Use ObligationCtxt in favor of TraitEngine in many places

compiler/rustc_trait_selection/src/traits/engine.rs

@@ -7,6 +7,7 @@ use crate::regions::InferCtxtRegionExt;
 use crate::solve::FulfillmentCtxt as NextFulfillmentCtxt;
 use crate::traits::error_reporting::TypeErrCtxtExt;
 use crate::traits::NormalizeExt;
+use crate::traits::StructurallyNormalizeExt;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -15,6 +16,7 @@ use rustc_infer::infer::canonical::{
     Canonical, CanonicalQueryResponse, CanonicalVarValues, QueryResponse,
 };
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
+use rustc_infer::infer::RegionResolutionError;
 use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, InferOk};
 use rustc_infer::traits::{
     FulfillmentError, Obligation, ObligationCause, PredicateObligation, TraitEngineExt as _,
@@ -117,6 +119,17 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         self.infcx.at(cause, param_env).deeply_normalize(value, &mut **self.engine.borrow_mut())
     }
 
+    pub fn structurally_normalize(
+        &self,
+        cause: &ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        value: Ty<'tcx>,
+    ) -> Result<Ty<'tcx>, Vec<FulfillmentError<'tcx>>> {
+        self.infcx
+            .at(cause, param_env)
+            .structurally_normalize(value, &mut **self.engine.borrow_mut())
+    }
+
     pub fn eq<T: ToTrace<'tcx>>(
         &self,
         cause: &ObligationCause<'tcx>,
@@ -182,6 +195,11 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         self.engine.borrow_mut().select_all_or_error(self.infcx)
     }
 
+    #[must_use]
+    pub fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
+        self.engine.borrow().pending_obligations()
+    }
+
     /// Resolves regions and reports errors.
     ///
     /// Takes ownership of the context as doing trait solving afterwards
@@ -199,6 +217,18 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         }
     }
 
+    /// Resolves regions and reports errors.
+    ///
+    /// Takes ownership of the context as doing trait solving afterwards
+    /// will result in region constraints getting ignored.
+    #[must_use]
+    pub fn resolve_regions(
+        self,
+        outlives_env: &OutlivesEnvironment<'tcx>,
+    ) -> Vec<RegionResolutionError<'tcx>> {
+        self.infcx.resolve_regions(outlives_env)
+    }
+
     pub fn assumed_wf_types_and_report_errors(
         &self,
         param_env: ty::ParamEnv<'tcx>,