Add all RPITITs when augmenting param-env with GAT bounds in check_type_bounds
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Michael Goulet
parent
bb74d7e97d
commit
dd571e472a
@ -2162,7 +2162,7 @@ pub(super) fn check_type_bounds<'tcx>(
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impl_ty: ty::AssocItem,
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impl_trait_ref: ty::TraitRef<'tcx>,
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) -> Result<(), ErrorGuaranteed> {
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let param_env = param_env_with_gat_bounds(tcx, trait_ty, impl_ty, impl_trait_ref);
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let param_env = param_env_with_gat_bounds(tcx, impl_ty, impl_trait_ref);
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debug!(?param_env);
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let container_id = impl_ty.container_id(tcx);
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@ -2288,7 +2288,6 @@ pub(super) fn check_type_bounds<'tcx>(
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/// the trait (notably, that `X: Eq` and `T: Family`).
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fn param_env_with_gat_bounds<'tcx>(
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tcx: TyCtxt<'tcx>,
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trait_ty: ty::AssocItem,
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impl_ty: ty::AssocItem,
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impl_trait_ref: ty::TraitRef<'tcx>,
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) -> ty::ParamEnv<'tcx> {
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@ -2296,85 +2295,112 @@ fn param_env_with_gat_bounds<'tcx>(
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let container_id = impl_ty.container_id(tcx);
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let mut predicates = param_env.caller_bounds().to_vec();
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let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
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smallvec::SmallVec::with_capacity(tcx.generics_of(impl_ty.def_id).params.len());
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// Extend the impl's identity args with late-bound GAT vars
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let normalize_impl_ty_args = ty::GenericArgs::identity_for_item(tcx, container_id).extend_to(
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tcx,
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impl_ty.def_id,
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|param, _| match param.kind {
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GenericParamDefKind::Type { .. } => {
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let kind = ty::BoundTyKind::Param(param.def_id, param.name);
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let bound_var = ty::BoundVariableKind::Ty(kind);
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bound_vars.push(bound_var);
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Ty::new_bound(
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tcx,
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ty::INNERMOST,
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ty::BoundTy { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
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)
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.into()
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}
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GenericParamDefKind::Lifetime => {
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let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
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let bound_var = ty::BoundVariableKind::Region(kind);
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bound_vars.push(bound_var);
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ty::Region::new_late_bound(
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tcx,
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ty::INNERMOST,
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ty::BoundRegion { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
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)
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.into()
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}
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GenericParamDefKind::Const { .. } => {
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let bound_var = ty::BoundVariableKind::Const;
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bound_vars.push(bound_var);
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ty::Const::new_bound(
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tcx,
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ty::INNERMOST,
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ty::BoundVar::from_usize(bound_vars.len() - 1),
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tcx.type_of(param.def_id)
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.no_bound_vars()
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.expect("const parameter types cannot be generic"),
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)
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.into()
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}
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},
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);
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// When checking something like
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//
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// trait X { type Y: PartialEq<<Self as X>::Y> }
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// impl X for T { default type Y = S; }
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//
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// We will have to prove the bound S: PartialEq<<T as X>::Y>. In this case
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// we want <T as X>::Y to normalize to S. This is valid because we are
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// checking the default value specifically here. Add this equality to the
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// ParamEnv for normalization specifically.
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let normalize_impl_ty = tcx.type_of(impl_ty.def_id).instantiate(tcx, normalize_impl_ty_args);
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let rebased_args = normalize_impl_ty_args.rebase_onto(tcx, container_id, impl_trait_ref.args);
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let bound_vars = tcx.mk_bound_variable_kinds(&bound_vars);
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match normalize_impl_ty.kind() {
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ty::Alias(ty::Projection, proj)
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if proj.def_id == trait_ty.def_id && proj.args == rebased_args =>
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{
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// Don't include this predicate if the projected type is
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// exactly the same as the projection. This can occur in
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// (somewhat dubious) code like this:
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//
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// impl<T> X for T where T: X { type Y = <T as X>::Y; }
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}
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_ => predicates.push(
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ty::Binder::bind_with_vars(
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ty::ProjectionPredicate {
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projection_ty: ty::AliasTy::new(tcx, trait_ty.def_id, rebased_args),
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term: normalize_impl_ty.into(),
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},
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bound_vars,
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)
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.to_predicate(tcx),
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),
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// for RPITITs, we should install predicates that allow us to project all
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// of the RPITITs associated with the same body. This is because checking
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// the item bounds of RPITITs often involves nested RPITITs having to prove
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// bounds about themselves.
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let impl_tys_to_install = match impl_ty.opt_rpitit_info {
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None => vec![impl_ty],
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Some(
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ty::ImplTraitInTraitData::Impl { fn_def_id }
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| ty::ImplTraitInTraitData::Trait { fn_def_id, .. },
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) => tcx
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.associated_types_for_impl_traits_in_associated_fn(fn_def_id)
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.iter()
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.map(|def_id| tcx.associated_item(*def_id))
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.collect(),
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};
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for impl_ty in impl_tys_to_install {
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let trait_ty = match impl_ty.container {
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ty::AssocItemContainer::TraitContainer => impl_ty,
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ty::AssocItemContainer::ImplContainer => {
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tcx.associated_item(impl_ty.trait_item_def_id.unwrap())
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}
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};
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let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
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smallvec::SmallVec::with_capacity(tcx.generics_of(impl_ty.def_id).params.len());
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// Extend the impl's identity args with late-bound GAT vars
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let normalize_impl_ty_args = ty::GenericArgs::identity_for_item(tcx, container_id)
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.extend_to(tcx, impl_ty.def_id, |param, _| match param.kind {
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GenericParamDefKind::Type { .. } => {
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let kind = ty::BoundTyKind::Param(param.def_id, param.name);
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let bound_var = ty::BoundVariableKind::Ty(kind);
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bound_vars.push(bound_var);
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Ty::new_bound(
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tcx,
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ty::INNERMOST,
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ty::BoundTy { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
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)
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.into()
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}
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GenericParamDefKind::Lifetime => {
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let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
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let bound_var = ty::BoundVariableKind::Region(kind);
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bound_vars.push(bound_var);
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ty::Region::new_late_bound(
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tcx,
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ty::INNERMOST,
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ty::BoundRegion {
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var: ty::BoundVar::from_usize(bound_vars.len() - 1),
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kind,
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},
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)
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.into()
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}
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GenericParamDefKind::Const { .. } => {
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let bound_var = ty::BoundVariableKind::Const;
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bound_vars.push(bound_var);
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ty::Const::new_bound(
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tcx,
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ty::INNERMOST,
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ty::BoundVar::from_usize(bound_vars.len() - 1),
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tcx.type_of(param.def_id)
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.no_bound_vars()
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.expect("const parameter types cannot be generic"),
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)
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.into()
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}
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});
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// When checking something like
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//
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// trait X { type Y: PartialEq<<Self as X>::Y> }
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// impl X for T { default type Y = S; }
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//
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// We will have to prove the bound S: PartialEq<<T as X>::Y>. In this case
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// we want <T as X>::Y to normalize to S. This is valid because we are
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// checking the default value specifically here. Add this equality to the
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// ParamEnv for normalization specifically.
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let normalize_impl_ty =
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tcx.type_of(impl_ty.def_id).instantiate(tcx, normalize_impl_ty_args);
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let rebased_args =
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normalize_impl_ty_args.rebase_onto(tcx, container_id, impl_trait_ref.args);
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let bound_vars = tcx.mk_bound_variable_kinds(&bound_vars);
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match normalize_impl_ty.kind() {
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ty::Alias(ty::Projection, proj)
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if proj.def_id == trait_ty.def_id && proj.args == rebased_args =>
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{
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// Don't include this predicate if the projected type is
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// exactly the same as the projection. This can occur in
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// (somewhat dubious) code like this:
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//
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// impl<T> X for T where T: X { type Y = <T as X>::Y; }
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}
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_ => predicates.push(
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ty::Binder::bind_with_vars(
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ty::ProjectionPredicate {
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projection_ty: ty::AliasTy::new(tcx, trait_ty.def_id, rebased_args),
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term: normalize_impl_ty.into(),
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},
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bound_vars,
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)
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.to_predicate(tcx),
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),
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};
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}
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ty::ParamEnv::new(tcx.mk_clauses(&predicates), Reveal::UserFacing)
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}
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11
tests/ui/impl-trait/in-trait/nested-rpitit-bounds.rs
Normal file
11
tests/ui/impl-trait/in-trait/nested-rpitit-bounds.rs
Normal file
@ -0,0 +1,11 @@
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// check-pass
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use std::ops::Deref;
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trait Foo {
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fn foo() -> impl Deref<Target = impl Deref<Target = impl Sized>> {
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&&()
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}
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}
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fn main() {}
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