anchor.diff:        // Unless this part ends with a separator, we'll need to add one before
         // the next part.
         needsSeparator = part.length > 0 &&
  -          !style.separatorPattern.hasMatch(part[part.length - 1]);
  +          !part[part.length - 1].contains(style.separatorPattern);
       }
   
       return buffer.toString();
  
positive.code:         buffer.clear();
          buffer.add(part);
        } else {
          if (part.length > 0 && style.separatorPattern.hasMatch(part[0])) {
            // The part starts with a separator, so we don't need to add one.
          } else if (needsSeparator) {
            buffer.add(separator);
  
negative.code:   /// "\" is the canonical one.
    final Pattern separatorPattern;
  
    // TODO(nweiz): make this a Pattern when issue 7080 is fixed.
    /// The [RegExp] that can be used to match the root prefix of an absolute
    /// path in this style.
    final RegExp _rootPattern;
  
    /// Gets the root prefix of [path] if path is absolute. If [path] is relative,
    /// returns `null`.
  