diff --git a/compiler/rustc_infer/src/infer/at.rs b/compiler/rustc_infer/src/infer/at.rs
index 37f7f04db3f..6ce47db8b9b 100644
--- a/compiler/rustc_infer/src/infer/at.rs
+++ b/compiler/rustc_infer/src/infer/at.rs
@@ -92,12 +92,7 @@ pub fn fork_with_intercrate(&self, intercrate: bool) -> Self {
 }
 
 pub trait ToTrace<'tcx>: Relate<TyCtxt<'tcx>> + Copy {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx>;
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx>;
 }
 
 impl<'a, 'tcx> At<'a, 'tcx> {
@@ -116,7 +111,7 @@ pub fn sup<T>(
     {
         let mut fields = CombineFields::new(
             self.infcx,
-            ToTrace::to_trace(self.cause, true, expected, actual),
+            ToTrace::to_trace(self.cause, expected, actual),
             self.param_env,
             define_opaque_types,
         );
@@ -136,7 +131,7 @@ pub fn sub<T>(
     {
         let mut fields = CombineFields::new(
             self.infcx,
-            ToTrace::to_trace(self.cause, true, expected, actual),
+            ToTrace::to_trace(self.cause, expected, actual),
             self.param_env,
             define_opaque_types,
         );
@@ -154,10 +149,7 @@ pub fn eq<T>(
     where
         T: ToTrace<'tcx>,
     {
-        let mut fields = CombineFields::new(
-            self.infcx,
-            ToTrace::to_trace(self.cause, true, expected, actual),
-            self.param_env,
+        self.eq_trace(
             define_opaque_types,
             ToTrace::to_trace(self.cause, expected, actual),
             expected,
@@ -209,7 +201,7 @@ pub fn eq_structurally_relating_aliases<T>(
         assert!(self.infcx.next_trait_solver());
         let mut fields = CombineFields::new(
             self.infcx,
-            ToTrace::to_trace(self.cause, true, expected, actual),
+            ToTrace::to_trace(self.cause, expected, actual),
             self.param_env,
             DefineOpaqueTypes::Yes,
         );
@@ -301,7 +293,7 @@ pub fn lub<T>(
     {
         let mut fields = CombineFields::new(
             self.infcx,
-            ToTrace::to_trace(self.cause, true, expected, actual),
+            ToTrace::to_trace(self.cause, expected, actual),
             self.param_env,
             define_opaque_types,
         );
@@ -323,7 +315,7 @@ pub fn glb<T>(
     {
         let mut fields = CombineFields::new(
             self.infcx,
-            ToTrace::to_trace(self.cause, true, expected, actual),
+            ToTrace::to_trace(self.cause, expected, actual),
             self.param_env,
             define_opaque_types,
         );
@@ -333,18 +325,13 @@ pub fn glb<T>(
 }
 
 impl<'tcx> ToTrace<'tcx> for ImplSubject<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         match (a, b) {
             (ImplSubject::Trait(trait_ref_a), ImplSubject::Trait(trait_ref_b)) => {
-                ToTrace::to_trace(cause, a_is_expected, trait_ref_a, trait_ref_b)
+                ToTrace::to_trace(cause, trait_ref_a, trait_ref_b)
             }
             (ImplSubject::Inherent(ty_a), ImplSubject::Inherent(ty_b)) => {
-                ToTrace::to_trace(cause, a_is_expected, ty_a, ty_b)
+                ToTrace::to_trace(cause, ty_a, ty_b)
             }
             (ImplSubject::Trait(_), ImplSubject::Inherent(_))
             | (ImplSubject::Inherent(_), ImplSubject::Trait(_)) => {
@@ -355,65 +342,45 @@ fn to_trace(
 }
 
 impl<'tcx> ToTrace<'tcx> for Ty<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
+            values: ValuePairs::Terms(ExpectedFound::new(true, a.into(), b.into())),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::Region<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::Regions(ExpectedFound::new(a_is_expected, a, b)),
+            values: ValuePairs::Regions(ExpectedFound::new(true, a, b)),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for Const<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
+            values: ValuePairs::Terms(ExpectedFound::new(true, a.into(), b.into())),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::GenericArg<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
             values: match (a.unpack(), b.unpack()) {
                 (GenericArgKind::Lifetime(a), GenericArgKind::Lifetime(b)) => {
-                    ValuePairs::Regions(ExpectedFound::new(a_is_expected, a, b))
+                    ValuePairs::Regions(ExpectedFound::new(true, a, b))
                 }
                 (GenericArgKind::Type(a), GenericArgKind::Type(b)) => {
-                    ValuePairs::Terms(ExpectedFound::new(a_is_expected, a.into(), b.into()))
+                    ValuePairs::Terms(ExpectedFound::new(true, a.into(), b.into()))
                 }
                 (GenericArgKind::Const(a), GenericArgKind::Const(b)) => {
-                    ValuePairs::Terms(ExpectedFound::new(a_is_expected, a.into(), b.into()))
+                    ValuePairs::Terms(ExpectedFound::new(true, a.into(), b.into()))
                 }
 
                 (
@@ -436,72 +403,47 @@ fn to_trace(
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::Term<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::Terms(ExpectedFound::new(a_is_expected, a, b)),
+            values: ValuePairs::Terms(ExpectedFound::new(true, a, b)),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::TraitRef<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::TraitRefs(ExpectedFound::new(a_is_expected, a, b)),
+            values: ValuePairs::TraitRefs(ExpectedFound::new(true, a, b)),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::AliasTy<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::Aliases(ExpectedFound::new(a_is_expected, a.into(), b.into())),
+            values: ValuePairs::Aliases(ExpectedFound::new(true, a.into(), b.into())),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::AliasTerm<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::Aliases(ExpectedFound::new(a_is_expected, a, b)),
+            values: ValuePairs::Aliases(ExpectedFound::new(true, a, b)),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::FnSig<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
             values: ValuePairs::PolySigs(ExpectedFound::new(
-                a_is_expected,
+                true,
                 ty::Binder::dummy(a),
                 ty::Binder::dummy(b),
             )),
@@ -510,43 +452,28 @@ fn to_trace(
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::PolyFnSig<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::PolySigs(ExpectedFound::new(a_is_expected, a, b)),
+            values: ValuePairs::PolySigs(ExpectedFound::new(true, a, b)),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::PolyExistentialTraitRef<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::ExistentialTraitRef(ExpectedFound::new(a_is_expected, a, b)),
+            values: ValuePairs::ExistentialTraitRef(ExpectedFound::new(true, a, b)),
         }
     }
 }
 
 impl<'tcx> ToTrace<'tcx> for ty::PolyExistentialProjection<'tcx> {
-    fn to_trace(
-        cause: &ObligationCause<'tcx>,
-        a_is_expected: bool,
-        a: Self,
-        b: Self,
-    ) -> TypeTrace<'tcx> {
+    fn to_trace(cause: &ObligationCause<'tcx>, a: Self, b: Self) -> TypeTrace<'tcx> {
         TypeTrace {
             cause: cause.clone(),
-            values: ValuePairs::ExistentialProjection(ExpectedFound::new(a_is_expected, a, b)),
+            values: ValuePairs::ExistentialProjection(ExpectedFound::new(true, a, b)),
         }
     }
 }
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index c3042ab9636..dbe05a33328 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2598,7 +2598,6 @@ fn match_upcast_principal(
                                     DefineOpaqueTypes::Yes,
                                     ToTrace::to_trace(
                                         &obligation.cause,
-                                        true,
                                         hr_target_principal,
                                         hr_source_principal,
                                     ),
@@ -2638,7 +2637,6 @@ fn match_upcast_principal(
                                                     DefineOpaqueTypes::Yes,
                                                     ToTrace::to_trace(
                                                         &obligation.cause,
-                                                        true,
                                                         hr_target_projection,
                                                         hr_source_projection,
                                                     ),
@@ -2669,7 +2667,6 @@ fn match_upcast_principal(
                                     DefineOpaqueTypes::Yes,
                                     ToTrace::to_trace(
                                         &obligation.cause,
-                                        true,
                                         hr_target_projection,
                                         hr_source_projection,
                                     ),