remove binder from query constraints

compiler/rustc_borrowck/src/type_check/constraint_conversion.rs

@@ -83,16 +83,8 @@ pub(super) fn convert_all(&mut self, query_constraints: &QueryRegionConstraints<
         }
         self.constraints.member_constraints = tmp;
 
-        for (predicate, constraint_category) in outlives {
-            // At the moment, we never generate any "higher-ranked"
-            // region constraints like `for<'a> 'a: 'b`. At some point
-            // when we move to universes, we will, and this assertion
-            // will start to fail.
-            let predicate = predicate.no_bound_vars().unwrap_or_else(|| {
-                bug!("query_constraint {:?} contained bound vars", predicate,);
-            });
-
-            self.convert(predicate, *constraint_category);
+        for &(predicate, constraint_category) in outlives {
+            self.convert(predicate, constraint_category);
         }
     }
 

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

@@ -268,14 +268,12 @@ pub fn instantiate_nll_query_response_and_region_obligations<R>(
                 (GenericArgKind::Lifetime(v_o), GenericArgKind::Lifetime(v_r)) => {
                     // To make `v_o = v_r`, we emit `v_o: v_r` and `v_r: v_o`.
                     if v_o != v_r {
-                        output_query_region_constraints.outlives.push((
-                            ty::Binder::dummy(ty::OutlivesPredicate(v_o.into(), v_r)),
-                            constraint_category,
-                        ));
-                        output_query_region_constraints.outlives.push((
-                            ty::Binder::dummy(ty::OutlivesPredicate(v_r.into(), v_o)),
-                            constraint_category,
-                        ));
+                        output_query_region_constraints
+                            .outlives
+                            .push((ty::OutlivesPredicate(v_o.into(), v_r), constraint_category));
+                        output_query_region_constraints
+                            .outlives
+                            .push((ty::OutlivesPredicate(v_r.into(), v_o), constraint_category));
                     }
                 }
 
@@ -318,10 +316,8 @@ pub fn instantiate_nll_query_response_and_region_obligations<R>(
             query_response.value.region_constraints.outlives.iter().filter_map(|&r_c| {
                 let r_c = substitute_value(self.tcx, &result_subst, r_c);
 
-                // Screen out `'a: 'a` cases -- we skip the binder here but
-                // only compare the inner values to one another, so they are still at
-                // consistent binding levels.
-                let ty::OutlivesPredicate(k1, r2) = r_c.0.skip_binder();
+                // Screen out `'a: 'a` cases.
+                let ty::OutlivesPredicate(k1, r2) = r_c.0;
                 if k1 != r2.into() { Some(r_c) } else { None }
             }),
         );
@@ -559,11 +555,11 @@ fn query_outlives_constraints_into_obligations<'a>(
 
     pub fn query_outlives_constraint_to_obligation(
         &self,
-        predicate: QueryOutlivesConstraint<'tcx>,
+        (predicate, _): QueryOutlivesConstraint<'tcx>,
         cause: ObligationCause<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
     ) -> Obligation<'tcx, ty::Predicate<'tcx>> {
-        let ty::OutlivesPredicate(k1, r2) = predicate.0.skip_binder();
+        let ty::OutlivesPredicate(k1, r2) = predicate;
 
         let atom = match k1.unpack() {
             GenericArgKind::Lifetime(r1) => {
@@ -578,7 +574,7 @@ pub fn query_outlives_constraint_to_obligation(
                 span_bug!(cause.span, "unexpected const outlives {:?}", predicate);
             }
         };
-        let predicate = predicate.0.rebind(atom);
+        let predicate = ty::Binder::dummy(atom);
 
         Obligation::new(self.tcx, cause, param_env, predicate)
     }
@@ -643,8 +639,7 @@ pub fn make_query_region_constraints<'tcx>(
     let outlives: Vec<_> = constraints
         .iter()
         .map(|(k, origin)| {
-            // no bound vars in the code above
-            let constraint = ty::Binder::dummy(match *k {
+            let constraint = match *k {
                 // Swap regions because we are going from sub (<=) to outlives
                 // (>=).
                 Constraint::VarSubVar(v1, v2) => ty::OutlivesPredicate(
@@ -658,16 +653,12 @@ pub fn make_query_region_constraints<'tcx>(
                     ty::OutlivesPredicate(tcx.mk_region(ty::ReVar(v2)).into(), r1)
                 }
                 Constraint::RegSubReg(r1, r2) => ty::OutlivesPredicate(r2.into(), r1),
-            });
+            };
             (constraint, origin.to_constraint_category())
         })
-        .chain(
-            outlives_obligations
-                // no bound vars in the code above
-                .map(|(ty, r, constraint_category)| {
-                    (ty::Binder::dummy(ty::OutlivesPredicate(ty.into(), r)), constraint_category)
-                }),
-        )
+        .chain(outlives_obligations.map(|(ty, r, constraint_category)| {
+            (ty::OutlivesPredicate(ty.into(), r), constraint_category)
+        }))
         .collect();
 
     QueryRegionConstraints { outlives, member_constraints: member_constraints.clone() }

compiler/rustc_middle/src/infer/canonical.rs

@@ -324,10 +324,8 @@ pub fn unchecked_rebind<W>(self, value: W) -> Canonical<'tcx, W> {
     }
 }
 
-pub type QueryOutlivesConstraint<'tcx> = (
-    ty::Binder<'tcx, ty::OutlivesPredicate<GenericArg<'tcx>, Region<'tcx>>>,
-    ConstraintCategory<'tcx>,
-);
+pub type QueryOutlivesConstraint<'tcx> =
+    (ty::OutlivesPredicate<GenericArg<'tcx>, Region<'tcx>>, ConstraintCategory<'tcx>);
 
 TrivialTypeTraversalAndLiftImpls! {
     for <'tcx> {