1 files changed, 44 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 00000000000..1a770459338
--- /dev/null
+++ b/compiler/rustc_trait_selection/src/solve/opaques.rs
@@ -0,0 +1,44 @@
+use rustc_infer::infer::InferOk;
+use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
+use rustc_middle::traits::{ObligationCause, Reveal};
+use rustc_middle::ty::ProjectionPredicate;
+
+use super::{EvalCtxt, SolverMode};
+
+impl<'tcx> EvalCtxt<'_, 'tcx> {
+    pub(super) fn normalize_opaque_type(
+        &mut self,
+        goal: Goal<'tcx, 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() {
+            Reveal::UserFacing => match self.solver_mode() {
+                SolverMode::Normal => self.probe(|ecx| {
+                    // FIXME: Check that the usage is "defining" (all free params), otherwise bail.
+                    // FIXME: This should probably just check the anchor directly
+                    let InferOk { value: (), obligations } = self.infcx.handle_opaque_type(
+                        expected,
+                        tcx.mk_opaque(opaque_ty.def_id, opaque_ty.substs),
+                        true,
+                        &ObligationCause::dummy(),
+                        goal.param_env,
+                    )?;
+                    // FIXME: Need to fold these to replace the opaque ty with the expected ty.
+                    ecx.add_goals(obligations.into_iter().map(Into::into));
+                    ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+                }),
+                SolverMode::Coherence => {
+                    self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
+                }
+            },
+            Reveal::All => self.probe(|ecx| {
+                let actual = tcx.type_of(opaque_ty.def_id).subst(tcx, opaque_ty.substs);
+                ecx.eq(goal.param_env, expected, actual)?;
+                ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            }),
+        }
+    }
+}