From 9125fbfd60afd9dafca843857498232503be365a Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Wed, 1 Sep 2021 11:55:03 +0000
Subject: [PATCH] Do not lint for ~const Drop bounds

---
 compiler/rustc_lint/src/traits.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/compiler/rustc_lint/src/traits.rs b/compiler/rustc_lint/src/traits.rs
index edb158dd378..ac1b106f73b 100644
--- a/compiler/rustc_lint/src/traits.rs
+++ b/compiler/rustc_lint/src/traits.rs
@@ -87,6 +87,7 @@ declare_lint_pass!(
 impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
         use rustc_middle::ty::PredicateKind::*;
+        use rustc_middle::ty;
 
         let predicates = cx.tcx.explicit_predicates_of(item.def_id);
         for &(predicate, span) in predicates.predicates {
@@ -94,6 +95,10 @@ impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
                 Trait(trait_predicate) => trait_predicate,
                 _ => continue,
             };
+            if trait_predicate.constness == ty::BoundConstness::ConstIfConst {
+                // `~const Drop` definitely have meanings so avoid linting here.
+                continue
+            }
             let def_id = trait_predicate.trait_ref.def_id;
             if cx.tcx.lang_items().drop_trait() == Some(def_id) {
                 // Explicitly allow `impl Drop`, a drop-guards-as-Voldemort-type pattern.