final def orElseU[Err2 >: Err, In2 <: In, Out2 >: Out, Value2 : ClassTag](that: => Syntax[Err2, In2, Out2, Value2])(implicit evidence$1: ClassTag[Value2], vtag: ClassTag[Value]): Syntax[Err2, In2, Out2, Value | Value2]
Assigns 'that' syntax as a fallback of this. First this parser or printer gets evaluated. In case it succeeds, the result is this syntax's result. In case it fails, the result is 'that' syntax's result.
Assigns 'that' syntax as a fallback of this. First this parser or printer gets evaluated. In case it succeeds, the result is this syntax's result. In case it fails, the result is 'that' syntax's result.
If auto-backtracking is on, this parser will backtrack before trying 'that' parser.