From e8c284ff2826e139fd77278af65a005a8b5b5bf3 Mon Sep 17 00:00:00 2001
From: Jack Huey <jack.huey@umassmed.edu>
Date: Fri, 14 May 2021 18:17:13 -0400
Subject: [PATCH] Make the UnifyValue for RegionVid ()

---
 compiler/rustc_infer/src/infer/region_constraints/mod.rs | 7 +++----
 compiler/rustc_middle/src/infer/unify_key.rs             | 2 +-
 src/test/ui/traits/inductive-overflow/lifetime.rs        | 2 ++
 src/test/ui/traits/inductive-overflow/lifetime.stderr    | 4 +++-
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 9ffcddfae99..abbcff30cda 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -3,7 +3,6 @@
 use self::CombineMapType::*;
 use self::UndoLog::*;
 
-use super::unify_key;
 use super::{
     InferCtxtUndoLogs, MiscVariable, RegionVariableOrigin, Rollback, Snapshot, SubregionOrigin,
 };
@@ -408,7 +407,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         if *any_unifications {
             *any_unifications = false;
             self.unification_table()
-                .reset_unifications(|vid| unify_key::RegionVidKey { min_vid: vid });
+                .reset_unifications(|_| ());
         }
 
         data
@@ -435,7 +434,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
     ) -> RegionVid {
         let vid = self.var_infos.push(RegionVariableInfo { origin, universe });
 
-        let u_vid = self.unification_table().new_key(unify_key::RegionVidKey { min_vid: vid });
+        let u_vid = self.unification_table().new_key(());
         assert_eq!(vid, u_vid);
         self.undo_log.push(AddVar(vid));
         debug!("created new region variable {:?} in {:?} with origin {:?}", vid, universe, origin);
@@ -618,7 +617,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
     }
 
     pub fn opportunistic_resolve_var(&mut self, rid: RegionVid) -> ty::RegionVid {
-        self.unification_table().probe_value(rid).min_vid
+        self.unification_table().find(rid)
     }
 
     fn combine_map(&mut self, t: CombineMapType) -> &mut CombineMap<'tcx> {
diff --git a/compiler/rustc_middle/src/infer/unify_key.rs b/compiler/rustc_middle/src/infer/unify_key.rs
index 641cf23781e..8209e3db739 100644
--- a/compiler/rustc_middle/src/infer/unify_key.rs
+++ b/compiler/rustc_middle/src/infer/unify_key.rs
@@ -38,7 +38,7 @@ impl UnifyValue for RegionVidKey {
 }
 
 impl UnifyKey for ty::RegionVid {
-    type Value = RegionVidKey;
+    type Value = ();
     fn index(&self) -> u32 {
         u32::from(*self)
     }
diff --git a/src/test/ui/traits/inductive-overflow/lifetime.rs b/src/test/ui/traits/inductive-overflow/lifetime.rs
index e23dfa57cd0..d66c30ed2dd 100644
--- a/src/test/ui/traits/inductive-overflow/lifetime.rs
+++ b/src/test/ui/traits/inductive-overflow/lifetime.rs
@@ -26,4 +26,6 @@ fn main() {
     // Should only be a few notes.
     is_send::<X<C<'static>>>();
     //~^ ERROR overflow evaluating
+    //~^^ 2 redundant
+    //~^^^ required because of
 }
diff --git a/src/test/ui/traits/inductive-overflow/lifetime.stderr b/src/test/ui/traits/inductive-overflow/lifetime.stderr
index 752154b35ca..cc913930395 100644
--- a/src/test/ui/traits/inductive-overflow/lifetime.stderr
+++ b/src/test/ui/traits/inductive-overflow/lifetime.stderr
@@ -7,11 +7,13 @@ LL | fn is_send<S: NotAuto>() {}
 LL |     is_send::<X<C<'static>>>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: required because of the requirements on the impl of `NotAuto` for `X<C<'static>>`
+note: required because of the requirements on the impl of `NotAuto` for `X<C<'_>>`
   --> $DIR/lifetime.rs:19:12
    |
 LL | impl<T: Y> NotAuto for X<T> where T::P: NotAuto {}
    |            ^^^^^^^     ^^^^
+   = note: 2 redundant requirements hidden
+   = note: required because of the requirements on the impl of `NotAuto` for `X<C<'static>>`
 
 error: aborting due to previous error