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Compute variances for lazy type aliases

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This commit is contained in:
León Orell Valerian Liehr 2023-08-03 01:03:31 +02:00
parent 8131b9774e
commit 263a0dec60
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GPG key ID: D17A07215F68E713
7 changed files with 109 additions and 13 deletions
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26
compiler/rustc_hir_analysis/src/check/wfcheck.rs
View file

@ -245,13 +245,14 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
}
// `ForeignItem`s are handled separately.
hir::ItemKind::ForeignMod { .. } => {}
hir::ItemKind::TyAlias(hir_ty, ..) => {
hir::ItemKind::TyAlias(hir_ty, ast_generics) => {
if tcx.features().lazy_type_alias
|| tcx.type_of(item.owner_id).skip_binder().has_opaque_types()
{
// Bounds of lazy type aliases and of eager ones that contain opaque types are respected.
// E.g: `type X = impl Trait;`, `type X = (impl Trait, Y);`.
check_item_type(tcx, def_id, hir_ty.span, UnsizedHandling::Allow);
check_variances_for_type_defn(tcx, item, ast_generics);
}
}
_ => {}
@ -1700,10 +1701,27 @@ fn check_variances_for_type_defn<'tcx>(
hir_generics: &hir::Generics<'_>,
) {
let identity_args = ty::GenericArgs::identity_for_item(tcx, item.owner_id);
for field in tcx.adt_def(item.owner_id).all_fields() {
if field.ty(tcx, identity_args).references_error() {
return;
match item.kind {
ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
for field in tcx.adt_def(item.owner_id).all_fields() {
if field.ty(tcx, identity_args).references_error() {
return;
}
}
}
ItemKind::TyAlias(..) => {
let ty = tcx.type_of(item.owner_id).instantiate_identity();
if tcx.features().lazy_type_alias || ty.has_opaque_types() {
if ty.references_error() {
return;
}
} else {
bug!();
}
}
_ => bug!(),
}
let ty_predicates = tcx.predicates_of(item.owner_id);

28
compiler/rustc_hir_analysis/src/variance/constraints.rs
View file

@ -6,7 +6,7 @@
use hir::def_id::{DefId, LocalDefId};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
use rustc_middle::ty::{GenericArgKind, GenericArgsRef};
use super::terms::VarianceTerm::*;
@ -78,6 +78,12 @@ pub fn add_constraints_from_crate<'a, 'tcx>(
}
}
DefKind::Fn | DefKind::AssocFn => constraint_cx.build_constraints_for_item(def_id),
DefKind::TyAlias
if tcx.features().lazy_type_alias
|| tcx.type_of(def_id).instantiate_identity().has_opaque_types() =>
{
constraint_cx.build_constraints_for_item(def_id)
}
_ => {}
}
}
@ -101,7 +107,18 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
let inferred_start = self.terms_cx.inferred_starts[&def_id];
let current_item = &CurrentItem { inferred_start };
match tcx.type_of(def_id).instantiate_identity().kind() {
let ty = tcx.type_of(def_id).instantiate_identity();
// The type as returned by `type_of` is the underlying type and generally not a weak projection.
// Therefore we need to check the `DefKind` first.
if let DefKind::TyAlias = tcx.def_kind(def_id)
&& (tcx.features().lazy_type_alias || ty.has_opaque_types())
{
self.add_constraints_from_ty(current_item, ty, self.covariant);
return;
}
match ty.kind() {
ty::Adt(def, _) => {
// Not entirely obvious: constraints on structs/enums do not
// affect the variance of their type parameters. See discussion
@ -127,6 +144,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
}
ty::Error(_) => {}
_ => {
span_bug!(
tcx.def_span(def_id),
@ -252,10 +270,14 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
self.add_constraints_from_args(current, def.did(), args, variance);
}
ty::Alias(_, ref data) => {
ty::Alias(ty::Projection | ty::Inherent | ty::Opaque, ref data) => {
self.add_constraints_from_invariant_args(current, data.args, variance);
}
ty::Alias(ty::Weak, ref data) => {
self.add_constraints_from_args(current, data.def_id, data.args, variance);
}
ty::Dynamic(data, r, _) => {
// The type `dyn Trait<T> +'a` is covariant w/r/t `'a`:
self.add_constraints_from_region(current, r, variance);

10
compiler/rustc_hir_analysis/src/variance/mod.rs
View file

@ -8,7 +8,7 @@ use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_middle::query::Providers;
use rustc_middle::ty::{self, CrateVariancesMap, GenericArgsRef, Ty, TyCtxt};
use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable};
use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt};
use std::ops::ControlFlow;
/// Defines the `TermsContext` basically houses an arena where we can
@ -56,6 +56,14 @@ fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
let crate_map = tcx.crate_variances(());
return crate_map.variances.get(&item_def_id.to_def_id()).copied().unwrap_or(&[]);
}
DefKind::TyAlias
if tcx.features().lazy_type_alias
|| tcx.type_of(item_def_id).instantiate_identity().has_opaque_types() =>
{
// These are inferred.
let crate_map = tcx.crate_variances(());
return crate_map.variances.get(&item_def_id.to_def_id()).copied().unwrap_or(&[]);
}
DefKind::OpaqueTy => {
return variance_of_opaque(tcx, item_def_id);
}

8
compiler/rustc_hir_analysis/src/variance/terms.rs
View file

@ -12,7 +12,7 @@
use rustc_arena::DroplessArena;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{LocalDefId, LocalDefIdMap};
use rustc_middle::ty::{self, TyCtxt};
use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
use std::fmt;
use self::VarianceTerm::*;
@ -97,6 +97,12 @@ pub fn determine_parameters_to_be_inferred<'a, 'tcx>(
}
}
DefKind::Fn | DefKind::AssocFn => terms_cx.add_inferreds_for_item(def_id),
DefKind::TyAlias
if tcx.features().lazy_type_alias
|| tcx.type_of(def_id).instantiate_identity().has_opaque_types() =>
{
terms_cx.add_inferreds_for_item(def_id)
}
_ => {}
}
}