Deduce outlives obligations from WF of coroutine interior types

Author: compiler-errors

compiler/rustc_middle/src/query/mod.rs

@@ -988,7 +988,7 @@ rustc_queries! {
  }
 
  query coroutine_hidden_types(
- def_id: DefId
+ def_id: DefId,
  ) -> ty::EarlyBinder<'tcx, ty::Binder<'tcx, ty::CoroutineWitnessTypes<TyCtxt<'tcx>>>> {
  desc { "looking up the hidden types stored across await points in a coroutine" }
  }

compiler/rustc_middle/src/ty/context.rs

@@ -3112,6 +3112,17 @@ impl<'tcx> TyCtxt<'tcx> {
  T::collect_and_apply(iter, |xs| self.mk_bound_variable_kinds(xs))
  }
 
+ pub fn mk_outlives_from_iter<I, T>(self, iter: I) -> T::Output
+ where
+ I: Iterator<Item = T>,
+ T: CollectAndApply<
+ ty::OutlivesPredicate<'tcx, ty::GenericArg<'tcx>>,
+ &'tcx ty::List<ty::OutlivesPredicate<'tcx, ty::GenericArg<'tcx>>>,
+ >,
+ {
+ T::collect_and_apply(iter, |xs| self.mk_outlives(xs))
+ }
+
  /// Emit a lint at `span` from a lint struct (some type that implements `LintDiagnostic`,
  /// typically generated by `#[derive(LintDiagnostic)]`).
  #[track_caller]

compiler/rustc_traits/src/coroutine_witnesses.rs

@@ -1,5 +1,10 @@
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::{self, TyCtxt, fold_regions};
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::infer::canonical::query_response::make_query_region_constraints;
+use rustc_infer::infer::resolve::OpportunisticRegionResolver;
+use rustc_infer::traits::{Obligation, ObligationCause};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, fold_regions};
+use rustc_trait_selection::traits::{ObligationCtxt, with_replaced_escaping_bound_vars};
 
 /// Return the set of types that should be taken into account when checking
 /// trait bounds on a coroutine's internal state. This properly replaces
@@ -29,8 +34,56 @@ pub(crate) fn coroutine_hidden_types<'tcx>(
  ty
  }),
  );
+
+ let assumptions = compute_assumptions(tcx, def_id, bound_tys);
+
  ty::EarlyBinder::bind(ty::Binder::bind_with_vars(
- ty::CoroutineWitnessTypes { types: bound_tys, assumptions: ty::List::empty() },
+ ty::CoroutineWitnessTypes { types: bound_tys, assumptions },
  tcx.mk_bound_variable_kinds(&vars),
  ))
 }
+
+fn compute_assumptions<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ def_id: DefId,
+ bound_tys: &'tcx ty::List<Ty<'tcx>>,
+) -> &'tcx ty::List<ty::OutlivesPredicate<'tcx, ty::GenericArg<'tcx>>> {
+ let infcx = tcx.infer_ctxt().build(ty::TypingMode::Analysis {
+ defining_opaque_types_and_generators: ty::List::empty(),
+ });
+ with_replaced_escaping_bound_vars(&infcx, &mut vec![None], bound_tys, |bound_tys| {
+ let param_env = tcx.param_env(def_id);
+ let ocx = ObligationCtxt::new(&infcx);
+
+ ocx.register_obligations(bound_tys.iter().map(|ty| {
+ Obligation::new(
+ tcx,
+ ObligationCause::dummy(),
+ param_env,
+ ty::ClauseKind::WellFormed(ty.into()),
+ )
+ }));
+ let _errors = ocx.select_all_or_error();
+
+ let region_obligations = infcx.take_registered_region_obligations();
+ let region_constraints = infcx.take_and_reset_region_constraints();
+
+ let outlives = make_query_region_constraints(
+ tcx,
+ region_obligations,
+ &region_constraints,
+ )
+ .outlives
+ .fold_with(&mut OpportunisticRegionResolver::new(&infcx));
+
+ tcx.mk_outlives_from_iter(
+ outlives
+ .into_iter()
+ .map(|(o, _)| o)
+ // FIXME(higher_ranked_auto): We probably should deeply resolve these before
+ // filtering out infers which only correspond to unconstrained infer regions
+ // which we can sometimes get.
+ .filter(|o| !o.has_infer()),
+ )
+ })
+}