From 2e3f0d26a0be066678d543bc8abd0143204311c2 Mon Sep 17 00:00:00 2001
From: Wilfred Hughes <me@wilfred.me.uk>
Date: Sat, 1 Jan 2022 19:31:34 -0800
Subject: [PATCH] Add some defensive assertions

---
 src/lines.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/lines.rs b/src/lines.rs
index 18c9d2882..6d0eac4de 100644
--- a/src/lines.rs
+++ b/src/lines.rs
@@ -70,6 +70,8 @@ impl NewlinePositions {
     /// Convert to single-line spans. If the original span crosses a
     /// newline, the vec will contain multiple items.
     pub fn from_offsets(&self, region_start: usize, region_end: usize) -> Vec<SingleLineSpan> {
+        assert!(region_start <= region_end);
+
         let mut res = vec![];
         for (line_num, line_start) in self.positions.iter().enumerate() {
             let line_end = match self.positions.get(line_num + 1) {
@@ -108,6 +110,8 @@ impl NewlinePositions {
         region_start: usize,
         region_end: usize,
     ) -> Vec<SingleLineSpan> {
+        assert!(region_start <= region_end);
+
         let mut res = vec![];
         for pos in self.from_offsets(region_start, region_end) {
             if pos.line.0 == 0 {