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Record impl args in the InsepctCandiate rather than rematching during select

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This commit is contained in:
Michael Goulet
2024-05-06 11:24:40 -04:00
parent fc47cf38e5
commit 207b4b8e88
7 changed files with 99 additions and 65 deletions
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81
compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs
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@@ -1,12 +1,11 @@
use std::ops::ControlFlow;
use rustc_hir::def_id::DefId;
use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, InferOk};
use rustc_infer::infer::InferCtxt;
use rustc_infer::traits::solve::inspect::ProbeKind;
use rustc_infer::traits::solve::{CandidateSource, Certainty, Goal};
use rustc_infer::traits::{
BuiltinImplSource, ImplSource, ImplSourceUserDefinedData, Obligation, ObligationCause,
PolyTraitObligation, PredicateObligation, Selection, SelectionError, SelectionResult,
PolyTraitObligation, Selection, SelectionError, SelectionResult,
};
use rustc_macros::extension;
use rustc_span::Span;
@@ -133,32 +132,33 @@ fn to_selection<'tcx>(
return None;
}
let make_nested = || {
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()
};
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();
Some(match cand.kind() {
ProbeKind::TraitCandidate { source, result: _ } => match source {
CandidateSource::Impl(impl_def_id) => {
// FIXME: Remove this in favor of storing this in the tree
// For impl candidates, we do the rematch manually to compute the args.
ImplSource::UserDefined(rematch_impl(cand.goal(), impl_def_id, span))
}
CandidateSource::BuiltinImpl(builtin) => ImplSource::Builtin(builtin, make_nested()),
CandidateSource::ParamEnv(_) => ImplSource::Param(make_nested()),
CandidateSource::AliasBound => {
ImplSource::Builtin(BuiltinImplSource::Misc, make_nested())
ImplSource::UserDefined(ImplSourceUserDefinedData {
impl_def_id,
args: impl_args.expect("expected recorded impl args for impl candidate"),
nested,
})
}
CandidateSource::BuiltinImpl(builtin) => ImplSource::Builtin(builtin, nested),
CandidateSource::ParamEnv(_) => ImplSource::Param(nested),
CandidateSource::AliasBound => ImplSource::Builtin(BuiltinImplSource::Misc, nested),
CandidateSource::CoherenceUnknowable => {
span_bug!(span, "didn't expect to select an unknowable candidate")
}
@@ -173,40 +173,3 @@ fn to_selection<'tcx>(
}
})
}
fn rematch_impl<'tcx>(
goal: &inspect::InspectGoal<'_, 'tcx>,
impl_def_id: DefId,
span: Span,
) -> ImplSourceUserDefinedData<'tcx, PredicateObligation<'tcx>> {
let infcx = goal.infcx();
let goal_trait_ref = infcx
.enter_forall_and_leak_universe(goal.goal().predicate.to_opt_poly_trait_pred().unwrap())
.trait_ref;
let args = infcx.fresh_args_for_item(span, impl_def_id);
let impl_trait_ref =
infcx.tcx.impl_trait_ref(impl_def_id).unwrap().instantiate(infcx.tcx, args);
let InferOk { value: (), obligations: mut nested } = infcx
.at(&ObligationCause::dummy_with_span(span), goal.goal().param_env)
.eq(DefineOpaqueTypes::Yes, goal_trait_ref, impl_trait_ref)
.expect("rematching impl failed");
// FIXME(-Znext-solver=coinductive): We need to add supertraits here eventually.
nested.extend(
infcx.tcx.predicates_of(impl_def_id).instantiate(infcx.tcx, args).into_iter().map(
|(clause, _)| {
Obligation::new(
infcx.tcx,
ObligationCause::dummy_with_span(span),
goal.goal().param_env,
clause,
)
},
),
);
ImplSourceUserDefinedData { impl_def_id, nested, args }
}