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hir typeck: look into nested goals

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uses a `ProofTreeVisitor` to look into nested
goals when looking at the pending obligations
during hir typeck. Used by closure signature
inference, coercion, and for async functions.
This commit is contained in:
lcnr
2024-03-12 14:26:30 +01:00
parent 662eadbafb
commit 03878c682a
23 changed files with 642 additions and 327 deletions
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26
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
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@@ -1,7 +1,7 @@
//! Code shared by trait and projection goals for candidate assembly.
use super::{EvalCtxt, SolverMode};
use crate::solve::GoalSource;
use crate::solve::{inspect, EvalCtxt, SolverMode};
use crate::traits::coherence;
use rustc_hir::def_id::DefId;
use rustc_infer::traits::query::NoSolution;
@@ -16,6 +16,7 @@ use rustc_middle::ty::{fast_reject, TypeFoldable};
use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
use rustc_span::{ErrorGuaranteed, DUMMY_SP};
use std::fmt::Debug;
use std::mem;
pub(super) mod structural_traits;
@@ -315,20 +316,17 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
fn forced_ambiguity(&mut self, cause: MaybeCause) -> Vec<Candidate<'tcx>> {
let source = CandidateSource::BuiltinImpl(BuiltinImplSource::Misc);
let certainty = Certainty::Maybe(cause);
// This may fail if `try_evaluate_added_goals` overflows because it
// fails to reach a fixpoint but ends up getting an error after
// running for some additional step.
//
// FIXME: Add a test for this. It seems to be necessary for typenum but
// is incredibly hard to minimize as it may rely on being inside of a
// trait solver cycle.
let result = self.evaluate_added_goals_and_make_canonical_response(certainty);
let mut dummy_probe = self.inspect.new_probe();
dummy_probe.probe_kind(ProbeKind::TraitCandidate { source, result });
self.inspect.finish_probe(dummy_probe);
if let Ok(result) = result { vec![Candidate { source, result }] } else { vec![] }
// cc trait-system-refactor-initiative#105
let source = CandidateSource::BuiltinImpl(BuiltinImplSource::Misc);
let certainty = Certainty::Maybe(cause);
let result = self
.probe_trait_candidate(source)
.enter(|this| this.evaluate_added_goals_and_make_canonical_response(certainty));
if let Ok(cand) = result { vec![cand] } else { vec![] }
}
#[instrument(level = "debug", skip_all)]
@@ -813,6 +811,11 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
goal: Goal<'tcx, G>,
candidates: &mut Vec<Candidate<'tcx>>,
) {
// HACK: We temporarily remove the `ProofTreeBuilder` to
// avoid adding `Trait` candidates to the candidates used
// to prove the current goal.
let inspect = mem::replace(&mut self.inspect, inspect::ProofTreeBuilder::new_noop());
let tcx = self.tcx();
let trait_goal: Goal<'tcx, ty::TraitPredicate<'tcx>> =
goal.with(tcx, goal.predicate.trait_ref(tcx));
@@ -846,6 +849,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
}
}
self.inspect = inspect;
}
/// If there are multiple ways to prove a trait or projection goal, we have