anchor.diff:          "Libraries changed: ${delta.newProgram.libraries.length}");
       print("Change '${changeSet.name}' - "
           "Incremental compilation took: ${iterTimer.elapsedMilliseconds}ms");
  +    if (delta.newProgram.libraries.length < 1) {
  +      throw "No libraries were changed";
  +    }
     }
   
     dir.deleteSync(recursive: true);
  
positive.code:   timer1.stop();
    print("Libraries changed: ${delta.newProgram.libraries.length}");
    print("Initial compilation took: ${timer1.elapsedMilliseconds}ms");
  
    for (final ChangeSet changeSet in changeSets) {
      await applyEdits(changeSet.edits, overlayFs, generator, uriTranslator);
  
negative.code:   final String replacement;
  
    Edit(String uriString, this.original, this.replacement)
        : uri = _resolveOverlayUri(uriString);
  
    String toString() => 'Edit($uri, "$original" -> "$replacement")';
  }
  