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Handle trait/projection predicates with bound regions correctly
This commit is contained in:
Matthew Jasper
Bastian Kauschke
parent
9a33b59154
commit
1b33f39126
@ -3,7 +3,7 @@ use rustc_data_structures::obligation_forest::ProcessResult;
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use rustc_data_structures::obligation_forest::{DoCompleted, Error, ForestObligation};
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use rustc_data_structures::obligation_forest::{ObligationForest, ObligationProcessor};
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use rustc_errors::ErrorReported;
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use rustc_infer::traits::{TraitEngine, TraitEngineExt as _};
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use rustc_infer::traits::{PolyTraitObligation, TraitEngine, TraitEngineExt as _};
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use rustc_middle::mir::interpret::ErrorHandled;
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use rustc_middle::ty::error::ExpectedFound;
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use rustc_middle::ty::{self, Binder, Const, ToPredicate, Ty, TypeFoldable};
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@ -20,6 +20,7 @@ use super::{FulfillmentError, FulfillmentErrorCode};
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use super::{ObligationCause, PredicateObligation};
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use crate::traits::error_reporting::InferCtxtExt as _;
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use crate::traits::project::PolyProjectionObligation;
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use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
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impl<'tcx> ForestObligation for PendingPredicateObligation<'tcx> {
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@ -318,65 +319,50 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
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let infcx = self.selcx.infcx();
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match obligation.predicate.kint(infcx.tcx) {
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ty::PredicateKint::ForAll(binder) => {
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let (pred, _) = infcx.replace_bound_vars_with_placeholders(binder);
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ProcessResult::Changed(mk_pending(vec![
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obligation.with(pred.to_predicate(infcx.tcx)),
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]))
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}
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ty::PredicateKint::ForAll(binder) => match binder.skip_binder() {
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// Evaluation will discard candidates using the leak check.
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// This means we need to pass it the bound version of our
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// predicate.
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rustc_middle::ty::PredicateKint::Trait(trait_ref, _constness) => {
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let trait_obligation = obligation.with(Binder::bind(*trait_ref));
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self.process_trait_obligation(
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obligation,
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trait_obligation,
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&mut pending_obligation.stalled_on,
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)
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}
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rustc_middle::ty::PredicateKint::Projection(projection) => {
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let project_obligation = obligation.with(Binder::bind(*projection));
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self.process_projection_obligation(
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project_obligation,
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&mut pending_obligation.stalled_on,
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)
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}
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rustc_middle::ty::PredicateKint::RegionOutlives(_)
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| rustc_middle::ty::PredicateKint::TypeOutlives(_)
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| rustc_middle::ty::PredicateKint::WellFormed(_)
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| rustc_middle::ty::PredicateKint::ObjectSafe(_)
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| rustc_middle::ty::PredicateKint::ClosureKind(..)
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| rustc_middle::ty::PredicateKint::Subtype(_)
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| rustc_middle::ty::PredicateKint::ConstEvaluatable(..)
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| rustc_middle::ty::PredicateKint::ConstEquate(..)
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| rustc_middle::ty::PredicateKint::ForAll(_) => {
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let (pred, _) = infcx.replace_bound_vars_with_placeholders(binder);
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ProcessResult::Changed(mk_pending(vec![
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obligation.with(pred.to_predicate(infcx.tcx)),
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]))
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}
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},
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ty::PredicateKint::Trait(ref data, _) => {
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let trait_obligation = obligation.with(Binder::dummy(*data));
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if obligation.predicate.is_global() {
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// no type variables present, can use evaluation for better caching.
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// FIXME: consider caching errors too.
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if infcx.predicate_must_hold_considering_regions(&obligation) {
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debug!(
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"selecting trait `{:?}` at depth {} evaluated to holds",
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data, obligation.recursion_depth
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);
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return ProcessResult::Changed(vec![]);
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}
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}
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match self.selcx.select(&trait_obligation) {
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Ok(Some(impl_source)) => {
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debug!(
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"selecting trait `{:?}` at depth {} yielded Ok(Some)",
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data, obligation.recursion_depth
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);
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ProcessResult::Changed(mk_pending(impl_source.nested_obligations()))
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}
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Ok(None) => {
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debug!(
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"selecting trait `{:?}` at depth {} yielded Ok(None)",
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data, obligation.recursion_depth
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);
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// This is a bit subtle: for the most part, the
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// only reason we can fail to make progress on
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// trait selection is because we don't have enough
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// information about the types in the trait.
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pending_obligation.stalled_on =
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trait_ref_infer_vars(self.selcx, data.trait_ref);
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debug!(
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"process_predicate: pending obligation {:?} now stalled on {:?}",
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infcx.resolve_vars_if_possible(obligation),
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pending_obligation.stalled_on
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);
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ProcessResult::Unchanged
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}
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Err(selection_err) => {
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info!(
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"selecting trait `{:?}` at depth {} yielded Err",
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data, obligation.recursion_depth
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);
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ProcessResult::Error(CodeSelectionError(selection_err))
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}
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}
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self.process_trait_obligation(
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obligation,
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trait_obligation,
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&mut pending_obligation.stalled_on,
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)
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}
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&ty::PredicateKint::RegionOutlives(data) => {
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@ -399,17 +385,11 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
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ty::PredicateKint::Projection(ref data) => {
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let project_obligation = obligation.with(Binder::dummy(*data));
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match project::poly_project_and_unify_type(self.selcx, &project_obligation) {
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Ok(None) => {
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pending_obligation.stalled_on = trait_ref_infer_vars(
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self.selcx,
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data.projection_ty.trait_ref(infcx.tcx),
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);
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ProcessResult::Unchanged
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}
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Ok(Some(os)) => ProcessResult::Changed(mk_pending(os)),
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Err(e) => ProcessResult::Error(CodeProjectionError(e)),
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}
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self.process_projection_obligation(
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project_obligation,
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&mut pending_obligation.stalled_on,
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)
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}
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&ty::PredicateKint::ObjectSafe(trait_def_id) => {
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@ -569,14 +549,96 @@ impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
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}
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}
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impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
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fn process_trait_obligation(
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&mut self,
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obligation: &PredicateObligation<'tcx>,
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trait_obligation: PolyTraitObligation<'tcx>,
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stalled_on: &mut Vec<TyOrConstInferVar<'tcx>>,
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) -> ProcessResult<PendingPredicateObligation<'tcx>, FulfillmentErrorCode<'tcx>> {
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let infcx = self.selcx.infcx();
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if obligation.predicate.is_global() {
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// no type variables present, can use evaluation for better caching.
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// FIXME: consider caching errors too.
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if infcx.predicate_must_hold_considering_regions(obligation) {
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debug!(
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"selecting trait `{:?}` at depth {} evaluated to holds",
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obligation.predicate, obligation.recursion_depth
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);
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return ProcessResult::Changed(vec![]);
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}
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}
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match self.selcx.select(&trait_obligation) {
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Ok(Some(impl_source)) => {
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debug!(
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"selecting trait `{:?}` at depth {} yielded Ok(Some)",
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trait_obligation.predicate, obligation.recursion_depth
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);
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ProcessResult::Changed(mk_pending(impl_source.nested_obligations()))
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}
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Ok(None) => {
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debug!(
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"selecting trait `{:?}` at depth {} yielded Ok(None)",
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trait_obligation.predicate, obligation.recursion_depth
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);
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// This is a bit subtle: for the most part, the
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// only reason we can fail to make progress on
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// trait selection is because we don't have enough
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// information about the types in the trait.
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*stalled_on = trait_ref_infer_vars(
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self.selcx,
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trait_obligation.predicate.map_bound(|pred| pred.trait_ref),
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);
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debug!(
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"process_predicate: pending obligation {:?} now stalled on {:?}",
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infcx.resolve_vars_if_possible(obligation),
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stalled_on
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);
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ProcessResult::Unchanged
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}
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Err(selection_err) => {
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info!(
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"selecting trait `{:?}` at depth {} yielded Err",
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trait_obligation.predicate, obligation.recursion_depth
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);
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ProcessResult::Error(CodeSelectionError(selection_err))
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}
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}
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}
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fn process_projection_obligation(
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&mut self,
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project_obligation: PolyProjectionObligation<'tcx>,
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stalled_on: &mut Vec<TyOrConstInferVar<'tcx>>,
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) -> ProcessResult<PendingPredicateObligation<'tcx>, FulfillmentErrorCode<'tcx>> {
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match project::poly_project_and_unify_type(self.selcx, &project_obligation) {
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Ok(None) => {
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*stalled_on = trait_ref_infer_vars(
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self.selcx,
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project_obligation.predicate.to_poly_trait_ref(self.selcx.tcx()),
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);
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ProcessResult::Unchanged
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}
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Ok(Some(os)) => ProcessResult::Changed(mk_pending(os)),
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Err(e) => ProcessResult::Error(CodeProjectionError(e)),
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}
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}
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}
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/// Returns the set of inference variables contained in a trait ref.
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fn trait_ref_infer_vars<'a, 'tcx>(
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selcx: &mut SelectionContext<'a, 'tcx>,
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trait_ref: ty::TraitRef<'tcx>,
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trait_ref: ty::PolyTraitRef<'tcx>,
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) -> Vec<TyOrConstInferVar<'tcx>> {
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selcx
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.infcx()
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.resolve_vars_if_possible(&trait_ref)
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.skip_binder()
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.substs
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.iter()
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// FIXME(eddyb) try using `skip_current_subtree` to skip everything that
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@ -4,7 +4,7 @@ error[E0477]: the type `&'a i32` does not fulfill the required lifetime
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LL | foo::<&'a i32>();
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| ^^^^^^^^^^^^^^
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= note: type must satisfy the static lifetime
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= note: type must outlive any other region
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error: aborting due to previous error
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