Stop using PolyTraitRef for closure/coroutine predicates already instantiated w placeholders

compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs

@@ -367,7 +367,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }),
         ) = error.code
             && let ty::Closure(def_id, _) | ty::Coroutine(def_id, ..) =
-                expected_trait_ref.skip_binder().self_ty().kind()
+                expected_trait_ref.self_ty().kind()
             && span.overlaps(self.tcx.def_span(*def_id))
         {
             true

compiler/rustc_middle/src/traits/mod.rs

@@ -620,11 +620,10 @@ pub enum SelectionError<'tcx> {
     OpaqueTypeAutoTraitLeakageUnknown(DefId),
 }
 
-// FIXME(@lcnr): The `Binder` here should be unnecessary. Just use `TraitRef` instead.
 #[derive(Clone, Debug, TypeVisitable)]
 pub struct SignatureMismatchData<'tcx> {
-    pub found_trait_ref: ty::PolyTraitRef<'tcx>,
-    pub expected_trait_ref: ty::PolyTraitRef<'tcx>,
+    pub found_trait_ref: ty::TraitRef<'tcx>,
+    pub expected_trait_ref: ty::TraitRef<'tcx>,
     pub terr: ty::error::TypeError<'tcx>,
 }
 

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1879,19 +1879,19 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         &self,
         span: Span,
         found_span: Option<Span>,
-        found: ty::PolyTraitRef<'tcx>,
-        expected: ty::PolyTraitRef<'tcx>,
+        found: ty::TraitRef<'tcx>,
+        expected: ty::TraitRef<'tcx>,
         cause: &ObligationCauseCode<'tcx>,
         found_node: Option<Node<'_>>,
         param_env: ty::ParamEnv<'tcx>,
     ) -> Diag<'tcx> {
         pub(crate) fn build_fn_sig_ty<'tcx>(
             infcx: &InferCtxt<'tcx>,
-            trait_ref: ty::PolyTraitRef<'tcx>,
+            trait_ref: ty::TraitRef<'tcx>,
         ) -> Ty<'tcx> {
-            let inputs = trait_ref.skip_binder().args.type_at(1);
+            let inputs = trait_ref.args.type_at(1);
             let sig = match inputs.kind() {
-                ty::Tuple(inputs) if infcx.tcx.is_fn_trait(trait_ref.def_id()) => {
+                ty::Tuple(inputs) if infcx.tcx.is_fn_trait(trait_ref.def_id) => {
                     infcx.tcx.mk_fn_sig(
                         *inputs,
                         infcx.next_ty_var(TypeVariableOrigin {
@@ -1915,10 +1915,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 ),
             };
 
-            Ty::new_fn_ptr(infcx.tcx, trait_ref.rebind(sig))
+            Ty::new_fn_ptr(infcx.tcx, ty::Binder::dummy(sig))
         }
 
-        let argument_kind = match expected.skip_binder().self_ty().kind() {
+        let argument_kind = match expected.self_ty().kind() {
             ty::Closure(..) => "closure",
             ty::Coroutine(..) => "coroutine",
             _ => "function",

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -3380,11 +3380,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
     fn report_cyclic_signature_error(
         &self,
         obligation: &PredicateObligation<'tcx>,
-        found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
-        expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
+        found_trait_ref: ty::TraitRef<'tcx>,
+        expected_trait_ref: ty::TraitRef<'tcx>,
         terr: TypeError<'tcx>,
     ) -> Diag<'tcx> {
-        let self_ty = found_trait_ref.self_ty().skip_binder();
+        let self_ty = found_trait_ref.self_ty();
         let (cause, terr) = if let ty::Closure(def_id, _) = self_ty.kind() {
             (
                 ObligationCause::dummy_with_span(self.tcx.def_span(def_id)),
@@ -3394,7 +3394,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             (obligation.cause.clone(), terr)
         };
         self.report_and_explain_type_error(
-            TypeTrace::poly_trait_refs(&cause, true, expected_trait_ref, found_trait_ref),
+            TypeTrace::poly_trait_refs(
+                &cause,
+                true,
+                ty::Binder::dummy(expected_trait_ref),
+                ty::Binder::dummy(found_trait_ref),
+            ),
             terr,
         )
     }
@@ -3434,17 +3439,14 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         &self,
         obligation: &PredicateObligation<'tcx>,
         span: Span,
-        found_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
-        expected_trait_ref: ty::Binder<'tcx, ty::TraitRef<'tcx>>,
+        found_trait_ref: ty::TraitRef<'tcx>,
+        expected_trait_ref: ty::TraitRef<'tcx>,
     ) -> Result<Diag<'tcx>, ErrorGuaranteed> {
         let found_trait_ref = self.resolve_vars_if_possible(found_trait_ref);
         let expected_trait_ref = self.resolve_vars_if_possible(expected_trait_ref);
 
         expected_trait_ref.self_ty().error_reported()?;
-
-        let Some(found_trait_ty) = found_trait_ref.self_ty().no_bound_vars() else {
-            self.dcx().bug("bound vars outside binder");
-        };
+        let found_trait_ty = found_trait_ref.self_ty();
 
         let found_did = match *found_trait_ty.kind() {
             ty::Closure(did, _) | ty::FnDef(did, _) | ty::Coroutine(did, ..) => Some(did),
@@ -3462,15 +3464,15 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
         let mut not_tupled = false;
 
-        let found = match found_trait_ref.skip_binder().args.type_at(1).kind() {
+        let found = match found_trait_ref.args.type_at(1).kind() {
             ty::Tuple(tys) => vec![ArgKind::empty(); tys.len()],
             _ => {
                 not_tupled = true;
                 vec![ArgKind::empty()]
             }
         };
 
-        let expected_ty = expected_trait_ref.skip_binder().args.type_at(1);
+        let expected_ty = expected_trait_ref.args.type_at(1);
         let expected = match expected_ty.kind() {
             ty::Tuple(tys) => {
                 tys.iter().map(|t| ArgKind::from_expected_ty(t, Some(span))).collect()
@@ -3487,15 +3489,15 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         // traits manually, but don't make it more confusing when it does
         // happen.
         Ok(
-            if Some(expected_trait_ref.def_id()) != self.tcx.lang_items().coroutine_trait()
+            if Some(expected_trait_ref.def_id) != self.tcx.lang_items().coroutine_trait()
                 && not_tupled
             {
                 self.report_and_explain_type_error(
                     TypeTrace::poly_trait_refs(
                         &obligation.cause,
                         true,
-                        expected_trait_ref,
-                        found_trait_ref,
+                        ty::Binder::dummy(expected_trait_ref),
+                        ty::Binder::dummy(found_trait_ref),
                     ),
                     ty::error::TypeError::Mismatch,
                 )

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -1079,8 +1079,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             })
             .map_err(|terr| {
                 SignatureMismatch(Box::new(SignatureMismatchData {
-                    expected_trait_ref: ty::Binder::dummy(obligation_trait_ref),
-                    found_trait_ref: ty::Binder::dummy(found_trait_ref),
+                    expected_trait_ref: obligation_trait_ref,
+                    found_trait_ref,
                     terr,
                 }))
             })