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Rollup merge of #127386 - compiler-errors:uplift-outlives-components, r=lcnr

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Uplift outlives components to `rustc_type_ir`

We need this to uplift `push_outlives_components`, since the elaborator uses `push_outlives_components` to elaborate type outlives obligations and I want to uplift elaboration.

This ends up reworking and inlining a fair portion of the `GenericArg::walk_shallow` function, whose only callsite was this one. I believe I got the logic correct, but may be worthwhile to look at it closely just in case. Unfortunately github was too dumb to understand that this is a rename + change -- I could also rework the git history to split the "copy the file over" part from the actual logical changes if that makes this easier to review.

r? lcnr
This commit is contained in:
Michael Goulet 2024-07-06 14:55:23 -04:00 committed by GitHub
commit dfc02d28c7
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15 changed files with 389 additions and 322 deletions
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2
compiler/rustc_hir_analysis/src/outlives/utils.rs
View File

@ -1,9 +1,9 @@
use rustc_data_structures::fx::FxIndexMap;
use rustc_infer::infer::outlives::components::{push_outlives_components, Component};
use rustc_middle::ty::{self, Region, Ty, TyCtxt};
use rustc_middle::ty::{GenericArg, GenericArgKind};
use rustc_middle::{bug, span_bug};
use rustc_span::Span;
use rustc_type_ir::outlives::{push_outlives_components, Component};
use smallvec::smallvec;
/// Tracks the `T: 'a` or `'a: 'a` predicates that we have inferred

266
compiler/rustc_infer/src/infer/outlives/components.rs
View File

@ -1,266 +0,0 @@
// The outlines relation `T: 'a` or `'a: 'b`. This code frequently
// refers to rules defined in RFC 1214 (`OutlivesFooBar`), so see that
// RFC for reference.
use rustc_data_structures::sso::SsoHashSet;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
use rustc_middle::ty::{GenericArg, GenericArgKind};
use smallvec::{smallvec, SmallVec};
#[derive(Debug)]
pub enum Component<'tcx> {
Region(ty::Region<'tcx>),
Param(ty::ParamTy),
Placeholder(ty::PlaceholderType),
UnresolvedInferenceVariable(ty::InferTy),
// Projections like `T::Foo` are tricky because a constraint like
// `T::Foo: 'a` can be satisfied in so many ways. There may be a
// where-clause that says `T::Foo: 'a`, or the defining trait may
// include a bound like `type Foo: 'static`, or -- in the most
// conservative way -- we can prove that `T: 'a` (more generally,
// that all components in the projection outlive `'a`). This code
// is not in a position to judge which is the best technique, so
// we just product the projection as a component and leave it to
// the consumer to decide (but see `EscapingProjection` below).
Alias(ty::AliasTy<'tcx>),
// In the case where a projection has escaping regions -- meaning
// regions bound within the type itself -- we always use
// the most conservative rule, which requires that all components
// outlive the bound. So for example if we had a type like this:
//
// for<'a> Trait1< <T as Trait2<'a,'b>>::Foo >
// ~~~~~~~~~~~~~~~~~~~~~~~~~
//
// then the inner projection (underlined) has an escaping region
// `'a`. We consider that outer trait `'c` to meet a bound if `'b`
// outlives `'b: 'c`, and we don't consider whether the trait
// declares that `Foo: 'static` etc. Therefore, we just return the
// free components of such a projection (in this case, `'b`).
//
// However, in the future, we may want to get smarter, and
// actually return a "higher-ranked projection" here. Therefore,
// we mark that these components are part of an escaping
// projection, so that implied bounds code can avoid relying on
// them. This gives us room to improve the regionck reasoning in
// the future without breaking backwards compat.
EscapingAlias(Vec<Component<'tcx>>),
}
/// Push onto `out` all the things that must outlive `'a` for the condition
/// `ty0: 'a` to hold. Note that `ty0` must be a **fully resolved type**.
pub fn push_outlives_components<'tcx>(
tcx: TyCtxt<'tcx>,
ty0: Ty<'tcx>,
out: &mut SmallVec<[Component<'tcx>; 4]>,
) {
let mut visited = SsoHashSet::new();
compute_components(tcx, ty0, out, &mut visited);
debug!("components({:?}) = {:?}", ty0, out);
}
fn compute_components<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
out: &mut SmallVec<[Component<'tcx>; 4]>,
visited: &mut SsoHashSet<GenericArg<'tcx>>,
) {
// Descend through the types, looking for the various "base"
// components and collecting them into `out`. This is not written
// with `collect()` because of the need to sometimes skip subtrees
// in the `subtys` iterator (e.g., when encountering a
// projection).
match *ty.kind() {
ty::FnDef(_, args) => {
// HACK(eddyb) ignore lifetimes found shallowly in `args`.
// This is inconsistent with `ty::Adt` (including all args)
// and with `ty::Closure` (ignoring all args other than
// upvars, of which a `ty::FnDef` doesn't have any), but
// consistent with previous (accidental) behavior.
// See https://github.com/rust-lang/rust/issues/70917
// for further background and discussion.
for child in args {
match child.unpack() {
GenericArgKind::Type(ty) => {
compute_components(tcx, ty, out, visited);
}
GenericArgKind::Lifetime(_) => {}
GenericArgKind::Const(_) => {
compute_components_recursive(tcx, child, out, visited);
}
}
}
}
ty::Pat(element, _) |
ty::Array(element, _) => {
// Don't look into the len const as it doesn't affect regions
compute_components(tcx, element, out, visited);
}
ty::Closure(_, args) => {
let tupled_ty = args.as_closure().tupled_upvars_ty();
compute_components(tcx, tupled_ty, out, visited);
}
ty::CoroutineClosure(_, args) => {
let tupled_ty = args.as_coroutine_closure().tupled_upvars_ty();
compute_components(tcx, tupled_ty, out, visited);
}
ty::Coroutine(_, args) => {
// Same as the closure case
let tupled_ty = args.as_coroutine().tupled_upvars_ty();
compute_components(tcx, tupled_ty, out, visited);
// We ignore regions in the coroutine interior as we don't
// want these to affect region inference
}
// All regions are bound inside a witness
ty::CoroutineWitness(..) => (),
// OutlivesTypeParameterEnv -- the actual checking that `X:'a`
// is implied by the environment is done in regionck.
ty::Param(p) => {
out.push(Component::Param(p));
}
ty::Placeholder(p) => {
out.push(Component::Placeholder(p));
}
// For projections, we prefer to generate an obligation like
// `<P0 as Trait<P1...Pn>>::Foo: 'a`, because this gives the
// regionck more ways to prove that it holds. However,
// regionck is not (at least currently) prepared to deal with
// higher-ranked regions that may appear in the
// trait-ref. Therefore, if we see any higher-ranked regions,
// we simply fallback to the most restrictive rule, which
// requires that `Pi: 'a` for all `i`.
ty::Alias(_, alias_ty) => {
if !alias_ty.has_escaping_bound_vars() {
// best case: no escaping regions, so push the
// projection and skip the subtree (thus generating no
// constraints for Pi). This defers the choice between
// the rules OutlivesProjectionEnv,
// OutlivesProjectionTraitDef, and
// OutlivesProjectionComponents to regionck.
out.push(Component::Alias(alias_ty));
} else {
// fallback case: hard code
// OutlivesProjectionComponents. Continue walking
// through and constrain Pi.
let mut subcomponents = smallvec![];
let mut subvisited = SsoHashSet::new();
compute_alias_components_recursive(tcx, ty, &mut subcomponents, &mut subvisited);
out.push(Component::EscapingAlias(subcomponents.into_iter().collect()));
}
}
// We assume that inference variables are fully resolved.
// So, if we encounter an inference variable, just record
// the unresolved variable as a component.
ty::Infer(infer_ty) => {
out.push(Component::UnresolvedInferenceVariable(infer_ty));
}
// Most types do not introduce any region binders, nor
// involve any other subtle cases, and so the WF relation
// simply constraints any regions referenced directly by
// the type and then visits the types that are lexically
// contained within. (The comments refer to relevant rules
// from RFC1214.)
ty::Bool | // OutlivesScalar
ty::Char | // OutlivesScalar
ty::Int(..) | // OutlivesScalar
ty::Uint(..) | // OutlivesScalar
ty::Float(..) | // OutlivesScalar
ty::Never | // ...
ty::Adt(..) | // OutlivesNominalType
ty::Foreign(..) | // OutlivesNominalType
ty::Str | // OutlivesScalar (ish)
ty::Slice(..) | // ...
ty::RawPtr(..) | // ...
ty::Ref(..) | // OutlivesReference
ty::Tuple(..) | // ...
ty::FnPtr(_) | // OutlivesFunction (*)
ty::Dynamic(..) | // OutlivesObject, OutlivesFragment (*)
ty::Bound(..) |
ty::Error(_) => {
// (*) Function pointers and trait objects are both binders.
// In the RFC, this means we would add the bound regions to
// the "bound regions list". In our representation, no such
// list is maintained explicitly, because bound regions
// themselves can be readily identified.
compute_components_recursive(tcx, ty.into(), out, visited);
}
}
}
/// Collect [Component]s for *all* the args of `parent`.
///
/// This should not be used to get the components of `parent` itself.
/// Use [push_outlives_components] instead.
pub(super) fn compute_alias_components_recursive<'tcx>(
tcx: TyCtxt<'tcx>,
alias_ty: Ty<'tcx>,
out: &mut SmallVec<[Component<'tcx>; 4]>,
visited: &mut SsoHashSet<GenericArg<'tcx>>,
) {
let ty::Alias(kind, alias_ty) = alias_ty.kind() else {
unreachable!("can only call `compute_alias_components_recursive` on an alias type")
};
let opt_variances = if *kind == ty::Opaque { tcx.variances_of(alias_ty.def_id) } else { &[] };
for (index, child) in alias_ty.args.iter().enumerate() {
if opt_variances.get(index) == Some(&ty::Bivariant) {
continue;
}
if !visited.insert(child) {
continue;
}
match child.unpack() {
GenericArgKind::Type(ty) => {
compute_components(tcx, ty, out, visited);
}
GenericArgKind::Lifetime(lt) => {
// Ignore higher ranked regions.
if !lt.is_bound() {
out.push(Component::Region(lt));
}
}
GenericArgKind::Const(_) => {
compute_components_recursive(tcx, child, out, visited);
}
}
}
}
/// Collect [Component]s for *all* the args of `parent`.
///
/// This should not be used to get the components of `parent` itself.
/// Use [push_outlives_components] instead.
fn compute_components_recursive<'tcx>(
tcx: TyCtxt<'tcx>,
parent: GenericArg<'tcx>,
out: &mut SmallVec<[Component<'tcx>; 4]>,
visited: &mut SsoHashSet<GenericArg<'tcx>>,
) {
for child in parent.walk_shallow(visited) {
match child.unpack() {
GenericArgKind::Type(ty) => {
compute_components(tcx, ty, out, visited);
}
GenericArgKind::Lifetime(lt) => {
// Ignore higher ranked regions.
if !lt.is_bound() {
out.push(Component::Region(lt));
}
}
GenericArgKind::Const(_) => {
compute_components_recursive(tcx, child, out, visited);
}
}
}
}

1
compiler/rustc_infer/src/infer/outlives/mod.rs
View File

@ -8,7 +8,6 @@ use crate::infer::lexical_region_resolve;
use rustc_middle::traits::query::{NoSolution, OutlivesBound};
use rustc_middle::ty;
pub mod components;
pub mod env;
pub mod for_liveness;
pub mod obligations;

4
compiler/rustc_infer/src/infer/outlives/obligations.rs
View File

@ -59,7 +59,6 @@
//! might later infer `?U` to something like `&'b u32`, which would
//! imply that `'b: 'a`.
use crate::infer::outlives::components::{push_outlives_components, Component};
use crate::infer::outlives::env::RegionBoundPairs;
use crate::infer::outlives::verify::VerifyBoundCx;
use crate::infer::resolve::OpportunisticRegionResolver;
@ -75,6 +74,7 @@ use rustc_middle::ty::{
};
use rustc_middle::ty::{GenericArgKind, PolyTypeOutlivesPredicate};
use rustc_span::DUMMY_SP;
use rustc_type_ir::outlives::{push_outlives_components, Component};
use smallvec::smallvec;
use super::env::OutlivesEnvironment;
@ -291,7 +291,7 @@ where
fn components_must_outlive(
&mut self,
origin: infer::SubregionOrigin<'tcx>,
components: &[Component<'tcx>],
components: &[Component<TyCtxt<'tcx>>],
region: ty::Region<'tcx>,
category: ConstraintCategory<'tcx>,
) {

6
compiler/rustc_infer/src/infer/outlives/verify.rs
View File

@ -1,10 +1,10 @@
use crate::infer::outlives::components::{compute_alias_components_recursive, Component};
use crate::infer::outlives::env::RegionBoundPairs;
use crate::infer::region_constraints::VerifyIfEq;
use crate::infer::{GenericKind, VerifyBound};
use rustc_data_structures::sso::SsoHashSet;
use rustc_middle::ty::GenericArg;
use rustc_middle::ty::{self, OutlivesPredicate, Ty, TyCtxt};
use rustc_type_ir::outlives::{compute_alias_components_recursive, Component};
use smallvec::smallvec;
@ -139,7 +139,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
fn bound_from_components(
&self,
components: &[Component<'tcx>],
components: &[Component<TyCtxt<'tcx>>],
visited: &mut SsoHashSet<GenericArg<'tcx>>,
) -> VerifyBound<'tcx> {
let mut bounds = components
@ -158,7 +158,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
fn bound_from_single_component(
&self,
component: &Component<'tcx>,
component: &Component<TyCtxt<'tcx>>,
visited: &mut SsoHashSet<GenericArg<'tcx>>,
) -> VerifyBound<'tcx> {
match *component {

2
compiler/rustc_infer/src/traits/util.rs
View File

@ -1,12 +1,12 @@
use smallvec::smallvec;
use crate::infer::outlives::components::{push_outlives_components, Component};
use crate::traits::{self, Obligation, ObligationCauseCode, PredicateObligation};
use rustc_data_structures::fx::FxHashSet;
use rustc_middle::ty::ToPolyTraitRef;
use rustc_middle::ty::{self, Ty, TyCtxt, Upcast};
use rustc_span::symbol::Ident;
use rustc_span::Span;
use rustc_type_ir::outlives::{push_outlives_components, Component};
pub fn anonymize_predicate<'tcx>(
tcx: TyCtxt<'tcx>,

7
compiler/rustc_middle/src/ty/consts/kind.rs
View File

@ -54,6 +54,13 @@ pub struct Expr<'tcx> {
pub kind: ExprKind,
args: ty::GenericArgsRef<'tcx>,
}
impl<'tcx> rustc_type_ir::inherent::ExprConst<TyCtxt<'tcx>> for Expr<'tcx> {
fn args(self) -> ty::GenericArgsRef<'tcx> {
self.args
}
}
impl<'tcx> Expr<'tcx> {
pub fn new_binop(
tcx: TyCtxt<'tcx>,

17
compiler/rustc_middle/src/ty/walk.rs
View File

@ -78,23 +78,6 @@ impl<'tcx> GenericArg<'tcx> {
pub fn walk(self) -> TypeWalker<'tcx> {
TypeWalker::new(self)
}
/// Iterator that walks the immediate children of `self`. Hence
/// `Foo<Bar<i32>, u32>` yields the sequence `[Bar<i32>, u32]`
/// (but not `i32`, like `walk`).
///
/// Iterator only walks items once.
/// It accepts visited set, updates it with all visited types
/// and skips any types that are already there.
pub fn walk_shallow(
self,
visited: &mut SsoHashSet<GenericArg<'tcx>>,
) -> impl Iterator<Item = GenericArg<'tcx>> {
let mut stack = SmallVec::new();
push_inner(&mut stack, self);
stack.retain(|a| visited.insert(*a));
stack.into_iter()
}
}
impl<'tcx> Ty<'tcx> {

4
compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
View File

@ -3,7 +3,6 @@ use crate::traits::wf;
use crate::traits::ObligationCtxt;
use rustc_infer::infer::canonical::Canonical;
use rustc_infer::infer::outlives::components::{push_outlives_components, Component};
use rustc_infer::infer::resolve::OpportunisticRegionResolver;
use rustc_infer::traits::query::OutlivesBound;
use rustc_macros::{HashStable, TypeFoldable, TypeVisitable};
@ -12,6 +11,7 @@ use rustc_middle::traits::ObligationCause;
use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt, TypeFolder, TypeVisitableExt};
use rustc_span::def_id::CRATE_DEF_ID;
use rustc_span::DUMMY_SP;
use rustc_type_ir::outlives::{push_outlives_components, Component};
use smallvec::{smallvec, SmallVec};
#[derive(Copy, Clone, Debug, HashStable, TypeFoldable, TypeVisitable)]
@ -284,7 +284,7 @@ pub fn compute_implied_outlives_bounds_compat_inner<'tcx>(
/// those relationships.
fn implied_bounds_from_components<'tcx>(
sub_region: ty::Region<'tcx>,
sup_components: SmallVec<[Component<'tcx>; 4]>,
sup_components: SmallVec<[Component<TyCtxt<'tcx>>; 4]>,
) -> Vec<OutlivesBound<'tcx>> {
sup_components
.into_iter()

8
compiler/rustc_type_ir/src/inherent.rs
View File

@ -232,6 +232,10 @@ pub trait Region<I: Interner<Region = Self>>:
fn new_anon_bound(interner: I, debruijn: ty::DebruijnIndex, var: ty::BoundVar) -> Self;
fn new_static(interner: I) -> Self;
fn is_bound(self) -> bool {
matches!(self.kind(), ty::ReBound(..))
}
}
pub trait Const<I: Interner<Const = Self>>:
@ -272,6 +276,10 @@ pub trait Const<I: Interner<Const = Self>>:
}
}
pub trait ExprConst<I: Interner<ExprConst = Self>>: Copy + Debug + Hash + Eq + Relate<I> {
fn args(self) -> I::GenericArgs;
}
pub trait GenericsOf<I: Interner<GenericsOf = Self>> {
fn count(&self) -> usize;
}

2
compiler/rustc_type_ir/src/interner.rs
View File

@ -109,7 +109,7 @@ pub trait Interner:
type ParamConst: Copy + Debug + Hash + Eq + ParamLike;
type BoundConst: Copy + Debug + Hash + Eq + BoundVarLike<Self>;
type ValueConst: Copy + Debug + Hash + Eq;
type ExprConst: Copy + Debug + Hash + Eq + Relate<Self>;
type ExprConst: ExprConst<Self>;
// Kinds of regions
type Region: Region<Self>;

1
compiler/rustc_type_ir/src/lib.rs
View File

@ -27,6 +27,7 @@ pub mod inherent;
pub mod ir_print;
pub mod lang_items;
pub mod lift;
pub mod outlives;
pub mod relate;
pub mod solve;

335
compiler/rustc_type_ir/src/outlives.rs Normal file
View File

@ -0,0 +1,335 @@
//! The outlives relation `T: 'a` or `'a: 'b`. This code frequently
//! refers to rules defined in RFC 1214 (`OutlivesFooBar`), so see that
//! RFC for reference.
use smallvec::{smallvec, SmallVec};
use tracing::debug;
use crate::data_structures::SsoHashSet;
use crate::inherent::*;
use crate::visit::TypeVisitableExt as _;
use crate::{self as ty, Interner};
#[derive(derivative::Derivative)]
#[derivative(Debug(bound = ""))]
pub enum Component<I: Interner> {
Region(I::Region),
Param(I::ParamTy),
Placeholder(I::PlaceholderTy),
UnresolvedInferenceVariable(ty::InferTy),
// Projections like `T::Foo` are tricky because a constraint like
// `T::Foo: 'a` can be satisfied in so many ways. There may be a
// where-clause that says `T::Foo: 'a`, or the defining trait may
// include a bound like `type Foo: 'static`, or -- in the most
// conservative way -- we can prove that `T: 'a` (more generally,
// that all components in the projection outlive `'a`). This code
// is not in a position to judge which is the best technique, so
// we just product the projection as a component and leave it to
// the consumer to decide (but see `EscapingProjection` below).
Alias(ty::AliasTy<I>),
// In the case where a projection has escaping regions -- meaning
// regions bound within the type itself -- we always use
// the most conservative rule, which requires that all components
// outlive the bound. So for example if we had a type like this:
//
// for<'a> Trait1< <T as Trait2<'a,'b>>::Foo >
// ~~~~~~~~~~~~~~~~~~~~~~~~~
//
// then the inner projection (underlined) has an escaping region
// `'a`. We consider that outer trait `'c` to meet a bound if `'b`
// outlives `'b: 'c`, and we don't consider whether the trait
// declares that `Foo: 'static` etc. Therefore, we just return the
// free components of such a projection (in this case, `'b`).
//
// However, in the future, we may want to get smarter, and
// actually return a "higher-ranked projection" here. Therefore,
// we mark that these components are part of an escaping
// projection, so that implied bounds code can avoid relying on
// them. This gives us room to improve the regionck reasoning in
// the future without breaking backwards compat.
EscapingAlias(Vec<Component<I>>),
}
/// Push onto `out` all the things that must outlive `'a` for the condition
/// `ty0: 'a` to hold. Note that `ty0` must be a **fully resolved type**.
pub fn push_outlives_components<I: Interner>(
tcx: I,
ty0: I::Ty,
out: &mut SmallVec<[Component<I>; 4]>,
) {
let mut visited = SsoHashSet::new();
compute_components_for_ty(tcx, ty0, out, &mut visited);
debug!("components({:?}) = {:?}", ty0, out);
}
fn compute_components_for_arg<I: Interner>(
tcx: I,
arg: I::GenericArg,
out: &mut SmallVec<[Component<I>; 4]>,
visited: &mut SsoHashSet<I::GenericArg>,
) {
match arg.kind() {
ty::GenericArgKind::Type(ty) => {
compute_components_for_ty(tcx, ty, out, visited);
}
ty::GenericArgKind::Lifetime(lt) => {
compute_components_for_lt(lt, out);
}
ty::GenericArgKind::Const(ct) => {
compute_components_for_const(tcx, ct, out, visited);
}
}
}
fn compute_components_for_ty<I: Interner>(
tcx: I,
ty: I::Ty,
out: &mut SmallVec<[Component<I>; 4]>,
visited: &mut SsoHashSet<I::GenericArg>,
) {
if !visited.insert(ty.into()) {
return;
}
// Descend through the types, looking for the various "base"
// components and collecting them into `out`. This is not written
// with `collect()` because of the need to sometimes skip subtrees
// in the `subtys` iterator (e.g., when encountering a
// projection).
match ty.kind() {
ty::FnDef(_, args) => {
// HACK(eddyb) ignore lifetimes found shallowly in `args`.
// This is inconsistent with `ty::Adt` (including all args)
// and with `ty::Closure` (ignoring all args other than
// upvars, of which a `ty::FnDef` doesn't have any), but
// consistent with previous (accidental) behavior.
// See https://github.com/rust-lang/rust/issues/70917
// for further background and discussion.
for child in args.iter() {
match child.kind() {
ty::GenericArgKind::Type(ty) => {
compute_components_for_ty(tcx, ty, out, visited);
}
ty::GenericArgKind::Lifetime(_) => {}
ty::GenericArgKind::Const(ct) => {
compute_components_for_const(tcx, ct, out, visited);
}
}
}
}
ty::Pat(element, _) | ty::Array(element, _) => {
compute_components_for_ty(tcx, element, out, visited);
}
ty::Closure(_, args) => {
let tupled_ty = args.as_closure().tupled_upvars_ty();
compute_components_for_ty(tcx, tupled_ty, out, visited);
}
ty::CoroutineClosure(_, args) => {
let tupled_ty = args.as_coroutine_closure().tupled_upvars_ty();
compute_components_for_ty(tcx, tupled_ty, out, visited);
}
ty::Coroutine(_, args) => {
// Same as the closure case
let tupled_ty = args.as_coroutine().tupled_upvars_ty();
compute_components_for_ty(tcx, tupled_ty, out, visited);
// We ignore regions in the coroutine interior as we don't
// want these to affect region inference
}
// All regions are bound inside a witness, and we don't emit
// higher-ranked outlives components currently.
ty::CoroutineWitness(..) => {},
// OutlivesTypeParameterEnv -- the actual checking that `X:'a`
// is implied by the environment is done in regionck.
ty::Param(p) => {
out.push(Component::Param(p));
}
ty::Placeholder(p) => {
out.push(Component::Placeholder(p));
}
// For projections, we prefer to generate an obligation like
// `<P0 as Trait<P1...Pn>>::Foo: 'a`, because this gives the
// regionck more ways to prove that it holds. However,
// regionck is not (at least currently) prepared to deal with
// higher-ranked regions that may appear in the
// trait-ref. Therefore, if we see any higher-ranked regions,
// we simply fallback to the most restrictive rule, which
// requires that `Pi: 'a` for all `i`.
ty::Alias(_, alias_ty) => {
if !alias_ty.has_escaping_bound_vars() {
// best case: no escaping regions, so push the
// projection and skip the subtree (thus generating no
// constraints for Pi). This defers the choice between
// the rules OutlivesProjectionEnv,
// OutlivesProjectionTraitDef, and
// OutlivesProjectionComponents to regionck.
out.push(Component::Alias(alias_ty));
} else {
// fallback case: hard code
// OutlivesProjectionComponents. Continue walking
// through and constrain Pi.
let mut subcomponents = smallvec![];
let mut subvisited = SsoHashSet::new();
compute_alias_components_recursive(tcx, ty, &mut subcomponents, &mut subvisited);
out.push(Component::EscapingAlias(subcomponents.into_iter().collect()));
}
}
// We assume that inference variables are fully resolved.
// So, if we encounter an inference variable, just record
// the unresolved variable as a component.
ty::Infer(infer_ty) => {
out.push(Component::UnresolvedInferenceVariable(infer_ty));
}
// Most types do not introduce any region binders, nor
// involve any other subtle cases, and so the WF relation
// simply constraints any regions referenced directly by
// the type and then visits the types that are lexically
// contained within. (The comments refer to relevant rules
// from RFC1214.)
ty::Bool | // OutlivesScalar
ty::Char | // OutlivesScalar
ty::Int(..) | // OutlivesScalar
ty::Uint(..) | // OutlivesScalar
ty::Float(..) | // OutlivesScalar
ty::Never | // OutlivesScalar
ty::Foreign(..) | // OutlivesNominalType
ty::Str | // OutlivesScalar (ish)
ty::Bound(..) |
ty::Error(_) => {
// Trivial.
}
// OutlivesNominalType
ty::Adt(_, args) => {
for arg in args.iter() {
compute_components_for_arg(tcx, arg, out, visited);
}
}
// OutlivesNominalType
ty::Slice(ty) |
ty::RawPtr(ty, _) => {
compute_components_for_ty(tcx, ty, out, visited);
}
ty::Tuple(tys) => {
for ty in tys.iter() {
compute_components_for_ty(tcx, ty, out, visited);
}
}
// OutlivesReference
ty::Ref(lt, ty, _) => {
compute_components_for_lt(lt, out);
compute_components_for_ty(tcx, ty, out, visited);
}
ty::Dynamic(preds, lt, _) => {
compute_components_for_lt(lt, out);
for pred in preds.iter() {
match pred.skip_binder() {
ty::ExistentialPredicate::Trait(tr) => {
for arg in tr.args.iter() {
compute_components_for_arg(tcx, arg, out, visited);
}
}
ty::ExistentialPredicate::Projection(proj) => {
for arg in proj.args.iter() {
compute_components_for_arg(tcx, arg, out, visited);
}
match proj.term.kind() {
ty::TermKind::Ty(ty) => {
compute_components_for_ty(tcx, ty, out, visited)
}
ty::TermKind::Const(ct) => {
compute_components_for_const(tcx, ct, out, visited)
}
}
}
ty::ExistentialPredicate::AutoTrait(..) => {}
}
}
}
ty::FnPtr(sig) => {
for ty in sig.skip_binder().inputs_and_output.iter() {
compute_components_for_ty(tcx, ty, out, visited);
}
}
}
}
/// Collect [Component]s for *all* the args of `parent`.
///
/// This should not be used to get the components of `parent` itself.
/// Use [push_outlives_components] instead.
pub fn compute_alias_components_recursive<I: Interner>(
tcx: I,
alias_ty: I::Ty,
out: &mut SmallVec<[Component<I>; 4]>,
visited: &mut SsoHashSet<I::GenericArg>,
) {
let ty::Alias(kind, alias_ty) = alias_ty.kind() else {
unreachable!("can only call `compute_alias_components_recursive` on an alias type")
};
let opt_variances =
if kind == ty::Opaque { Some(tcx.variances_of(alias_ty.def_id)) } else { None };
for (index, child) in alias_ty.args.iter().enumerate() {
if opt_variances.and_then(|variances| variances.get(index)) == Some(ty::Bivariant) {
continue;
}
compute_components_for_arg(tcx, child, out, visited);
}
}
fn compute_components_for_lt<I: Interner>(lt: I::Region, out: &mut SmallVec<[Component<I>; 4]>) {
if !lt.is_bound() {
out.push(Component::Region(lt));
}
}
fn compute_components_for_const<I: Interner>(
tcx: I,
ct: I::Const,
out: &mut SmallVec<[Component<I>; 4]>,
visited: &mut SsoHashSet<I::GenericArg>,
) {
if !visited.insert(ct.into()) {
return;
}
match ct.kind() {
ty::ConstKind::Param(_)
| ty::ConstKind::Bound(_, _)
| ty::ConstKind::Infer(_)
| ty::ConstKind::Placeholder(_)
| ty::ConstKind::Error(_) => {
// Trivial
}
ty::ConstKind::Expr(e) => {
for arg in e.args().iter() {
compute_components_for_arg(tcx, arg, out, visited);
}
}
ty::ConstKind::Value(ty, _) => {
compute_components_for_ty(tcx, ty, out, visited);
}
ty::ConstKind::Unevaluated(uv) => {
for arg in uv.args.iter() {
compute_components_for_arg(tcx, arg, out, visited);
}
}
}
}

28
tests/ui/async-await/in-trait/async-generics-and-bounds.stderr
View File

@ -1,17 +1,3 @@
error[E0311]: the parameter type `U` may not live long enough
--> $DIR/async-generics-and-bounds.rs:9:5
|
LL | async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
| ^^^^^^^^^^^^^-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| | |
| | the parameter type `U` must be valid for the anonymous lifetime as defined here...
| ...so that the reference type `&(T, U)` does not outlive the data it points at
|
help: consider adding an explicit lifetime bound
|
LL | async fn foo<'a>(&'a self) -> &'a (T, U) where T: Debug + Sized, U: Hash, U: 'a;
| ++++ ++ ++ +++++++
error[E0311]: the parameter type `T` may not live long enough
--> $DIR/async-generics-and-bounds.rs:9:5
|
@ -26,6 +12,20 @@ help: consider adding an explicit lifetime bound
LL | async fn foo<'a>(&'a self) -> &'a (T, U) where T: Debug + Sized, U: Hash, T: 'a;
| ++++ ++ ++ +++++++
error[E0311]: the parameter type `U` may not live long enough
--> $DIR/async-generics-and-bounds.rs:9:5
|
LL | async fn foo(&self) -> &(T, U) where T: Debug + Sized, U: Hash;
| ^^^^^^^^^^^^^-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| | |
| | the parameter type `U` must be valid for the anonymous lifetime as defined here...
| ...so that the reference type `&(T, U)` does not outlive the data it points at
|
help: consider adding an explicit lifetime bound
|
LL | async fn foo<'a>(&'a self) -> &'a (T, U) where T: Debug + Sized, U: Hash, U: 'a;
| ++++ ++ ++ +++++++
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0311`.

28
tests/ui/async-await/in-trait/async-generics.stderr
View File

@ -1,17 +1,3 @@
error[E0311]: the parameter type `U` may not live long enough
--> $DIR/async-generics.rs:6:5
|
LL | async fn foo(&self) -> &(T, U);
| ^^^^^^^^^^^^^-^^^^^^^^^^^^^^^^^
| | |
| | the parameter type `U` must be valid for the anonymous lifetime as defined here...
| ...so that the reference type `&(T, U)` does not outlive the data it points at
|
help: consider adding an explicit lifetime bound
|
LL | async fn foo<'a>(&'a self) -> &'a (T, U) where U: 'a;
| ++++ ++ ++ +++++++++++
error[E0311]: the parameter type `T` may not live long enough
--> $DIR/async-generics.rs:6:5
|
@ -26,6 +12,20 @@ help: consider adding an explicit lifetime bound
LL | async fn foo<'a>(&'a self) -> &'a (T, U) where T: 'a;
| ++++ ++ ++ +++++++++++
error[E0311]: the parameter type `U` may not live long enough
--> $DIR/async-generics.rs:6:5
|
LL | async fn foo(&self) -> &(T, U);
| ^^^^^^^^^^^^^-^^^^^^^^^^^^^^^^^
| | |
| | the parameter type `U` must be valid for the anonymous lifetime as defined here...
| ...so that the reference type `&(T, U)` does not outlive the data it points at
|
help: consider adding an explicit lifetime bound
|
LL | async fn foo<'a>(&'a self) -> &'a (T, U) where U: 'a;
| ++++ ++ ++ +++++++++++
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0311`.