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Rollup merge of #109545 - compiler-errors:rpitit-wf, r=eholk
Deeply check well-formedness of return-position `impl Trait` in trait
Walk the bounds of RPITITs to see if we find any more RPITITs 😸
This commit is contained in:
Matthias Krüger
GitHub
commit
3b49ad3814
@ -1544,42 +1544,81 @@ fn check_return_position_impl_trait_in_trait_bounds<'tcx>(
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span: Span,
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) {
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let tcx = wfcx.tcx();
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if let Some(assoc_item) = tcx.opt_associated_item(fn_def_id.to_def_id())
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&& assoc_item.container == ty::AssocItemContainer::TraitContainer
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{
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// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): Even with the new lowering
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// strategy, we can't just call `check_associated_item` on the new RPITITs,
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// because tests like `tests/ui/async-await/in-trait/implied-bounds.rs` will fail.
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// That's because we need to check that the bounds of the RPITIT hold using
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// the special substs that we create during opaque type lowering, otherwise we're
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// getting a bunch of early bound and free regions mixed up... Haven't looked too
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// deep into this, though.
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for arg in fn_output.walk() {
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if let ty::GenericArgKind::Type(ty) = arg.unpack()
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// RPITITs are always eagerly normalized into opaques, so always look for an
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// opaque here.
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&& let ty::Alias(ty::Opaque, opaque_ty) = ty.kind()
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&& let Some(opaque_def_id) = opaque_ty.def_id.as_local()
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&& let opaque = tcx.hir().expect_item(opaque_def_id).expect_opaque_ty()
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&& let hir::OpaqueTyOrigin::FnReturn(source) | hir::OpaqueTyOrigin::AsyncFn(source) = opaque.origin
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&& source == fn_def_id
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let Some(assoc_item) = tcx.opt_associated_item(fn_def_id.to_def_id()) else {
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return;
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};
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if assoc_item.container != ty::AssocItemContainer::TraitContainer {
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return;
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}
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fn_output.visit_with(&mut ImplTraitInTraitFinder {
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wfcx,
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fn_def_id,
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depth: ty::INNERMOST,
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seen: FxHashSet::default(),
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});
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}
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// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): Even with the new lowering
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// strategy, we can't just call `check_associated_item` on the new RPITITs,
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// because tests like `tests/ui/async-await/in-trait/implied-bounds.rs` will fail.
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// That's because we need to check that the bounds of the RPITIT hold using
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// the special substs that we create during opaque type lowering, otherwise we're
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// getting a bunch of early bound and free regions mixed up... Haven't looked too
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// deep into this, though.
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struct ImplTraitInTraitFinder<'a, 'tcx> {
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wfcx: &'a WfCheckingCtxt<'a, 'tcx>,
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fn_def_id: LocalDefId,
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depth: ty::DebruijnIndex,
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seen: FxHashSet<DefId>,
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}
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impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
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type BreakTy = !;
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fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<!> {
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let tcx = self.wfcx.tcx();
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if let ty::Alias(ty::Opaque, unshifted_opaque_ty) = *ty.kind()
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&& self.seen.insert(unshifted_opaque_ty.def_id)
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&& let Some(opaque_def_id) = unshifted_opaque_ty.def_id.as_local()
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&& let opaque = tcx.hir().expect_item(opaque_def_id).expect_opaque_ty()
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&& let hir::OpaqueTyOrigin::FnReturn(source) | hir::OpaqueTyOrigin::AsyncFn(source) = opaque.origin
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&& source == self.fn_def_id
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{
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let opaque_ty = tcx.fold_regions(unshifted_opaque_ty, |re, depth| {
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if let ty::ReLateBound(index, bv) = re.kind() {
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if depth != ty::INNERMOST {
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return tcx.mk_re_error_with_message(
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DUMMY_SP,
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"we shouldn't walk non-predicate binders with `impl Trait`...",
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);
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}
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tcx.mk_re_late_bound(index.shifted_out_to_binder(self.depth), bv)
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} else {
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re
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}
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});
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for (bound, bound_span) in tcx
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.bound_explicit_item_bounds(opaque_ty.def_id)
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.subst_iter_copied(tcx, opaque_ty.substs)
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{
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let span = tcx.def_span(opaque_ty.def_id);
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let bounds = wfcx.tcx().explicit_item_bounds(opaque_ty.def_id);
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let wf_obligations = bounds.iter().flat_map(|&(bound, bound_span)| {
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let bound = ty::EarlyBinder(bound).subst(tcx, opaque_ty.substs);
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let normalized_bound = wfcx.normalize(span, None, bound);
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traits::wf::predicate_obligations(
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wfcx.infcx,
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wfcx.param_env,
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wfcx.body_def_id,
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normalized_bound,
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bound_span,
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)
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});
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wfcx.register_obligations(wf_obligations);
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let bound = self.wfcx.normalize(bound_span, None, bound);
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self.wfcx.register_obligations(traits::wf::predicate_obligations(
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self.wfcx.infcx,
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self.wfcx.param_env,
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self.wfcx.body_def_id,
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bound,
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bound_span,
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));
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// Set the debruijn index back to innermost here, since we already eagerly
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// shifted the substs that we use to generate these bounds. This is unfortunately
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// subtly different behavior than the `ImplTraitInTraitFinder` we use in `param_env`,
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// but that function doesn't actually need to normalize the bound it's visiting
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// (whereas we have to do so here)...
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let old_depth = std::mem::replace(&mut self.depth, ty::INNERMOST);
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bound.visit_with(self);
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self.depth = old_depth;
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}
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}
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ty.super_visit_with(self)
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}
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}
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@ -1,5 +1,5 @@
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/wf-bounds.rs:11:22
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--> $DIR/wf-bounds.rs:13:22
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LL | fn nya() -> impl Wf<Vec<[u8]>>;
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| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
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@ -9,7 +9,7 @@ note: required by a bound in `Vec`
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--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/wf-bounds.rs:14:23
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--> $DIR/wf-bounds.rs:16:23
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LL | fn nya2() -> impl Wf<[u8]>;
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| ^^^^^^^^ doesn't have a size known at compile-time
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@ -18,13 +18,23 @@ LL | fn nya2() -> impl Wf<[u8]>;
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note: required by a bound in `Wf`
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--> $DIR/wf-bounds.rs:8:10
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LL | trait Wf<T> {}
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LL | trait Wf<T> {
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| ^ required by this bound in `Wf`
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help: consider relaxing the implicit `Sized` restriction
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LL | trait Wf<T: ?Sized> {}
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LL | trait Wf<T: ?Sized> {
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| ++++++++
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error: aborting due to 2 previous errors
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/wf-bounds.rs:19:44
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LL | fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
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| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
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= help: the trait `Sized` is not implemented for `[u8]`
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note: required by a bound in `Vec`
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--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0277`.
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@ -1,5 +1,5 @@
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/wf-bounds.rs:11:22
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--> $DIR/wf-bounds.rs:13:22
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LL | fn nya() -> impl Wf<Vec<[u8]>>;
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| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
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@ -9,7 +9,7 @@ note: required by a bound in `Vec`
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--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/wf-bounds.rs:14:23
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--> $DIR/wf-bounds.rs:16:23
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LL | fn nya2() -> impl Wf<[u8]>;
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| ^^^^^^^^ doesn't have a size known at compile-time
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@ -18,13 +18,23 @@ LL | fn nya2() -> impl Wf<[u8]>;
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note: required by a bound in `Wf`
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--> $DIR/wf-bounds.rs:8:10
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LL | trait Wf<T> {}
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LL | trait Wf<T> {
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| ^ required by this bound in `Wf`
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help: consider relaxing the implicit `Sized` restriction
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LL | trait Wf<T: ?Sized> {}
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LL | trait Wf<T: ?Sized> {
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| ++++++++
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error: aborting due to 2 previous errors
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error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
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--> $DIR/wf-bounds.rs:19:44
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LL | fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
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| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
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= help: the trait `Sized` is not implemented for `[u8]`
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note: required by a bound in `Vec`
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--> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0277`.
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@ -5,7 +5,9 @@
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#![feature(return_position_impl_trait_in_trait)]
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#![allow(incomplete_features)]
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trait Wf<T> {}
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trait Wf<T> {
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type Output;
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}
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trait Uwu {
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fn nya() -> impl Wf<Vec<[u8]>>;
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@ -13,6 +15,9 @@ trait Uwu {
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fn nya2() -> impl Wf<[u8]>;
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//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
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fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
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//~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
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}
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fn main() {}
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