anchor.diff:    
     /// Inserts a [key].
     void encodeKey(String key) {
  -    _buf.write(key);
  +    if(bareKeyRegExp.hasMatch(key)){
  +      _buf.write(key);
  +    }
  +    else{
  +      basicString(key);
  +    }
     }
     
     /// Applies a [TomlValueEncoder] on [value].
  
positive.code:   @override
    String toString() => _buf.toString();
    
  }
negative.code: 
  /// TOML document builder.
  class TomlDocumentBuilder {
    
    /**
     * Regular expression of a bare key.
     */
    static final RegExp bareKeyRegExp = new RegExp(r'^[A-Za-z0-9_-]+$');
    
    /// A buffer which holds the textual representation of the document.
    final StringBuffer _buf = new StringBuffer();
  