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Check projections are well-formed when using projection candidates

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This commit is contained in:
Matthew Jasper 2020-06-28 12:41:46 +01:00
parent 87f2f42dc2
commit b3057f4d5f
13 changed files with 278 additions and 30 deletions
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29
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -1159,7 +1159,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
fn match_projection_obligation_against_definition_bounds(
&mut self,
obligation: &TraitObligation<'tcx>,
) -> bool {
) -> Option<ty::PolyTraitRef<'tcx>> {
let poly_trait_predicate = self.infcx().resolve_vars_if_possible(&obligation.predicate);
let (placeholder_trait_predicate, _) =
self.infcx().replace_bound_vars_with_placeholders(&poly_trait_predicate);
@ -1170,9 +1170,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
);
let tcx = self.infcx.tcx;
let predicates = match *placeholder_trait_predicate.trait_ref.self_ty().kind() {
ty::Projection(ref data) => tcx.item_bounds(data.item_def_id).subst(tcx, data.substs),
ty::Opaque(def_id, substs) => tcx.item_bounds(def_id).subst(tcx, substs),
let (def_id, substs) = match *placeholder_trait_predicate.trait_ref.self_ty().kind() {
ty::Projection(ref data) => (data.item_def_id, data.substs),
ty::Opaque(def_id, substs) => (def_id, substs),
_ => {
span_bug!(
obligation.cause.span,
@ -1182,12 +1182,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
);
}
};
let bounds = tcx.item_bounds(def_id).subst(tcx, substs);
let matching_bound = predicates.iter().find_map(|bound| {
let matching_bound = bounds.iter().find_map(|bound| {
if let ty::PredicateAtom::Trait(pred, _) = bound.skip_binders() {
let bound = ty::Binder::bind(pred.trait_ref);
if self.infcx.probe(|_| {
self.match_projection(obligation, bound, placeholder_trait_predicate.trait_ref)
.is_ok()
}) {
return Some(bound);
}
@ -1200,17 +1202,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
matching_bound={:?}",
matching_bound
);
match matching_bound {
None => false,
Some(bound) => {
// Repeat the successful match, if any, this time outside of a probe.
let result =
self.match_projection(obligation, bound, placeholder_trait_predicate.trait_ref);
assert!(result);
true
}
}
matching_bound
}
fn match_projection(
@ -1218,12 +1210,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligation: &TraitObligation<'tcx>,
trait_bound: ty::PolyTraitRef<'tcx>,
placeholder_trait_ref: ty::TraitRef<'tcx>,
) -> bool {
) -> Result<Vec<PredicateObligation<'tcx>>, ()> {
debug_assert!(!placeholder_trait_ref.has_escaping_bound_vars());
self.infcx
.at(&obligation.cause, obligation.param_env)
.sup(ty::Binder::dummy(placeholder_trait_ref), trait_bound)
.is_ok()
.map(|InferOk { obligations, .. }| obligations)
.map_err(|_| ())
}
fn evaluate_where_clause<'o>(