From cd6a8cae2aa07bd456a1816196e3c9aa2fcb72d6 Mon Sep 17 00:00:00 2001
From: CAD97 <cad97@cad97.com>
Date: Thu, 28 May 2020 01:11:46 -0400
Subject: [PATCH] FIx off-by-one in char::steps_between

---
 src/libcore/iter/range.rs | 2 +-
 src/libcore/tests/iter.rs | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/libcore/iter/range.rs b/src/libcore/iter/range.rs
index 5db790e491c2d..fc4454ede3588 100644
--- a/src/libcore/iter/range.rs
+++ b/src/libcore/iter/range.rs
@@ -408,7 +408,7 @@ unsafe impl Step for char {
         let start = start as u32;
         let end = end as u32;
         if start <= end {
-            let count = end - start + 1;
+            let count = end - start;
             if start < 0xD800 && 0xE000 <= end {
                 usize::try_from(count - 0x800).ok()
             } else {
diff --git a/src/libcore/tests/iter.rs b/src/libcore/tests/iter.rs
index 6605249f18004..c5d636ac8da55 100644
--- a/src/libcore/tests/iter.rs
+++ b/src/libcore/tests/iter.rs
@@ -1939,7 +1939,9 @@ fn test_char_range() {
     assert!(('\0'..=char::MAX).rev().eq((0..=char::MAX as u32).filter_map(char::from_u32).rev()));
 
     assert_eq!(('\u{D7FF}'..='\u{E000}').count(), 2);
+    assert_eq!(('\u{D7FF}'..='\u{E000}').size_hint(), (2, Some(2)));
     assert_eq!(('\u{D7FF}'..'\u{E000}').count(), 1);
+    assert_eq!(('\u{D7FF}'..'\u{E000}').size_hint(), (1, Some(1)));
 }
 
 #[test]