Open a new document `test.rs` and type the following: `di//<esc><C-c>` The margin calculation pushes the range out of bounds for the comment marker when there are no characters (newline) after it. thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Char range out of bounds: char range 0..3, Rope/RopeSlice char length 2', ropey-1.6.0/src/rope.rs:546:37 The debug build catches the error in the transaction: thread 'main' panicked at 'attempt to subtract with overflow', helix-core/src/transaction.rs:503:26