Use ObligationCtxt intead of dyn TraitEngine

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -4,13 +4,12 @@ pub mod suggestions;
 
 use super::{
     FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes, Obligation, ObligationCause,
-    ObligationCauseCode, OutputTypeParameterMismatch, Overflow, PredicateObligation,
-    SelectionContext, SelectionError, TraitNotObjectSafe,
+    ObligationCauseCode, ObligationCtxt, OutputTypeParameterMismatch, Overflow,
+    PredicateObligation, SelectionContext, SelectionError, TraitNotObjectSafe,
 };
 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::{self, InferCtxt, TyCtxtInferExt};
-use crate::traits::engine::TraitEngineExt as _;
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
 use crate::traits::query::normalize::AtExt as _;
 use crate::traits::specialize::to_pretty_impl_header;
@@ -30,7 +29,6 @@ use rustc_hir::Item;
 use rustc_hir::Node;
 use rustc_infer::infer::error_reporting::TypeErrCtxt;
 use rustc_infer::infer::TypeTrace;
-use rustc_infer::traits::TraitEngine;
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::error::ExpectedFound;
@@ -354,9 +352,9 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
                     param_env,
                     ty.rebind(ty::TraitPredicate { trait_ref, constness, polarity }),
                 );
-                let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new_in_snapshot(self.tcx);
-                fulfill_cx.register_predicate_obligation(self, obligation);
-                if fulfill_cx.select_all_or_error(self).is_empty() {
+                let ocx = ObligationCtxt::new_in_snapshot(self);
+                ocx.register_obligation(obligation);
+                if ocx.select_all_or_error().is_empty() {
                     return Ok((
                         ty::ClosureKind::from_def_id(self.tcx, trait_def_id)
                             .expect("expected to map DefId to ClosureKind"),

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -31,7 +31,6 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
-use rustc_infer::traits::TraitEngineExt as _;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::TypeVisitable;
 use rustc_middle::ty::{
@@ -403,9 +402,9 @@ pub fn fully_solve_obligation<'tcx>(
     infcx: &InferCtxt<'tcx>,
     obligation: PredicateObligation<'tcx>,
 ) -> Vec<FulfillmentError<'tcx>> {
-    let mut engine = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
-    engine.register_predicate_obligation(infcx, obligation);
-    engine.select_all_or_error(infcx)
+    let ocx = ObligationCtxt::new(infcx);
+    ocx.register_obligation(obligation);
+    ocx.select_all_or_error()
 }
 
 /// Process a set of obligations (and any nested obligations that come from them)
@@ -414,9 +413,9 @@ pub fn fully_solve_obligations<'tcx>(
     infcx: &InferCtxt<'tcx>,
     obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
 ) -> Vec<FulfillmentError<'tcx>> {
-    let mut engine = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
-    engine.register_predicate_obligations(infcx, obligations);
-    engine.select_all_or_error(infcx)
+    let ocx = ObligationCtxt::new(infcx);
+    ocx.register_obligations(obligations);
+    ocx.select_all_or_error()
 }
 
 /// Process a bound (and any nested obligations that come from it) to completion.
@@ -429,9 +428,9 @@ pub fn fully_solve_bound<'tcx>(
     ty: Ty<'tcx>,
     bound: DefId,
 ) -> Vec<FulfillmentError<'tcx>> {
-    let mut engine = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
-    engine.register_bound(infcx, param_env, ty, bound, cause);
-    engine.select_all_or_error(infcx)
+    let ocx = ObligationCtxt::new(infcx);
+    ocx.register_bound(cause, param_env, ty, bound);
+    ocx.select_all_or_error()
 }
 
 /// Normalizes the predicates and checks whether they hold in an empty environment. If this

compiler/rustc_trait_selection/src/traits/specialize/mod.rs

@@ -10,14 +10,14 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/specialization.html
 
 pub mod specialization_graph;
-use rustc_infer::traits::{TraitEngine, TraitEngineExt as _};
 use specialization_graph::GraphExt;
 
 use crate::errors::NegativePositiveConflict;
 use crate::infer::{InferCtxt, InferOk, TyCtxtInferExt};
-use crate::traits::engine::TraitEngineExt as _;
 use crate::traits::select::IntercrateAmbiguityCause;
-use crate::traits::{self, coherence, FutureCompatOverlapErrorKind, ObligationCause};
+use crate::traits::{
+    self, coherence, FutureCompatOverlapErrorKind, ObligationCause, ObligationCtxt,
+};
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{error_code, DelayDm, Diagnostic};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -204,12 +204,12 @@ fn fulfill_implication<'tcx>(
 
     // Needs to be `in_snapshot` because this function is used to rebase
     // substitutions, which may happen inside of a select within a probe.
-    let mut engine = <dyn TraitEngine<'tcx>>::new_in_snapshot(infcx.tcx);
+    let ocx = ObligationCtxt::new_in_snapshot(infcx);
     // attempt to prove all of the predicates for impl2 given those for impl1
     // (which are packed up in penv)
-    engine.register_predicate_obligations(infcx, obligations.chain(more_obligations));
+    ocx.register_obligations(obligations.chain(more_obligations));
 
-    let errors = engine.select_all_or_error(infcx);
+    let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
         // no dice!
         debug!(

compiler/rustc_trait_selection/src/traits/structural_match.rs

@@ -1,6 +1,5 @@
 use crate::infer::{InferCtxt, TyCtxtInferExt};
-use crate::traits::ObligationCause;
-use crate::traits::{TraitEngine, TraitEngineExt};
+use crate::traits::{ObligationCause, ObligationCtxt};
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
@@ -72,28 +71,16 @@ fn type_marked_structural<'tcx>(
     adt_ty: Ty<'tcx>,
     cause: ObligationCause<'tcx>,
 ) -> bool {
-    let mut fulfillment_cx = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
+    let ocx = ObligationCtxt::new(infcx);
     // require `#[derive(PartialEq)]`
     let structural_peq_def_id =
         infcx.tcx.require_lang_item(LangItem::StructuralPeq, Some(cause.span));
-    fulfillment_cx.register_bound(
-        infcx,
-        ty::ParamEnv::empty(),
-        adt_ty,
-        structural_peq_def_id,
-        cause.clone(),
-    );
+    ocx.register_bound(cause.clone(), ty::ParamEnv::empty(), adt_ty, structural_peq_def_id);
     // for now, require `#[derive(Eq)]`. (Doing so is a hack to work around
     // the type `for<'a> fn(&'a ())` failing to implement `Eq` itself.)
     let structural_teq_def_id =
         infcx.tcx.require_lang_item(LangItem::StructuralTeq, Some(cause.span));
-    fulfillment_cx.register_bound(
-        infcx,
-        ty::ParamEnv::empty(),
-        adt_ty,
-        structural_teq_def_id,
-        cause,
-    );
+    ocx.register_bound(cause, ty::ParamEnv::empty(), adt_ty, structural_teq_def_id);
 
     // We deliberately skip *reporting* fulfillment errors (via
     // `report_fulfillment_errors`), for two reasons:
@@ -104,7 +91,7 @@ fn type_marked_structural<'tcx>(
     //
     // 2. We are sometimes doing future-incompatibility lints for
     //    now, so we do not want unconditional errors here.
-    fulfillment_cx.select_all_or_error(infcx).is_empty()
+    ocx.select_all_or_error().is_empty()
 }
 
 /// This implements the traversal over the structure of a given type to try to