From 27d1cd857e8998c423f329efce7c995a26dcdb6c Mon Sep 17 00:00:00 2001
From: CAD97 <cad97@cad97.com>
Date: Thu, 21 May 2020 13:21:55 -0400
Subject: [PATCH] Add safety annotations in iter::range

---
 src/libcore/iter/range.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/libcore/iter/range.rs b/src/libcore/iter/range.rs
index 3fa4cf2ca0da6..5db790e491c2d 100644
--- a/src/libcore/iter/range.rs
+++ b/src/libcore/iter/range.rs
@@ -427,6 +427,8 @@ unsafe impl Step for char {
             res = Step::forward_checked(res, 0x800)?;
         }
         if res <= char::MAX as u32 {
+            // SAFETY: res is a valid unicode scalar
+            // (below 0x110000 and not in 0xD800..0xE000)
             Some(unsafe { char::from_u32_unchecked(res) })
         } else {
             None
@@ -440,6 +442,8 @@ unsafe impl Step for char {
         if start >= 0xE000 && 0xE000 > res {
             res = Step::backward_checked(res, 0x800)?;
         }
+        // SAFETY: res is a valid unicode scalar
+        // (below 0x110000 and not in 0xD800..0xE000)
         Some(unsafe { char::from_u32_unchecked(res) })
     }