Highlight ranges in source description

1 files changed, 6 insertions, 3 deletions

diff --git a/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java b/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
index fe0c6271..0fc05672 100644
--- a/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
+++ b/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
@@ -22,7 +22,10 @@ public record FileFragmentSource(
                 return context(
                     line,
                     lineIndex,
-                    characterIndexStart - position
+                    characterIndexStart - position,
+                    nextLinePosition <= characterIndexEnd
+                        ? 1
+                        : Math.max(characterIndexEnd - characterIndexStart, 1)
                 );
             }
             position = nextLinePosition;
@@ -64,9 +67,9 @@ public record FileFragmentSource(
         return at(length, length);
     }
 
-    private String context(String line, int lineIndex, int columnIndex) {
+    private String context(String line, int lineIndex, int columnIndex, int length) {
         var lineNumber = lineIndex + 1;
         var columnNumber = columnIndex + 1;
-        return filename + ":" + lineNumber + ":" + columnNumber + "\n" + line + "\n" + " ".repeat(columnIndex) + "^";
+        return filename + ":" + lineNumber + ":" + columnNumber + "\n" + line + "\n" + " ".repeat(columnIndex) + "^".repeat(length);
     }
 }