From f8a4b6d2ba2ad2a0897cd26cf6196cca23045f96 Mon Sep 17 00:00:00 2001
From: Christopher Durham <cad97@cad97.com>
Date: Mon, 25 Nov 2019 17:55:26 -0500
Subject: [PATCH] impl TrustedLen for vec::Drain

---
 src/liballoc/vec.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index 07e4358d644c6..ab9e2a23cb03e 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -2701,6 +2701,9 @@ impl<T> ExactSizeIterator for Drain<'_, T> {
     }
 }
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<T> TrustedLen for Drain<'_, T> {}
+
 #[stable(feature = "fused", since = "1.26.0")]
 impl<T> FusedIterator for Drain<'_, T> {}