From e3f01b2b6ff177359504e42a99665a8abc388cb7 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Wed, 19 Jan 2022 00:40:05 -0800
Subject: [PATCH] never type is const Drop

---
 .../src/traits/select/candidate_assembly.rs                 | 2 +-
 .../rustc_trait_selection/src/traits/select/confirmation.rs | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 20297518a59..77db3bd2692 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -932,7 +932,6 @@ fn assemble_const_drop_candidates(
             | ty::Bound(..)
             | ty::Param(_)
             | ty::Placeholder(_)
-            | ty::Never
             | ty::Foreign(_)
             | ty::Projection(_) => {
                 // We don't know if these are `~const Drop`, at least
@@ -951,6 +950,7 @@ fn assemble_const_drop_candidates(
             | ty::Ref(..)
             | ty::FnDef(..)
             | ty::FnPtr(_)
+            | ty::Never
             | ty::Array(..)
             | ty::Slice(_)
             | ty::Closure(..)
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 9d62614031c..35aebd9900f 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -1103,6 +1103,7 @@ fn confirm_const_drop_candidate(
         let tcx = self.tcx();
         let self_ty = self.infcx.shallow_resolve(obligation.self_ty());
 
+        // Skip binder here (*)
         let nested_tys = match *self_ty.skip_binder().kind() {
             ty::Bool
             | ty::Char
@@ -1116,7 +1117,7 @@ fn confirm_const_drop_candidate(
             | ty::Ref(..)
             | ty::FnDef(..)
             | ty::FnPtr(_)
-            | ty::Projection(_) => vec![],
+            | ty::Never => vec![],
 
             ty::Adt(def, substs) => def.all_fields().map(|f| f.ty(tcx, substs)).collect(),
 
@@ -1138,8 +1139,8 @@ fn confirm_const_drop_candidate(
             | ty::Bound(_, _)
             | ty::Param(_)
             | ty::Placeholder(_)
-            | ty::Never
             | ty::Foreign(_)
+            | ty::Projection(_)
             | ty::Infer(_) => {
                 unreachable!();
             }
@@ -1165,6 +1166,7 @@ fn confirm_const_drop_candidate(
                     obligation.param_env,
                     cause.clone(),
                     obligation.recursion_depth + 1,
+                    // Rebinding here (*)
                     self_ty
                         .rebind(ty::TraitPredicate {
                             trait_ref: ty::TraitRef {