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a small wf and clause cleanup #116261

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Oct 3, 2023
Merged

a small wf and clause cleanup #116261

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a4f6770
a small wf and clause cleanup
lcnr Sep 29, 2023
aac29a0
specialization: use clause
lcnr Sep 29, 2023
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9 changes: 5 additions & 4 deletions compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ use rustc_infer::traits::util;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::BottomUpFolder;
use rustc_middle::ty::util::ExplicitSelf;
use rustc_middle::ty::ToPredicate;
use rustc_middle::ty::{
self, GenericArgs, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
};
Expand Down Expand Up @@ -2279,16 +2280,16 @@ pub(super) fn check_type_bounds<'tcx>(
//
// impl<T> X for T where T: X { type Y = <T as X>::Y; }
}
_ => predicates.push(ty::Clause::from_projection_clause(
tcx,
_ => predicates.push(
ty::Binder::bind_with_vars(
ty::ProjectionPredicate {
projection_ty: tcx.mk_alias_ty(trait_ty.def_id, rebased_args),
term: normalize_impl_ty.into(),
},
bound_vars,
),
)),
)
.to_predicate(tcx),
),
};
ty::ParamEnv::new(tcx.mk_clauses(&predicates), Reveal::UserFacing)
};
Expand Down
14 changes: 4 additions & 10 deletions compiler/rustc_hir_analysis/src/check/wfcheck.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1105,11 +1105,11 @@ fn check_associated_type_bounds(wfcx: &WfCheckingCtxt<'_, '_>, item: ty::AssocIt
let wf_obligations =
bounds.instantiate_identity_iter_copied().flat_map(|(bound, bound_span)| {
let normalized_bound = wfcx.normalize(span, None, bound);
traits::wf::predicate_obligations(
traits::wf::clause_obligations(
wfcx.infcx,
wfcx.param_env,
wfcx.body_def_id,
normalized_bound.as_predicate(),
normalized_bound,
bound_span,
)
});
Expand Down Expand Up @@ -1209,7 +1209,7 @@ fn check_impl<'tcx>(
wfcx.infcx,
wfcx.param_env,
wfcx.body_def_id,
&trait_pred,
trait_pred,
ast_trait_ref.path.span,
item,
);
Expand Down Expand Up @@ -1418,13 +1418,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
debug!(?predicates.predicates);
assert_eq!(predicates.predicates.len(), predicates.spans.len());
let wf_obligations = predicates.into_iter().flat_map(|(p, sp)| {
traits::wf::predicate_obligations(
infcx,
wfcx.param_env,
wfcx.body_def_id,
p.as_predicate(),
sp,
)
traits::wf::clause_obligations(infcx, wfcx.param_env, wfcx.body_def_id, p, sp)
});
let obligations: Vec<_> = wf_obligations.chain(default_obligations).collect();
wfcx.register_obligations(obligations);
Expand Down
60 changes: 23 additions & 37 deletions compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -376,9 +376,9 @@ fn check_predicates<'tcx>(
let always_applicable_traits = impl1_predicates
.iter()
.copied()
.filter(|(clause, _span)| {
.filter(|&(clause, _span)| {
matches!(
trait_predicate_kind(tcx, clause.as_predicate()),
trait_specialization_kind(tcx, clause),
Some(TraitSpecializationKind::AlwaysApplicable)
)
})
Expand All @@ -402,7 +402,7 @@ fn check_predicates<'tcx>(
.iter()
.any(|pred2| trait_predicates_eq(tcx, clause.as_predicate(), *pred2, span))
{
check_specialization_on(tcx, clause.as_predicate(), span)
check_specialization_on(tcx, clause, span)
}
}
}
Expand Down Expand Up @@ -441,19 +441,16 @@ fn trait_predicates_eq<'tcx>(
}

#[instrument(level = "debug", skip(tcx))]
fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tcx>, span: Span) {
match predicate.kind().skip_binder() {
fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, clause: ty::Clause<'tcx>, span: Span) {
match clause.kind().skip_binder() {
// Global predicates are either always true or always false, so we
// are fine to specialize on.
_ if predicate.is_global() => (),
_ if clause.is_global() => (),
// We allow specializing on explicitly marked traits with no associated
// items.
ty::PredicateKind::Clause(ty::ClauseKind::Trait(ty::TraitPredicate {
trait_ref,
polarity: _,
})) => {
ty::ClauseKind::Trait(ty::TraitPredicate { trait_ref, polarity: _ }) => {
if !matches!(
trait_predicate_kind(tcx, predicate),
trait_specialization_kind(tcx, clause),
Some(TraitSpecializationKind::Marker)
) {
tcx.sess
Expand All @@ -467,18 +464,15 @@ fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
.emit();
}
}
ty::PredicateKind::Clause(ty::ClauseKind::Projection(ty::ProjectionPredicate {
projection_ty,
term,
})) => {
ty::ClauseKind::Projection(ty::ProjectionPredicate { projection_ty, term }) => {
tcx.sess
.struct_span_err(
span,
format!("cannot specialize on associated type `{projection_ty} == {term}`",),
)
.emit();
}
ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(..)) => {
ty::ClauseKind::ConstArgHasType(..) => {
// FIXME(min_specialization), FIXME(const_generics):
// It probably isn't right to allow _every_ `ConstArgHasType` but I am somewhat unsure
// about the actual rules that would be sound. Can't just always error here because otherwise
Expand All @@ -490,33 +484,25 @@ fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
}
_ => {
tcx.sess
.struct_span_err(span, format!("cannot specialize on predicate `{predicate}`"))
.struct_span_err(span, format!("cannot specialize on predicate `{clause}`"))
.emit();
}
}
}

fn trait_predicate_kind<'tcx>(
fn trait_specialization_kind<'tcx>(
tcx: TyCtxt<'tcx>,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
) -> Option<TraitSpecializationKind> {
match predicate.kind().skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Trait(ty::TraitPredicate {
trait_ref,
polarity: _,
})) => Some(tcx.trait_def(trait_ref.def_id).specialization_kind),
ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(_))
| ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(_))
| ty::PredicateKind::Clause(ty::ClauseKind::Projection(_))
| ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(..))
| ty::PredicateKind::AliasRelate(..)
| ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_))
| ty::PredicateKind::Subtype(_)
| ty::PredicateKind::Coerce(_)
| ty::PredicateKind::ObjectSafe(_)
| ty::PredicateKind::ClosureKind(..)
| ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(..))
| ty::PredicateKind::ConstEquate(..)
| ty::PredicateKind::Ambiguous => None,
match clause.kind().skip_binder() {
ty::ClauseKind::Trait(ty::TraitPredicate { trait_ref, polarity: _ }) => {
Some(tcx.trait_def(trait_ref.def_id).specialization_kind)
}
ty::ClauseKind::RegionOutlives(_)
| ty::ClauseKind::TypeOutlives(_)
| ty::ClauseKind::Projection(_)
| ty::ClauseKind::ConstArgHasType(..)
| ty::ClauseKind::WellFormed(_)
| ty::ClauseKind::ConstEvaluatable(..) => None,
}
}
25 changes: 17 additions & 8 deletions compiler/rustc_middle/src/ty/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -578,11 +578,6 @@ impl rustc_errors::IntoDiagnosticArg for Clause<'_> {
pub struct Clause<'tcx>(Interned<'tcx, WithCachedTypeInfo<ty::Binder<'tcx, PredicateKind<'tcx>>>>);

impl<'tcx> Clause<'tcx> {
pub fn from_projection_clause(tcx: TyCtxt<'tcx>, pred: PolyProjectionPredicate<'tcx>) -> Self {
let pred: Predicate<'tcx> = pred.to_predicate(tcx);
pred.expect_clause()
}

pub fn as_predicate(self) -> Predicate<'tcx> {
Predicate(self.0)
}
Expand Down Expand Up @@ -1296,12 +1291,25 @@ impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef
}
}

impl<'tcx> ToPredicate<'tcx> for TraitPredicate<'tcx> {
fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
PredicateKind::Clause(ClauseKind::Trait(self)).to_predicate(tcx)
}
}

impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
self.map_bound(|p| PredicateKind::Clause(ClauseKind::Trait(p))).to_predicate(tcx)
}
}

impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for TraitPredicate<'tcx> {
fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
let p: Predicate<'tcx> = self.to_predicate(tcx);
p.expect_clause()
}
}

impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for PolyTraitPredicate<'tcx> {
fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
let p: Predicate<'tcx> = self.to_predicate(tcx);
Expand Down Expand Up @@ -1340,9 +1348,10 @@ impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for ProjectionPredicate<'tcx> {
}
}

impl<'tcx> ToPredicate<'tcx> for TraitPredicate<'tcx> {
fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
PredicateKind::Clause(ClauseKind::Trait(self)).to_predicate(tcx)
impl<'tcx> ToPredicate<'tcx, Clause<'tcx>> for PolyProjectionPredicate<'tcx> {
fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Clause<'tcx> {
let p: Predicate<'tcx> = self.to_predicate(tcx);
p.expect_clause()
}
}

Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_middle/src/ty/sty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -725,7 +725,7 @@ impl<'tcx> PolyExistentialPredicate<'tcx> {
self.rebind(tr).with_self_ty(tcx, self_ty).to_predicate(tcx)
}
ExistentialPredicate::Projection(p) => {
ty::Clause::from_projection_clause(tcx, self.rebind(p.with_self_ty(tcx, self_ty)))
self.rebind(p.with_self_ty(tcx, self_ty)).to_predicate(tcx)
}
ExistentialPredicate::AutoTrait(did) => {
let generics = tcx.generics_of(did);
Expand Down
9 changes: 4 additions & 5 deletions compiler/rustc_trait_selection/src/solve/project_goals.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -346,14 +346,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
ty::TraitRef::from_lang_item(tcx, LangItem::Sized, DUMMY_SP, [output])
});

let pred = ty::Clause::from_projection_clause(
tcx,
tupled_inputs_and_output.map_bound(|(inputs, output)| ty::ProjectionPredicate {
let pred = tupled_inputs_and_output
.map_bound(|(inputs, output)| ty::ProjectionPredicate {
projection_ty: tcx
.mk_alias_ty(goal.predicate.def_id(), [goal.predicate.self_ty(), inputs]),
term: output.into(),
}),
);
})
.to_predicate(tcx);

// A built-in `Fn` impl only holds if the output is sized.
// (FIXME: technically we only need to check this if the type is a fn ptr...)
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_trait_selection/src/traits/project.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1644,7 +1644,7 @@ fn assemble_candidates_from_object_ty<'cx, 'tcx>(
let env_predicates = data
.projection_bounds()
.filter(|bound| bound.item_def_id() == obligation.predicate.def_id)
.map(|p| ty::Clause::from_projection_clause(tcx, p.with_self_ty(tcx, object_ty)));
.map(|p| p.with_self_ty(tcx, object_ty).to_predicate(tcx));

assemble_candidates_from_predicates(
selcx,
Expand Down
52 changes: 22 additions & 30 deletions compiler/rustc_trait_selection/src/traits/wf.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -105,13 +105,13 @@ pub fn unnormalized_obligations<'tcx>(

/// Returns the obligations that make this trait reference
/// well-formed. For example, if there is a trait `Set` defined like
/// `trait Set<K:Eq>`, then the trait reference `Foo: Set<Bar>` is WF
/// `trait Set<K: Eq>`, then the trait bound `Foo: Set<Bar>` is WF
/// if `Bar: Eq`.
pub fn trait_obligations<'tcx>(
infcx: &InferCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
body_id: LocalDefId,
trait_pred: &ty::TraitPredicate<'tcx>,
trait_pred: ty::TraitPredicate<'tcx>,
span: Span,
item: &'tcx hir::Item<'tcx>,
) -> Vec<traits::PredicateObligation<'tcx>> {
Expand All @@ -129,12 +129,17 @@ pub fn trait_obligations<'tcx>(
wf.normalize(infcx)
}

/// Returns the requirements for `clause` to be well-formed.
///
/// For example, if there is a trait `Set` defined like
/// `trait Set<K: Eq>`, then the trait bound `Foo: Set<Bar>` is WF
/// if `Bar: Eq`.
#[instrument(skip(infcx), ret)]
pub fn predicate_obligations<'tcx>(
pub fn clause_obligations<'tcx>(
infcx: &InferCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
body_id: LocalDefId,
predicate: ty::Predicate<'tcx>,
clause: ty::Clause<'tcx>,
span: Span,
) -> Vec<traits::PredicateObligation<'tcx>> {
let mut wf = WfPredicates {
Expand All @@ -148,45 +153,32 @@ pub fn predicate_obligations<'tcx>(
};

// It's ok to skip the binder here because wf code is prepared for it
match predicate.kind().skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Trait(t)) => {
wf.compute_trait_pred(&t, Elaborate::None);
match clause.kind().skip_binder() {
ty::ClauseKind::Trait(t) => {
wf.compute_trait_pred(t, Elaborate::None);
}
ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(..)) => {}
ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(
ty,
_reg,
))) => {
ty::ClauseKind::RegionOutlives(..) => {}
ty::ClauseKind::TypeOutlives(ty::OutlivesPredicate(ty, _reg)) => {
wf.compute(ty.into());
}
ty::PredicateKind::Clause(ty::ClauseKind::Projection(t)) => {
ty::ClauseKind::Projection(t) => {
wf.compute_projection(t.projection_ty);
wf.compute(match t.term.unpack() {
ty::TermKind::Ty(ty) => ty.into(),
ty::TermKind::Const(c) => c.into(),
})
}
ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
ty::ClauseKind::ConstArgHasType(ct, ty) => {
wf.compute(ct.into());
wf.compute(ty.into());
}
ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
ty::ClauseKind::WellFormed(arg) => {
wf.compute(arg);
}

ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(ct)) => {
ty::ClauseKind::ConstEvaluatable(ct) => {
wf.compute(ct.into());
}

ty::PredicateKind::ObjectSafe(_)
| ty::PredicateKind::ClosureKind(..)
| ty::PredicateKind::Subtype(..)
| ty::PredicateKind::Coerce(..)
| ty::PredicateKind::ConstEquate(..)
| ty::PredicateKind::Ambiguous
| ty::PredicateKind::AliasRelate(..) => {
bug!("We should only wf check where clauses, unexpected predicate: {predicate:?}")
}
}

wf.normalize(infcx)
Expand Down Expand Up @@ -233,7 +225,7 @@ enum Elaborate {

fn extend_cause_with_original_assoc_item_obligation<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ref: &ty::TraitRef<'tcx>,
trait_ref: ty::TraitRef<'tcx>,
item: Option<&hir::Item<'tcx>>,
cause: &mut traits::ObligationCause<'tcx>,
pred: ty::Predicate<'tcx>,
Expand Down Expand Up @@ -336,9 +328,9 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
}

/// Pushes the obligations required for `trait_ref` to be WF into `self.out`.
fn compute_trait_pred(&mut self, trait_pred: &ty::TraitPredicate<'tcx>, elaborate: Elaborate) {
fn compute_trait_pred(&mut self, trait_pred: ty::TraitPredicate<'tcx>, elaborate: Elaborate) {
let tcx = self.tcx();
let trait_ref = &trait_pred.trait_ref;
let trait_ref = trait_pred.trait_ref;

// Negative trait predicates don't require supertraits to hold, just
// that their args are WF.
Expand Down Expand Up @@ -411,7 +403,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {

// Compute the obligations that are required for `trait_ref` to be WF,
// given that it is a *negative* trait predicate.
fn compute_negative_trait_pred(&mut self, trait_ref: &ty::TraitRef<'tcx>) {
fn compute_negative_trait_pred(&mut self, trait_ref: ty::TraitRef<'tcx>) {
for arg in trait_ref.args {
self.compute(arg);
}
Expand Down
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