Use TraitEngine in more places that don't specifically need FulfillmentCtxt::new_in_snapshot

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -10,7 +10,7 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::{self, subst::SubstsRef, AdtDef, Ty};
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::traits::{
-    self, FulfillmentContext, ImplSource, Obligation, ObligationCause, SelectionContext,
+    self, ImplSource, Obligation, ObligationCause, SelectionContext, TraitEngineExt,
 };
 
 use super::ConstCx;
@@ -191,7 +191,7 @@ impl Qualif for NeedsNonConstDrop {
 
             // If we successfully found one, then select all of the predicates
             // implied by our const drop impl.
-            let mut fcx = FulfillmentContext::new();
+            let mut fcx = <dyn TraitEngine<'tcx>>::new(cx.tcx);
             for nested in impl_src.nested_obligations() {
                 fcx.register_predicate_obligation(&infcx, nested);
             }

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -205,7 +205,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
             // At this point, we already have all of the bounds we need. FulfillmentContext is used
             // to store all of the necessary region/lifetime bounds in the InferContext, as well as
             // an additional sanity check.
-            let mut fulfill = FulfillmentContext::new();
+            let mut fulfill = <dyn TraitEngine<'tcx>>::new(tcx);
             fulfill.register_bound(&infcx, full_env, ty, trait_did, ObligationCause::dummy());
             let errors = fulfill.select_all_or_error(&infcx);
 

compiler/rustc_trait_selection/src/traits/codegen.rs

@@ -5,7 +5,7 @@
 
 use crate::infer::{DefiningAnchor, TyCtxtInferExt};
 use crate::traits::{
-    FulfillmentContext, ImplSource, Obligation, ObligationCause, SelectionContext, TraitEngine,
+    ImplSource, Obligation, ObligationCause, SelectionContext, TraitEngine, TraitEngineExt,
     Unimplemented,
 };
 use rustc_middle::traits::CodegenObligationError;
@@ -55,7 +55,7 @@ pub fn codegen_fulfill_obligation<'tcx>(
         // Currently, we use a fulfillment context to completely resolve
         // all nested obligations. This is because they can inform the
         // inference of the impl's type parameters.
-        let mut fulfill_cx = FulfillmentContext::new();
+        let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(tcx);
         let impl_source = selection.map(|predicate| {
             fulfill_cx.register_predicate_obligation(&infcx, predicate);
         });

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -11,7 +11,7 @@ use crate::traits::util::impl_subject_and_oblig;
 use crate::traits::SkipLeakCheck;
 use crate::traits::{
     self, FulfillmentContext, Normalized, Obligation, ObligationCause, PredicateObligation,
-    PredicateObligations, SelectionContext,
+    PredicateObligations, SelectionContext, TraitEngineExt,
 };
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::Diagnostic;
@@ -385,7 +385,7 @@ fn resolve_negative_obligation<'cx, 'tcx>(
         return false;
     };
 
-    let mut fulfillment_cx = FulfillmentContext::new();
+    let mut fulfillment_cx = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
     fulfillment_cx.register_predicate_obligation(infcx, o);
 
     let errors = fulfillment_cx.select_all_or_error(infcx);

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -163,7 +163,7 @@ pub fn type_known_to_meet_bound_modulo_regions<'a, 'tcx>(
         // The handling of regions in this area of the code is terrible,
         // see issue #29149. We should be able to improve on this with
         // NLL.
-        let mut fulfill_cx = FulfillmentContext::new();
+        let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
 
         // We can use a dummy node-id here because we won't pay any mind
         // to region obligations that arise (there shouldn't really be any

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

@@ -14,7 +14,9 @@ use specialization_graph::GraphExt;
 
 use crate::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use crate::traits::select::IntercrateAmbiguityCause;
-use crate::traits::{self, coherence, FutureCompatOverlapErrorKind, ObligationCause, TraitEngine};
+use crate::traits::{
+    self, coherence, FutureCompatOverlapErrorKind, ObligationCause, TraitEngine, TraitEngineExt,
+};
 use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_errors::{struct_span_err, EmissionGuarantee, LintDiagnosticBuilder};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -24,8 +26,8 @@ use rustc_session::lint::builtin::COHERENCE_LEAK_CHECK;
 use rustc_session::lint::builtin::ORDER_DEPENDENT_TRAIT_OBJECTS;
 use rustc_span::{Span, DUMMY_SP};
 
-use super::util;
+use super::SelectionContext;
-use super::{FulfillmentContext, SelectionContext};
+use super::{util, FulfillmentContext};
 
 /// Information pertinent to an overlapping impl error.
 #[derive(Debug)]
@@ -207,7 +209,7 @@ fn fulfill_implication<'a, 'tcx>(
     // (which are packed up in penv)
 
     infcx.save_and_restore_in_snapshot_flag(|infcx| {
-        let mut fulfill_cx = FulfillmentContext::new();
+        let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
         for oblig in obligations.chain(more_obligations) {
             fulfill_cx.register_predicate_obligation(&infcx, oblig);
         }

compiler/rustc_trait_selection/src/traits/structural_match.rs

@@ -1,6 +1,6 @@
 use crate::infer::{InferCtxt, TyCtxtInferExt};
 use crate::traits::ObligationCause;
-use crate::traits::{self, TraitEngine};
+use crate::traits::{TraitEngine, TraitEngineExt};
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
@@ -78,7 +78,7 @@ fn type_marked_structural<'tcx>(
     adt_ty: Ty<'tcx>,
     cause: ObligationCause<'tcx>,
 ) -> bool {
-    let mut fulfillment_cx = traits::FulfillmentContext::new();
+    let mut fulfillment_cx = <dyn TraitEngine<'tcx>>::new(infcx.tcx);
     // require `#[derive(PartialEq)]`
     let structural_peq_def_id =
         infcx.tcx.require_lang_item(LangItem::StructuralPeq, Some(cause.span));

compiler/rustc_traits/src/implied_outlives_bounds.rs

@@ -14,8 +14,7 @@ use rustc_span::source_map::DUMMY_SP;
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
 use rustc_trait_selection::traits::query::{CanonicalTyGoal, Fallible, NoSolution};
 use rustc_trait_selection::traits::wf;
-use rustc_trait_selection::traits::FulfillmentContext;
+use rustc_trait_selection::traits::{TraitEngine, TraitEngineExt};
-use rustc_trait_selection::traits::TraitEngine;
 use smallvec::{smallvec, SmallVec};
 
 pub(crate) fn provide(p: &mut Providers) {
@@ -52,7 +51,7 @@ fn compute_implied_outlives_bounds<'tcx>(
 
     let mut implied_bounds = vec![];
 
-    let mut fulfill_cx = FulfillmentContext::new();
+    let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(tcx);
 
     while let Some(arg) = wf_args.pop() {
         if !checked_wf_args.insert(arg) {

compiler/rustc_typeck/src/coherence/builtin.rs

@@ -117,7 +117,7 @@ fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
                 // it is not immediately clear why Copy is not implemented for a field, since
                 // all we point at is the field itself.
                 tcx.infer_ctxt().ignoring_regions().enter(|infcx| {
-                    let mut fulfill_cx = traits::FulfillmentContext::new();
+                    let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
                     fulfill_cx.register_bound(
                         &infcx,
                         param_env,

compiler/rustc_typeck/src/hir_wf_check.rs

@@ -7,7 +7,7 @@ use rustc_infer::traits::TraitEngine;
 use rustc_infer::traits::{ObligationCause, WellFormedLoc};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, Region, ToPredicate, TyCtxt, TypeFoldable, TypeFolder};
-use rustc_trait_selection::traits;
+use rustc_trait_selection::traits::{self, TraitEngineExt};
 
 pub fn provide(providers: &mut Providers) {
     *providers = Providers { diagnostic_hir_wf_check, ..*providers };
@@ -66,7 +66,7 @@ fn diagnostic_hir_wf_check<'tcx>(
     impl<'tcx> Visitor<'tcx> for HirWfCheck<'tcx> {
         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
             self.tcx.infer_ctxt().enter(|infcx| {
-                let mut fulfill = traits::FulfillmentContext::new();
+                let mut fulfill = <dyn TraitEngine<'tcx>>::new(self.tcx);
                 let tcx_ty =
                     self.icx.to_ty(ty).fold_with(&mut EraseAllBoundRegions { tcx: self.tcx });
                 let cause = traits::ObligationCause::new(

compiler/rustc_typeck/src/outlives/outlives_bounds.rs

@@ -3,7 +3,7 @@ use rustc_middle::ty::{self, Ty};
 use rustc_trait_selection::infer::InferCtxt;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOp, TypeOpOutput};
 use rustc_trait_selection::traits::query::NoSolution;
-use rustc_trait_selection::traits::{FulfillmentContext, ObligationCause, TraitEngine};
+use rustc_trait_selection::traits::{ObligationCause, TraitEngine, TraitEngineExt};
 
 pub use rustc_middle::traits::query::OutlivesBound;
 
@@ -63,7 +63,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
         if let Some(constraints) = constraints {
             // Instantiation may have produced new inference variables and constraints on those
             // variables. Process these constraints.
-            let mut fulfill_cx = FulfillmentContext::new();
+            let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(self.tcx);
             let cause = ObligationCause::misc(span, body_id);
             for &constraint in &constraints.outlives {
                 let obligation = self.query_outlives_constraint_to_obligation(