Disable dyn* upcasting
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parent
70f8737b2f
commit
c620a972f3
7 changed files with 75 additions and 35 deletions
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@ -755,20 +755,9 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
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if let ty::Dynamic(a_data, _, _) = a.kind()
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&& let ty::Dynamic(b_data, _, _) = b.kind()
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&& a_data.principal_def_id() == b_data.principal_def_id()
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{
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if a_data.principal_def_id() == b_data.principal_def_id() {
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return self.unify_and(a, b, |_| vec![]);
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} else if !self.tcx().features().trait_upcasting {
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let mut err = feature_err(
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&self.tcx.sess.parse_sess,
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sym::trait_upcasting,
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self.cause.span,
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&format!(
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"cannot cast `{a}` to `{b}`, trait upcasting coercion is experimental"
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),
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);
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err.emit();
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}
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return self.unify_and(a, b, |_| vec![]);
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}
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// Check the obligations of the cast -- for example, when casting
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@ -796,19 +785,16 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
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])
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.collect();
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// Enforce that the type is `usize`/pointer-sized. For now, only those
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// can be coerced to `dyn*`, except for `dyn* -> dyn*` upcasts.
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if !a.is_dyn_star() {
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obligations.push(Obligation::new(
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self.tcx,
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self.cause.clone(),
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self.param_env,
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ty::Binder::dummy(
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self.tcx.at(self.cause.span).mk_trait_ref(hir::LangItem::PointerSized, [a]),
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)
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.to_poly_trait_predicate(),
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));
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}
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// Enforce that the type is `usize`/pointer-sized.
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obligations.push(Obligation::new(
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self.tcx,
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self.cause.clone(),
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self.param_env,
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ty::Binder::dummy(
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self.tcx.at(self.cause.span).mk_trait_ref(hir::LangItem::PointerSized, [a]),
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)
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.to_poly_trait_predicate(),
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));
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Ok(InferOk {
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value: (vec![Adjustment { kind: Adjust::DynStar, target: b }], b),
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@ -776,9 +776,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
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match (source.kind(), target.kind()) {
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// Trait+Kx+'a -> Trait+Ky+'b (upcasts).
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(&ty::Dynamic(ref data_a, _, dyn_a), &ty::Dynamic(ref data_b, _, dyn_b))
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if dyn_a == dyn_b =>
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{
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(&ty::Dynamic(ref data_a, _, ty::Dyn), &ty::Dynamic(ref data_b, _, ty::Dyn)) => {
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// Upcast coercions permit several things:
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//
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// 1. Dropping auto traits, e.g., `Foo + Send` to `Foo`
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@ -803,9 +803,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
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let upcast_trait_ref;
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match (source.kind(), target.kind()) {
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// TraitA+Kx+'a -> TraitB+Ky+'b (trait upcasting coercion).
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(&ty::Dynamic(ref data_a, r_a, repr_a), &ty::Dynamic(ref data_b, r_b, repr_b))
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if repr_a == repr_b =>
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{
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(
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&ty::Dynamic(ref data_a, r_a, repr_a @ ty::Dyn),
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&ty::Dynamic(ref data_b, r_b, ty::Dyn),
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) => {
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// See `assemble_candidates_for_unsizing` for more info.
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// We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
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let principal_a = data_a.principal().unwrap();
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@ -831,7 +832,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
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.map(ty::Binder::dummy),
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);
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let existential_predicates = tcx.mk_poly_existential_predicates(iter);
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let source_trait = tcx.mk_dynamic(existential_predicates, r_b, repr_b);
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let source_trait = tcx.mk_dynamic(existential_predicates, r_b, repr_a);
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// Require that the traits involved in this upcast are **equal**;
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// only the **lifetime bound** is changed.
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