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Make the Elaboratable trait take clauses #113144

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Jun 30, 2023
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Make the Elaboratable trait take clauses #113144

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82 changes: 42 additions & 40 deletions compiler/rustc_infer/src/traits/util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -80,14 +80,14 @@ pub struct Elaborator<'tcx, O> {
pub trait Elaboratable<'tcx> {
fn predicate(&self) -> ty::Predicate<'tcx>;

// Makes a new `Self` but with a different predicate.
fn child(&self, predicate: ty::Predicate<'tcx>) -> Self;
// Makes a new `Self` but with a different clause that comes from elaboration.
fn child(&self, clause: ty::Clause<'tcx>) -> Self;

// Makes a new `Self` but with a different predicate and a different cause
// code (if `Self` has one).
// Makes a new `Self` but with a different clause and a different cause
// code (if `Self` has one, such as [`PredicateObligation`]).
fn child_with_derived_cause(
&self,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
span: Span,
parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
index: usize,
Expand All @@ -99,18 +99,18 @@ impl<'tcx> Elaboratable<'tcx> for PredicateObligation<'tcx> {
self.predicate
}

fn child(&self, predicate: ty::Predicate<'tcx>) -> Self {
fn child(&self, clause: ty::Clause<'tcx>) -> Self {
Obligation {
cause: self.cause.clone(),
param_env: self.param_env,
recursion_depth: 0,
predicate,
predicate: clause.as_predicate(),
}
}

fn child_with_derived_cause(
&self,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
span: Span,
parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
index: usize,
Expand All @@ -123,7 +123,12 @@ impl<'tcx> Elaboratable<'tcx> for PredicateObligation<'tcx> {
span,
}))
});
Obligation { cause, param_env: self.param_env, recursion_depth: 0, predicate }
Obligation {
cause,
param_env: self.param_env,
recursion_depth: 0,
predicate: clause.as_predicate(),
}
}
}

Expand All @@ -132,18 +137,18 @@ impl<'tcx> Elaboratable<'tcx> for ty::Predicate<'tcx> {
*self
}

fn child(&self, predicate: ty::Predicate<'tcx>) -> Self {
predicate
fn child(&self, clause: ty::Clause<'tcx>) -> Self {
clause.as_predicate()
}

fn child_with_derived_cause(
&self,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
_span: Span,
_parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
_index: usize,
) -> Self {
predicate
clause.as_predicate()
}
}

Expand All @@ -152,18 +157,18 @@ impl<'tcx> Elaboratable<'tcx> for (ty::Predicate<'tcx>, Span) {
self.0
}

fn child(&self, predicate: ty::Predicate<'tcx>) -> Self {
(predicate, self.1)
fn child(&self, clause: ty::Clause<'tcx>) -> Self {
(clause.as_predicate(), self.1)
}

fn child_with_derived_cause(
&self,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
_span: Span,
_parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
_index: usize,
) -> Self {
(predicate, self.1)
(clause.as_predicate(), self.1)
}
}

Expand All @@ -172,18 +177,18 @@ impl<'tcx> Elaboratable<'tcx> for (ty::Clause<'tcx>, Span) {
self.0.as_predicate()
}

fn child(&self, predicate: ty::Predicate<'tcx>) -> Self {
(predicate.expect_clause(), self.1)
fn child(&self, clause: ty::Clause<'tcx>) -> Self {
(clause, self.1)
}

fn child_with_derived_cause(
&self,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
_span: Span,
_parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
_index: usize,
) -> Self {
(predicate.expect_clause(), self.1)
(clause, self.1)
}
}

Expand All @@ -192,18 +197,18 @@ impl<'tcx> Elaboratable<'tcx> for ty::Clause<'tcx> {
self.as_predicate()
}

fn child(&self, predicate: ty::Predicate<'tcx>) -> Self {
predicate.expect_clause()
fn child(&self, clause: ty::Clause<'tcx>) -> Self {
clause
}

fn child_with_derived_cause(
&self,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
_span: Span,
_parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
_index: usize,
) -> Self {
predicate.expect_clause()
clause
}
}

Expand Down Expand Up @@ -252,14 +257,13 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
};

let obligations =
predicates.predicates.iter().enumerate().map(|(index, &(mut pred, span))| {
predicates.predicates.iter().enumerate().map(|(index, &(mut clause, span))| {
// when parent predicate is non-const, elaborate it to non-const predicates.
if data.constness == ty::BoundConstness::NotConst {
pred = pred.without_const(tcx);
clause = clause.without_const(tcx);
}
elaboratable.child_with_derived_cause(
pred.subst_supertrait(tcx, &bound_predicate.rebind(data.trait_ref))
.as_predicate(),
clause.subst_supertrait(tcx, &bound_predicate.rebind(data.trait_ref)),
span,
bound_predicate.rebind(data),
index,
Expand Down Expand Up @@ -333,26 +337,25 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
if r.is_late_bound() {
None
} else {
Some(ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(
ty::OutlivesPredicate(r, r_min),
Some(ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(
r, r_min,
)))
}
}

Component::Param(p) => {
let ty = tcx.mk_ty_param(p.index, p.name);
Some(ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(
ty::OutlivesPredicate(ty, r_min),
)))
Some(ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty, r_min)))
}

Component::UnresolvedInferenceVariable(_) => None,

Component::Alias(alias_ty) => {
// We might end up here if we have `Foo<<Bar as Baz>::Assoc>: 'a`.
// With this, we can deduce that `<Bar as Baz>::Assoc: 'a`.
Some(ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(
ty::OutlivesPredicate(alias_ty.to_ty(tcx), r_min),
Some(ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(
alias_ty.to_ty(tcx),
r_min,
)))
}

Expand All @@ -362,10 +365,9 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
None
}
})
.map(|predicate_kind| {
bound_predicate.rebind(predicate_kind).to_predicate(tcx)
})
.map(|predicate| elaboratable.child(predicate)),
.map(|clause| {
elaboratable.child(bound_predicate.rebind(clause).to_predicate(tcx))
}),
);
}
ty::PredicateKind::Clause(ty::ClauseKind::TypeWellFormedFromEnv(..)) => {
Expand Down