From 7f39b0c9ab7c2c3beeb9dd3a54f51b3a5f7e21a0 Mon Sep 17 00:00:00 2001
From: Bastian Kauschke <bastian_kauschke@hotmail.de>
Date: Thu, 18 Jun 2020 00:18:58 +0200
Subject: [PATCH] subst_supertrait

---
 src/librustc_infer/traits/util.rs |  4 +--
 src/librustc_middle/ty/mod.rs     | 41 +++++++++----------------------
 2 files changed, 14 insertions(+), 31 deletions(-)

diff --git a/src/librustc_infer/traits/util.rs b/src/librustc_infer/traits/util.rs
index ddb7e7adbc6..9dfe23b5aad 100644
--- a/src/librustc_infer/traits/util.rs
+++ b/src/librustc_infer/traits/util.rs
@@ -156,10 +156,10 @@ impl Elaborator<'tcx> {
                 // Get predicates declared on the trait.
                 let predicates = tcx.super_predicates_of(data.def_id());
 
-                let obligations = predicates.predicates.iter().map(|(pred, span)| {
+                let obligations = predicates.predicates.iter().map(|&(pred, span)| {
                     predicate_obligation(
                         pred.subst_supertrait(tcx, &data.to_poly_trait_ref()),
-                        Some(*span),
+                        Some(span),
                     )
                 });
                 debug!("super_predicates: data={:?}", data);
diff --git a/src/librustc_middle/ty/mod.rs b/src/librustc_middle/ty/mod.rs
index b72dd638219..ac1642ec866 100644
--- a/src/librustc_middle/ty/mod.rs
+++ b/src/librustc_middle/ty/mod.rs
@@ -1303,37 +1303,20 @@ impl<'tcx> Predicate<'tcx> {
         // this trick achieves that).
 
         let substs = trait_ref.skip_binder().substs;
-        let kind = self.kind();
-        let new = match kind {
-            &PredicateKind::Trait(ref binder, constness) => {
-                PredicateKind::Trait(binder.map_bound(|data| data.subst(tcx, substs)), constness)
-            }
-            PredicateKind::Subtype(binder) => {
-                PredicateKind::Subtype(binder.map_bound(|data| data.subst(tcx, substs)))
-            }
-            PredicateKind::RegionOutlives(binder) => {
-                PredicateKind::RegionOutlives(binder.map_bound(|data| data.subst(tcx, substs)))
-            }
-            PredicateKind::TypeOutlives(binder) => {
-                PredicateKind::TypeOutlives(binder.map_bound(|data| data.subst(tcx, substs)))
-            }
-            PredicateKind::Projection(binder) => {
-                PredicateKind::Projection(binder.map_bound(|data| data.subst(tcx, substs)))
-            }
-            &PredicateKind::WellFormed(data) => PredicateKind::WellFormed(data.subst(tcx, substs)),
-            &PredicateKind::ObjectSafe(trait_def_id) => PredicateKind::ObjectSafe(trait_def_id),
-            &PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
-                PredicateKind::ClosureKind(closure_def_id, closure_substs.subst(tcx, substs), kind)
-            }
-            &PredicateKind::ConstEvaluatable(def_id, const_substs) => {
-                PredicateKind::ConstEvaluatable(def_id, const_substs.subst(tcx, substs))
-            }
-            PredicateKind::ConstEquate(c1, c2) => {
-                PredicateKind::ConstEquate(c1.subst(tcx, substs), c2.subst(tcx, substs))
-            }
+        let kind = match self.kint(tcx) {
+            PredicateKint::ForAll(binder) => *binder.skip_binder(),
+            kind => kind,
         };
 
-        if new != *kind { new.to_predicate(tcx) } else { self }
+        let new = kind.subst(tcx, substs);
+
+        let rebound = if new.has_escaping_bound_vars() {
+            PredicateKint::ForAll(Binder::bind(tcx.intern_predicate_kint(new)))
+        } else {
+            new
+        };
+
+        if rebound != *kind { rebound.to_predicate(tcx) } else { self }
     }
 }