From 8823bf0b403b0ebf348e1f3fa59d74f2843f0c8b Mon Sep 17 00:00:00 2001
From: Stein Somers <git@steinsomers.be>
Date: Wed, 9 Jan 2019 22:19:54 +0100
Subject: Fix poor worst case performance of is_disjoint

---
 src/libstd/collections/hash/set.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'src/libstd')

diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index 627846411bc..c55dd049ec6 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -599,7 +599,11 @@ impl<T, S> HashSet<T, S>
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn is_disjoint(&self, other: &HashSet<T, S>) -> bool {
-        self.iter().all(|v| !other.contains(v))
+        if self.len() <= other.len() {
+            self.iter().all(|v| !other.contains(v))
+        } else {
+            other.iter().all(|v| !self.contains(v))
+        }
     }
 
     /// Returns `true` if the set is a subset of another,
@@ -1510,7 +1514,6 @@ mod test_set {
         let mut a = HashSet::new();
         let mut b = HashSet::new();
         assert!(a.intersection(&b).next().is_none());
-        assert!(b.intersection(&a).next().is_none());
 
         assert!(a.insert(11));
         assert!(a.insert(1));
-- 
cgit 1.4.1-3-g733a5