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Inherit generics for impl-trait.

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This commit is contained in:
Camille GILLOT 2022-10-23 20:38:34 +00:00
parent b95650930b
commit 5fc261e9a0
6 changed files with 144 additions and 72 deletions
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31
compiler/rustc_hir_analysis/src/astconv/mod.rs
View file

@ -2767,35 +2767,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
// Our own parameters are the resolved lifetimes.
if let GenericParamDefKind::Lifetime = param.kind {
if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
let GenericParamDefKind::Lifetime { .. } = param.kind else { bug!() };
let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] else { bug!() };
self.ast_region_to_region(lifetime, None).into()
} else {
bug!()
}
} else {
bug!()
}
} else {
match param.kind {
// For RPIT (return position impl trait), only lifetimes
// mentioned in the impl Trait predicate are captured by
// the opaque type, so the lifetime parameters from the
// parent item need to be replaced with `'static`.
//
// For `impl Trait` in the types of statics, constants,
// locals and type aliases. These capture all parent
// lifetimes, so they can use their identity subst.
GenericParamDefKind::Lifetime
if matches!(
origin,
hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..)
) =>
{
tcx.lifetimes.re_static.into()
}
_ => tcx.mk_param_from_def(param),
}
tcx.mk_param_from_def(param)
}
});
debug!("impl_trait_ty_to_ty: substs={:?}", substs);
@ -2972,6 +2948,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
Some(tcx.liberate_late_bound_regions(fn_hir_id.expect_owner().to_def_id(), ty))
}
#[instrument(level = "trace", skip(self, generate_err))]
fn validate_late_bound_regions(
&self,
constrained_regions: FxHashSet<ty::BoundRegionKind>,

91
compiler/rustc_hir_analysis/src/check/check.rs
View file

@ -240,6 +240,7 @@ fn check_opaque<'tcx>(tcx: TyCtxt<'tcx>, id: hir::ItemId) {
}
check_opaque_meets_bounds(tcx, item.owner_id.def_id, substs, span, &origin);
}
/// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
/// in "inheriting lifetimes".
#[instrument(level = "debug", skip(tcx, span))]
@ -251,15 +252,19 @@ pub(super) fn check_opaque_for_inheriting_lifetimes<'tcx>(
let item = tcx.hir().expect_item(def_id);
debug!(?item, ?span);
#[derive(Debug)]
struct FoundParentLifetime;
struct FindParentLifetimeVisitor<'tcx>(&'tcx ty::Generics);
struct FindParentLifetimeVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
parent_count: u32,
}
impl<'tcx> ty::visit::TypeVisitor<'tcx> for FindParentLifetimeVisitor<'tcx> {
type BreakTy = FoundParentLifetime;
#[instrument(level = "trace", skip(self), ret)]
fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
debug!("FindParentLifetimeVisitor: r={:?}", r);
if let ty::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = *r {
if index < self.0.parent_count as u32 {
if index < self.parent_count {
return ControlFlow::Break(FoundParentLifetime);
} else {
return ControlFlow::CONTINUE;
@ -269,6 +274,63 @@ pub(super) fn check_opaque_for_inheriting_lifetimes<'tcx>(
r.super_visit_with(self)
}
#[instrument(level = "trace", skip(self), ret)]
fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
// We're only interested in types involving regions
if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) {
return ControlFlow::CONTINUE;
}
match ty.kind() {
ty::Closure(_, ref substs) => {
// Skip lifetime parameters of the enclosing item(s)
substs.as_closure().tupled_upvars_ty().visit_with(self)?;
substs.as_closure().sig_as_fn_ptr_ty().visit_with(self)?;
}
ty::Generator(_, ref substs, _) => {
// Skip lifetime parameters of the enclosing item(s)
// Also skip the witness type, because that has no free regions.
substs.as_generator().tupled_upvars_ty().visit_with(self)?;
substs.as_generator().return_ty().visit_with(self)?;
substs.as_generator().yield_ty().visit_with(self)?;
substs.as_generator().resume_ty().visit_with(self)?;
}
ty::Opaque(def_id, ref substs) => {
// Skip lifetime paramters that are not captures.
let variances = self.tcx.variances_of(*def_id);
for (v, s) in std::iter::zip(variances, substs.iter()) {
if *v != ty::Variance::Bivariant {
s.visit_with(self)?;
}
}
}
ty::Projection(proj)
if self.tcx.def_kind(proj.item_def_id) == DefKind::ImplTraitPlaceholder =>
{
// Skip lifetime paramters that are not captures.
let variances = self.tcx.variances_of(proj.item_def_id);
for (v, s) in std::iter::zip(variances, proj.substs.iter()) {
if *v != ty::Variance::Bivariant {
s.visit_with(self)?;
}
}
}
_ => {
ty.super_visit_with(self)?;
}
}
ControlFlow::CONTINUE
}
fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
if let ty::ConstKind::Unevaluated(..) = c.kind() {
// FIXME(#72219) We currently don't detect lifetimes within substs
@ -291,11 +353,14 @@ pub(super) fn check_opaque_for_inheriting_lifetimes<'tcx>(
type BreakTy = Ty<'tcx>;
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
debug!(?t, "root_visit_ty");
if t == self.opaque_identity_ty {
ControlFlow::CONTINUE
} else {
t.super_visit_with(&mut FindParentLifetimeVisitor(self.generics))
t.visit_with(&mut FindParentLifetimeVisitor {
tcx: self.tcx,
parent_count: self.generics.parent_count as u32,
})
.map_break(|FoundParentLifetime| t)
}
}
@ -329,14 +394,18 @@ pub(super) fn check_opaque_for_inheriting_lifetimes<'tcx>(
if let ItemKind::OpaqueTy(hir::OpaqueTy {
origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
in_trait,
..
}) = item.kind
{
let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
let opaque_identity_ty = if in_trait {
tcx.mk_projection(def_id.to_def_id(), substs)
} else {
tcx.mk_opaque(def_id.to_def_id(), substs)
};
let mut visitor = ProhibitOpaqueVisitor {
opaque_identity_ty: tcx.mk_opaque(
def_id.to_def_id(),
InternalSubsts::identity_for_item(tcx, def_id.to_def_id()),
),
opaque_identity_ty,
generics: tcx.generics_of(def_id),
tcx,
selftys: vec![],
@ -345,10 +414,6 @@ pub(super) fn check_opaque_for_inheriting_lifetimes<'tcx>(
.explicit_item_bounds(def_id)
.iter()
.try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
debug!(
"check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}, visitor.opaque_identity_ty={:?}, visitor.generics={:?}",
prohibit_opaque, visitor.opaque_identity_ty, visitor.generics
);
if let Some(ty) = prohibit_opaque.break_value() {
visitor.visit_item(&item);

1
compiler/rustc_infer/src/infer/error_reporting/mod.rs
View file

@ -261,6 +261,7 @@ fn label_msg_span(
}
}
#[instrument(level = "trace", skip(tcx))]
pub fn unexpected_hidden_region_diagnostic<'tcx>(
tcx: TyCtxt<'tcx>,
span: Span,

63
compiler/rustc_infer/src/infer/opaque_types.rs
View file

@ -332,32 +332,11 @@ impl<'tcx> InferCtxt<'tcx> {
concrete_ty: Ty<'tcx>,
span: Span,
) {
let def_id = opaque_type_key.def_id;
let tcx = self.tcx;
let concrete_ty = self.resolve_vars_if_possible(concrete_ty);
debug!(?concrete_ty);
let first_own_region = match self.opaque_ty_origin_unchecked(def_id, span) {
hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) => {
// We lower
//
// fn foo<'l0..'ln>() -> impl Trait<'l0..'lm>
//
// into
//
// type foo::<'p0..'pn>::Foo<'q0..'qm>
// fn foo<l0..'ln>() -> foo::<'static..'static>::Foo<'l0..'lm>.
//
// For these types we only iterate over `'l0..lm` below.
tcx.generics_of(def_id).parent_count
}
// These opaque type inherit all lifetime parameters from their
// parent, so we have to check them all.
hir::OpaqueTyOrigin::TyAlias => 0,
};
let variances = self.tcx.variances_of(opaque_type_key.def_id);
debug!(?variances);
// For a case like `impl Foo<'a, 'b>`, we would generate a constraint
// `'r in ['a, 'b, 'static]` for each region `'r` that appears in the
@ -370,9 +349,12 @@ impl<'tcx> InferCtxt<'tcx> {
// type can be equal to any of the region parameters of the
// opaque type definition.
let choice_regions: Lrc<Vec<ty::Region<'tcx>>> = Lrc::new(
opaque_type_key.substs[first_own_region..]
opaque_type_key
.substs
.iter()
.filter_map(|arg| match arg.unpack() {
.enumerate()
.filter(|(i, _)| variances[*i] == ty::Variance::Invariant)
.filter_map(|(_, arg)| match arg.unpack() {
GenericArgKind::Lifetime(r) => Some(r),
GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
})
@ -381,6 +363,7 @@ impl<'tcx> InferCtxt<'tcx> {
);
concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
tcx: self.tcx,
op: |r| self.member_constraint(opaque_type_key, span, concrete_ty, r, &choice_regions),
});
}
@ -440,11 +423,12 @@ impl<'tcx> InferCtxt<'tcx> {
//
// We ignore any type parameters because impl trait values are assumed to
// capture all the in-scope type parameters.
struct ConstrainOpaqueTypeRegionVisitor<OP> {
struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP> {
tcx: TyCtxt<'tcx>,
op: OP,
}
impl<'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<OP>
impl<'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
where
OP: FnMut(ty::Region<'tcx>),
{
@ -490,6 +474,31 @@ where
substs.as_generator().yield_ty().visit_with(self);
substs.as_generator().resume_ty().visit_with(self);
}
ty::Opaque(def_id, ref substs) => {
// Skip lifetime paramters that are not captures.
let variances = self.tcx.variances_of(*def_id);
for (v, s) in std::iter::zip(variances, substs.iter()) {
if *v != ty::Variance::Bivariant {
s.visit_with(self);
}
}
}
ty::Projection(proj)
if self.tcx.def_kind(proj.item_def_id) == DefKind::ImplTraitPlaceholder =>
{
// Skip lifetime paramters that are not captures.
let variances = self.tcx.variances_of(proj.item_def_id);
for (v, s) in std::iter::zip(variances, proj.substs.iter()) {
if *v != ty::Variance::Bivariant {
s.visit_with(self);
}
}
}
_ => {
ty.super_visit_with(self);
}

4
compiler/rustc_middle/src/ty/mod.rs
View file

@ -1338,8 +1338,8 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
// HACK: The HIR lowering for async fn does not generate
// any `+ Captures<'x>` bounds for the `impl Future<...>`, so all async fns with lifetimes
// would now fail to compile. We should probably just make hir lowering fill this in properly.
OpaqueTyOrigin::AsyncFn(_) => map.collect(),
OpaqueTyOrigin::FnReturn(_) | OpaqueTyOrigin::TyAlias => {
OpaqueTyOrigin::FnReturn(_) | OpaqueTyOrigin::AsyncFn(_) => map.collect(),
OpaqueTyOrigin::TyAlias => {
// Opaque types may only use regions that are bound. So for
// ```rust
// type Foo<'a, 'b, 'c> = impl Trait<'a> + 'b;

22
compiler/rustc_middle/src/ty/relate.rs
View file

@ -170,6 +170,26 @@ pub fn relate_substs_with_variances<'tcx, R: TypeRelation<'tcx>>(
tcx.mk_substs(params)
}
#[instrument(level = "trace", skip(relation), ret)]
fn relate_opaque_item_substs<'tcx, R: TypeRelation<'tcx>>(
relation: &mut R,
def_id: DefId,
a_subst: SubstsRef<'tcx>,
b_subst: SubstsRef<'tcx>,
) -> RelateResult<'tcx, SubstsRef<'tcx>> {
let tcx = relation.tcx();
let variances = tcx.variances_of(def_id);
debug!(?variances);
let params = iter::zip(a_subst, b_subst).enumerate().map(|(i, (a, b))| {
let variance = variances[i];
let variance_info = ty::VarianceDiagInfo::default();
relation.relate_with_variance(variance, variance_info, a, b)
});
tcx.mk_substs(params)
}
impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> {
fn relate<R: TypeRelation<'tcx>>(
relation: &mut R,
@ -561,7 +581,7 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
(&ty::Opaque(a_def_id, a_substs), &ty::Opaque(b_def_id, b_substs))
if a_def_id == b_def_id =>
{
let substs = relate_substs(relation, a_substs, b_substs)?;
let substs = relate_opaque_item_substs(relation, a_def_id, a_substs, b_substs)?;
Ok(tcx.mk_opaque(a_def_id, substs))
}