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Rollup merge of #109198 - compiler-errors:new-rpitit-default-body, r=spastorino

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Install projection from RPITIT to default trait method opaque correctly

1. For new lowering strategy `-Zlower-impl-trait-in-trait-to-assoc-ty`, install the correct default trait method projection predicates (RPITIT -> opaque). This makes default trait body tests pass!

2. Fix two WF-checking bugs -- first, we want to make sure that we're always looking for an opaque type in `check_return_position_impl_trait_in_trait_bounds`. That's because the RPITIT projections are normalized to opaques during wfcheck. Second, fix RPITIT's param-envs by not adding the projection predicates that we install on trait methods to make default RPITITs work -- I left a comment why.

3. Also, just a small drive-by for `rustc_on_unimplemented`. Not sure if it affects any tests, but can't hurt.

r? ````@spastorino,```` based off of #109140
This commit is contained in:
Matthias Krüger
2023-03-17 08:42:40 +01:00
committed by GitHub
parent edd6b42565 8d922eba79
commit 246d989a30
50 changed files with 419 additions and 107 deletions
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2
compiler/rustc_hir_analysis/src/check/check.rs
View File

@@ -557,7 +557,7 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
check_opaque(tcx, id);
}
DefKind::ImplTraitPlaceholder => {
let parent = tcx.impl_trait_in_trait_parent(id.owner_id.to_def_id());
let parent = tcx.impl_trait_in_trait_parent_fn(id.owner_id.to_def_id());
// Only check the validity of this opaque type if the function has a default body
if let hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),

24
compiler/rustc_hir_analysis/src/check/wfcheck.rs
View File

@@ -1,7 +1,6 @@
use crate::autoderef::Autoderef;
use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter};
use hir::def::DefKind;
use rustc_ast as ast;
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
@@ -1548,16 +1547,27 @@ fn check_return_position_impl_trait_in_trait_bounds<'tcx>(
if let Some(assoc_item) = tcx.opt_associated_item(fn_def_id.to_def_id())
&& assoc_item.container == ty::AssocItemContainer::TraitContainer
{
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): Even with the new lowering
// strategy, we can't just call `check_associated_item` on the new RPITITs,
// because tests like `tests/ui/async-await/in-trait/implied-bounds.rs` will fail.
// That's because we need to check that the bounds of the RPITIT hold using
// the special substs that we create during opaque type lowering, otherwise we're
// getting a bunch of early bound and free regions mixed up... Haven't looked too
// deep into this, though.
for arg in fn_output.walk() {
if let ty::GenericArgKind::Type(ty) = arg.unpack()
&& let ty::Alias(ty::Opaque, proj) = ty.kind()
&& tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder
&& tcx.impl_trait_in_trait_parent(proj.def_id) == fn_def_id.to_def_id()
// RPITITs are always eagerly normalized into opaques, so always look for an
// opaque here.
&& let ty::Alias(ty::Opaque, opaque_ty) = ty.kind()
&& let Some(opaque_def_id) = opaque_ty.def_id.as_local()
&& let opaque = tcx.hir().expect_item(opaque_def_id).expect_opaque_ty()
&& let hir::OpaqueTyOrigin::FnReturn(source) | hir::OpaqueTyOrigin::AsyncFn(source) = opaque.origin
&& source == fn_def_id
{
let span = tcx.def_span(proj.def_id);
let bounds = wfcx.tcx().explicit_item_bounds(proj.def_id);
let span = tcx.def_span(opaque_ty.def_id);
let bounds = wfcx.tcx().explicit_item_bounds(opaque_ty.def_id);
let wf_obligations = bounds.iter().flat_map(|&(bound, bound_span)| {
let bound = ty::EarlyBinder(bound).subst(tcx, proj.substs);
let bound = ty::EarlyBinder(bound).subst(tcx, opaque_ty.substs);
let normalized_bound = wfcx.normalize(span, None, bound);
traits::wf::predicate_obligations(
wfcx.infcx,