bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Auto merge of #114602 - compiler-errors:rpit-outlives-sadness, r=oli-obk

Browse source 
Map RPIT duplicated lifetimes back to fn captured lifetimes

Use the [`lifetime_mapping`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/hir/struct.OpaqueTy.html#structfield.lifetime_mapping) to map an RPIT's captured lifetimes back to the early- or late-bound lifetimes from its parent function. We may be going thru several layers of mapping, since opaques can be nested, so we introduce `TyCtxt::map_rpit_lifetime_to_fn_lifetime` to loop through several opaques worth of mapping, and handle turning it into a `ty::Region` as well.

We can then use this instead of the identity substs for RPITs in `check_opaque_meets_bounds` to address #114285.

We can then also use `map_rpit_lifetime_to_fn_lifetime` to properly install bidirectional-outlives predicates for both RPITs and RPITITs. This addresses #114601.

I based this on #114574, but I don't actually know how much of that PR we still need, so some code may be redundant now... 🤷

---

Fixes #114597
Fixes #114579
Fixes #114285

Also fixes #114601, since it turns out we had other bugs with RPITITs and their duplicated lifetime params 😅.

Supersedes #114574

r? `@oli-obk`
This commit is contained in:
bors 2023-08-08 13:03:10 +00:00
commit bf62436bce
9 changed files with 194 additions and 218 deletions
Download patch file Download diff file Expand all files Collapse all files

35
compiler/rustc_ty_utils/src/implied_bounds.rs
View file

@ -2,7 +2,6 @@ use rustc_data_structures::fx::FxHashMap;
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::LocalDefId;
use rustc_middle::middle::resolve_bound_vars as rbv;
use rustc_middle::query::Providers;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::Span;
@ -52,9 +51,7 @@ fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'
tcx.arena.alloc_from_iter(tys.into_iter().map(|ty| (ty, impl_spans.next().unwrap())))
}
DefKind::AssocTy if let Some(data) = tcx.opt_rpitit_info(def_id.to_def_id()) => match data {
ty::ImplTraitInTraitData::Trait { fn_def_id, opaque_def_id } => {
let hir::OpaqueTy { lifetime_mapping, .. } =
*tcx.hir().expect_item(opaque_def_id.expect_local()).expect_opaque_ty();
ty::ImplTraitInTraitData::Trait { fn_def_id, .. } => {
// We need to remap all of the late-bound lifetimes in theassumed wf types
// of the fn (which are represented as ReFree) to the early-bound lifetimes
// of the RPITIT (which are represented by ReEarlyBound owned by the opaque).
@ -66,28 +63,22 @@ fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'
// predicates we insert in the `explicit_predicates_of` query for RPITITs.
let mut mapping = FxHashMap::default();
let generics = tcx.generics_of(def_id);
for &(lifetime, new_early_bound_def_id) in
lifetime_mapping.expect("expected lifetime mapping for RPITIT")
{
if let Some(rbv::ResolvedArg::LateBound(_, _, def_id)) =
tcx.named_bound_var(lifetime.hir_id)
{
let name = tcx.hir().name(lifetime.hir_id);
let index = generics
.param_def_id_to_index(tcx, new_early_bound_def_id.to_def_id())
.unwrap();
// For each captured opaque lifetime, if it's late-bound (`ReFree` in this case,
// since it has been liberated), map it back to the early-bound lifetime of
// the GAT. Since RPITITs also have all of the fn's generics, we slice only
// the end of the list corresponding to the opaque's generics.
for param in &generics.params[tcx.generics_of(fn_def_id).params.len()..] {
let orig_lt = tcx.map_rpit_lifetime_to_fn_lifetime(param.def_id.expect_local());
if matches!(*orig_lt, ty::ReFree(..)) {
mapping.insert(
ty::Region::new_free(
tcx,
fn_def_id,
ty::BoundRegionKind::BrNamed(def_id, name),
),
orig_lt,
ty::Region::new_early_bound(
tcx,
ty::EarlyBoundRegion {
def_id: new_early_bound_def_id.to_def_id(),
index,
name,
def_id: param.def_id,
index: param.index,
name: param.name,
},
),
);