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Allow to self reference associated types in where clauses

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This commit is contained in:
Santiago Pastorino 2020-11-13 14:01:16 -03:00
parent 24dcf6f7a2
commit 2ca4964db5
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GPG Key ID: 8131A24E0C79EFAF
8 changed files with 205 additions and 64 deletions
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35
compiler/rustc_infer/src/traits/util.rs
View File

@ -4,6 +4,7 @@ use crate::traits::{Obligation, ObligationCause, PredicateObligation};
use rustc_data_structures::fx::FxHashSet;
use rustc_middle::ty::outlives::Component;
use rustc_middle::ty::{self, ToPredicate, TyCtxt, WithConstness};
use rustc_span::symbol::Ident;
pub fn anonymize_predicate<'tcx>(
tcx: TyCtxt<'tcx>,
@ -89,6 +90,32 @@ pub fn elaborate_trait_refs<'tcx>(
elaborate_predicates(tcx, predicates)
}
pub fn elaborate_trait_refs_that_define_assoc_type<'tcx>(
tcx: TyCtxt<'tcx>,
trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
assoc_name: Ident,
) -> FxHashSet<ty::PolyTraitRef<'tcx>> {
let mut stack: Vec<_> = trait_refs.collect();
let mut trait_refs = FxHashSet::default();
while let Some(trait_ref) = stack.pop() {
if trait_refs.insert(trait_ref) {
let super_predicates =
tcx.super_predicates_that_define_assoc_type((trait_ref.def_id(), Some(assoc_name)));
for (super_predicate, _) in super_predicates.predicates {
let bound_predicate = super_predicate.bound_atom();
let subst_predicate = super_predicate
.subst_supertrait(tcx, &bound_predicate.rebind(trait_ref.skip_binder()));
if let Some(binder) = subst_predicate.to_opt_poly_trait_ref() {
stack.push(binder.value);
}
}
}
}
trait_refs
}
pub fn elaborate_predicates<'tcx>(
tcx: TyCtxt<'tcx>,
predicates: impl Iterator<Item = ty::Predicate<'tcx>>,
@ -287,6 +314,14 @@ pub fn transitive_bounds<'tcx>(
elaborate_trait_refs(tcx, bounds).filter_to_traits()
}
pub fn transitive_bounds_that_define_assoc_type<'tcx>(
tcx: TyCtxt<'tcx>,
bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
assoc_name: Ident,
) -> FxHashSet<ty::PolyTraitRef<'tcx>> {
elaborate_trait_refs_that_define_assoc_type(tcx, bounds, assoc_name)
}
///////////////////////////////////////////////////////////////////////////
// Other
///////////////////////////////////////////////////////////////////////////

10
compiler/rustc_middle/src/query/mod.rs
View File

@ -436,6 +436,16 @@ rustc_queries! {
desc { |tcx| "computing the supertraits of `{}`", tcx.def_path_str(key) }
}
/// Maps from the `DefId` of a trait to the list of
/// super-predicates. This is a subset of the full list of
/// predicates. We store these in a separate map because we must
/// evaluate them even during type conversion, often before the
/// full predicates are available (note that supertraits have
/// additional acyclicity requirements).
query super_predicates_that_define_assoc_type(key: (DefId, Option<rustc_span::symbol::Ident>)) -> ty::GenericPredicates<'tcx> {
desc { |tcx| "computing the supertraits of `{}`", tcx.def_path_str(key.0) }
}
/// To avoid cycles within the predicates of a single item we compute
/// per-type-parameter predicates for resolving `T::AssocTy`.
query type_param_predicates(key: (DefId, LocalDefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {

11
compiler/rustc_middle/src/ty/query/keys.rs
View File

@ -149,6 +149,17 @@ impl Key for (LocalDefId, DefId) {
}
}
impl Key for (DefId, Option<Ident>) {
type CacheSelector = DefaultCacheSelector;
fn query_crate(&self) -> CrateNum {
self.0.krate
}
fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
tcx.def_span(self.0)
}
}
impl Key for (DefId, LocalDefId, Ident) {
type CacheSelector = DefaultCacheSelector;

3
compiler/rustc_trait_selection/src/traits/mod.rs
View File

@ -65,7 +65,8 @@ pub use self::util::{
get_vtable_index_of_object_method, impl_item_is_final, predicate_for_trait_def, upcast_choices,
};
pub use self::util::{
supertrait_def_ids, supertraits, transitive_bounds, SupertraitDefIds, Supertraits,
supertrait_def_ids, supertraits, transitive_bounds, transitive_bounds_that_define_assoc_type,
SupertraitDefIds, Supertraits,
};
pub use self::chalk_fulfill::FulfillmentContext as ChalkFulfillmentContext;

49
compiler/rustc_typeck/src/astconv/mod.rs
View File

@ -6,6 +6,7 @@ mod errors;
mod generics;
use crate::bounds::Bounds;
use crate::collect::super_traits_of;
use crate::collect::PlaceholderHirTyCollector;
use crate::errors::{
AmbiguousLifetimeBound, MultipleRelaxedDefaultBounds, TraitObjectDeclaredWithNoTraits,
@ -768,7 +769,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
// Returns `true` if a bounds list includes `?Sized`.
pub fn is_unsized(&self, ast_bounds: &[hir::GenericBound<'_>], span: Span) -> bool {
pub fn is_unsized(&self, ast_bounds: &[&hir::GenericBound<'_>], span: Span) -> bool {
let tcx = self.tcx();
// Try to find an unbound in bounds.
@ -826,7 +827,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
fn add_bounds(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
ast_bounds: &[&hir::GenericBound<'_>],
bounds: &mut Bounds<'tcx>,
) {
let mut trait_bounds = Vec::new();
@ -844,7 +845,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {}
hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => self
.instantiate_lang_item_trait_ref(
lang_item, span, hir_id, args, param_ty, bounds,
*lang_item, *span, *hir_id, args, param_ty, bounds,
),
hir::GenericBound::Outlives(ref l) => region_bounds.push(l),
}
@ -878,7 +879,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
pub fn compute_bounds(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
ast_bounds: &[&hir::GenericBound<'_>],
sized_by_default: SizedByDefault,
span: Span,
) -> Bounds<'tcx> {
@ -896,6 +897,39 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
bounds
}
pub fn compute_bounds_that_match_assoc_type(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
sized_by_default: SizedByDefault,
span: Span,
assoc_name: Ident,
) -> Bounds<'tcx> {
let mut result = Vec::new();
for ast_bound in ast_bounds {
if let Some(trait_ref) = ast_bound.trait_ref() {
if let Some(trait_did) = trait_ref.trait_def_id() {
if super_traits_of(self.tcx(), trait_did).any(|trait_did| {
self.tcx()
.associated_items(trait_did)
.find_by_name_and_kind(
self.tcx(),
assoc_name,
ty::AssocKind::Type,
trait_did,
)
.is_some()
}) {
result.push(ast_bound);
}
}
}
}
self.compute_bounds(param_ty, &result, sized_by_default, span)
}
/// Given an HIR binding like `Item = Foo` or `Item: Foo`, pushes the corresponding predicates
/// onto `bounds`.
///
@ -1050,7 +1084,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
// Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty`
// parameter to have a skipped binder.
let param_ty = tcx.mk_projection(assoc_ty.def_id, candidate.skip_binder().substs);
self.add_bounds(param_ty, ast_bounds, bounds);
let ast_bounds: Vec<_> = ast_bounds.iter().collect();
self.add_bounds(param_ty, &ast_bounds, bounds);
}
}
Ok(())
@ -1377,12 +1412,14 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
let param_name = tcx.hir().ty_param_name(param_hir_id);
self.one_bound_for_assoc_type(
|| {
traits::transitive_bounds(
traits::transitive_bounds_that_define_assoc_type(
tcx,
predicates.iter().filter_map(|(p, _)| {
p.to_opt_poly_trait_ref().map(|trait_ref| trait_ref.value)
}),
assoc_name,
)
.into_iter()
},
|| param_name.to_string(),
assoc_name,

143
compiler/rustc_typeck/src/collect.rs
View File

@ -1,3 +1,4 @@
// ignore-tidy-filelength
//! "Collection" is the process of determining the type and other external
//! details of each item in Rust. Collection is specifically concerned
//! with *inter-procedural* things -- for example, for a function
@ -79,6 +80,7 @@ pub fn provide(providers: &mut Providers) {
projection_ty_from_predicates,
explicit_predicates_of,
super_predicates_of,
super_predicates_that_define_assoc_type,
trait_explicit_predicates_and_bounds,
type_param_predicates,
trait_def,
@ -651,17 +653,10 @@ impl ItemCtxt<'tcx> {
hir::GenericBound::Trait(poly_trait_ref, _) => {
let trait_ref = &poly_trait_ref.trait_ref;
let trait_did = trait_ref.trait_def_id().unwrap();
let traits_did = super_traits_of(self.tcx, trait_did);
traits_did.iter().any(|trait_did| {
super_traits_of(self.tcx, trait_did).any(|trait_did| {
self.tcx
.associated_items(*trait_did)
.find_by_name_and_kind(
self.tcx,
assoc_name,
ty::AssocKind::Type,
*trait_did,
)
.associated_items(trait_did)
.find_by_name_and_kind(self.tcx, assoc_name, ty::AssocKind::Type, trait_did)
.is_some()
})
}
@ -1035,55 +1030,91 @@ fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
/// the transitive super-predicates are converted.
fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
debug!("super_predicates(trait_def_id={:?})", trait_def_id);
let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
}
let item = match tcx.hir().get(trait_hir_id) {
Node::Item(item) => item,
_ => bug!("trait_node_id {} is not an item", trait_hir_id),
};
let (generics, bounds) = match item.kind {
hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
_ => span_bug!(item.span, "super_predicates invoked on non-trait"),
};
let icx = ItemCtxt::new(tcx, trait_def_id);
// Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
let self_param_ty = tcx.types.self_param;
let superbounds1 =
AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
// Convert any explicit superbounds in the where-clause,
// e.g., `trait Foo where Self: Bar`.
// In the case of trait aliases, however, we include all bounds in the where-clause,
// so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
// as one of its "superpredicates".
let is_trait_alias = tcx.is_trait_alias(trait_def_id);
let superbounds2 = icx.type_parameter_bounds_in_generics(
generics,
item.hir_id,
self_param_ty,
OnlySelfBounds(!is_trait_alias),
None,
/// Ensures that the super-predicates of the trait with a `DefId`
/// of `trait_def_id` are converted and stored. This also ensures that
/// the transitive super-predicates are converted.
fn super_predicates_that_define_assoc_type(
tcx: TyCtxt<'_>,
(trait_def_id, assoc_name): (DefId, Option<Ident>),
) -> ty::GenericPredicates<'_> {
debug!(
"super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
trait_def_id, assoc_name
);
if trait_def_id.is_local() {
debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
// Combine the two lists to form the complete set of superbounds:
let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
let item = match tcx.hir().get(trait_hir_id) {
Node::Item(item) => item,
_ => bug!("trait_node_id {} is not an item", trait_hir_id),
};
// Now require that immediate supertraits are converted,
// which will, in turn, reach indirect supertraits.
for &(pred, span) in superbounds {
debug!("superbound: {:?}", pred);
if let ty::PredicateAtom::Trait(bound, _) = pred.skip_binders() {
tcx.at(span).super_predicates_of(bound.def_id());
let (generics, bounds) = match item.kind {
hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
_ => span_bug!(item.span, "super_predicates invoked on non-trait"),
};
let icx = ItemCtxt::new(tcx, trait_def_id);
// Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
let self_param_ty = tcx.types.self_param;
let superbounds1 = if let Some(assoc_name) = assoc_name {
AstConv::compute_bounds_that_match_assoc_type(
&icx,
self_param_ty,
&bounds,
SizedByDefault::No,
item.span,
assoc_name,
)
} else {
let bounds: Vec<_> = bounds.iter().collect();
AstConv::compute_bounds(&icx, self_param_ty, &bounds, SizedByDefault::No, item.span)
};
let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
// Convert any explicit superbounds in the where-clause,
// e.g., `trait Foo where Self: Bar`.
// In the case of trait aliases, however, we include all bounds in the where-clause,
// so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
// as one of its "superpredicates".
let is_trait_alias = tcx.is_trait_alias(trait_def_id);
let superbounds2 = icx.type_parameter_bounds_in_generics(
generics,
item.hir_id,
self_param_ty,
OnlySelfBounds(!is_trait_alias),
assoc_name,
);
// Combine the two lists to form the complete set of superbounds:
let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
// Now require that immediate supertraits are converted,
// which will, in turn, reach indirect supertraits.
if assoc_name.is_none() {
// FIXME: move this into the `super_predicates_of` query
for &(pred, span) in superbounds {
debug!("superbound: {:?}", pred);
if let ty::PredicateAtom::Trait(bound, _) = pred.skip_binders() {
tcx.at(span).super_predicates_of(bound.def_id());
}
}
}
}
ty::GenericPredicates { parent: None, predicates: superbounds }
ty::GenericPredicates { parent: None, predicates: superbounds }
} else {
// if `assoc_name` is None, then the query should've been redirected to an
// external provider
assert!(assoc_name.is_some());
tcx.super_predicates_of(trait_def_id)
}
}
pub fn super_traits_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> impl Iterator<Item = DefId> {
@ -1123,6 +1154,8 @@ pub fn super_traits_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> impl Iterator<It
}
}
}
set.into_iter()
}
fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
@ -1976,8 +2009,8 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
index += 1;
let sized = SizedByDefault::Yes;
let bounds =
AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
let bounds: Vec<_> = param.bounds.iter().collect();
let bounds = AstConv::compute_bounds(&icx, param_ty, &bounds, sized, param.span);
predicates.extend(bounds.predicates(tcx, param_ty));
}
GenericParamKind::Const { .. } => {

6
compiler/rustc_typeck/src/collect/item_bounds.rs
View File

@ -25,10 +25,11 @@ fn associated_type_bounds<'tcx>(
InternalSubsts::identity_for_item(tcx, assoc_item_def_id),
);
let bounds: Vec<_> = bounds.iter().collect();
let bounds = AstConv::compute_bounds(
&ItemCtxt::new(tcx, assoc_item_def_id),
item_ty,
bounds,
&bounds,
SizedByDefault::Yes,
span,
);
@ -65,10 +66,11 @@ fn opaque_type_bounds<'tcx>(
let item_ty =
tcx.mk_opaque(opaque_def_id, InternalSubsts::identity_for_item(tcx, opaque_def_id));
let bounds: Vec<_> = bounds.iter().collect();
let bounds = AstConv::compute_bounds(
&ItemCtxt::new(tcx, opaque_def_id),
item_ty,
bounds,
&bounds,
SizedByDefault::Yes,
span,
)

12
src/test/ui/associated-type-bounds/super-trait-referencing-self.rs Normal file
View File

@ -0,0 +1,12 @@
// check-pass
trait Foo {
type Bar;
}
trait Qux: Foo + AsRef<Self::Bar> {}
trait Foo2 {}
trait Qux2: Foo2 + AsRef<Self::Bar> {
type Bar;
}
fn main() {}