+fn find_opaque_ty_constraints_for_rpit(
+ tcx: TyCtxt<'_>,
+ def_id: LocalDefId,
+ owner_def_id: LocalDefId,
+) -> Ty<'_> {
+ use rustc_hir::{Expr, ImplItem, Item, TraitItem};
+
+ struct ConstraintChecker<'tcx> {
+ tcx: TyCtxt<'tcx>,
+
+ /// def_id of the opaque type whose defining uses are being checked
+ def_id: LocalDefId,
+
+ found: ty::OpaqueHiddenType<'tcx>,
+ }
+
+ impl ConstraintChecker<'_> {
+ #[instrument(skip(self), level = "debug")]
+ fn check(&self, def_id: LocalDefId) {
+ // Use borrowck to get the type with unerased regions.
+ let concrete_opaque_types = &self.tcx.mir_borrowck(def_id).concrete_opaque_types;
+ debug!(?concrete_opaque_types);
+ for &(def_id, concrete_type) in concrete_opaque_types {
+ if def_id != self.def_id {
+ // Ignore constraints for other opaque types.
+ continue;
+ }
+
+ debug!(?concrete_type, "found constraint");
+
+ if concrete_type.ty != self.found.ty
+ && !(concrete_type, self.found).references_error()
+ {
+ self.found.report_mismatch(&concrete_type, self.tcx);
+ }
+ }
+ }
+ }
+
+ impl<'tcx> intravisit::Visitor<'tcx> for ConstraintChecker<'tcx> {
+ type NestedFilter = nested_filter::OnlyBodies;
+
+ fn nested_visit_map(&mut self) -> Self::Map {
+ self.tcx.hir()
+ }
+ fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
+ if let hir::ExprKind::Closure { .. } = ex.kind {
+ let def_id = self.tcx.hir().local_def_id(ex.hir_id);
+ self.check(def_id);
+ }
+ intravisit::walk_expr(self, ex);
+ }
+ fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
+ trace!(?it.def_id);
+ // The opaque type itself or its children are not within its reveal scope.
+ if it.def_id != self.def_id {
+ self.check(it.def_id);
+ intravisit::walk_item(self, it);
+ }
+ }
+ fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
+ trace!(?it.def_id);
+ // The opaque type itself or its children are not within its reveal scope.
+ if it.def_id != self.def_id {
+ self.check(it.def_id);
+ intravisit::walk_impl_item(self, it);
+ }
+ }
+ fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
+ trace!(?it.def_id);
+ self.check(it.def_id);
+ intravisit::walk_trait_item(self, it);
+ }
+ }
+
+ let concrete = tcx.mir_borrowck(owner_def_id).concrete_opaque_types.get(&def_id).copied();
+
+ if let Some(concrete) = concrete {
+ let scope = tcx.hir().local_def_id_to_hir_id(owner_def_id);
+ debug!(?scope);
+ let mut locator = ConstraintChecker { def_id: def_id, tcx, found: concrete };
+
+ match tcx.hir().get(scope) {
+ Node::Item(it) => intravisit::walk_item(&mut locator, it),
+ Node::ImplItem(it) => intravisit::walk_impl_item(&mut locator, it),
+ Node::TraitItem(it) => intravisit::walk_trait_item(&mut locator, it),
+ other => bug!("{:?} is not a valid scope for an opaque type item", other),
+ }
+ }
+
+ concrete.map(|concrete| concrete.ty).unwrap_or_else(|| {
+ let table = tcx.typeck(owner_def_id);
+ if let Some(_) = table.tainted_by_errors {
+ // Some error in the
+ // owner fn prevented us from populating
+ // the `concrete_opaque_types` table.
+ tcx.ty_error()
+ } else {
+ table
+ .concrete_opaque_types
+ .get(&def_id)
+ .copied()
+ .unwrap_or_else(|| {
+ // We failed to resolve the opaque type or it
+ // resolves to itself. We interpret this as the
+ // no values of the hidden type ever being constructed,
+ // so we can just make the hidden type be `!`.
+ // For backwards compatibility reasons, we fall back to
+ // `()` until we the diverging default is changed.
+ Some(tcx.mk_diverging_default())
+ })
+ .expect("RPIT always have a hidden type from typeck")
+ }
+ })
+}
+