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Simplify via map_rpit_lifetime_to_fn_lifetime

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This commit is contained in:
Michael Goulet 2023-08-07 23:54:04 +00:00
parent 67703b9161
commit ef2a611803
2 changed files with 21 additions and 145 deletions
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155
compiler/rustc_hir_analysis/src/check/check.rs
View File

@ -13,7 +13,7 @@
use rustc_hir::{ItemKind, Node, PathSegment};
use rustc_infer::infer::opaque_types::ConstrainOpaqueTypeRegionVisitor;
use rustc_infer::infer::outlives::env::OutlivesEnvironment;
use rustc_infer::infer::{LateBoundRegionConversionTime, RegionVariableOrigin, TyCtxtInferExt};
use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
use rustc_infer::traits::{Obligation, TraitEngineExt as _};
use rustc_lint_defs::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS;
use rustc_middle::hir::nested_filter;
@ -407,38 +407,17 @@ fn check_opaque_meets_bounds<'tcx>(
.build();
let ocx = ObligationCtxt::new(&infcx);
let mut args = GenericArgs::identity_for_item(tcx, def_id.to_def_id());
assert!(!args.has_escaping_bound_vars(), "{args:#?}");
if let hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) = origin {
// Find use of the RPIT in the function signature and thus find the right args to
// convert it into the parameter space of the function signature. This is needed,
// because that's what `type_of` returns, against which we compare later.
let ret = tcx.fn_sig(defining_use_anchor).instantiate_identity().output();
let a = ret
.skip_binder()
.visit_with(&mut FindOpaqueTypeArgs {
let args = match *origin {
hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
GenericArgs::identity_for_item(tcx, parent).extend_to(
tcx,
opaque: def_id.to_def_id(),
fn_def_id: defining_use_anchor.to_def_id(),
seen: Default::default(),
depth: ty::INNERMOST,
})
.break_value()
.ok_or_else(|| {
tcx.sess.delay_span_bug(
tcx.def_span(defining_use_anchor),
format!("return type of {defining_use_anchor:?} does not contain {def_id:?}"),
)
})?;
let a = infcx.instantiate_binder_with_fresh_vars(
span,
LateBoundRegionConversionTime::HigherRankedType,
ret.rebind(a),
);
assert!(!a.has_escaping_bound_vars(), "{a:#?}");
args = ty::EarlyBinder::bind(args).instantiate(tcx, a);
}
def_id.to_def_id(),
|param, _| tcx.map_rpit_lifetime_to_fn_lifetime(param.def_id.expect_local()).into(),
)
}
hir::OpaqueTyOrigin::TyAlias { .. } => GenericArgs::identity_for_item(tcx, def_id),
};
let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), args);
// `ReErased` regions appear in the "parent_args" of closures/generators.
@ -551,118 +530,6 @@ fn sanity_check_found_hidden_type<'tcx>(
}
}
/// In case it is in a nested opaque type, find that opaque type's
/// usage in the function signature and use the generic arguments from the usage site.
/// We need to do because RPITs ignore the lifetimes of the function,
/// as they have their own copies of all the lifetimes they capture.
/// So the only way to get the lifetimes represented in terms of the function,
/// is to look how they are used in the function signature (or do some other fancy
/// recording of this mapping at ast -> hir lowering time).
///
/// As an example:
/// ```text
/// trait Id {
/// type Assoc;
/// }
/// impl<'a> Id for &'a () {
/// type Assoc = &'a ();
/// }
/// fn func<'a>(x: &'a ()) -> impl Id<Assoc = impl Sized + 'a> { x }
/// // desugared to
/// fn func<'a>(x: &'a () -> Outer<'a> where <Outer<'a> as Id>::Assoc = Inner<'a> {
/// // Note that in contrast to other nested items, RPIT type aliases can
/// // access their parents' generics.
///
/// // hidden type is `&'aDupOuter ()`
/// // During wfcheck the hidden type of `Inner<'aDupOuter>` is `&'a ()`, but
/// // `typeof(Inner<'aDupOuter>) = &'aDupOuter ()`.
/// // So we walk the signature of `func` to find the use of `Inner<'a>`
/// // and then use that to replace the lifetimes in the hidden type, obtaining
/// // `&'a ()`.
/// type Outer<'aDupOuter> = impl Id<Assoc = Inner<'aDupOuter>>;
///
/// // hidden type is `&'aDupInner ()`
/// type Inner<'aDupInner> = impl Sized + 'aDupInner;
///
/// x
/// }
/// ```
struct FindOpaqueTypeArgs<'tcx> {
tcx: TyCtxt<'tcx>,
opaque: DefId,
seen: FxHashSet<DefId>,
fn_def_id: DefId,
depth: ty::DebruijnIndex,
}
impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for FindOpaqueTypeArgs<'tcx> {
type BreakTy = GenericArgsRef<'tcx>;
#[instrument(level = "trace", skip(self), ret)]
fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
&mut self,
t: &ty::Binder<'tcx, T>,
) -> ControlFlow<Self::BreakTy> {
self.depth.shift_in(1);
let binder = t.super_visit_with(self);
self.depth.shift_out(1);
binder
}
#[instrument(level = "trace", skip(self), ret)]
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
trace!("{:#?}", t.kind());
match t.kind() {
ty::Alias(ty::Opaque, alias) => {
trace!(?alias.def_id);
if alias.def_id == self.opaque {
let args = self.tcx.fold_regions(alias.args, |re, depth| {
if let ty::ReLateBound(index, bv) = re.kind() {
if depth != ty::INNERMOST {
return ty::Region::new_error_with_message(
self.tcx,
self.tcx.def_span(self.opaque),
"opaque type behind meaningful binders are not supported yet",
);
}
ty::Region::new_late_bound(
self.tcx,
index.shifted_out_to_binder(self.depth),
bv,
)
} else {
re
}
});
return ControlFlow::Break(args);
} else if self.seen.insert(alias.def_id) {
for clause in self
.tcx
.explicit_item_bounds(alias.def_id)
.iter_instantiated_copied(self.tcx, alias.args)
{
trace!(?clause);
clause.visit_with(self)?;
}
}
}
ty::Alias(ty::Projection, alias) => {
if let Some(ty::ImplTraitInTraitData::Trait { fn_def_id, .. }) = self.tcx.opt_rpitit_info(alias.def_id) && fn_def_id == self.fn_def_id {
self.tcx.type_of(alias.def_id).instantiate(self.tcx, alias.args).visit_with(self)?;
}
}
ty::Alias(ty::Weak, alias) => {
self.tcx
.type_of(alias.def_id)
.instantiate(self.tcx, alias.args)
.visit_with(self)?;
}
_ => (),
}
t.super_visit_with(self)
}
}
fn is_enum_of_nonnullable_ptr<'tcx>(
tcx: TyCtxt<'tcx>,
adt_def: AdtDef<'tcx>,

11
compiler/rustc_middle/src/ty/context.rs
View File

@ -1995,7 +1995,16 @@ pub fn map_rpit_lifetime_to_fn_lifetime(
),
);
}
_ => bug!(),
Some(resolve_bound_vars::ResolvedArg::Error(guar)) => {
return ty::Region::new_error(self, guar);
}
_ => {
return ty::Region::new_error_with_message(
self,
lifetime.ident.span,
"cannot resolve lifetime",
);
}
}
}
}