Introduce expand_weak_alias_tys

This commit is contained in:
León Orell Valerian Liehr 2024-02-20 12:38:23 +01:00
parent 05ce209d20
commit 515d805a0e
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GPG Key ID: D17A07215F68E713
13 changed files with 165 additions and 41 deletions

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@ -181,9 +181,10 @@ fn add_kind(&mut self, kind: &ty::TyKind<'_>) {
&ty::Alias(kind, data) => {
self.add_flags(match kind {
ty::Weak | ty::Projection => TypeFlags::HAS_TY_PROJECTION,
ty::Inherent => TypeFlags::HAS_TY_INHERENT,
ty::Projection => TypeFlags::HAS_TY_PROJECTION,
ty::Weak => TypeFlags::HAS_TY_WEAK,
ty::Opaque => TypeFlags::HAS_TY_OPAQUE,
ty::Inherent => TypeFlags::HAS_TY_INHERENT,
});
self.add_alias_ty(data);

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@ -11,6 +11,7 @@
use rustc_apfloat::Float as _;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::stable_hasher::{Hash128, HashStable, StableHasher};
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_errors::ErrorGuaranteed;
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind, Res};
@ -867,6 +868,30 @@ pub fn with_opt_host_effect_param(
self.mk_args_from_iter(args.into_iter().map(|arg| arg.into()).chain(opt_const_param))
}
/// Expand any [weak alias types][weak] contained within the given `value`.
///
/// This should be used over other normalization routines in situations where
/// it's important not to normalize other alias types and where the predicates
/// on the corresponding type alias shouldn't be taken into consideration.
///
/// Whenever possible **prefer not to use this function**! Instead, use standard
/// normalization routines or if feasible don't normalize at all.
///
/// This function comes in handy if you want to mimic the behavior of eager
/// type alias expansion in a localized manner.
///
/// <div class="warning">
/// This delays a bug on overflow! Therefore you need to be certain that the
/// contained types get fully normalized at a later stage. Note that even on
/// overflow all well-behaved weak alias types get expanded correctly, so the
/// result is still useful.
/// </div>
///
/// [weak]: ty::Weak
pub fn expand_weak_alias_tys<T: TypeFoldable<TyCtxt<'tcx>>>(self, value: T) -> T {
value.fold_with(&mut WeakAliasTypeExpander { tcx: self, depth: 0 })
}
}
struct OpaqueTypeExpander<'tcx> {
@ -1002,6 +1027,42 @@ fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
}
}
struct WeakAliasTypeExpander<'tcx> {
tcx: TyCtxt<'tcx>,
depth: usize,
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for WeakAliasTypeExpander<'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
if !ty.has_type_flags(ty::TypeFlags::HAS_TY_WEAK) {
return ty;
}
let ty::Alias(ty::Weak, alias) = ty.kind() else {
return ty.super_fold_with(self);
};
if !self.tcx.recursion_limit().value_within_limit(self.depth) {
let guar = self.tcx.dcx().delayed_bug("overflow expanding weak alias type");
return Ty::new_error(self.tcx, guar);
}
self.depth += 1;
ensure_sufficient_stack(|| {
self.tcx.type_of(alias.def_id).instantiate(self.tcx, alias.args).fold_with(self)
})
}
fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
if !ct.ty().has_type_flags(ty::TypeFlags::HAS_TY_WEAK) {
return ct;
}
ct.super_fold_with(self)
}
}
impl<'tcx> Ty<'tcx> {
/// Returns the `Size` for primitive types (bool, uint, int, char, float).
pub fn primitive_size(self, tcx: TyCtxt<'tcx>) -> Size {

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@ -131,12 +131,13 @@ pub fn collect_referenced_late_bound_regions<T>(
fn collect_late_bound_regions<T>(
self,
value: &Binder<'tcx, T>,
just_constraint: bool,
just_constrained: bool,
) -> FxHashSet<ty::BoundRegionKind>
where
T: TypeVisitable<TyCtxt<'tcx>>,
{
let mut collector = LateBoundRegionsCollector::new(just_constraint);
let mut collector = LateBoundRegionsCollector::new(self, just_constrained);
let value = if just_constrained { self.expand_weak_alias_tys(value) } else { value };
let result = value.as_ref().skip_binder().visit_with(&mut collector);
assert!(result.is_continue()); // should never have stopped early
collector.regions
@ -258,11 +259,7 @@ struct LateBoundRegionsCollector {
impl LateBoundRegionsCollector {
fn new(just_constrained: bool) -> Self {
LateBoundRegionsCollector {
current_index: ty::INNERMOST,
regions: Default::default(),
just_constrained,
}
Self { current_index: ty::INNERMOST, regions: Default::default(), just_constrained }
}
}
@ -278,12 +275,16 @@ fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
}
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
// if we are only looking for "constrained" region, we have to
// ignore the inputs to a projection, as they may not appear
// in the normalized form
if self.just_constrained {
if let ty::Alias(..) = t.kind() {
return ControlFlow::Continue(());
match t.kind() {
// If we are only looking for "constrained" regions, we have to ignore the
// inputs to a projection as they may not appear in the normalized form.
ty::Alias(ty::Projection | ty::Inherent | ty::Opaque, _) => {
return ControlFlow::Continue(());
}
// All weak alias types should've been expanded beforehand.
ty::Alias(ty::Weak, _) => bug!("unexpected weak alias type"),
_ => {}
}
}

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@ -101,19 +101,17 @@ pub(super) fn needs_normalization<'tcx, T: TypeVisitable<TyCtxt<'tcx>>>(
value: &T,
reveal: Reveal,
) -> bool {
let mut flags = ty::TypeFlags::HAS_TY_PROJECTION
| ty::TypeFlags::HAS_TY_WEAK
| ty::TypeFlags::HAS_TY_INHERENT
| ty::TypeFlags::HAS_CT_PROJECTION;
match reveal {
Reveal::UserFacing => value.has_type_flags(
ty::TypeFlags::HAS_TY_PROJECTION
| ty::TypeFlags::HAS_TY_INHERENT
| ty::TypeFlags::HAS_CT_PROJECTION,
),
Reveal::All => value.has_type_flags(
ty::TypeFlags::HAS_TY_PROJECTION
| ty::TypeFlags::HAS_TY_INHERENT
| ty::TypeFlags::HAS_TY_OPAQUE
| ty::TypeFlags::HAS_CT_PROJECTION,
),
Reveal::UserFacing => {}
Reveal::All => flags |= ty::TypeFlags::HAS_TY_OPAQUE,
}
value.has_type_flags(flags)
}
struct AssocTypeNormalizer<'a, 'b, 'tcx> {

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@ -69,32 +69,35 @@ pub struct TypeFlags: u32 {
/// Does this have `Projection`?
const HAS_TY_PROJECTION = 1 << 10;
/// Does this have `Inherent`?
const HAS_TY_INHERENT = 1 << 11;
/// Does this have `Weak`?
const HAS_TY_WEAK = 1 << 11;
/// Does this have `Opaque`?
const HAS_TY_OPAQUE = 1 << 12;
/// Does this have `Inherent`?
const HAS_TY_INHERENT = 1 << 13;
/// Does this have `ConstKind::Unevaluated`?
const HAS_CT_PROJECTION = 1 << 13;
const HAS_CT_PROJECTION = 1 << 14;
/// Could this type be normalized further?
const HAS_PROJECTION = TypeFlags::HAS_TY_PROJECTION.bits()
| TypeFlags::HAS_TY_WEAK.bits()
| TypeFlags::HAS_TY_OPAQUE.bits()
| TypeFlags::HAS_TY_INHERENT.bits()
| TypeFlags::HAS_CT_PROJECTION.bits();
/// Is an error type/const reachable?
const HAS_ERROR = 1 << 14;
const HAS_ERROR = 1 << 15;
/// Does this have any region that "appears free" in the type?
/// Basically anything but `ReBound` and `ReErased`.
const HAS_FREE_REGIONS = 1 << 15;
const HAS_FREE_REGIONS = 1 << 16;
/// Does this have any `ReBound` regions?
const HAS_RE_BOUND = 1 << 16;
const HAS_RE_BOUND = 1 << 17;
/// Does this have any `Bound` types?
const HAS_TY_BOUND = 1 << 17;
const HAS_TY_BOUND = 1 << 18;
/// Does this have any `ConstKind::Bound` consts?
const HAS_CT_BOUND = 1 << 18;
const HAS_CT_BOUND = 1 << 19;
/// Does this have any bound variables?
/// Used to check if a global bound is safe to evaluate.
const HAS_BOUND_VARS = TypeFlags::HAS_RE_BOUND.bits()
@ -102,22 +105,22 @@ pub struct TypeFlags: u32 {
| TypeFlags::HAS_CT_BOUND.bits();
/// Does this have any `ReErased` regions?
const HAS_RE_ERASED = 1 << 19;
const HAS_RE_ERASED = 1 << 20;
/// Does this value have parameters/placeholders/inference variables which could be
/// replaced later, in a way that would change the results of `impl` specialization?
const STILL_FURTHER_SPECIALIZABLE = 1 << 20;
const STILL_FURTHER_SPECIALIZABLE = 1 << 21;
/// Does this value have `InferTy::FreshTy/FreshIntTy/FreshFloatTy`?
const HAS_TY_FRESH = 1 << 21;
const HAS_TY_FRESH = 1 << 22;
/// Does this value have `InferConst::Fresh`?
const HAS_CT_FRESH = 1 << 22;
const HAS_CT_FRESH = 1 << 23;
/// Does this have `Coroutine` or `CoroutineWitness`?
const HAS_TY_COROUTINE = 1 << 23;
const HAS_TY_COROUTINE = 1 << 24;
/// Does this have any binders with bound vars (e.g. that need to be anonymized)?
const HAS_BINDER_VARS = 1 << 24;
const HAS_BINDER_VARS = 1 << 25;
}
}

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@ -0,0 +1,15 @@
//@ check-pass
// Weak alias types constrain late-bound regions if their normalized form constrains them.
#![feature(lazy_type_alias)]
#![allow(incomplete_features)]
type Ref<'a> = &'a ();
type FnPtr = for<'a> fn(Ref<'a>) -> &'a (); // OK
type DynCl = dyn for<'a> Fn(Ref<'a>) -> &'a (); // OK
fn map0(_: Ref) -> Ref { &() } // OK
fn map1(_: Ref<'_>) -> Ref<'_> { &() } // OK
fn main() {}

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@ -0,0 +1,23 @@
// Weak alias types only constrain late-bound regions if their normalized form constrains them.
#![feature(lazy_type_alias)]
#![allow(incomplete_features)]
type NotInjective<'a> = <() as Discard>::Output<'a>;
type FnPtr0 = for<'a> fn(NotInjective<'a>) -> &'a ();
//~^ ERROR references lifetime `'a`, which is not constrained by the fn input types
type FnPtr1 = for<'a> fn(NotInjectiveEither<'a, ()>) -> NotInjectiveEither<'a, ()>;
//~^ ERROR references lifetime `'a`, which is not constrained by the fn input types
type DynCl = dyn for<'a> Fn(NotInjective<'a>) -> &'a ();
//~^ ERROR references lifetime `'a`, which does not appear in the trait input types
trait Discard { type Output<'a>; }
impl Discard for () { type Output<'_a> = (); }
type NotInjectiveEither<'a, Linchpin> = Linchpin
where
Linchpin: Fn() -> &'a ();
fn main() {}

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@ -0,0 +1,22 @@
error[E0581]: return type references lifetime `'a`, which is not constrained by the fn input types
--> $DIR/unconstrained-late-bound-regions.rs:8:47
|
LL | type FnPtr0 = for<'a> fn(NotInjective<'a>) -> &'a ();
| ^^^^^^
error[E0581]: return type references lifetime `'a`, which is not constrained by the fn input types
--> $DIR/unconstrained-late-bound-regions.rs:10:57
|
LL | type FnPtr1 = for<'a> fn(NotInjectiveEither<'a, ()>) -> NotInjectiveEither<'a, ()>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0582]: binding for associated type `Output` references lifetime `'a`, which does not appear in the trait input types
--> $DIR/unconstrained-late-bound-regions.rs:12:50
|
LL | type DynCl = dyn for<'a> Fn(NotInjective<'a>) -> &'a ();
| ^^^^^^
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0581, E0582.
For more information about an error, try `rustc --explain E0581`.

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@ -1,5 +1,5 @@
error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
--> $DIR/unconstrained-param-due-to-overflow.rs:4:6
--> $DIR/unconstrained-params-in-impl-due-to-overflow.rs:4:6
|
LL | impl<T> Loop<T> {}
| ^ unconstrained type parameter

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@ -1,5 +1,5 @@
error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
--> $DIR/unconstrained-params.rs:4:6
--> $DIR/unconstrained-params-in-impl.rs:4:6
|
LL | impl<T> NotInjective<T> {}
| ^ unconstrained type parameter