mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Compute variances for lazy type aliases

Browse Source
This commit is contained in:
León Orell Valerian Liehr 2023-08-03 01:03:31 +02:00
parent 8131b9774e
commit 263a0dec60
No known key found for this signature in database
GPG Key ID: D17A07215F68E713
7 changed files with 109 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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 @@ fn build_constraints_for_item(&mut self, def_id: LocalDefId) {
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 @@ fn build_constraints_for_item(&mut self, def_id: LocalDefId) {
}
ty::Error(_) => {}
_ => {
span_bug!(
tcx.def_span(def_id),
@ -252,10 +270,14 @@ fn add_constraints_from_ty(
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_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)
}
_ => {}
}
}

10
compiler/rustc_metadata/src/rmeta/encoder.rs
View File

@ -30,6 +30,7 @@
use rustc_middle::traits::specialization_graph;
use rustc_middle::ty::codec::TyEncoder;
use rustc_middle::ty::fast_reject::{self, SimplifiedType, TreatParams};
use rustc_middle::ty::TypeVisitableExt;
use rustc_middle::ty::{self, AssocItemContainer, SymbolName, Ty, TyCtxt};
use rustc_middle::util::common::to_readable_str;
use rustc_serialize::{opaque, Decodable, Decoder, Encodable, Encoder};
@ -1034,7 +1035,7 @@ fn should_encode_mir(tcx: TyCtxt<'_>, def_id: LocalDefId) -> (bool, bool) {
}
}
fn should_encode_variances(def_kind: DefKind) -> bool {
fn should_encode_variances<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, def_kind: DefKind) -> bool {
match def_kind {
DefKind::Struct
| DefKind::Union
@ -1053,7 +1054,6 @@ fn should_encode_variances(def_kind: DefKind) -> bool {
| DefKind::Static(..)
| DefKind::Const
| DefKind::ForeignMod
| DefKind::TyAlias
| DefKind::Impl { .. }
| DefKind::Trait
| DefKind::TraitAlias
@ -1067,6 +1067,10 @@ fn should_encode_variances(def_kind: DefKind) -> bool {
| DefKind::Closure
| DefKind::Generator
| DefKind::ExternCrate => false,
DefKind::TyAlias => {
tcx.features().lazy_type_alias
|| tcx.type_of(def_id).instantiate_identity().has_opaque_types()
}
}
}
@ -1349,7 +1353,7 @@ fn encode_def_ids(&mut self) {
self.encode_default_body_stability(def_id);
self.encode_deprecation(def_id);
}
if should_encode_variances(def_kind) {
if should_encode_variances(tcx, def_id, def_kind) {
let v = self.tcx.variances_of(def_id);
record_array!(self.tables.variances_of[def_id] <- v);
}

2
compiler/rustc_middle/src/query/mod.rs
View File

@ -749,7 +749,7 @@
separate_provide_extern
}
/// Gets a map with the variance of every item; use `item_variance` instead.
/// Gets a map with the variance of every item; use `variances_of` instead.
query crate_variances(_: ()) -> &'tcx ty::CrateVariancesMap<'tcx> {
arena_cache
desc { "computing the variances for items in this crate" }

38
tests/ui/lazy-type-alias/variance.rs Normal file
View File

@ -0,0 +1,38 @@
// This is a regression test for issue #114221.
// Check that we compute variances for lazy type aliases.
// check-pass
#![feature(lazy_type_alias)]
#![allow(incomplete_features)]
// [+] `A` is covariant over `'a`.
struct A<'a>(Co<'a>);
// [+] `Co` is covariant over `'a`.
type Co<'a> = &'a ();
fn co<'a>(x: A<'static>) {
let _: A<'a> = x;
}
// [-] `B` is contravariant over `'a`.
struct B<'a>(Contra<'a>);
// [-] `Contra` is contravariant over `'a`.
type Contra<'a> = fn(&'a ());
fn contra<'a>(x: B<'a>) {
let _: B<'static> = x;
}
struct C<T, U>(CoContra<T, U>);
// [+, -] `CoContra` is covariant over `T` and contravariant over `U`.
type CoContra<T, U> = Option<(T, fn(U))>;
fn co_contra<'a>(x: C<&'static (), &'a ()>) -> C<&'a (), &'static ()> {
x
}
fn main() {}