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Implement const effect predicate in new solver

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This commit is contained in:
Michael Goulet
2024-10-20 19:49:11 +00:00
parent a16d491054
commit cde29b9ec9
127 changed files with 1702 additions and 1170 deletions
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239
compiler/rustc_hir_analysis/src/collect/predicates_of.rs
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@@ -12,6 +12,7 @@ use rustc_span::symbol::Ident;
use rustc_span::{DUMMY_SP, Span};
use tracing::{debug, instrument, trace};
use super::item_bounds::explicit_item_bounds_with_filter;
use crate::bounds::Bounds;
use crate::collect::ItemCtxt;
use crate::constrained_generic_params as cgp;
@@ -685,29 +686,76 @@ pub(super) fn assert_only_contains_predicates_from<'tcx>(
assert_eq!(
trait_predicate.self_ty(),
ty,
"expected `Self` predicate when computing `{filter:?}` implied bounds: {clause:?}"
"expected `Self` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}
ty::ClauseKind::Projection(projection_predicate) => {
assert_eq!(
projection_predicate.self_ty(),
ty,
"expected `Self` predicate when computing `{filter:?}` implied bounds: {clause:?}"
"expected `Self` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}
ty::ClauseKind::TypeOutlives(outlives_predicate) => {
assert_eq!(
outlives_predicate.0, ty,
"expected `Self` predicate when computing `{filter:?}` implied bounds: {clause:?}"
"expected `Self` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}
ty::ClauseKind::RegionOutlives(_)
| ty::ClauseKind::ConstArgHasType(_, _)
| ty::ClauseKind::WellFormed(_)
| ty::ClauseKind::ConstEvaluatable(_) => {
| ty::ClauseKind::ConstEvaluatable(_)
| ty::ClauseKind::HostEffect(..) => {
bug!(
"unexpected non-`Self` predicate when computing `{filter:?}` implied bounds: {clause:?}"
"unexpected non-`Self` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}
}
}
}
PredicateFilter::ConstIfConst => {
for (clause, _) in bounds {
match clause.kind().skip_binder() {
ty::ClauseKind::HostEffect(ty::HostEffectPredicate {
trait_ref: _,
host: ty::HostPolarity::Maybe,
}) => {}
_ => {
bug!(
"unexpected non-`HostEffect` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}
}
}
}
PredicateFilter::SelfConstIfConst => {
for (clause, _) in bounds {
match clause.kind().skip_binder() {
ty::ClauseKind::HostEffect(pred) => {
assert_eq!(
pred.host,
ty::HostPolarity::Maybe,
"expected `~const` predicate when computing `{filter:?}` \
implied bounds: {clause:?}",
);
assert_eq!(
pred.trait_ref.self_ty(),
ty,
"expected `Self` predicate when computing `{filter:?}` \
implied bounds: {clause:?}"
);
}
_ => {
bug!(
"unexpected non-`HostEffect` predicate when computing \
`{filter:?}` implied bounds: {clause:?}"
);
}
}
@@ -829,3 +877,184 @@ impl<'tcx> ItemCtxt<'tcx> {
bounds.clauses(self.tcx).collect()
}
}
/// Compute the conditions that need to hold for a conditionally-const item to be const.
/// That is, compute the set of `~const` where clauses for a given item.
///
/// This query also computes the `~const` where clauses for associated types, which are
/// not "const", but which have item bounds which may be `~const`. These must hold for
/// the `~const` item bound to hold.
pub(super) fn const_conditions<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
) -> ty::ConstConditions<'tcx> {
// This logic is spaghetti, and should be cleaned up. The current methods that are
// defined to deal with constness are very unintuitive.
if tcx.is_const_fn_raw(def_id.to_def_id()) {
// Ok, const fn or method in const trait.
} else {
match tcx.def_kind(def_id) {
DefKind::Trait => {
if !tcx.is_const_trait(def_id.to_def_id()) {
return Default::default();
}
}
DefKind::Impl { .. } => {
// FIXME(effects): Should be using a dedicated function to
// test if this is a const trait impl.
if tcx.constness(def_id) != hir::Constness::Const {
return Default::default();
}
}
DefKind::AssocTy | DefKind::AssocFn => {
let parent_def_id = tcx.local_parent(def_id).to_def_id();
match tcx.associated_item(def_id).container {
ty::AssocItemContainer::TraitContainer => {
if !tcx.is_const_trait(parent_def_id) {
return Default::default();
}
}
ty::AssocItemContainer::ImplContainer => {
// FIXME(effects): Should be using a dedicated function to
// test if this is a const trait impl.
if tcx.constness(parent_def_id) != hir::Constness::Const {
return Default::default();
}
}
}
}
DefKind::Closure | DefKind::OpaqueTy => {
// Closures and RPITs will eventually have const conditions
// for `~const` bounds.
return Default::default();
}
_ => return Default::default(),
}
}
let (generics, trait_def_id_and_supertraits, has_parent) = match tcx.hir_node_by_def_id(def_id)
{
Node::Item(item) => match item.kind {
hir::ItemKind::Impl(impl_) => (impl_.generics, None, false),
hir::ItemKind::Fn(_, generics, _) => (generics, None, false),
hir::ItemKind::Trait(_, _, generics, supertraits, _) => {
(generics, Some((item.owner_id.def_id, supertraits)), false)
}
_ => return Default::default(),
},
// While associated types are not really const, we do allow them to have `~const`
// bounds and where clauses. `const_conditions` is responsible for gathering
// these up so we can check them in `compare_type_predicate_entailment`, and
// in `HostEffect` goal computation.
Node::TraitItem(item) => match item.kind {
hir::TraitItemKind::Fn(_, _) | hir::TraitItemKind::Type(_, _) => {
(item.generics, None, true)
}
_ => return Default::default(),
},
Node::ImplItem(item) => match item.kind {
hir::ImplItemKind::Fn(_, _) | hir::ImplItemKind::Type(_) => (item.generics, None, true),
_ => return Default::default(),
},
_ => return Default::default(),
};
let icx = ItemCtxt::new(tcx, def_id);
let mut bounds = Bounds::default();
for pred in generics.predicates {
match pred {
hir::WherePredicate::BoundPredicate(bound_pred) => {
let ty = icx.lowerer().lower_ty_maybe_return_type_notation(bound_pred.bounded_ty);
let bound_vars = tcx.late_bound_vars(bound_pred.hir_id);
icx.lowerer().lower_bounds(
ty,
bound_pred.bounds.iter(),
&mut bounds,
bound_vars,
PredicateFilter::ConstIfConst,
);
}
_ => {}
}
}
if let Some((def_id, supertraits)) = trait_def_id_and_supertraits {
bounds.push_const_bound(
tcx,
ty::Binder::dummy(ty::TraitRef::identity(tcx, def_id.to_def_id())),
ty::HostPolarity::Maybe,
DUMMY_SP,
);
icx.lowerer().lower_bounds(
tcx.types.self_param,
supertraits.into_iter(),
&mut bounds,
ty::List::empty(),
PredicateFilter::ConstIfConst,
);
}
ty::ConstConditions {
parent: has_parent.then(|| tcx.local_parent(def_id).to_def_id()),
predicates: tcx.arena.alloc_from_iter(bounds.clauses(tcx).map(|(clause, span)| {
(
clause.kind().map_bound(|clause| match clause {
ty::ClauseKind::HostEffect(ty::HostEffectPredicate {
trait_ref,
host: ty::HostPolarity::Maybe,
}) => trait_ref,
_ => bug!("converted {clause:?}"),
}),
span,
)
})),
}
}
pub(super) fn implied_const_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: LocalDefId,
) -> ty::EarlyBinder<'tcx, &'tcx [(ty::PolyTraitRef<'tcx>, Span)]> {
let bounds = match tcx.hir_node_by_def_id(def_id) {
Node::Item(hir::Item { kind: hir::ItemKind::Trait(..), .. }) => {
if !tcx.is_const_trait(def_id.to_def_id()) {
return ty::EarlyBinder::bind(&[]);
}
implied_predicates_with_filter(
tcx,
def_id.to_def_id(),
PredicateFilter::SelfConstIfConst,
)
}
Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Type(..), .. }) => {
if !tcx.is_const_trait(tcx.local_parent(def_id).to_def_id()) {
return ty::EarlyBinder::bind(&[]);
}
explicit_item_bounds_with_filter(tcx, def_id, PredicateFilter::ConstIfConst)
}
Node::OpaqueTy(..) => {
// We should eventually collect the `~const` bounds on opaques.
return ty::EarlyBinder::bind(&[]);
}
_ => return ty::EarlyBinder::bind(&[]),
};
bounds.map_bound(|bounds| {
&*tcx.arena.alloc_from_iter(bounds.iter().copied().map(|(clause, span)| {
(
clause.kind().map_bound(|clause| match clause {
ty::ClauseKind::HostEffect(ty::HostEffectPredicate {
trait_ref,
host: ty::HostPolarity::Maybe,
}) => trait_ref,
_ => bug!("converted {clause:?}"),
}),
span,
)
}))
})
}