From cc3656f33feaa69a6ae1560d46e0284a82dbdcac Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 10 Jul 2021 16:19:33 +0100
Subject: [PATCH] zcoord: Reject attempt to make range [X,X>

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 base/zcoord.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/base/zcoord.rs b/base/zcoord.rs
index f236ba1d..dbf37491 100644
--- a/base/zcoord.rs
+++ b/base/zcoord.rs
@@ -107,6 +107,8 @@ pub struct ParseError;
 pub enum RangeImpossible {
   #[error("Z coordinate range has end before start, cannot iterate")]
   Backwards,
+  #[error("Z coordinate range has end equal to start, cannot iterate")]
+  Empty,
 }
 
 #[derive(Error,Clone,Copy,Debug,Eq,PartialEq,Serialize,Deserialize)]
@@ -382,7 +384,7 @@ impl Mutable {
     let aso = 'ok: loop { for i in 0.. {
       if i >= a.limbs.len() && i >= b.limbs.len() {
 	// Oh actually these numbers are equal!
-	break 'ok ASRD { i: 0, step: ZERO };
+	throw!(RangeImpossible::Empty);
       }
       current.extend_to_limb(i);
 
-- 
2.30.2