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Move winnowing to assembly

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This commit is contained in:
Michael Goulet 2023-02-08 19:25:21 +00:00
parent 8987e68247
commit 654f43f34e
3 changed files with 81 additions and 140 deletions
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76
compiler/rustc_trait_selection/src/solve/assembly.rs
View File

@ -3,7 +3,7 @@
use super::infcx_ext::InferCtxtExt;
#[cfg(doc)]
use super::trait_goals::structural_traits::*;
use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, QueryResult};
use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, MaybeCause, QueryResult};
use rustc_hir::def_id::DefId;
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::util::elaborate_predicates;
@ -459,4 +459,78 @@ fn assemble_object_bound_candidates<G: GoalKind<'tcx>>(
}
}
}
#[instrument(level = "debug", skip(self), ret)]
pub(super) fn merge_candidates_and_discard_reservation_impls(
&mut self,
mut candidates: Vec<Candidate<'tcx>>,
) -> QueryResult<'tcx> {
match candidates.len() {
0 => return Err(NoSolution),
1 => return Ok(self.discard_reservation_impl(candidates.pop().unwrap()).result),
_ => {}
}
if candidates.len() > 1 {
let mut i = 0;
'outer: while i < candidates.len() {
for j in (0..candidates.len()).filter(|&j| i != j) {
if self.trait_candidate_should_be_dropped_in_favor_of(
&candidates[i],
&candidates[j],
) {
debug!(candidate = ?candidates[i], "Dropping candidate #{}/{}", i, candidates.len());
candidates.swap_remove(i);
continue 'outer;
}
}
debug!(candidate = ?candidates[i], "Retaining candidate #{}/{}", i, candidates.len());
i += 1;
}
// If there are *STILL* multiple candidates, give up
// and report ambiguity.
if candidates.len() > 1 {
let certainty = if candidates.iter().all(|x| {
matches!(x.result.value.certainty, Certainty::Maybe(MaybeCause::Overflow))
}) {
Certainty::Maybe(MaybeCause::Overflow)
} else {
Certainty::AMBIGUOUS
};
return self.make_canonical_response(certainty);
}
}
Ok(self.discard_reservation_impl(candidates.pop().unwrap()).result)
}
fn trait_candidate_should_be_dropped_in_favor_of(
&self,
candidate: &Candidate<'tcx>,
other: &Candidate<'tcx>,
) -> bool {
// FIXME: implement this
match (candidate.source, other.source) {
(CandidateSource::Impl(_), _)
| (CandidateSource::ParamEnv(_), _)
| (CandidateSource::AliasBound, _)
| (CandidateSource::BuiltinImpl, _) => false,
}
}
fn discard_reservation_impl(&self, mut candidate: Candidate<'tcx>) -> Candidate<'tcx> {
if let CandidateSource::Impl(def_id) = candidate.source {
if let ty::ImplPolarity::Reservation = self.tcx().impl_polarity(def_id) {
debug!("Selected reservation impl");
// We assemble all candidates inside of a probe so by
// making a new canonical response here our result will
// have no constraints.
candidate.result = self.make_canonical_response(Certainty::AMBIGUOUS).unwrap();
}
}
candidate
}
}

65
compiler/rustc_trait_selection/src/solve/project_goals.rs
View File

@ -1,9 +1,9 @@
use crate::traits::{specialization_graph, translate_substs};
use super::assembly::{self, Candidate, CandidateSource};
use super::assembly;
use super::infcx_ext::InferCtxtExt;
use super::trait_goals::structural_traits;
use super::{Certainty, EvalCtxt, Goal, MaybeCause, QueryResult};
use super::{Certainty, EvalCtxt, Goal, QueryResult};
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
@ -34,7 +34,7 @@ pub(super) fn compute_projection_goal(
// projection cache in the solver.
if self.term_is_fully_unconstrained(goal) {
let candidates = self.assemble_and_evaluate_candidates(goal);
self.merge_project_candidates(candidates)
self.merge_candidates_and_discard_reservation_impls(candidates)
} else {
let predicate = goal.predicate;
let unconstrained_rhs = match predicate.term.unpack() {
@ -153,65 +153,6 @@ fn eq_term_and_make_canonical_response(
self.make_canonical_response(normalization_certainty.unify_and(rhs_certainty))
}
fn merge_project_candidates(
&mut self,
mut candidates: Vec<Candidate<'tcx>>,
) -> QueryResult<'tcx> {
match candidates.len() {
0 => return Err(NoSolution),
1 => return Ok(candidates.pop().unwrap().result),
_ => {}
}
if candidates.len() > 1 {
let mut i = 0;
'outer: while i < candidates.len() {
for j in (0..candidates.len()).filter(|&j| i != j) {
if self.project_candidate_should_be_dropped_in_favor_of(
&candidates[i],
&candidates[j],
) {
debug!(candidate = ?candidates[i], "Dropping candidate #{}/{}", i, candidates.len());
candidates.swap_remove(i);
continue 'outer;
}
}
debug!(candidate = ?candidates[i], "Retaining candidate #{}/{}", i, candidates.len());
// If there are *STILL* multiple candidates, give up
// and report ambiguity.
i += 1;
}
if candidates.len() > 1 {
let certainty = if candidates.iter().all(|x| {
matches!(x.result.value.certainty, Certainty::Maybe(MaybeCause::Overflow))
}) {
Certainty::Maybe(MaybeCause::Overflow)
} else {
Certainty::AMBIGUOUS
};
return self.make_canonical_response(certainty);
}
}
Ok(candidates.pop().unwrap().result)
}
fn project_candidate_should_be_dropped_in_favor_of(
&self,
candidate: &Candidate<'tcx>,
other: &Candidate<'tcx>,
) -> bool {
// FIXME: implement this
match (candidate.source, other.source) {
(CandidateSource::Impl(_), _)
| (CandidateSource::ParamEnv(_), _)
| (CandidateSource::BuiltinImpl, _)
| (CandidateSource::AliasBound, _) => false,
}
}
}
impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {

80
compiler/rustc_trait_selection/src/solve/trait_goals.rs
View File

@ -2,9 +2,9 @@
use std::iter;
use super::assembly::{self, Candidate, CandidateSource};
use super::assembly;
use super::infcx_ext::InferCtxtExt;
use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, MaybeCause, QueryResult};
use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, QueryResult};
use rustc_hir::def_id::DefId;
use rustc_infer::infer::InferCtxt;
use rustc_infer::traits::query::NoSolution;
@ -479,80 +479,6 @@ pub(super) fn compute_trait_goal(
goal: Goal<'tcx, TraitPredicate<'tcx>>,
) -> QueryResult<'tcx> {
let candidates = self.assemble_and_evaluate_candidates(goal);
self.merge_trait_candidates_discard_reservation_impls(candidates)
}
#[instrument(level = "debug", skip(self), ret)]
pub(super) fn merge_trait_candidates_discard_reservation_impls(
&mut self,
mut candidates: Vec<Candidate<'tcx>>,
) -> QueryResult<'tcx> {
match candidates.len() {
0 => return Err(NoSolution),
1 => return Ok(self.discard_reservation_impl(candidates.pop().unwrap()).result),
_ => {}
}
if candidates.len() > 1 {
let mut i = 0;
'outer: while i < candidates.len() {
for j in (0..candidates.len()).filter(|&j| i != j) {
if self.trait_candidate_should_be_dropped_in_favor_of(
&candidates[i],
&candidates[j],
) {
debug!(candidate = ?candidates[i], "Dropping candidate #{}/{}", i, candidates.len());
candidates.swap_remove(i);
continue 'outer;
}
}
debug!(candidate = ?candidates[i], "Retaining candidate #{}/{}", i, candidates.len());
// If there are *STILL* multiple candidates, give up
// and report ambiguity.
i += 1;
}
if candidates.len() > 1 {
let certainty = if candidates.iter().all(|x| {
matches!(x.result.value.certainty, Certainty::Maybe(MaybeCause::Overflow))
}) {
Certainty::Maybe(MaybeCause::Overflow)
} else {
Certainty::AMBIGUOUS
};
return self.make_canonical_response(certainty);
}
}
Ok(self.discard_reservation_impl(candidates.pop().unwrap()).result)
}
fn trait_candidate_should_be_dropped_in_favor_of(
&self,
candidate: &Candidate<'tcx>,
other: &Candidate<'tcx>,
) -> bool {
// FIXME: implement this
match (candidate.source, other.source) {
(CandidateSource::Impl(_), _)
| (CandidateSource::ParamEnv(_), _)
| (CandidateSource::AliasBound, _)
| (CandidateSource::BuiltinImpl, _) => false,
}
}
fn discard_reservation_impl(&self, mut candidate: Candidate<'tcx>) -> Candidate<'tcx> {
if let CandidateSource::Impl(def_id) = candidate.source {
if let ty::ImplPolarity::Reservation = self.tcx().impl_polarity(def_id) {
debug!("Selected reservation impl");
// We assemble all candidates inside of a probe so by
// making a new canonical response here our result will
// have no constraints.
candidate.result = self.make_canonical_response(Certainty::AMBIGUOUS).unwrap();
}
}
candidate
self.merge_candidates_and_discard_reservation_impls(candidates)
}
}