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Higher ranked goal source, do overflow handling less badly

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This commit is contained in:
Michael Goulet 2024-05-02 13:51:13 -04:00
parent 3e03b1b190
commit 34e91ece90
15 changed files with 163 additions and 144 deletions
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2
compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
View file

@ -454,7 +454,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
} else {
self.infcx.enter_forall(kind, |kind| {
let goal = goal.with(self.tcx(), ty::Binder::dummy(kind));
self.add_goal(GoalSource::ImplWhereBound, goal);
self.add_goal(GoalSource::InstantiateHigherRanked, goal);
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}

151
compiler/rustc_trait_selection/src/solve/fulfill.rs
View file

@ -7,10 +7,10 @@ use rustc_infer::traits::solve::inspect::ProbeKind;
use rustc_infer::traits::solve::{CandidateSource, GoalSource, MaybeCause};
use rustc_infer::traits::{
self, FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes, Obligation,
PredicateObligation, SelectionError, TraitEngine,
ObligationCause, PredicateObligation, SelectionError, TraitEngine,
};
use rustc_middle::ty;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::{self, TyCtxt};
use super::eval_ctxt::GenerateProofTree;
use super::inspect::{ProofTreeInferCtxtExt, ProofTreeVisitor};
@ -219,14 +219,14 @@ fn fulfillment_error_for_no_solution<'tcx>(
}
ty::PredicateKind::Subtype(pred) => {
let (a, b) = infcx.enter_forall_and_leak_universe(
root_obligation.predicate.kind().rebind((pred.a, pred.b)),
obligation.predicate.kind().rebind((pred.a, pred.b)),
);
let expected_found = ExpectedFound::new(true, a, b);
FulfillmentErrorCode::SubtypeError(expected_found, TypeError::Sorts(expected_found))
}
ty::PredicateKind::Coerce(pred) => {
let (a, b) = infcx.enter_forall_and_leak_universe(
root_obligation.predicate.kind().rebind((pred.a, pred.b)),
obligation.predicate.kind().rebind((pred.a, pred.b)),
);
let expected_found = ExpectedFound::new(false, a, b);
FulfillmentErrorCode::SubtypeError(expected_found, TypeError::Sorts(expected_found))
@ -272,6 +272,20 @@ fn fulfillment_error_for_stalled<'tcx>(
}
}
fn find_best_leaf_obligation<'tcx>(
infcx: &InferCtxt<'tcx>,
obligation: &PredicateObligation<'tcx>,
) -> PredicateObligation<'tcx> {
let obligation = infcx.resolve_vars_if_possible(obligation.clone());
infcx
.visit_proof_tree(
obligation.clone().into(),
&mut BestObligation { obligation: obligation.clone() },
)
.break_value()
.unwrap_or(obligation)
}
struct BestObligation<'tcx> {
obligation: PredicateObligation<'tcx>,
}
@ -279,10 +293,9 @@ struct BestObligation<'tcx> {
impl<'tcx> BestObligation<'tcx> {
fn with_derived_obligation(
&mut self,
derive_obligation: impl FnOnce(&mut Self) -> PredicateObligation<'tcx>,
derived_obligation: PredicateObligation<'tcx>,
and_then: impl FnOnce(&mut Self) -> <Self as ProofTreeVisitor<'tcx>>::Result,
) -> <Self as ProofTreeVisitor<'tcx>>::Result {
let derived_obligation = derive_obligation(self);
let old_obligation = std::mem::replace(&mut self.obligation, derived_obligation);
let res = and_then(self);
self.obligation = old_obligation;
@ -298,13 +311,10 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
}
fn visit_goal(&mut self, goal: &super::inspect::InspectGoal<'_, 'tcx>) -> Self::Result {
// FIXME: Throw out candidates that have no failing WC and >0 failing misc goal.
// This most likely means that the goal just didn't unify at all, e.g. a param
// candidate with an alias in it.
let candidates = goal.candidates();
// FIXME: Throw out candidates that have no failing WC and >1 failing misc goal.
// HACK:
if self.obligation.recursion_depth > 3 {
return ControlFlow::Break(self.obligation.clone());
}
let [candidate] = candidates.as_slice() else {
return ControlFlow::Break(self.obligation.clone());
@ -320,80 +330,71 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
let tcx = goal.infcx().tcx;
let mut impl_where_bound_count = 0;
for nested_goal in candidate.instantiate_nested_goals(self.span()) {
if matches!(nested_goal.source(), GoalSource::ImplWhereBound) {
impl_where_bound_count += 1;
} else {
continue;
let obligation;
match nested_goal.source() {
GoalSource::Misc => {
continue;
}
GoalSource::ImplWhereBound => {
obligation = Obligation {
cause: derive_cause(
tcx,
candidate.kind(),
self.obligation.cause.clone(),
impl_where_bound_count,
parent_trait_pred,
),
param_env: nested_goal.goal().param_env,
predicate: nested_goal.goal().predicate,
recursion_depth: self.obligation.recursion_depth + 1,
};
impl_where_bound_count += 1;
}
GoalSource::InstantiateHigherRanked => {
obligation = self.obligation.clone();
}
}
// Skip nested goals that hold.
//FIXME: We should change the max allowed certainty based on if we're
// visiting an ambiguity or error obligation.
if matches!(nested_goal.result(), Ok(Certainty::Yes)) {
continue;
}
self.with_derived_obligation(
|self_| {
let mut cause = self_.obligation.cause.clone();
cause = match candidate.kind() {
ProbeKind::TraitCandidate {
source: CandidateSource::Impl(impl_def_id),
result: _,
} => {
let idx = impl_where_bound_count - 1;
if let Some((_, span)) = tcx
.predicates_of(impl_def_id)
.instantiate_identity(tcx)
.iter()
.nth(idx)
{
cause.derived_cause(parent_trait_pred, |derived| {
traits::ImplDerivedObligation(Box::new(
traits::ImplDerivedObligationCause {
derived,
impl_or_alias_def_id: impl_def_id,
impl_def_predicate_index: Some(idx),
span,
},
))
})
} else {
cause
}
}
ProbeKind::TraitCandidate {
source: CandidateSource::BuiltinImpl(..),
result: _,
} => {
cause.derived_cause(parent_trait_pred, traits::BuiltinDerivedObligation)
}
_ => cause,
};
Obligation {
cause,
param_env: nested_goal.goal().param_env,
predicate: nested_goal.goal().predicate,
recursion_depth: self_.obligation.recursion_depth + 1,
}
},
|self_| self_.visit_goal(&nested_goal),
)?;
self.with_derived_obligation(obligation, |this| nested_goal.visit_with(this))?;
}
ControlFlow::Break(self.obligation.clone())
}
}
fn find_best_leaf_obligation<'tcx>(
infcx: &InferCtxt<'tcx>,
obligation: &PredicateObligation<'tcx>,
) -> PredicateObligation<'tcx> {
let obligation = infcx.resolve_vars_if_possible(obligation.clone());
infcx
.visit_proof_tree(
obligation.clone().into(),
&mut BestObligation { obligation: obligation.clone() },
)
.break_value()
.unwrap_or(obligation)
fn derive_cause<'tcx>(
tcx: TyCtxt<'tcx>,
candidate_kind: ProbeKind<'tcx>,
mut cause: ObligationCause<'tcx>,
idx: usize,
parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
) -> ObligationCause<'tcx> {
match candidate_kind {
ProbeKind::TraitCandidate { source: CandidateSource::Impl(impl_def_id), result: _ } => {
if let Some((_, span)) =
tcx.predicates_of(impl_def_id).instantiate_identity(tcx).iter().nth(idx)
{
cause = cause.derived_cause(parent_trait_pred, |derived| {
traits::ImplDerivedObligation(Box::new(traits::ImplDerivedObligationCause {
derived,
impl_or_alias_def_id: impl_def_id,
impl_def_predicate_index: Some(idx),
span,
}))
})
}
}
ProbeKind::TraitCandidate { source: CandidateSource::BuiltinImpl(..), result: _ } => {
cause = cause.derived_cause(parent_trait_pred, traits::BuiltinDerivedObligation);
}
_ => {}
};
cause
}

14
compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
View file

@ -128,10 +128,8 @@ impl<'a, 'tcx> InspectCandidate<'a, 'tcx> {
/// back their inference constraints. This function modifies
/// the state of the `infcx`.
pub fn visit_nested_no_probe<V: ProofTreeVisitor<'tcx>>(&self, visitor: &mut V) -> V::Result {
if self.goal.depth < visitor.config().max_depth {
for goal in self.instantiate_nested_goals(visitor.span()) {
try_visit!(visitor.visit_goal(&goal));
}
for goal in self.instantiate_nested_goals(visitor.span()) {
try_visit!(goal.visit_with(visitor));
}
V::Result::output()
@ -360,6 +358,14 @@ impl<'a, 'tcx> InspectGoal<'a, 'tcx> {
source,
}
}
pub(crate) fn visit_with<V: ProofTreeVisitor<'tcx>>(&self, visitor: &mut V) -> V::Result {
if self.depth < visitor.config().max_depth {
try_visit!(visitor.visit_goal(self));
}
V::Result::output()
}
}
/// The public API to interact with proof trees.