From c25b82f5bb9770374db31906dedb497034a151fd Mon Sep 17 00:00:00 2001
From: CAD97 <cad97@cad97.com>
Date: Wed, 20 May 2020 23:50:28 -0400
Subject: [PATCH] Use Step::forward_unchecked in RangeInclusive::next

---
 src/libcore/iter/range.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/libcore/iter/range.rs b/src/libcore/iter/range.rs
index 6837aab7af1a..3fa4cf2ca0da 100644
--- a/src/libcore/iter/range.rs
+++ b/src/libcore/iter/range.rs
@@ -646,7 +646,11 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
         }
         let is_iterating = self.start < self.end;
         Some(if is_iterating {
-            let n = Step::forward(self.start.clone(), 1);
+            // SAFETY: just checked precondition
+            // We use the unchecked version here, because
+            // otherwise `for _ in '\0'..=char::MAX`
+            // does not successfully remove panicking code.
+            let n = unsafe { Step::forward_unchecked(self.start.clone(), 1) };
             mem::replace(&mut self.start, n)
         } else {
             self.exhausted = true;