addBundleAsNotes

    pub fn addBundleAsNotes(wip: *Wip, other: ErrorBundle) Allocator.Error!void {
        const gpa = wip.gpa;

        try wip.string_bytes.ensureUnusedCapacity(gpa, other.string_bytes.len);
        try wip.extra.ensureUnusedCapacity(gpa, other.extra.len);

        const other_list = other.getMessages();

        // The ensureUnusedCapacity call above guarantees this.
        const notes_start = wip.reserveNotes(@intCast(other_list.len)) catch unreachable;
        for (notes_start.., other_list) |note, message| {
            // This line can cause `wip.extra.items` to be resized.
            const note_index = @backingInt(wip.addOtherMessage(other, message) catch unreachable);
            wip.extra.items[note] = note_index;
        }
    }