drop region constraints for ambiguous goals · rust-lang/rust@24b5466 (original) (raw)
`@@ -99,6 +99,13 @@ impl<'tcx> EvalCtxt<'_, InferCtxt<'tcx>> {
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`` previous call to try_evaluate_added_goals!"
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`);
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// We only check for leaks from universes which were entered inside
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// of the query.
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self.infcx.leak_check(self.max_input_universe, None).map_err(|e| {
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trace!(?e, "failed the leak check");
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NoSolution
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})?;
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`// When normalizing, we've replaced the expected term with an unconstrained
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`// inference variable. This means that we dropped information which could
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`// have been important. We handle this by instead returning the nested goals
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`@@ -121,7 +128,7 @@ impl<'tcx> EvalCtxt<'_, InferCtxt<'tcx>> {
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`};
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`let external_constraints =
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``
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self.compute_external_query_constraints(normalization_nested_goals)?;
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self.compute_external_query_constraints(certainty, normalization_nested_goals);
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`let (var_values, mut external_constraints) =
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`(self.var_values, external_constraints).fold_with(&mut EagerResolver::new(self.infcx));
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`// Remove any trivial region constraints once we've resolved regions
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`@@ -170,38 +177,45 @@ impl<'tcx> EvalCtxt<'_, InferCtxt<'tcx>> {
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`#[instrument(level = "trace", skip(self), ret)]
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`fn compute_external_query_constraints(
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`&self,
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certainty: Certainty,
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`normalization_nested_goals: NestedNormalizationGoals<'tcx>,
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``
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) -> Result<ExternalConstraintsData<'tcx>, NoSolution> {
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``
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// We only check for leaks from universes which were entered inside
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``
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// of the query.
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self.infcx.leak_check(self.max_input_universe, None).map_err(|e| {
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trace!(?e, "failed the leak check");
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``
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NoSolution
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})?;
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``
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// Cannot use take_registered_region_obligations as we may compute the response
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// inside of a probe whenever we have multiple choices inside of the solver.
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let region_obligations = self.infcx.inner.borrow().region_obligations().to_owned();
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let mut region_constraints = self.infcx.with_region_constraints(|region_constraints| {
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make_query_region_constraints(
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self.tcx(),
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region_obligations
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``
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.iter()
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``
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.map(|r_o| (r_o.sup_type, r_o.sub_region, r_o.origin.to_constraint_category())),
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region_constraints,
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)
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});
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let mut seen = FxHashSet::default();
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region_constraints.outlives.retain(|outlives| seen.insert(*outlives));
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) -> ExternalConstraintsData<'tcx> {
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// We only return region constraints once the certainty is Yes. This
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// is necessary as we may drop nested goals on ambiguity, which may result
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// in unconstrained inference variables in the region constraints. It also
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// prevents us from emitting duplicate region constraints, avoiding some
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// unnecessary work. This slightly weakens the leak check in case it uses
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// region constraints from an ambiguous nested goal. This is tested in both
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// tests/ui/higher-ranked/leak-check/leak-check-in-selection-5-ambig.rs and
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// tests/ui/higher-ranked/leak-check/leak-check-in-selection-6-ambig-unify.rs.
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let region_constraints = if certainty == Certainty::Yes {
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// Cannot use take_registered_region_obligations as we may compute the response
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// inside of a probe whenever we have multiple choices inside of the solver.
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let region_obligations = self.infcx.inner.borrow().region_obligations().to_owned();
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let mut region_constraints = self.infcx.with_region_constraints(|region_constraints| {
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make_query_region_constraints(
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self.tcx(),
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region_obligations.iter().map(|r_o| {
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(r_o.sup_type, r_o.sub_region, r_o.origin.to_constraint_category())
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}),
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region_constraints,
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)
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});
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let mut seen = FxHashSet::default();
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region_constraints.outlives.retain(|outlives| seen.insert(*outlives));
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region_constraints
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} else {
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Default::default()
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};
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`let mut opaque_types = self.infcx.clone_opaque_types_for_query_response();
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`// Only return opaque type keys for newly-defined opaques
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` opaque_types.retain(|(a, _)| {
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`self.predefined_opaques_in_body.opaque_types.iter().all(|(pa, _)| pa != a)
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`});
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Ok(ExternalConstraintsData { region_constraints, opaque_types, normalization_nested_goals })
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ExternalConstraintsData { region_constraints, opaque_types, normalization_nested_goals }
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`}
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`/// After calling a canonical query, we apply the constraints returned
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