6 files changed, 20 insertions, 27 deletions
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 1732913e191..1dbc1ae7ddd 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -15,8 +15,8 @@ use crate::infer::canonical::{
 use crate::infer::region_constraints::{Constraint, RegionConstraintData};
 use crate::infer::{DefineOpaqueTypes, InferCtxt, InferOk, InferResult};
 use crate::traits::query::NoSolution;
+use crate::traits::TraitEngine;
 use crate::traits::{Obligation, ObligationCause, PredicateObligation};
-use crate::traits::{TraitEngine, TraitEngineExt};
 use rustc_data_structures::captures::Captures;
 use rustc_index::Idx;
 use rustc_index::IndexVec;
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index c8bb6cf5f9b..617e6a245ed 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -12,7 +12,7 @@ pub use SubregionOrigin::*;
 pub use ValuePairs::*;
 
 use crate::traits::{
-    self, ObligationCause, ObligationInspector, PredicateObligations, TraitEngine, TraitEngineExt,
+    self, ObligationCause, ObligationInspector, PredicateObligations, TraitEngine,
 };
 use error_reporting::TypeErrCtxt;
 use free_regions::RegionRelations;
diff --git a/compiler/rustc_infer/src/traits/engine.rs b/compiler/rustc_infer/src/traits/engine.rs
index e27e6a0a4a1..a4bcd9d2c8a 100644
--- a/compiler/rustc_infer/src/traits/engine.rs
+++ b/compiler/rustc_infer/src/traits/engine.rs
@@ -1,7 +1,6 @@
 use crate::infer::InferCtxt;
 use crate::traits::Obligation;
 use rustc_hir::def_id::DefId;
-use rustc_macros::extension;
 use rustc_middle::ty::{self, Ty, Upcast};
 
 use super::FulfillmentError;
@@ -37,28 +36,10 @@ pub trait TraitEngine<'tcx>: 'tcx {
         obligation: PredicateObligation<'tcx>,
     );
 
-    #[must_use]
-    fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
-
-    fn collect_remaining_errors(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
-
-    fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
-
-    /// Among all pending obligations, collect those are stalled on a inference variable which has
-    /// changed since the last call to `select_where_possible`. Those obligations are marked as
-    /// successful and returned.
-    fn drain_unstalled_obligations(
-        &mut self,
-        infcx: &InferCtxt<'tcx>,
-    ) -> Vec<PredicateObligation<'tcx>>;
-}
-
-#[extension(pub trait TraitEngineExt<'tcx>)]
-impl<'tcx, T: ?Sized + TraitEngine<'tcx>> T {
     fn register_predicate_obligations(
         &mut self,
         infcx: &InferCtxt<'tcx>,
-        obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
+        obligations: Vec<PredicateObligation<'tcx>>,
     ) {
         for obligation in obligations {
             self.register_predicate_obligation(infcx, obligation);
@@ -66,6 +47,11 @@ impl<'tcx, T: ?Sized + TraitEngine<'tcx>> T {
     }
 
     #[must_use]
+    fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
+
+    fn collect_remaining_errors(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
+
+    #[must_use]
     fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
         let errors = self.select_where_possible(infcx);
         if !errors.is_empty() {
@@ -74,4 +60,14 @@ impl<'tcx, T: ?Sized + TraitEngine<'tcx>> T {
 
         self.collect_remaining_errors(infcx)
     }
+
+    fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
+
+    /// Among all pending obligations, collect those are stalled on a inference variable which has
+    /// changed since the last call to `select_where_possible`. Those obligations are marked as
+    /// successful and returned.
+    fn drain_unstalled_obligations(
+        &mut self,
+        infcx: &InferCtxt<'tcx>,
+    ) -> Vec<PredicateObligation<'tcx>>;
 }
diff --git a/compiler/rustc_infer/src/traits/mod.rs b/compiler/rustc_infer/src/traits/mod.rs
index 0ae4340098b..8304fa3c8a2 100644
--- a/compiler/rustc_infer/src/traits/mod.rs
+++ b/compiler/rustc_infer/src/traits/mod.rs
@@ -23,7 +23,7 @@ pub use self::ImplSource::*;
 pub use self::SelectionError::*;
 use crate::infer::InferCtxt;
 
-pub use self::engine::{TraitEngine, TraitEngineExt};
+pub use self::engine::TraitEngine;
 pub use self::project::MismatchedProjectionTypes;
 pub(crate) use self::project::UndoLog;
 pub use self::project::{
diff --git a/compiler/rustc_trait_selection/src/solve/normalize.rs b/compiler/rustc_trait_selection/src/solve/normalize.rs
index 5d5161e092e..970848544c5 100644
--- a/compiler/rustc_trait_selection/src/solve/normalize.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalize.rs
@@ -4,7 +4,6 @@ use crate::traits::{BoundVarReplacer, PlaceholderReplacer};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_infer::infer::at::At;
 use rustc_infer::infer::InferCtxt;
-use rustc_infer::traits::TraitEngineExt;
 use rustc_infer::traits::{FulfillmentError, Obligation, TraitEngine};
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::{self, Ty, TyCtxt, UniverseIndex};
diff --git a/compiler/rustc_trait_selection/src/traits/engine.rs b/compiler/rustc_trait_selection/src/traits/engine.rs
index 4684c7171d8..6fed24c49e0 100644
--- a/compiler/rustc_trait_selection/src/traits/engine.rs
+++ b/compiler/rustc_trait_selection/src/traits/engine.rs
@@ -18,9 +18,7 @@ use rustc_infer::infer::canonical::{
 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 _,
-};
+use rustc_infer::traits::{FulfillmentError, Obligation, ObligationCause, PredicateObligation};
 use rustc_macros::extension;
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::traits::query::NoSolution;