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Take RPITITs inherit the assumed_wf_types of their parent fn

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This commit is contained in:
Michael Goulet 2023-07-14 18:37:12 +00:00
parent 03a57254b5
commit 349a2372ed
6 changed files with 57 additions and 100 deletions
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99
compiler/rustc_hir_analysis/src/check/wfcheck.rs
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@ -284,6 +284,17 @@ fn check_trait_item(tcx: TyCtxt<'_>, trait_item: &hir::TraitItem<'_>) {
};
check_object_unsafe_self_trait_by_name(tcx, trait_item);
check_associated_item(tcx, def_id, span, method_sig);
if matches!(trait_item.kind, hir::TraitItemKind::Fn(..)) {
for &assoc_ty_def_id in tcx.associated_types_for_impl_traits_in_associated_fn(def_id) {
check_associated_item(
tcx,
assoc_ty_def_id.expect_local(),
tcx.def_span(assoc_ty_def_id),
None,
);
}
}
}
/// Require that the user writes where clauses on GATs for the implicit
@ -1466,13 +1477,6 @@ fn check_fn_or_method<'tcx>(
check_where_clauses(wfcx, span, def_id);
check_return_position_impl_trait_in_trait_bounds(
wfcx,
def_id,
sig.output(),
hir_decl.output.span(),
);
if sig.abi == Abi::RustCall {
let span = tcx.def_span(def_id);
let has_implicit_self = hir_decl.implicit_self != hir::ImplicitSelfKind::None;
@ -1507,87 +1511,6 @@ fn check_fn_or_method<'tcx>(
}
}
/// Basically `check_associated_type_bounds`, but separated for now and should be
/// deduplicated when RPITITs get lowered into real associated items.
#[tracing::instrument(level = "trace", skip(wfcx))]
fn check_return_position_impl_trait_in_trait_bounds<'tcx>(
wfcx: &WfCheckingCtxt<'_, 'tcx>,
fn_def_id: LocalDefId,
fn_output: Ty<'tcx>,
span: Span,
) {
let tcx = wfcx.tcx();
let Some(assoc_item) = tcx.opt_associated_item(fn_def_id.to_def_id()) else {
return;
};
if assoc_item.container != ty::AssocItemContainer::TraitContainer {
return;
}
fn_output.visit_with(&mut ImplTraitInTraitFinder {
wfcx,
fn_def_id,
depth: ty::INNERMOST,
seen: FxHashSet::default(),
});
}
// 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 args 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.
struct ImplTraitInTraitFinder<'a, 'tcx> {
wfcx: &'a WfCheckingCtxt<'a, 'tcx>,
fn_def_id: LocalDefId,
depth: ty::DebruijnIndex,
seen: FxHashSet<DefId>,
}
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
type BreakTy = !;
fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<!> {
let tcx = self.wfcx.tcx();
if let ty::Alias(ty::Opaque, unshifted_opaque_ty) = *ty.kind()
&& self.seen.insert(unshifted_opaque_ty.def_id)
&& let Some(opaque_def_id) = unshifted_opaque_ty.def_id.as_local()
&& let origin = tcx.opaque_type_origin(opaque_def_id)
&& let hir::OpaqueTyOrigin::FnReturn(source) | hir::OpaqueTyOrigin::AsyncFn(source) = origin
&& source == self.fn_def_id
{
let opaque_ty = tcx.fold_regions(unshifted_opaque_ty, |re, _depth| {
match re.kind() {
ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReError(_) | ty::ReStatic => re,
r => bug!("unexpected region: {r:?}"),
}
});
for (bound, bound_span) in tcx
.explicit_item_bounds(opaque_ty.def_id)
.iter_instantiated_copied(tcx, opaque_ty.args)
{
let bound = self.wfcx.normalize(bound_span, None, bound);
self.wfcx.register_obligations(traits::wf::predicate_obligations(
self.wfcx.infcx,
self.wfcx.param_env,
self.wfcx.body_def_id,
bound.as_predicate(),
bound_span,
));
// Set the debruijn index back to innermost here, since we already eagerly
// shifted the args that we use to generate these bounds. This is unfortunately
// subtly different behavior than the `ImplTraitInTraitFinder` we use in `param_env`,
// but that function doesn't actually need to normalize the bound it's visiting
// (whereas we have to do so here)...
let old_depth = std::mem::replace(&mut self.depth, ty::INNERMOST);
bound.visit_with(self);
self.depth = old_depth;
}
}
ty.super_visit_with(self)
}
}
const HELP_FOR_SELF_TYPE: &str = "consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, \
`self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one \
of the previous types except `Self`)";