Remove unnecessary extension trait

compiler/rustc_infer/src/infer/canonical/query_response.rs

@@ -15,8 +15,8 @@
 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;

compiler/rustc_infer/src/infer/mod.rs

@@ -12,7 +12,7 @@
 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;

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;
@@ -37,11 +36,31 @@ fn register_predicate_obligation(
         obligation: PredicateObligation<'tcx>,
     );
 
+    fn register_predicate_obligations(
+        &mut self,
+        infcx: &InferCtxt<'tcx>,
+        obligations: Vec<PredicateObligation<'tcx>>,
+    ) {
+        for obligation in obligations {
+            self.register_predicate_obligation(infcx, obligation);
+        }
+    }
+
     #[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() {
+            return errors;
+        }
+
+        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
@@ -52,26 +71,3 @@ fn drain_unstalled_obligations(
         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>>,
-    ) {
-        for obligation in obligations {
-            self.register_predicate_obligation(infcx, obligation);
-        }
-    }
-
-    #[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() {
-            return errors;
-        }
-
-        self.collect_remaining_errors(infcx)
-    }
-}

compiler/rustc_infer/src/traits/mod.rs

@@ -23,7 +23,7 @@
 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::{

compiler/rustc_trait_selection/src/solve/normalize.rs

@@ -4,7 +4,6 @@
 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};

compiler/rustc_trait_selection/src/traits/engine.rs

@@ -18,9 +18,7 @@
 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;