Move trait into attr so it's greppable

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

@@ -13,8 +13,8 @@ use rustc_middle::ty::{self, TyCtxt};
 
 /// FIXME(-Znext-solver): This or public because it is shared with the
 /// new trait solver implementation. We should deduplicate canonicalization.
-#[extension]
-pub impl<'tcx, V> CanonicalExt<'tcx, V> for Canonical<'tcx, V> {
+#[extension(pub trait CanonicalExt<'tcx, V>)]
+impl<'tcx, V> Canonical<'tcx, V> {
     /// Instantiate the wrapped value, replacing each canonical value
     /// with the value given in `var_values`.
     fn instantiate(&self, tcx: TyCtxt<'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2786,8 +2786,8 @@ pub enum FailureCode {
     Error0644,
 }
 
-#[extension]
-pub impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
+#[extension(pub trait ObligationCauseExt<'tcx>)]
+impl<'tcx> ObligationCause<'tcx> {
     fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
         use self::FailureCode::*;
         use crate::traits::ObligationCauseCode::*;

compiler/rustc_infer/src/infer/mod.rs

@@ -626,8 +626,8 @@ pub struct InferCtxtBuilder<'tcx> {
     next_trait_solver: bool,
 }
 
-#[extension]
-pub impl<'tcx> TyCtxtInferExt<'tcx> for TyCtxt<'tcx> {
+#[extension(pub trait TyCtxtInferExt<'tcx>)]
+impl<'tcx> TyCtxt<'tcx> {
     fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
         InferCtxtBuilder {
             tcx: self,

compiler/rustc_infer/src/traits/engine.rs

@@ -52,8 +52,8 @@ pub trait TraitEngine<'tcx>: 'tcx {
     ) -> Vec<PredicateObligation<'tcx>>;
 }
 
-#[extension]
-pub impl<'tcx, T: ?Sized + TraitEngine<'tcx>> TraitEngineExt<'tcx> for T {
+#[extension(pub trait TraitEngineExt<'tcx>)]
+impl<'tcx, T: ?Sized + TraitEngine<'tcx>> T {
     fn register_predicate_obligations(
         &mut self,
         infcx: &InferCtxt<'tcx>,