1 files changed, 76 insertions, 0 deletions
diff --git a/compiler/rustc_infer/src/traits/engine.rs b/compiler/rustc_infer/src/traits/engine.rs
new file mode 100644
index 000000000..736278ba0
--- /dev/null
+++ b/compiler/rustc_infer/src/traits/engine.rs
@@ -0,0 +1,76 @@
+use crate::infer::InferCtxt;
+use crate::traits::Obligation;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty::{self, ToPredicate, Ty};
+
+use super::FulfillmentError;
+use super::{ObligationCause, PredicateObligation};
+
+pub trait TraitEngine<'tcx>: 'tcx {
+    fn normalize_projection_type(
+        &mut self,
+        infcx: &InferCtxt<'_, 'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        projection_ty: ty::ProjectionTy<'tcx>,
+        cause: ObligationCause<'tcx>,
+    ) -> Ty<'tcx>;
+
+    /// Requires that `ty` must implement the trait with `def_id` in
+    /// the given environment. This trait must not have any type
+    /// parameters (except for `Self`).
+    fn register_bound(
+        &mut self,
+        infcx: &InferCtxt<'_, 'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: Ty<'tcx>,
+        def_id: DefId,
+        cause: ObligationCause<'tcx>,
+    ) {
+        let trait_ref = ty::TraitRef { def_id, substs: infcx.tcx.mk_substs_trait(ty, &[]) };
+        self.register_predicate_obligation(
+            infcx,
+            Obligation {
+                cause,
+                recursion_depth: 0,
+                param_env,
+                predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(infcx.tcx),
+            },
+        );
+    }
+
+    fn register_predicate_obligation(
+        &mut self,
+        infcx: &InferCtxt<'_, 'tcx>,
+        obligation: PredicateObligation<'tcx>,
+    );
+
+    fn select_all_or_error(&mut self, infcx: &InferCtxt<'_, 'tcx>) -> Vec<FulfillmentError<'tcx>>;
+
+    fn select_where_possible(&mut self, infcx: &InferCtxt<'_, 'tcx>)
+    -> Vec<FulfillmentError<'tcx>>;
+
+    fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
+
+    fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships>;
+}
+
+pub trait TraitEngineExt<'tcx> {
+    fn register_predicate_obligations(
+        &mut self,
+        infcx: &InferCtxt<'_, 'tcx>,
+        obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
+    );
+}
+
+impl<'tcx, T: ?Sized + TraitEngine<'tcx>> TraitEngineExt<'tcx> for T {
+    fn register_predicate_obligations(
+        &mut self,
+        infcx: &InferCtxt<'_, 'tcx>,
+        obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
+    ) {
+        for obligation in obligations {
+            self.register_predicate_obligation(infcx, obligation);
+        }
+    }
+}