From a0957c9d2685178d1d19406661a7082bac506acb Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sun, 28 Mar 2021 00:51:31 -0400
Subject: [PATCH] Avoid sorting by DefId for `necessary_variants()`

---
 compiler/rustc_hir/src/pat_util.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_hir/src/pat_util.rs b/compiler/rustc_hir/src/pat_util.rs
index 9e0a6aae24272..c6a40b51a8658 100644
--- a/compiler/rustc_hir/src/pat_util.rs
+++ b/compiler/rustc_hir/src/pat_util.rs
@@ -1,6 +1,7 @@
 use crate::def::{CtorOf, DefKind, Res};
 use crate::def_id::DefId;
 use crate::hir::{self, HirId, PatKind};
+use rustc_data_structures::stable_set::FxHashSet;
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 
@@ -138,8 +139,10 @@ impl hir::Pat<'_> {
             }
             _ => true,
         });
-        variants.sort();
-        variants.dedup();
+        // We remove duplicates by inserting into a `FxHashSet` to avoid re-ordering
+        // the bounds
+        let mut duplicates = FxHashSet::default();
+        variants.retain(|def_id| duplicates.insert(*def_id));
         variants
     }