1 files changed, 67 insertions, 0 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/opaques.rs b/compiler/rustc_trait_selection/src/solve/opaques.rs
new file mode 100644
index 000000000..a5de4ddee
--- /dev/null
+++ b/compiler/rustc_trait_selection/src/solve/opaques.rs
@@ -0,0 +1,67 @@
+use rustc_middle::traits::query::NoSolution;
+use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
+use rustc_middle::traits::Reveal;
+use rustc_middle::ty;
+use rustc_middle::ty::util::NotUniqueParam;
+
+use super::{EvalCtxt, SolverMode};
+
+impl<'tcx> EvalCtxt<'_, 'tcx> {
+    pub(super) fn normalize_opaque_type(
+        &mut self,
+        goal: Goal<'tcx, ty::ProjectionPredicate<'tcx>>,
+    ) -> QueryResult<'tcx> {
+        let tcx = self.tcx();
+        let opaque_ty = goal.predicate.projection_ty;
+        let expected = goal.predicate.term.ty().expect("no such thing as an opaque const");
+
+        match (goal.param_env.reveal(), self.solver_mode()) {
+            (Reveal::UserFacing, SolverMode::Normal) => {
+                let Some(opaque_ty_def_id) = opaque_ty.def_id.as_local() else {
+                    return Err(NoSolution);
+                };
+                let opaque_ty =
+                    ty::OpaqueTypeKey { def_id: opaque_ty_def_id, substs: opaque_ty.substs };
+                // FIXME: at some point we should call queries without defining
+                // new opaque types but having the existing opaque type definitions.
+                // This will require moving this below "Prefer opaques registered already".
+                if !self.can_define_opaque_ty(opaque_ty_def_id) {
+                    return Err(NoSolution);
+                }
+                // FIXME: This may have issues when the substs contain aliases...
+                match self.tcx().uses_unique_placeholders_ignoring_regions(opaque_ty.substs) {
+                    Err(NotUniqueParam::NotParam(param)) if param.is_non_region_infer() => {
+                        return self.evaluate_added_goals_and_make_canonical_response(
+                            Certainty::AMBIGUOUS,
+                        );
+                    }
+                    Err(_) => {
+                        return Err(NoSolution);
+                    }
+                    Ok(()) => {}
+                }
+                // Prefer opaques registered already.
+                let matches = self.unify_existing_opaque_tys(goal.param_env, opaque_ty, expected);
+                if !matches.is_empty() {
+                    if let Some(response) = self.try_merge_responses(&matches) {
+                        return Ok(response);
+                    } else {
+                        return self.flounder(&matches);
+                    }
+                }
+                // Otherwise, define a new opaque type
+                self.register_opaque_ty(opaque_ty, expected, goal.param_env)?;
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            }
+            (Reveal::UserFacing, SolverMode::Coherence) => {
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
+            }
+            (Reveal::All, _) => {
+                // FIXME: Add an assertion that opaque type storage is empty.
+                let actual = tcx.type_of(opaque_ty.def_id).subst(tcx, opaque_ty.substs);
+                self.eq(goal.param_env, expected, actual)?;
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            }
+        }
+    }
+}