From 8a4e269a1ecd0092c82e3fccbe7af9baf09fdf1e Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Thu, 21 Dec 2023 16:06:03 +0000
Subject: Check that character range is valid

---
 src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java b/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
index 2a8e6bdf..fe0c6271 100644
--- a/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
+++ b/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
@@ -32,11 +32,14 @@ public record FileFragmentSource(
 
     @Override
     public Source at(int characterIndexStart, int characterIndexEnd) {
+        if (characterIndexStart > characterIndexEnd) {
+            throw new IllegalArgumentException("characterIndexStart > characterIndexEnd");
+        }
+
         return new FileFragmentSource(
             filename,
             contents,
             this.characterIndexStart + characterIndexStart,
-            // TODO: check this is less than characterIndexEnd
             this.characterIndexStart + characterIndexEnd
         );
     }
-- 
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