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Auto merge of #141927 - compiler-errors:perf-select, r=lcnr

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Clear nested candidates in select if certainty is yes

Proving these goals is redundant.
This commit is contained in:
bors
2025-06-07 15:26:34 +00:00
parent 5e0bdaa9dd 1e5cd122f0
commit 2f2c8c3512
2 changed files with 70 additions and 41 deletions
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81
compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
View File

@@ -133,45 +133,25 @@ impl<'a, 'tcx> InspectCandidate<'a, 'tcx> {
/// Instantiate the nested goals for the candidate without rolling back their
/// inference constraints. This function modifies the state of the `infcx`.
///
/// See [`Self::instantiate_nested_goals_and_opt_impl_args`] if you need the impl args too.
pub fn instantiate_nested_goals(&self, span: Span) -> Vec<InspectGoal<'a, 'tcx>> {
self.instantiate_nested_goals_and_opt_impl_args(span).0
}
/// Instantiate the nested goals for the candidate without rolling back their
/// inference constraints, and optionally the args of an impl if this candidate
/// came from a `CandidateSource::Impl`. This function modifies the state of the
/// `infcx`.
/// See [`Self::instantiate_impl_args`] if you need the impl args too.
#[instrument(
level = "debug",
skip_all,
fields(goal = ?self.goal.goal, steps = ?self.steps)
)]
pub fn instantiate_nested_goals_and_opt_impl_args(
&self,
span: Span,
) -> (Vec<InspectGoal<'a, 'tcx>>, Option<ty::GenericArgsRef<'tcx>>) {
pub fn instantiate_nested_goals(&self, span: Span) -> Vec<InspectGoal<'a, 'tcx>> {
let infcx = self.goal.infcx;
let param_env = self.goal.goal.param_env;
let mut orig_values = self.goal.orig_values.to_vec();
let mut instantiated_goals = vec![];
let mut opt_impl_args = None;
for step in &self.steps {
match **step {
inspect::ProbeStep::AddGoal(source, goal) => instantiated_goals.push((
source,
instantiate_canonical_state(infcx, span, param_env, &mut orig_values, goal),
)),
inspect::ProbeStep::RecordImplArgs { impl_args } => {
opt_impl_args = Some(instantiate_canonical_state(
infcx,
span,
param_env,
&mut orig_values,
impl_args,
));
}
inspect::ProbeStep::RecordImplArgs { .. } => {}
inspect::ProbeStep::MakeCanonicalResponse { .. }
| inspect::ProbeStep::NestedProbe(_) => unreachable!(),
}
@@ -187,14 +167,59 @@ impl<'a, 'tcx> InspectCandidate<'a, 'tcx> {
let _ = term_hack.constrain(infcx, span, param_env);
}
let opt_impl_args = opt_impl_args.map(|impl_args| eager_resolve_vars(infcx, impl_args));
let goals = instantiated_goals
instantiated_goals
.into_iter()
.map(|(source, goal)| self.instantiate_proof_tree_for_nested_goal(source, goal, span))
.collect();
.collect()
}
(goals, opt_impl_args)
/// Instantiate the args of an impl if this candidate came from a
/// `CandidateSource::Impl`. This function modifies the state of the
/// `infcx`.
#[instrument(
level = "debug",
skip_all,
fields(goal = ?self.goal.goal, steps = ?self.steps)
)]
pub fn instantiate_impl_args(&self, span: Span) -> ty::GenericArgsRef<'tcx> {
let infcx = self.goal.infcx;
let param_env = self.goal.goal.param_env;
let mut orig_values = self.goal.orig_values.to_vec();
for step in &self.steps {
match **step {
inspect::ProbeStep::RecordImplArgs { impl_args } => {
let impl_args = instantiate_canonical_state(
infcx,
span,
param_env,
&mut orig_values,
impl_args,
);
let () = instantiate_canonical_state(
infcx,
span,
param_env,
&mut orig_values,
self.final_state,
);
// No reason we couldn't support this, but we don't need to for select.
assert!(
self.goal.normalizes_to_term_hack.is_none(),
"cannot use `instantiate_impl_args` with a `NormalizesTo` goal"
);
return eager_resolve_vars(infcx, impl_args);
}
inspect::ProbeStep::AddGoal(..) => {}
inspect::ProbeStep::MakeCanonicalResponse { .. }
| inspect::ProbeStep::NestedProbe(_) => unreachable!(),
}
}
bug!("expected impl args probe step for `instantiate_impl_args`");
}
pub fn instantiate_proof_tree_for_nested_goal(

30
compiler/rustc_trait_selection/src/solve/select.rs
View File

@@ -10,6 +10,7 @@ use rustc_infer::traits::{
use rustc_macros::extension;
use rustc_middle::{bug, span_bug};
use rustc_span::Span;
use thin_vec::thin_vec;
use crate::solve::inspect::{self, ProofTreeInferCtxtExt};
@@ -146,18 +147,21 @@ fn to_selection<'tcx>(
return None;
}
let (nested, impl_args) = cand.instantiate_nested_goals_and_opt_impl_args(span);
let nested = nested
.into_iter()
.map(|nested| {
Obligation::new(
nested.infcx().tcx,
ObligationCause::dummy_with_span(span),
nested.goal().param_env,
nested.goal().predicate,
)
})
.collect();
let nested = match cand.result().expect("expected positive result") {
Certainty::Yes => thin_vec![],
Certainty::Maybe(_) => cand
.instantiate_nested_goals(span)
.into_iter()
.map(|nested| {
Obligation::new(
nested.infcx().tcx,
ObligationCause::dummy_with_span(span),
nested.goal().param_env,
nested.goal().predicate,
)
})
.collect(),
};
Some(match cand.kind() {
ProbeKind::TraitCandidate { source, result: _ } => match source {
@@ -166,7 +170,7 @@ fn to_selection<'tcx>(
// For impl candidates, we do the rematch manually to compute the args.
ImplSource::UserDefined(ImplSourceUserDefinedData {
impl_def_id,
args: impl_args.expect("expected recorded impl args for impl candidate"),
args: cand.instantiate_impl_args(span),
nested,
})
}