence; use crate::delegate::SolverDelegate; use crate::solve::inspect::{self, ProofTreeBuilder}; @@ -476,13 +477,8 @@ where Ok(response) => response, }; - let has_changed = if !response.value.var_values.is_identity_modulo_regions() - || !response.value.external_constraints.opaque_types.is_empty() - { - HasChanged::Yes - } else { - HasChanged::No - }; + let has_changed = + if !has_only_region_constraints(response) { HasChanged::Yes } else { HasChanged::No }; let (normalization_nested_goals, certainty) = self.instantiate_and_apply_query_response(goal.param_env, orig_values, response); diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs index 0695c5acdca..d9cf84787a0 100644 --- a/compiler/rustc_next_trait_solver/src/solve/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs @@ -70,6 +70,17 @@ fn has_no_inference_or_external_constraints<I: Interner>( && normalization_nested_goals.is_empty() } +fn has_only_region_constraints<I: Interner>(response: ty::Canonical<I, Response<I>>) -> bool { + let ExternalConstraintsData { + region_constraints: _, + ref opaque_types, + ref normalization_nested_goals, + } = *response.value.external_constraints; + response.value.var_values.is_identity_modulo_regions() + && opaque_types.is_empty() + && normalization_nested_goals.is_empty() +} + impl<'a, D, I> EvalCtxt<'a, D> where D: SolverDelegate<Interner = I>, diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs index 9466901683e..119d197de13 100644 --- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs @@ -213,9 +213,6 @@ where ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) }; - // In case the associated item is hidden due to specialization, we have to - // return ambiguity this would otherwise be incomplete, resulting in - // unsoundness during coherence (#105782). let target_item_def_id = match ecx.fetch_eligible_assoc_item( goal_trait_ref, goal.predicate.def_id(), @@ -223,8 +220,28 @@ where ) { Ok(Some(target_item_def_id)) => target_item_def_id, Ok(None) => { - return ecx - .evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS); + match ecx.typing_mode() { + // In case the associated item is hidden due to specialization, we have to + // return ambiguity this would otherwise be incomplete, resulting in + // unsoundness during coherence (#105782). + ty::TypingMode::Coherence => { + return ecx.evaluate_added_goals_and_make_canonical_response( + Certainty::AMBIGUOUS, + ); + } + // Outside of coherence, we treat the associated item as rigid instead. + ty::TypingMode::Analysis { .. } + | ty::TypingMode::Borrowck { .. } + | ty::TypingMode::PostBorrowckAnalysis { .. } + | ty::TypingMode::PostAnalysis => { + ecx.structurally_instantiate_normalizes_to_term( + goal, + goal.predicate.alias, + ); + return ecx + .evaluate_added_goals_and_make_canonical_response(Certainty::Yes); + } + }; } Err(guar) => return error_response(ecx, guar), }; diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs index 3404c47bba2..24657496df6 100644 --- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs +++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs @@ -13,7 +13,7 @@ use tracing::{instrument, trace}; use crate::delegate::SolverDelegate; use crate::solve::assembly::structural_traits::{self, AsyncCallableRelevantTypes}; -use crate::solve::assembly::{self, AssembleCandidatesFrom, Candidate}; +use crate::solve::assembly::{self, AllowInferenceConstraints, AssembleCandidatesFrom, Candidate}; use crate::solve::inspect::ProbeKind; use crate::solve::{ BuiltinImplSource, CandidateSource, Certainty, EvalCtxt, Goal, GoalSource, MaybeCause, @@ -1338,6 +1338,8 @@ where }; } + self.filter_specialized_impls(AllowInferenceConstraints::No, &mut candidates); + // If there are *only* global where bounds, then make sure to return that this // is still reported as being proven-via the param-env so that rigid projections // operate correctly. Otherwise, drop all global where-bounds before merging the |